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Makowski H, Lamb K, Galloway LF. Support for Baker's law: Facultative self-fertilization ability decreases pollen limitation in experimental colonization. AMERICAN JOURNAL OF BOTANY 2024; 111:e16351. [PMID: 38812263 DOI: 10.1002/ajb2.16351] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/29/2023] [Revised: 03/13/2024] [Accepted: 03/14/2024] [Indexed: 05/31/2024]
Abstract
PREMISE The ability to self-fertilize is predicted to provide an advantage in colonization because a single individual can reproduce and establish a next generation in a new location regardless of the density of mates. While there is theoretical and correlative support for this idea, the strength of mate limitation as a selective agent has not yet been delineated from other factors that can also select for self-fertilization in colonization of new habitats. We used known mating-system variation in the American bellflower (Campanula americana) to explore how plants' ability to self-fertilize can mitigate density-dependent reproduction and impact colonization success. METHODS We created experimental populations of single individuals or a small number of plants to emulate isolated colonization events. These populations were composed of plants that differed in their ability to self-fertilize. We compared pollen limitation of the single individuals to that of small populations. RESULTS Experimental populations of plants that readily self-fertilize produced consistent seed numbers regardless of population size, whereas plants with lower ability to self-fertilize had density-dependent reproduction with greater seed production in small populations than in populations composed of a single individual. CONCLUSIONS We experimentally isolated the effect of mate limitation in colonization and found that it can select for increased self-fertilization. We show the benefit of self-fertilization in colonization, which helps to explain geographic patterns of self-fertilization and shows support for Baker's law, a long-held hypothesis in the field of mating-system evolution.
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Affiliation(s)
- Hanna Makowski
- Department of Biology, University of Virginia, PO Box 400328, Charlottesville, 22904, Virginia, USA
- Black Rock Forest, 65 Reservoir Road, Cornwall, New York, 12518, USA
| | - Keric Lamb
- Department of Biology, University of Virginia, PO Box 400328, Charlottesville, 22904, Virginia, USA
| | - Laura F Galloway
- Department of Biology, University of Virginia, PO Box 400328, Charlottesville, 22904, Virginia, USA
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2
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Daco L, Colling G, Matthies D. Clinal variation in quantitative traits but not in evolutionary potential along elevational and latitudinal gradients in the widespread Anthyllis vulneraria. AMERICAN JOURNAL OF BOTANY 2024; 111:e16360. [PMID: 38888183 DOI: 10.1002/ajb2.16360] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/14/2023] [Revised: 04/12/2024] [Accepted: 04/12/2024] [Indexed: 06/20/2024]
Abstract
PREMISE Strong elevational and latitudinal gradients allow the study of genetic differentiation in response to similar environmental changes. However, it is uncertain whether the environmental changes along the two types of gradients result in similar genetically based changes in quantitative traits. Peripheral arctic and alpine populations are thought to have less evolutionary potential than more central populations do. METHODS We studied quantitative traits of the widespread Anthyllis vulneraria in a common garden. Plants originated from 20 populations along a 2000-m elevational gradient from the lowlands to the elevational limit of the species in the Alps, and from 20 populations along a 2400-km latitudinal gradient from the center of the distribution of the species in Central Europe to its northern distributional margin. RESULTS Most traits showed similar clinal variations with elevation and latitude of origin, and the magnitude of all measured traits in relation to mean annual temperature was similar. Higher QST values than FST values in several traits indicated diversifying selection, but for others QST was smaller than FST. Genetic diversity of quantitative traits and neutral molecular markers was not correlated. Plasticity in response to favorable conditions declined with elevation and less strongly with latitude of origin, but the evolvability of traits did not. CONCLUSIONS The clinal variation suggests adaptive differentiation of quantitative traits along the two gradients. The evolutionary potential of peripheral populations is not necessarily reduced, but lower plasticity may threaten their survival under rapidly changing climatic conditions.
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Affiliation(s)
- Laura Daco
- Musée national d'histoire naturelle, 25 rue Münster, Luxembourg, L-2160, Luxembourg
- Department of Biology, University of Marburg, Karl-von-Frisch-Str. 8, Marburg, D-35043, Germany
- Fondation faune-flore, 24 rue Münster, Luxembourg, L-2160, Luxembourg
| | - Guy Colling
- Musée national d'histoire naturelle, 25 rue Münster, Luxembourg, L-2160, Luxembourg
| | - Diethart Matthies
- Department of Biology, University of Marburg, Karl-von-Frisch-Str. 8, Marburg, D-35043, Germany
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3
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Coffey ML, Simons AM. Latitudinal trends in mating system traits in the highly self-fertilizing Lobelia inflata revealed by community science. Ecol Evol 2023; 13:e10746. [PMID: 38034331 PMCID: PMC10682567 DOI: 10.1002/ece3.10746] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2023] [Revised: 10/13/2023] [Accepted: 11/06/2023] [Indexed: 12/02/2023] Open
Abstract
Mating systems in angiosperms range from obligate outcrossing to highly self-fertilizing. The belief that obligate selfing does not exist is contradicted by genetic evidence in several populations of L. inflata, in which selfing is enforced by the anthers enclosing the style. However, whether the mating systems of these populations are typical, or an extreme across the species range is unknown. Such trends are hypothesized to result from selection for reproductive assurance under mate limitation at range margins. Here, we use ~7500 iNaturalist community science images, in which stylar exsertion can be observed, to test this hypothesis in L. inflata and, for comparison, in four typical congeneric Lobelias that express a staminate, then a pistillate phase (protandry). Specifically, we analyzed the effects of latitude and range marginality on the frequency of stylar exsertion and number of exserted flowers. Outcrossing capacity in L. inflata increased at low latitudes and near the overall range center, supporting our hypothesis, with exsertion frequencies significantly lower than in congenerics. Interestingly, in outcrossing capable individuals, the number of style-exserted flowers was consistent across the species range and among species, indicating outcrossing capable L. inflata individuals resemble congenerics. These findings suggest that variation in stylar exsertion is expressed among individuals rather than by all individuals within populations. However, whether this is a result of differences in exsertion allele frequencies or of differentiation in the induction of a threshold trait requires further study. Moreover, the trends in outcrossing capability revealed here imply the potential for geographic variation in L. inflata mating system.
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4
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Kolesnikova UK, Scott AD, Van de Velde JD, Burns R, Tikhomirov NP, Pfordt U, Clarke AC, Yant L, Seregin AP, Vekemans X, Laurent S, Novikova PY. Transition to Self-compatibility Associated With Dominant S-allele in a Diploid Siberian Progenitor of Allotetraploid Arabidopsis kamchatica Revealed by Arabidopsis lyrata Genomes. Mol Biol Evol 2023; 40:msad122. [PMID: 37432770 PMCID: PMC10335350 DOI: 10.1093/molbev/msad122] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/13/2023] Open
Abstract
A transition to selfing can be beneficial when mating partners are scarce, for example, due to ploidy changes or at species range edges. Here, we explain how self-compatibility evolved in diploid Siberian Arabidopsis lyrata, and how it contributed to the establishment of allotetraploid Arabidopsis kamchatica. First, we provide chromosome-level genome assemblies for two self-fertilizing diploid A. lyrata accessions, one from North America and one from Siberia, including a fully assembled S-locus for the latter. We then propose a sequence of events leading to the loss of self-incompatibility in Siberian A. lyrata, date this independent transition to ∼90 Kya, and infer evolutionary relationships between Siberian and North American A. lyrata, showing an independent transition to selfing in Siberia. Finally, we provide evidence that this selfing Siberian A. lyrata lineage contributed to the formation of the allotetraploid A. kamchatica and propose that the selfing of the latter is mediated by the loss-of-function mutation in a dominant S-allele inherited from A. lyrata.
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Affiliation(s)
- Uliana K Kolesnikova
- Department of Chromosome Biology, Max Planck Institute for Plant Breeding Research, Cologne, Germany
| | - Alison Dawn Scott
- Department of Chromosome Biology, Max Planck Institute for Plant Breeding Research, Cologne, Germany
| | - Jozefien D Van de Velde
- Department of Chromosome Biology, Max Planck Institute for Plant Breeding Research, Cologne, Germany
| | - Robin Burns
- Department of Plant Sciences, University of Cambridge, Cambridge, United Kingdom
| | - Nikita P Tikhomirov
- Faculty of Biology, Lomonosov Moscow State University, Moscow, Russia
- Papanin Institute for Biology of Inland Waters, Russian Academy of Sciences, Borok, Russia
| | - Ursula Pfordt
- Department of Chromosome Biology, Max Planck Institute for Plant Breeding Research, Cologne, Germany
| | - Andrew C Clarke
- Future Food Beacon of Excellence and School of Biosciences, University of Nottingham, Sutton Bonington, United Kingdom
| | - Levi Yant
- Future Food Beacon of Excellence and School of Life Sciences, University of Nottingham, Nottingham, United Kingdom
| | - Alexey P Seregin
- Herbarium (MW), Faculty of Biology, M. V. Lomonosov Moscow State University, Moscow, Russia
| | - Xavier Vekemans
- University Lille, CNRS, UMR 8198—Evo-Eco-Paleo, Lille, France
| | - Stefan Laurent
- Department of Comparative Development and Genetics, Max Planck Institute for Plant Breeding Research, Cologne, Germany
| | - Polina Yu Novikova
- Department of Chromosome Biology, Max Planck Institute for Plant Breeding Research, Cologne, Germany
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5
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Cisternas-Fuentes A, Koski MH. Drivers of strong isolation and small effective population size at a leading range edge of a widespread plant. Heredity (Edinb) 2023:10.1038/s41437-023-00610-z. [PMID: 37016137 DOI: 10.1038/s41437-023-00610-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2022] [Revised: 03/09/2023] [Accepted: 03/09/2023] [Indexed: 04/06/2023] Open
Abstract
Climate change has influenced species distributions worldwide with upward elevational shifts observed in many systems. Leading range edge populations, like those at upper elevation limits, are crucial for climate change responses but can exhibit low genetic diversity due to founder effects, isolation, or limited outbreeding. These factors can hamper local adaptation at range limits. Using the widespread herb, Argentina anserina, we measured ecological attributes (population density on the landscape, area of population occupancy, and plant and flower density) spanning a 1000 m elevation gradient, with high elevation populations at the range limit. We measured vegetative clonal potential in the greenhouse for populations spanning the gradient. We combined these data with a ddRAD-seq dataset to test the hypotheses that high elevation populations would exhibit ecological and genomic signatures of leading range edge populations. We found that population density on the landscape declined towards the high elevation limit, as is expected towards range edges. However, plant density was elevated within edge populations. In the greenhouse, high elevation plants exhibited stronger clonal potential than low elevation plants, likely explaining increased plant density in the field. Phylogeographic analysis supported more recent colonization of high elevation populations which were also more genetically isolated, had more extreme heterozygote excess and had smaller effective population size than low. Results support that colonization of high elevations was likely accompanied by increased asexuality, contributing to a decline in effective population size. Despite high plant density in leading edge populations, their small effective size, isolation and clonality could constrain adaptive potential.
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Affiliation(s)
- Anita Cisternas-Fuentes
- Department of Biological Sciences, Clemson University, 132 Long Hall, Clemson, SC, 29634, USA.
| | - Matthew H Koski
- Department of Biological Sciences, Clemson University, 132 Long Hall, Clemson, SC, 29634, USA.
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6
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Jaegle B, Pisupati R, Soto-Jiménez LM, Burns R, Rabanal FA, Nordborg M. Extensive sequence duplication in Arabidopsis revealed by pseudo-heterozygosity. Genome Biol 2023; 24:44. [PMID: 36895055 PMCID: PMC9999624 DOI: 10.1186/s13059-023-02875-3] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2021] [Accepted: 02/13/2023] [Indexed: 03/11/2023] Open
Abstract
BACKGROUND It is apparent that genomes harbor much structural variation that is largely undetected for technical reasons. Such variation can cause artifacts when short-read sequencing data are mapped to a reference genome. Spurious SNPs may result from mapping of reads to unrecognized duplicated regions. Calling SNP using the raw reads of the 1001 Arabidopsis Genomes Project we identified 3.3 million (44%) heterozygous SNPs. Given that Arabidopsis thaliana (A. thaliana) is highly selfing, and that extensively heterozygous individuals have been removed, we hypothesize that these SNPs reflected cryptic copy number variation. RESULTS The heterozygosity we observe consists of particular SNPs being heterozygous across individuals in a manner that strongly suggests it reflects shared segregating duplications rather than random tracts of residual heterozygosity due to occasional outcrossing. Focusing on such pseudo-heterozygosity in annotated genes, we use genome-wide association to map the position of the duplicates. We identify 2500 putatively duplicated genes and validate them using de novo genome assemblies from six lines. Specific examples included an annotated gene and nearby transposon that transpose together. We also demonstrate that cryptic structural variation produces highly inaccurate estimates of DNA methylation polymorphism. CONCLUSIONS Our study confirms that most heterozygous SNP calls in A. thaliana are artifacts and suggest that great caution is needed when analyzing SNP data from short-read sequencing. The finding that 10% of annotated genes exhibit copy-number variation, and the realization that neither gene- nor transposon-annotation necessarily tells us what is actually mobile in the genome suggests that future analyses based on independently assembled genomes will be very informative.
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Affiliation(s)
- Benjamin Jaegle
- Gregor Mendel Institute, Austrian Academy of Sciences, Vienna Biocenter, Vienna, Austria
| | - Rahul Pisupati
- Gregor Mendel Institute, Austrian Academy of Sciences, Vienna Biocenter, Vienna, Austria
| | | | - Robin Burns
- Gregor Mendel Institute, Austrian Academy of Sciences, Vienna Biocenter, Vienna, Austria
- Department of Plant Sciences, University of Cambridge, Cambridge, UK
| | | | - Magnus Nordborg
- Gregor Mendel Institute, Austrian Academy of Sciences, Vienna Biocenter, Vienna, Austria.
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7
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Novikova PY, Kolesnikova UK, Scott AD. Ancestral self-compatibility facilitates the establishment of allopolyploids in Brassicaceae. PLANT REPRODUCTION 2023; 36:125-138. [PMID: 36282331 PMCID: PMC9957919 DOI: 10.1007/s00497-022-00451-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/29/2022] [Accepted: 09/20/2022] [Indexed: 05/15/2023]
Abstract
Self-incompatibility systems based on self-recognition evolved in hermaphroditic plants to maintain genetic variation of offspring and mitigate inbreeding depression. Despite these benefits in diploid plants, for polyploids who often face a scarcity of mating partners, self-incompatibility can thwart reproduction. In contrast, self-compatibility provides an immediate advantage: a route to reproductive viability. Thus, diploid selfing lineages may facilitate the formation of new allopolyploid species. Here, we describe the mechanism of establishment of at least four allopolyploid species in Brassicaceae (Arabidopsis suecica, Arabidopsis kamchatica, Capsella bursa-pastoris, and Brassica napus), in a manner dependent on the prior loss of the self-incompatibility mechanism in one of the ancestors. In each case, the degraded S-locus from one parental lineage was dominant over the functional S-locus of the outcrossing parental lineage. Such dominant loss-of-function mutations promote an immediate transition to selfing in allopolyploids and may facilitate their establishment.
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Affiliation(s)
- Polina Yu Novikova
- Department of Chromosome Biology, Max Planck Institute for Plant Breeding Research, Carl-von-Linne-Weg 10, 50829, Cologne, Germany.
| | - Uliana K Kolesnikova
- Department of Chromosome Biology, Max Planck Institute for Plant Breeding Research, Carl-von-Linne-Weg 10, 50829, Cologne, Germany
| | - Alison Dawn Scott
- Department of Chromosome Biology, Max Planck Institute for Plant Breeding Research, Carl-von-Linne-Weg 10, 50829, Cologne, Germany
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8
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Perrier A, Willi Y. Intraspecific variation in reproductive barriers between two closely related Arabidopsis sister species. J Evol Biol 2023; 36:121-130. [PMID: 36436201 PMCID: PMC10100320 DOI: 10.1111/jeb.14122] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2022] [Revised: 09/07/2022] [Accepted: 09/25/2022] [Indexed: 11/29/2022]
Abstract
Reproductive isolation (RI) is a critical component of speciation and varies strongly in timing and strength among different sister taxa, depending on, for example the geography of speciation and divergence time. However, these factors may also produce variation in timing and strength among populations within species. Here we tested for variation in the expression of RI among replicate population pairs between the sister taxa Arabidopsis lyrata subsp. lyrata and A. arenicola. While the former is predominantly outcrossing, the latter is predominantly selfing. We focused on intrinsic prezygotic and postzygotic RI as both species occur largely in allopatry. We assessed RI by performing within-population crosses and interspecific between-population crosses, and by raising offspring. RI was generally high between all interspecific population pairs, but it varied in timing and strength depending on population history. Prezygotic isolation was strongest between the closest-related population pair, while early postzygotic isolation was high for all other population pairs. Furthermore, the timing and strength of RI depended strongly on cross direction. Our study provides empirical support that reproductive barriers between species are highly variable among population pairs and asymmetric within population pairs, and this variation seems to follow patterns typically described across species pairs.
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Affiliation(s)
- Antoine Perrier
- Department of Environmental Sciences, University of Basel, Basel, Switzerland.,Department of Biology, University of Virginia, Charlottesville, Virginia, USA
| | - Yvonne Willi
- Department of Environmental Sciences, University of Basel, Basel, Switzerland
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9
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Rose JP, Sytsma KJ. Phylogeography and genetic variation in Western Jacob's ladder (Polemonium occidentale) provide insights into the origin and conservation of rare species in the Great Lakes region. Mol Ecol 2023; 32:79-94. [PMID: 36217576 DOI: 10.1111/mec.16730] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2022] [Revised: 09/27/2022] [Accepted: 10/06/2022] [Indexed: 12/29/2022]
Abstract
The perennial herb Western Jacob's Ladder (Polemonium occidentale, Polemoniaceae) is widespread in the mountains of western North America but reappears as a disjunct in the Great Lakes Region in Minnesota and Wisconsin, USA as the narrow endemic P. occidentale subsp. lacustre. This distribution is shown by a diverse assemblage of angiosperms. It has been hypothesized that these species became isolated just after the Last Glacial Maximum, but this has not been tested. Additionally, the genetic diversity and population connectivity of the endemic Great Lakes flora has been understudied, with important conservation implications. Using genotyping-by-sequencing, we examined the relationship of P. occidentale subsp. lacustre to its closest relatives, relationships among all known populations, and genetic diversity within these populations. Polemonium occidentale subsp. lacustre represents an isolated, unique lineage that diverged from its closest relatives 1.3 Ma and arrived in the Great Lakes Region by at least 38 ka. Nearly all extant populations diverged prior to the Last Glacial Maximum, are genetically distinct, and show little within-population genetic diversity. Clonality may mitigate reduction in diversity due to drift. Mixed population signal between Wisconsin and some Minnesota populations may be due to gene flow during the Late Pleistocene. While populations of P. occidentale subsp. lacustre may be relictual from a now extinct western relative, it is best treated as a distinct species. Conservation efforts should focus more on ensuring that current populations remain rather than maintaining large populations sizes across a few populations. However, encouraging habitat heterogeneity may accomplish both simultaneously.
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Affiliation(s)
- Jeffrey P Rose
- Department of Botany, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Kenneth J Sytsma
- Department of Botany, University of Wisconsin-Madison, Madison, Wisconsin, USA
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10
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Recent speciation associated with range expansion and a shift to self-fertilization in North American Arabidopsis. Nat Commun 2022; 13:7564. [PMID: 36481740 PMCID: PMC9732334 DOI: 10.1038/s41467-022-35368-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2022] [Accepted: 11/30/2022] [Indexed: 12/13/2022] Open
Abstract
The main processes classically evoked for promoting reproductive isolation and speciation are geographic separation reducing gene flow among populations, divergent selection, and chance genomic change. In a case study, we present evidence that the additional factors of climate change, range expansion and a shift in mating towards inbreeding can initiate the processes leading to parapatric speciation. At the end of the last Pleistocene glaciation cycle, the North American plant Arabidopsis lyrata expanded its range and concomitantly lost its reproductive mode of outcrossing multiple times. We show that in one of the newly colonized areas, the self-fertilizing recolonization lineage of A. lyrata gave rise to selfing A. arenicola, which expanded its range to subarctic and arctic Canada and Greenland, while the parental species remained restricted to temperate North America. Despite the vast range expansion by the new species, mutational load did not increase, probably because of selfing and quasi-clonal selection. We conclude that such peripheral parapatric speciation combined with range expansion and inbreeding may be an important but so far overlooked mode of speciation.
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Latron M, Arnaud J, Schmitt E, Duputié A. Idiosyncratic shifts in life‐history traits at species' geographic range edges. OIKOS 2022. [DOI: 10.1111/oik.09098] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
| | | | - Eric Schmitt
- Univ. Lille, CNRS, UMR 8198 – Evo‐Eco‐Paleo Lille France
| | - Anne Duputié
- Univ. Lille, CNRS, UMR 8198 – Evo‐Eco‐Paleo Lille France
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12
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Sánchez-Castro D, Armbruster G, Willi Y. Reduced pollinator service in small populations of Arabidopsis lyrata at its southern range limit. Oecologia 2022; 200:107-117. [PMID: 36053350 PMCID: PMC9547784 DOI: 10.1007/s00442-022-05237-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2021] [Accepted: 07/27/2022] [Indexed: 11/28/2022]
Abstract
Even though a high fraction of angiosperm plants depends on animal pollinators for sexual reproduction, little is known how pollinator service changes across the ranges of plant species and whether it may contribute to range limits. Here, we tested for variation in pollinator service in the North American Arabidopsis lyrata from its southern to northern range edge and evaluated the driving mechanisms. We monitored insect pollinators using time-lapse cameras in 13 populations over two years and spotted 67 pollinating insect taxa, indicating the generalist nature of this plant-pollinator system. Pollinator service was highest at intermediate local flower densities and higher in large compared to small plant populations. Southern populations had generally smaller population sizes, and visitation rate and pollination ratio decreased with latitude. We also found that pollinator visitation was positively correlated with the richness of other flowering plants. This study indicates that plant populations at southern range edges receive only marginal pollinator service if they are small, and the effect of lower pollination is also detectable within populations across the range when the local flower density is low. Results, therefore, suggest the potential for an Allee effect in pollination that manifests itself across spatial scales.
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Affiliation(s)
- Darío Sánchez-Castro
- Department of Environmental Sciences, University of Basel, 4056 Basel, Switzerland
| | - Georg Armbruster
- Department of Environmental Sciences, University of Basel, 4056 Basel, Switzerland
| | - Yvonne Willi
- Department of Environmental Sciences, University of Basel, 4056 Basel, Switzerland
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13
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Xu K. The genetic basis of selfing rate evolution. Evolution 2022; 76:883-898. [PMID: 35395695 DOI: 10.1111/evo.14480] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2021] [Revised: 02/02/2022] [Accepted: 02/28/2022] [Indexed: 01/21/2023]
Abstract
Evolution of selfing is common in plant populations, but the genetic basis of selfing rate evolution remains unclear. Although the effects of genetic properties on fixation for mating-unrelated alleles have been investigated, loci that modify the selfing rate (selfing modifiers) differ from mating-unrelated loci in several aspects. Using population genetic models, I investigate the genetic basis of selfing rate evolution. For mating-unrelated alleles, selfing promotes fixation only for recessive mutations, but for selfing modifiers, because the selection coefficient depends on the background selfing rate, selfing can promote fixation even for dominant modifiers. For mating-unrelated alleles, the fixation probability from standing variation is independent of dominance and decreases with an increased background selfing rate. However, for selfing modifiers, the fixation probability peaks at an intermediate selfing rate and when alleles are recessive, because a change of its selection coefficient necessarily involves a change of the inbreeding coefficient, because both depend on the level of inbreeding depression. Furthermore, evolution of selfing involving multiple modifier loci is more likely when selfing is controlled by few large-effect rather than many slight-effect modifiers. I discuss how these characteristics of selfing modifiers have implications for the unidirectional transition from outcrossing to selfing and other empirical patterns.
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Affiliation(s)
- Kuangyi Xu
- Department of Biology, University of North Carolina at Chapel Hill, Coker Hall, 120 South Road, Chapel Hill, North Carolina, 27599, United States
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14
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Perrier A, Sánchez‐Castro D, Willi Y. Environment dependence of the expression of mutational load and species' range limits. J Evol Biol 2022; 35:731-741. [PMID: 35290676 PMCID: PMC9314787 DOI: 10.1111/jeb.13997] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2021] [Revised: 02/10/2022] [Accepted: 02/21/2022] [Indexed: 12/21/2022]
Abstract
Theoretical and empirical research on the causes of species' range limits suggest the contribution of several intrinsic and extrinsic factors, with potentially complex interactions among them. An intrinsic factor proposed by recent theory is mutational load increasing towards range edges because of genetic drift. Furthermore, environmental quality may decline towards range edges and enhance the expression of load. Here, we tested whether the expression of mutational load associated with range limits in the North American plant Arabidopsis lyrata was enhanced under stressful environmental conditions by comparing the performance of within- versus between-population crosses at common garden sites across the species' distribution and beyond. Heterosis, reflecting the expression of load, increased with heightened estimates of genomic load and with environmental stress caused by warming, but the interaction was not significant. We conclude that range-edge populations suffer from a twofold genetic Allee effect caused by increased mutational load and stress-dependent load linked to general heterozygote deficiency, but there is no synergistic effect between them.
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Affiliation(s)
- Antoine Perrier
- Department of BiologyUniversity of VirginiaCharlottesvilleVirginiaUSA
- Department of Environmental SciencesUniversity of BaselBaselSwitzerland
| | | | - Yvonne Willi
- Department of Environmental SciencesUniversity of BaselBaselSwitzerland
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15
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Ochoa-Zavala M, Osorio-Olvera L, Cerón-Souza I, Rivera-Ocasio E, Jiménez-Lobato V, Núñez-Farfán J. Reduction of Genetic Variation When Far From the Niche Centroid: Prediction for Mangrove Species. FRONTIERS IN CONSERVATION SCIENCE 2022. [DOI: 10.3389/fcosc.2021.795365] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The niche-centroid hypothesis states that populations that are distributed near the centroid of the species' ecological niche will have higher fitness-related attributes, such as population abundance and genetic diversity than populations near the edges of the niche. Empirical evidence based on abundance and, more recently, genetic diversity data support this hypothesis. However, there are few studies that test this hypothesis in coastal species, such as mangroves. Here, we focused on the black mangrove Avicennia germinans. We combined ecological, heterozygosity, and allelic richness information from 1,419 individuals distributed in 40 populations with three main goals: (1) test the relationship between distance to the niche centroid and genetic diversity, (2) determine the set of environmental variables that best explain heterozygosity and allelic richness, and (3) predict the spatial variation in genetic diversity throughout most of the species' natural geographic range. We found a strong correlation between the distance to the niche centroid and both observed heterozygosity (Ho; ρ2 = 0.67 P < 0.05) and expected heterozygosity (He; ρ2 = 0.65, P < 0.05). The niche variables that best explained geographic variation in genetic diversity were soil type and precipitation seasonality. This suggests that these environmental variables influence mangrove growth and establishment, indirectly impacting standing genetic variation. We also predicted the spatial heterozygosity of A. germinans across its natural geographic range in the Americas using regression model coefficients. They showed significant power in predicting the observed data (R2 = 0.65 for Ho; R2 = 0.60 for He), even when we considered independent data sets (R2= 0.28 for Ho; R2 = 0.25 for He). Using this approach, several genetic diversity estimates can be implemented and may take advantage of population genomics to improve genetic diversity predictions. We conclude that the level of genetic diversity in A. germinans is in agreement with expectations of the niche-centroid hypothesis, namely that the highest heterozygosity and allelic richness (the basic genetic units for adaptation) are higher at locations of high environmental suitability. This shows that this approach is a potentially powerful tool in the conservation and management of this species, including for modelling changes in the face of climate change.
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Stritt C, Gimmi EL, Wyler M, Bakali AH, Skalska A, Hasterok R, Mur LAJ, Pecchioni N, Roulin AC. Migration without interbreeding: Evolutionary history of a highly selfing Mediterranean grass inferred from whole genomes. Mol Ecol 2022; 31:70-85. [PMID: 34601787 PMCID: PMC9298040 DOI: 10.1111/mec.16207] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2021] [Revised: 09/07/2021] [Accepted: 09/28/2021] [Indexed: 11/30/2022]
Abstract
Wild plant populations show extensive genetic subdivision and are far from the ideal of panmixia which permeates population genetic theory. Understanding the spatial and temporal scale of population structure is therefore fundamental for empirical population genetics - and of interest in itself, as it yields insights into the history and biology of a species. In this study we extend the genomic resources for the wild Mediterranean grass Brachypodium distachyon to investigate the scale of population structure and its underlying history at whole-genome resolution. A total of 86 accessions were sampled at local and regional scales in Italy and France, which closes a conspicuous gap in the collection for this model organism. The analysis of 196 accessions, spanning the Mediterranean from Spain to Iraq, suggests that the interplay of high selfing and seed dispersal rates has shaped genetic structure in B. distachyon. At the continental scale, the evolution in B. distachyon is characterized by the independent expansion of three lineages during the Upper Pleistocene. Today, these lineages may occur on the same meadow yet do not interbreed. At the regional scale, dispersal and selfing interact and maintain high genotypic diversity, thus challenging the textbook notion that selfing in finite populations implies reduced diversity. Our study extends the population genomic resources for B. distachyon and suggests that an important use of this wild plant model is to investigate how selfing and dispersal, two processes typically studied separately, interact in colonizing plant species.
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Affiliation(s)
- Christoph Stritt
- Institute for Plant and Microbial Biology, University of Zurich, Zurich, Switzerland
| | - Elena L Gimmi
- Institute for Plant and Microbial Biology, University of Zurich, Zurich, Switzerland
| | - Michele Wyler
- Institute for Plant and Microbial Biology, University of Zurich, Zurich, Switzerland
| | - Abdelmonaim H Bakali
- National Institute of Agronomy, Regional Center of Errachidia, Errachidia, Morocco
| | - Aleksandra Skalska
- Institute of Biology, Biotechnology and Environmental Protection, Faculty of Natural Sciences, University of Silesia in Katowice, Katowice, Poland
| | - Robert Hasterok
- Institute of Biology, Biotechnology and Environmental Protection, Faculty of Natural Sciences, University of Silesia in Katowice, Katowice, Poland
| | - Luis A J Mur
- Institute of Biological, Environmental and Rural Sciences, Aberystwyth University, Wales, UK
| | - Nicola Pecchioni
- Research Centre for Cereal and Industrial Crops, CREA - Council for Agricultural Research and Economics, Foggia, Italy
| | - Anne C Roulin
- Institute for Plant and Microbial Biology, University of Zurich, Zurich, Switzerland
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17
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Zhang W, Hu YF, He X, Zhou W, Shao JW. Evolution of Autonomous Selfing in Marginal Habitats: Spatiotemporal Variation in the Floral Traits of the Distylous Primula wannanensis. FRONTIERS IN PLANT SCIENCE 2021; 12:781281. [PMID: 34975966 PMCID: PMC8716950 DOI: 10.3389/fpls.2021.781281] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/22/2021] [Accepted: 11/09/2021] [Indexed: 06/08/2023]
Abstract
Outcrossing plant species are more likely to exhibit autonomous selfing in marginal habitats to ensure reproduction under conditions of limited pollinator and/or mate availability. Distyly is a classical paradigm that promotes outcrossing; however, little is known about the variation in floral traits associated with distylous syndrome in marginal populations. In this study, we compared the variation in floral traits including stigma and anther height, corolla tube length, herkogamy, and corolla diameter between the central and peripheral populations of the distylous Primula wannanensis, and assessed the variation of floral traits at early and late florescence stages for each population. To evaluate the potential consequences of the variation in floral traits on the mating system, we investigated seed set in each population under both open-pollinated and pollinator-excluded conditions. The flower size of both short- and long-styled morphs was significantly reduced in late-opening flowers compared with early opening flowers in both central and peripheral populations. Sex-organ reciprocity was perfect in early opening flowers; however, it was largely weakened in the late-opening flowers of peripheral populations compared with central populations. Of these flowers, disproportionate change in stigma height (elongated in S-morph and shortened in L-morph) was the main cause of reduced herkogamy, and seed set was fairly high under pollinator-excluded condition. Our results provide empirical support for the hypothesis on the evolution of delayed autonomous selfing in marginal populations of distylous species. Unsatisfactory pollinator service is likely to have promoted reproductive assurance of distylous plants with largely reduced herkogamy mimicking "homostyles."
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Affiliation(s)
- Wei Zhang
- College of Life Sciences, Anhui Normal University, Wuhu, China
- Provincial Key Laboratory of Conservation and Utilization of Biological Resources, Wuhu, China
| | - Ying Feng Hu
- College of Life Sciences, Anhui Normal University, Wuhu, China
| | - Xiao He
- College of Life Sciences, Anhui Normal University, Wuhu, China
| | - Wei Zhou
- Germplasm Bank of Wild Species, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, China
- CAS Key Laboratory for Plant Diversity and Biogeography of East Asia, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, China
- Lijiang Forest Biodiversity National Observation and Research Station, Kunming Institute of Botany, Chinese Academy of Sciences, Lijiang, China
| | - Jian Wen Shao
- College of Life Sciences, Anhui Normal University, Wuhu, China
- Provincial Key Laboratory of Conservation and Utilization of Biological Resources, Wuhu, China
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18
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Prior CJ, Busch JW. Selfing rate variation within species is unrelated to life-history traits or geographic range position. AMERICAN JOURNAL OF BOTANY 2021; 108:2294-2308. [PMID: 34632564 DOI: 10.1002/ajb2.1766] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/12/2021] [Revised: 08/25/2021] [Accepted: 08/27/2021] [Indexed: 06/13/2023]
Abstract
PREMISE In plants, populations and species vary widely along the continuum from outcrossing to selfing. Life-history traits and ecological circumstances influence among-species variation in selfing rates, but their general role in explaining intraspecific variation is unknown. Using a database of plant species, we test whether life-history traits, geographic range position, or abundance predict selfing rate variation among populations. METHODS We identified species where selfing rates were estimated in at least three populations at known locations. Two key life-history traits (generation time and growth form) were used to predict within-species selfing rate variation. Populations sampled within a species' native range were assessed for proximity to the nearest edge and abundance. Finally, we conducted linear and segmented regressions to determine functional relationships between selfing rate and geographic range position within species. RESULTS Selfing rates for woody species varied less than for herbs, which is explained by the lower average selfing rate of woody species. Relationships between selfing and peripherality or abundance significantly varied among species in their direction and magnitude. However, there was no general pattern of increased selfing toward range edges. A power analysis shows that tests of this hypothesis require studying many (i.e., 40+) populations. CONCLUSIONS Intraspecific variation in plant mating systems is often substantial yet remains difficult to explain. Beyond sampling more populations, future tests of biogeographic hypotheses will benefit from phylogeographic information concerning specific range edges, the study of traits influencing mating system (e.g., herkogamy), and measures of abundance at local scales (e.g., population density).
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Affiliation(s)
- Carly J Prior
- School of Biological Sciences, Washington State University, Pullman, WA, 99164, USA
| | - Jeremiah W Busch
- School of Biological Sciences, Washington State University, Pullman, WA, 99164, USA
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19
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Clo J, Opedal ØH. Genetics of quantitative traits with dominance under stabilizing and directional selection in partially selfing species. Evolution 2021; 75:1920-1935. [PMID: 34219233 DOI: 10.1111/evo.14304] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2020] [Revised: 05/06/2021] [Accepted: 06/07/2021] [Indexed: 12/19/2022]
Abstract
Recurrent self-fertilization is thought to lead to reduced adaptive potential by decreasing the genetic diversity of populations, thus leading selfing lineages down an evolutionary "blind alley." Although well supported theoretically, empirical support for reduced adaptability in selfing species is limited. One limitation of classical theoretical models is that they assume pure additivity of the fitness-related traits that are under stabilizing selection, despite ample evidence that quantitative traits are subject to dominance. Here, we relax this assumption and explore the effect of dominance on a fitness-related trait under stabilizing selection for populations that differ in selfing rates. By decomposing the genetic variance into additional components specific to inbred populations, we show that dominance components can explain a substantial part of the genetic variance of inbred populations. We also show that ignoring these components leads to an upward bias in the predicted response to selection. Finally, we show that when considering the effect of dominance, the short-term evolutionary potential of populations remains comparable across the entire gradient in outcrossing rates, and genetic associations can even make selfing populations more evolvable on the longer term, reconciling theoretical, and empirical results.
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Affiliation(s)
- Josselin Clo
- AGAP, Univ Montpellier, CIRAD, INRAE, Institut Agro, Montpellier, 34000, France.,Department of Botany, Charles University, Prague, Czechia
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20
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Pennington LK, Slatyer RA, Ruiz-Ramos DV, Veloz SD, Sexton JP. How is adaptive potential distributed within species ranges? Evolution 2021; 75:2152-2166. [PMID: 34164814 DOI: 10.1111/evo.14292] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2020] [Revised: 05/20/2021] [Accepted: 05/26/2021] [Indexed: 12/20/2022]
Abstract
Quantitative genetic variation (QGV) represents a major component of adaptive potential and, if reduced toward range-edge populations, could prevent a species' expansion or adaptive response to rapid ecological change. It has been hypothesized that QGV will be lower at the range edge due to small populations-often the result of poor habitat quality-and potentially decreased gene flow. However, whether central populations are higher in QGV is unknown. We used a meta-analytic approach to test for a general QGV-range position relationship, including geographic and climatic distance from range centers. We identified 35 studies meeting our criteria, yielding nearly 1000 estimates of QGV (including broad-sense heritability, narrow-sense heritability, and evolvability) from 34 species. The relationship between QGV and distance from the geographic range or climatic niche center depended on the focal trait and how QGV was estimated. We found some evidence that QGV declines from geographic centers but that it increases toward niche edges; niche and geographic distances were uncorrelated. Nevertheless, few studies have compared QGV in both central and marginal regions or environments within the same species. We call for more research in this area and discuss potential research avenues related to adaptive potential in the context of global change.
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Affiliation(s)
- Lillie K Pennington
- Environmental Systems Graduate Group, University of California, Merced, California, 95343
| | - Rachel A Slatyer
- Department of Entomology, University of Wisconsin-Madison, Madison, Wisconsin, 53703.,Current Address: Research School of Biology, Australian National University, Acton, ACT, 2600, Australia
| | - Dannise V Ruiz-Ramos
- Life and Environmental Sciences Department, University of California, Merced, California, 95343.,Current Address: U.S. Geological Survey, Columbia Environmental Research Center, Columbia, Missouri, 65201
| | - Samuel D Veloz
- Point Blue Conservation Science, Petaluma, California, 94954
| | - Jason P Sexton
- Life and Environmental Sciences Department, University of California, Merced, California, 95343
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21
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Bontrager M, Usui T, Lee-Yaw JA, Anstett DN, Branch HA, Hargreaves AL, Muir CD, Angert AL. Adaptation across geographic ranges is consistent with strong selection in marginal climates and legacies of range expansion. Evolution 2021; 75:1316-1333. [PMID: 33885152 DOI: 10.1111/evo.14231] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2020] [Accepted: 03/14/2021] [Indexed: 12/27/2022]
Abstract
Every species experiences limits to its geographic distribution. Some evolutionary models predict that populations at range edges are less well adapted to their local environments due to drift, expansion load, or swamping gene flow from the range interior. Alternatively, populations near range edges might be uniquely adapted to marginal environments. In this study, we use a database of transplant studies that quantify performance at broad geographic scales to test how local adaptation, site quality, and population quality change from spatial and climatic range centers toward edges. We find that populations from poleward edges perform relatively poorly, both on average across all sites (15% lower population quality) and when compared to other populations at home (31% relative fitness disadvantage), consistent with these populations harboring high genetic load. Populations from equatorial edges also perform poorly on average (18% lower population quality) but, in contrast, outperform foreign populations (16% relative fitness advantage), suggesting that populations from equatorial edges have strongly adapted to unique environments. Finally, we find that populations from sites that are thermally extreme relative to the species' niche demonstrate strong local adaptation, regardless of their geographic position. Our findings indicate that both nonadaptive processes and adaptive evolution contribute to variation in adaptation across species' ranges.
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Affiliation(s)
- Megan Bontrager
- Department of Botany and Biodiversity Research Centre, University of British Columbia, Vancouver, V6T 1Z4, Canada.,Current Address: Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, M5S 3B2, Canada
| | - Takuji Usui
- Department of Botany and Biodiversity Research Centre, University of British Columbia, Vancouver, V6T 1Z4, Canada
| | - Julie A Lee-Yaw
- Department of Biological Sciences, University of Lethbridge, Lethbridge, T1K 3M4, Canada
| | - Daniel N Anstett
- Department of Botany and Biodiversity Research Centre, University of British Columbia, Vancouver, V6T 1Z4, Canada
| | - Haley A Branch
- Department of Botany and Biodiversity Research Centre, University of British Columbia, Vancouver, V6T 1Z4, Canada
| | | | - Christopher D Muir
- School of Life Sciences, University of Hawaii, Honolulu, Hawaii, 96822, United States
| | - Amy L Angert
- Departments of Botany and Zoology and the Biodiversity Research Centre, University of British Columbia, Vancouver, V6T 1Z4, Canada
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22
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Takou M, Hämälä T, Koch EM, Steige KA, Dittberner H, Yant L, Genete M, Sunyaev S, Castric V, Vekemans X, Savolainen O, de Meaux J. Maintenance of Adaptive Dynamics and No Detectable Load in a Range-Edge Outcrossing Plant Population. Mol Biol Evol 2021; 38:1820-1836. [PMID: 33480994 PMCID: PMC8097302 DOI: 10.1093/molbev/msaa322] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
During range expansion, edge populations are expected to face increased genetic drift, which in turn can alter and potentially compromise adaptive dynamics, preventing the removal of deleterious mutations and slowing down adaptation. Here, we contrast populations of the European subspecies Arabidopsis lyrata ssp. petraea, which expanded its Northern range after the last glaciation. We document a sharp decline in effective population size in the range-edge population and observe that nonsynonymous variants segregate at higher frequencies. We detect a 4.9% excess of derived nonsynonymous variants per individual in the range-edge population, suggesting an increase of the genomic burden of deleterious mutations. Inference of the fitness effects of mutations and modeling of allele frequencies under the explicit demographic history of each population predicts a depletion of rare deleterious variants in the range-edge population, but an enrichment for fixed ones, consistent with the bottleneck effect. However, the demographic history of the range-edge population predicts a small net decrease in per-individual fitness. Consistent with this prediction, the range-edge population is not impaired in its growth and survival measured in a common garden experiment. We further observe that the allelic diversity at the self-incompatibility locus, which ensures strict outcrossing and evolves under negative frequency-dependent selection, has remained unchanged. Genomic footprints indicative of selective sweeps are broader in the Northern population but not less frequent. We conclude that the outcrossing species A. lyrata ssp. petraea shows a strong resilience to the effect of range expansion.
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Affiliation(s)
- Margarita Takou
- Institute of Botany, University of Cologne, Cologne, Germany
| | - Tuomas Hämälä
- Department of Plant and Microbial Biology, University of Minnesota, St. Paul, MN, USA
| | - Evan M Koch
- Department of Biomedical Informatics, Harvard Medical School, Boston, MA, USA
| | - Kim A Steige
- Institute of Botany, University of Cologne, Cologne, Germany
| | | | - Levi Yant
- School of Life Sciences, University of Nottingham, Nottingham, United Kingdom
| | - Mathieu Genete
- CNRS, UMR 8198 – Evo-Eco-Paleo, University of Lille, Lille, France
| | - Shamil Sunyaev
- Department of Biomedical Informatics, Harvard Medical School, Boston, MA, USA
| | - Vincent Castric
- CNRS, UMR 8198 – Evo-Eco-Paleo, University of Lille, Lille, France
| | - Xavier Vekemans
- CNRS, UMR 8198 – Evo-Eco-Paleo, University of Lille, Lille, France
| | - Outi Savolainen
- Department of Ecology and Genetics, University of Oulu, Oulu, Finland
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23
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Lucek K, Willi Y. Drivers of linkage disequilibrium across a species' geographic range. PLoS Genet 2021; 17:e1009477. [PMID: 33770075 PMCID: PMC8026057 DOI: 10.1371/journal.pgen.1009477] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2020] [Revised: 04/07/2021] [Accepted: 03/09/2021] [Indexed: 11/25/2022] Open
Abstract
While linkage disequilibrium (LD) is an important parameter in genetics and evolutionary biology, the drivers of LD remain elusive. Using whole-genome sequences from across a species’ range, we assessed the impact of demographic history and mating system on LD. Both range expansion and a shift from outcrossing to selfing in North American Arabidopsis lyrata were associated with increased average genome-wide LD. Our results indicate that range expansion increases short-distance LD at the farthest range edges by about the same amount as a shift to selfing. However, the extent over which LD in genic regions unfolds was shorter for range expansion compared to selfing. Linkage among putatively neutral variants and between neutral and deleterious variants increased to a similar degree with range expansion, providing support that genome-wide LD was positively associated with mutational load. As a consequence, LD combined with mutational load may decelerate range expansions and set range limits. Finally, a small number of genes were identified as LD outliers, suggesting that they experience selection by either of the two demographic processes. These included genes involved in flowering and photoperiod for range expansion, and the self-incompatibility locus for mating system. Nearby genomic variants are often co-inherited because of limited recombination. The extent of non-random association of alleles at different loci is called linkage disequilibrium (LD) and is commonly used in genomic analyses, for example to detect regions under selection or to determine effective population size. Here we reversed testing and addressed how demographic history may affect LD within a species. Using genomic data from more than a thousand individuals of North American Arabidopsis lyrata from across the entire species’ range, we quantified the effect of postglacial range expansion and a shift in mating system from outcrossing to selfing on LD. We show that both factors lead to increased LD, and that the maximal effect of range expansion is comparable with a shift in mating system to selfing. Heightened LD involves deleterious mutations, and therefore, LD can also serve as an indicator of mutation accumulation. Furthermore, we provide evidence that some genes experienced stronger increases in LD possibly due to selection associated with the two demographic changes. Our results provide a novel and broad view on the evolutionary factors shaping LD that may also apply to the very many species that underwent postglacial range expansion.
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Affiliation(s)
- Kay Lucek
- Department of Environmental Sciences, University of Basel, Basel, Switzerland
- * E-mail:
| | - Yvonne Willi
- Department of Environmental Sciences, University of Basel, Basel, Switzerland
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24
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Casazza G, Macrì C, Dagnino D, Guerrina M, Juin M, Minuto L, Thompson JD, Baumel A, Médail F. When ecological marginality is not geographically peripheral: exploring genetic predictions of the centre-periphery hypothesis in the endemic plant Lilium pomponium. PeerJ 2021; 9:e11039. [PMID: 33854841 PMCID: PMC7955672 DOI: 10.7717/peerj.11039] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2020] [Accepted: 02/09/2021] [Indexed: 01/14/2023] Open
Abstract
Background Quantifying variation of genetic traits over the geographical range of species is crucial for understanding the factors driving their range dynamics. The center-periphery hypothesis postulates, and many studies support, the idea that genetic diversity decreases and genetic differentiation increases toward the geographical periphery due to population isolation. The effects of environmental marginality on genetic variation has however received much less attention. Methods We tested the concordance between geographical and environmental gradients and the genetic predictions of center-periphery hypothesis for endemic Lilium pomponium in the southern Alps. Results We found little evidence for concordance between genetic variation and both geographical and environmental gradients. Although the prediction of increased differentiation at range limits is met, genetic diversity does not decrease towards the geographical periphery. Increased differentiation among peripheral populations, that are not ecologically marginal, may be explained by a decrease in habitat availability that reduces population connectivity. In contrast, a decrease of genetic diversity along environmental but not geographical gradients may be due to the presence of low quality habitats in the different parts of the range of a species that reduce effective population size or increase environmental constraints. As a result, environmental factors may affect population dynamics irrespective of distance from the geographical center of the range. In such situations of discordance between geographical and environmental gradients, the predictions of decreasing genetic diversity and increasing differentiation toward the geographical periphery may not be respected.
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Affiliation(s)
- Gabriele Casazza
- Institut Méditerranéen de Biodiversité et d'Ecologie marine et continentale (IMBE), Aix Marseille Université, Avignon Université, CNRS, IRD. Technopôle de l'Arbois-Méditerranée, Aix en Provence, France
| | - Carmelo Macrì
- Department for the Earth, Environment and Life Sciences (DISTAV), University of Genoa, Genova, Italy
| | - Davide Dagnino
- Department for the Earth, Environment and Life Sciences (DISTAV), University of Genoa, Genova, Italy
| | - Maria Guerrina
- Department for the Earth, Environment and Life Sciences (DISTAV), University of Genoa, Genova, Italy
| | - Marianick Juin
- Institut Méditerranéen de Biodiversité et d'Ecologie marine et continentale (IMBE), Aix Marseille Université, Avignon Université, CNRS, IRD. Technopôle de l'Arbois-Méditerranée, Aix en Provence, France
| | - Luigi Minuto
- Department for the Earth, Environment and Life Sciences (DISTAV), University of Genoa, Genova, Italy
| | - John D Thompson
- CEFE, Univ Montpellier, CNRS, EPHE, IRD, Univ Paul Valéry Montpellier 3, Montpellier, France
| | - Alex Baumel
- Institut Méditerranéen de Biodiversité et d'Ecologie marine et continentale (IMBE), Aix Marseille Université, Avignon Université, CNRS, IRD. Technopôle de l'Arbois-Méditerranée, Aix en Provence, France
| | - Frédéric Médail
- Institut Méditerranéen de Biodiversité et d'Ecologie marine et continentale (IMBE), Aix Marseille Université, Avignon Université, CNRS, IRD. Technopôle de l'Arbois-Méditerranée, Aix en Provence, France
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25
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Macrì C, Dagnino D, Guerrina M, Médail F, Minuto L, Thompson JD, Casazza G. Effects of environmental heterogeneity on phenotypic variation of the endemic plant Lilium pomponium in the Maritime and Ligurian Alps. Oecologia 2020; 195:93-103. [PMID: 33269409 PMCID: PMC7882563 DOI: 10.1007/s00442-020-04806-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2019] [Accepted: 11/12/2020] [Indexed: 11/29/2022]
Abstract
Geographical limits of species’ distributions are assumed to be coincident with ecological margins, although this assumption might not always be true. Indeed, harsh environments such as Alpine and Mediterranean ecosystems may favour high phenotypic variability among populations, especially those in peripheral sites. Floral traits are often found to be less variable and less affected by environmental heterogeneity than vegetative traits because variation in the former may have negative effects on fitness. For this reason, it is important to quantify variation in floral traits and plant fecundity in study range limits. The objective of the study is to examine phenotypic variation and differences in reproduction in endemic Lilium pomponium in the Maritime and Ligurian Alps in relation to environmental variation across its distribution range. In this species, marginal climatic populations occur both in the peripheral and central geographical locations of the distribution range; hence, geographical and ecological gradients are not concordant. Floral trait variation is related to local environmental conditions with an array of interactions among resource availability, potential pollen limitation and population size that are differentially related to floral traits. Contrary to the general expectation, all central and peripheral populations had similar, moderate seed production with each group limited by different factors acting on different stages of the life-history strategy. Our results are in line with the idea that general expectations are confirmed only when its assumptions are met and that the differences in pollination environment along an environmental gradient may not be the main determinant of the distribution limit.
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Affiliation(s)
- Carmelo Macrì
- Dipartimento di Scienze della Terra dell'Ambiente e della Vita (DISTAV), University of Genoa, Corso Europa 26, 16132, Genoa, Italy
| | - Davide Dagnino
- Dipartimento di Scienze della Terra dell'Ambiente e della Vita (DISTAV), University of Genoa, Corso Europa 26, 16132, Genoa, Italy
| | - Maria Guerrina
- Dipartimento di Scienze della Terra dell'Ambiente e della Vita (DISTAV), University of Genoa, Corso Europa 26, 16132, Genoa, Italy
| | - Frédéric Médail
- Institut Méditerranéen de Biodiversité et d'Ecologie marine et continentale (IMBE), Aix Marseille Université, Avignon Université, CNRS, IRD, Technopôle de l'Arbois-Méditerranée, BP 80, 13545, Aix-en-Provence Cedex 4, France
| | - Luigi Minuto
- Dipartimento di Scienze della Terra dell'Ambiente e della Vita (DISTAV), University of Genoa, Corso Europa 26, 16132, Genoa, Italy.
| | - John D Thompson
- Centre d'Ecologie Fonctionnelle et Evolutive, CNRS, 1919 route de Mende, 34293, Montpellier Cedex 5, France
| | - Gabriele Casazza
- Institut Méditerranéen de Biodiversité et d'Ecologie marine et continentale (IMBE), Aix Marseille Université, Avignon Université, CNRS, IRD, Technopôle de l'Arbois-Méditerranée, BP 80, 13545, Aix-en-Provence Cedex 4, France
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26
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Willi Y, Fracassetti M, Bachmann O, Van Buskirk J. Demographic Processes Linked to Genetic Diversity and Positive Selection across a Species' Range. PLANT COMMUNICATIONS 2020; 1:100111. [PMID: 33367266 PMCID: PMC7747977 DOI: 10.1016/j.xplc.2020.100111] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/27/2020] [Revised: 07/27/2020] [Accepted: 09/09/2020] [Indexed: 06/12/2023]
Abstract
Demography determines the strength of genetic drift, which generally reduces genetic variation and the efficacy of selection. Here, we disentangled the importance of demographic processes at a local scale (census size and mating system) and at a species-range scale (old split between population clusters, recolonization after the last glaciation cycle, and admixture) in determining within-population genomic diversity and genomic signatures of positive selection. Analyses were based on re-sequence data from 52 populations of North American Arabidopsis lyrata collected across its entire distribution. The mating system and range dynamics since the last glaciation cycle explained around 60% of the variation in genomic diversity among populations and 52% of the variation in the signature of positive selection. Diversity was lowest in selfing compared with outcrossing populations and in areas further away from glacial refugia. In parallel, reduced positive selection was found in selfing populations and in populations with a longer route of postglacial range expansion. The signature of positive selection was also reduced in populations without admixture. We conclude that recent range expansion can have a profound influence on diversity in coding and non-coding DNA, similar in magnitude to the shift toward selfing. Distribution limits may in fact be caused by reduced effective population size and compromised positive selection in recently colonized parts of the range.
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Affiliation(s)
- Yvonne Willi
- Department of Environmental Sciences, University of Basel, Schönbeinstrasse 6, CH-4056 Basel, Switzerland
| | - Marco Fracassetti
- Department of Environmental Sciences, University of Basel, Schönbeinstrasse 6, CH-4056 Basel, Switzerland
| | - Olivier Bachmann
- Department of Environmental Sciences, University of Basel, Schönbeinstrasse 6, CH-4056 Basel, Switzerland
| | - Josh Van Buskirk
- Department of Evolutionary Biology and Environmental Studies, University of Zürich, CH-8057 Zürich, Switzerland
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27
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Encinas-Viso F, Young AG, Pannell JR. The loss of self-incompatibility in a range expansion. J Evol Biol 2020; 33:1235-1244. [PMID: 32557922 DOI: 10.1111/jeb.13665] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2019] [Revised: 06/09/2020] [Accepted: 06/10/2020] [Indexed: 11/27/2022]
Abstract
It is commonly observed that plant species' range margins are enriched for increased selfing rates and, in otherwise self-incompatible species, for self-compatibility (SC). This has often been attributed to a response to selection under mate and/or pollinator limitation. However, range expansion can also cause reduced inbreeding depression, and this could facilitate the evolution of selfing in the absence of mate or pollinator limitation. Here, we explore this idea using spatially explicit individual-based simulations of a range expansion, in which inbreeding depression, variation in self-incompatibility (SI), and mate availability evolve. Under a wide range of conditions, the simulated range expansion brought about the evolution of selfing after the loss of SI in range-marginal populations. Under conditions of high recombination between the self-incompatibility locus (S-locus) and viability loci, SC remained marginal in the expanded metapopulation and could not invade the range core, which remained self-incompatible. In contrast, under low recombination and migration rates, SC was frequently able to displace SI in the range core by maintaining its association with a genomic background with purged genetic load. We conclude that the evolution of inbreeding depression during a range expansion promotes the evolution of SC at range margins, especially under high rates of recombination..
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Affiliation(s)
- Francisco Encinas-Viso
- Centre for Australian National Biodiversity Research, CSIRO National Research Collections, Canberra, ACT, Australia
| | - Andrew G Young
- Centre for Australian National Biodiversity Research, CSIRO National Research Collections, Canberra, ACT, Australia.,Centre for Biodiversity Analysis, The Australian National University, Canberra, ACT, Australia
| | - John R Pannell
- Department of Ecology and Evolution, University of Lausanne, Lausanne, Switzerland
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28
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Durand E, Chantreau M, Le Veve A, Stetsenko R, Dubin M, Genete M, Llaurens V, Poux C, Roux C, Billiard S, Vekemans X, Castric V. Evolution of self-incompatibility in the Brassicaceae: Lessons from a textbook example of natural selection. Evol Appl 2020; 13:1279-1297. [PMID: 32684959 PMCID: PMC7359833 DOI: 10.1111/eva.12933] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2019] [Revised: 01/25/2020] [Accepted: 01/29/2020] [Indexed: 12/14/2022] Open
Abstract
Self-incompatibility (SI) is a self-recognition genetic system enforcing outcrossing in hermaphroditic flowering plants and results in one of the arguably best understood forms of natural (balancing) selection maintaining genetic variation over long evolutionary times. A rich theoretical and empirical population genetics literature has considerably clarified how the distribution of SI phenotypes translates into fitness differences among individuals by a combination of inbreeding avoidance and rare-allele advantage. At the same time, the molecular mechanisms by which self-pollen is specifically recognized and rejected have been described in exquisite details in several model organisms, such that the genotype-to-phenotype map is also pretty well understood, notably in the Brassicaceae. Here, we review recent advances in these two fronts and illustrate how the joint availability of detailed characterization of genotype-to-phenotype and phenotype-to-fitness maps on a single genetic system (plant self-incompatibility) provides the opportunity to understand the evolutionary process in a unique perspective, bringing novel insight on general questions about the emergence, maintenance, and diversification of a complex genetic system.
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Affiliation(s)
| | | | - Audrey Le Veve
- CNRSUniv. LilleUMR 8198 ‐ Evo‐Eco‐PaleoF-59000 LilleFrance
| | | | - Manu Dubin
- CNRSUniv. LilleUMR 8198 ‐ Evo‐Eco‐PaleoF-59000 LilleFrance
| | - Mathieu Genete
- CNRSUniv. LilleUMR 8198 ‐ Evo‐Eco‐PaleoF-59000 LilleFrance
| | - Violaine Llaurens
- Institut de Systématique, Evolution et Biodiversité (ISYEB)Muséum national d'Histoire naturelleCNRS, Sorbonne Université, EPHE, Université des Antilles CP 5057 rue Cuvier, 75005 ParisFrance
| | - Céline Poux
- CNRSUniv. LilleUMR 8198 ‐ Evo‐Eco‐PaleoF-59000 LilleFrance
| | - Camille Roux
- CNRSUniv. LilleUMR 8198 ‐ Evo‐Eco‐PaleoF-59000 LilleFrance
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29
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Perrier A, Sánchez-Castro D, Willi Y. Expressed mutational load increases toward the edge of a species' geographic range. Evolution 2020; 74:1711-1723. [PMID: 32538471 DOI: 10.1111/evo.14042] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2020] [Revised: 05/26/2020] [Accepted: 06/05/2020] [Indexed: 12/14/2022]
Abstract
There is no general explanation for why species have restricted geographic distributions. One hypothesis posits that range expansion or increasing scarcity of suitable habitat results in accumulation of mutational load due to enhanced genetic drift, which constrains population performance toward range limits and further expansion. We tested this hypothesis in the North American plant, Arabidopsis lyrata. We experimentally assessed mutational load by crossing plants of 20 populations from across the entire species range and by raising the offspring of within- and between-population crosses at five common garden sites within and beyond the range. Offspring performance was tracked over three growing seasons. The heterosis effect, depicting expressed mutational load, was increased in populations with heightened genomic estimates of load, longer expansion distance or long-term isolation, and a selfing mating system. The decline in performance of within-population crosses amounted to 80%. Mutation accumulation due to past range expansion and long-term isolation of populations in the area of range margins is therefore a strong determinant of population-mean performance, and the magnitude of effect may be sufficient to cause range limits.
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Affiliation(s)
- Antoine Perrier
- Department of Environmental Sciences, University of Basel, Basel, 4056, Switzerland
| | - Darío Sánchez-Castro
- Department of Environmental Sciences, University of Basel, Basel, 4056, Switzerland
| | - Yvonne Willi
- Department of Environmental Sciences, University of Basel, Basel, 4056, Switzerland
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30
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Latron M, Arnaud JF, Ferla H, Godé C, Duputié A. Effects of contemporary shifts of range margins on patterns of genetic structure and mating system in two coastal plant species. Heredity (Edinb) 2020; 124:336-350. [PMID: 31541203 PMCID: PMC6972893 DOI: 10.1038/s41437-019-0269-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2019] [Revised: 07/19/2019] [Accepted: 07/23/2019] [Indexed: 11/08/2022] Open
Abstract
Species' geographical ranges are often restricted due to niche limitation resulting in geographical isolation and reduced population size at range margins. Under the "abundant center" paradigm, static marginal populations are thus expected to show higher genetic differentiation and lower genetic diversity than core populations. Low mate availability may also drive shifts toward higher propensity for selfing in geographically marginal populations. However, these predictions remain to be validated for contemporary range shifts occurring under current environmental change. This study is devoted to bridging this gap and assesses the spatial patterns of genetic structure and mating system across the geographical range of two coastal plant species characterized by contrasting contemporary range dynamics: the receding myrmecochorous Dune pansy (Viola tricolor subsp. curtisii) and the widespread expanding hydrochorous Rock samphire (Crithmum maritimum). Both species exhibited high propensity for selfing, with indications of inbreeding depression acting at early life stages. In Dune pansy, a biogeographical break was observed between core and marginal populations, with trailing-edge populations showing higher levels of genetic differentiation, reduced genetic diversity, and higher levels of selfing estimated through progeny arrays. In contrast, genetic structuring was weak in Rock samphire and no clear spatial trends were observed in genetic diversity nor in mating system, likely the result of efficient long-distance seed dispersal by sea-surface currents. Our study highlights that key species differences in life-history traits related to dispersal and/or mate limitation modify the expectations of genetic diversity loss and mating system shift in contemporary range-expanding populations, as compared with historical core populations.
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Affiliation(s)
- Mathilde Latron
- University of Lille, CNRS, UMR 8198-Evo-Eco-Paleo, F-59000, Lille, France
| | | | - Héloïse Ferla
- University of Lille, CNRS, UMR 8198-Evo-Eco-Paleo, F-59000, Lille, France
| | - Cécile Godé
- University of Lille, CNRS, UMR 8198-Evo-Eco-Paleo, F-59000, Lille, France
| | - Anne Duputié
- University of Lille, CNRS, UMR 8198-Evo-Eco-Paleo, F-59000, Lille, France.
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31
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Kennedy JP, Preziosi RF, Rowntree JK, Feller IC. Is the central-marginal hypothesis a general rule? Evidence from three distributions of an expanding mangrove species, Avicennia germinans (L.) L. Mol Ecol 2020; 29:704-719. [PMID: 31990426 PMCID: PMC7065085 DOI: 10.1111/mec.15365] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2019] [Revised: 12/17/2019] [Accepted: 01/16/2020] [Indexed: 12/24/2022]
Abstract
The central-marginal hypothesis (CMH) posits that range margins exhibit less genetic diversity and greater inter-population genetic differentiation compared to range cores. CMH predictions are based on long-held "abundant-centre" assumptions of a decline in ecological conditions and abundances towards range margins. Although much empirical research has confirmed CMH, exceptions remain almost as common. We contend that mangroves provide a model system to test CMH that alleviates common confounding factors and may help clarify this lack of consensus. Here, we document changes in black mangrove (Avicennia germinans) population genetics with 12 nuclear microsatellite loci along three replicate coastlines in the United States (only two of three conform to underlying "abundant-centre" assumptions). We then test an implicit prediction of CMH (reduced genetic diversity may constrain adaptation at range margins) by measuring functional traits of leaves associated with cold tolerance, the climatic factor that controls these mangrove distributional limits. CMH predictions were confirmed only along the coastlines that conform to "abundant-centre" assumptions and, in contrast to theory, range margin A. germinans exhibited functional traits consistent with greater cold tolerance compared to range cores. These findings support previous accounts that CMH may not be a general rule across species and that reduced neutral genetic diversity at range margins may not be a constraint to shifts in functional trait variation along climatic gradients.
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Affiliation(s)
- John Paul Kennedy
- Smithsonian Marine StationSmithsonian InstitutionFort PierceFLUSA
- Department of Natural SciencesFaculty of Science and Engineering, Ecology and Environment Research CentreManchester Metropolitan UniversityManchesterUK
| | - Richard F. Preziosi
- Department of Natural SciencesFaculty of Science and Engineering, Ecology and Environment Research CentreManchester Metropolitan UniversityManchesterUK
| | - Jennifer K. Rowntree
- Department of Natural SciencesFaculty of Science and Engineering, Ecology and Environment Research CentreManchester Metropolitan UniversityManchesterUK
| | - Ilka C. Feller
- Smithsonian Environmental Research CenterSmithsonian InstitutionEdgewaterMDUSA
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32
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Walden N, Lucek K, Willi Y. Lineage‐specific adaptation to climate involves flowering time in North American
Arabidopsis lyrata. Mol Ecol 2020; 29:1436-1451. [DOI: 10.1111/mec.15338] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2019] [Revised: 11/16/2019] [Accepted: 12/10/2019] [Indexed: 01/06/2023]
Affiliation(s)
- Nora Walden
- Department of Environmental Sciences University of Basel Basel Switzerland
- Centre for Organismal Studies Heidelberg University of Heidelberg Heidelberg Germany
| | - Kay Lucek
- Department of Environmental Sciences University of Basel Basel Switzerland
| | - Yvonne Willi
- Department of Environmental Sciences University of Basel Basel Switzerland
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33
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Brom T, Castric V, Billiard S. Breakdown of gametophytic self-incompatibility in subdivided populations. Evolution 2020; 74:270-282. [PMID: 31845323 DOI: 10.1111/evo.13897] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2018] [Revised: 11/04/2019] [Accepted: 11/11/2019] [Indexed: 01/11/2023]
Abstract
In many hermaphroditic flowering plants, self-fertilization is prevented by self-incompatibility (SI), often controlled by a single locus, the S-locus. In single isolated populations, the maintenance of SI depends chiefly on inbreeding depression and the number of SI alleles at the S-locus. In subdivided populations, however, population subdivision has complicated effects on both the number of SI alleles and the level of inbreeding depression, rendering the maintenance of SI difficult to predict. Here, we explore the conditions for the invasion of a self-compatible mutant in a structured population. We find that the maintenance of SI is strongly compromised when a population becomes subdivided. We show that this effect is mainly caused by the decrease in the local diversity of SI alleles rather than by a change in the dynamics of inbreeding depression. Strikingly, we also find that the diversity of SI alleles at the whole population level is a poor predictor of the maintenance of SI. We discuss the implications of our results for the interpretation of empirical data on the loss of SI in natural populations.
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Affiliation(s)
- Thomas Brom
- University Lille, UMR 8198 - Evo-Eco-Paleo, F-59000, Lille, France.,CNRS, UMR 8198, F-59000, Lille, France
| | - Vincent Castric
- University Lille, UMR 8198 - Evo-Eco-Paleo, F-59000, Lille, France.,CNRS, UMR 8198, F-59000, Lille, France
| | - Sylvain Billiard
- University Lille, UMR 8198 - Evo-Eco-Paleo, F-59000, Lille, France.,CNRS, UMR 8198, F-59000, Lille, France
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34
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Lucek K, Hohmann N, Willi Y. Postglacial ecotype formation under outcrossing and self-fertilization in Arabidopsis lyrata. Mol Ecol 2019; 28:1043-1055. [PMID: 30719799 DOI: 10.1111/mec.15035] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2017] [Revised: 01/18/2019] [Accepted: 01/28/2019] [Indexed: 12/01/2022]
Abstract
The formation of ecotypes has been invoked as an important driver of postglacial biodiversity, because many species colonized heterogeneous habitats and experienced divergent selection. Ecotype formation has been predominantly studied in outcrossing taxa, while far less attention has been paid to the implications of mating system shifts. Here, we addressed whether substrate-related ecotypes exist in selfing and outcrossing populations of Arabidopsis lyrata subsp. lyrata and whether the genomic footprint differs between mating systems. The North American subspecies colonized both rocky and sandy habitats during postglacial range expansion and shifted the mating system from predominantly outcrossing to predominantly selfing in a number of regions. We performed an association study on pooled whole-genome sequence data of 20 selfing or outcrossing populations, which suggested genes involved in adaptation to substrate. Motivated by enriched gene ontology terms, we compared root growth between plants from the two substrates in a common environment and found that plants originating from sand grew roots faster and produced more side roots, independent of mating system. Furthermore, single nucleotide polymorphisms associated with substrate-related ecotypes were more clustered among selfing populations. Our study provides evidence for substrate-related ecotypes in A. lyrata and divergence in the genomic footprint between mating systems. The latter is the likely result of selfing populations having experienced divergent selection on larger genomic regions due to higher genome-wide linkage disequilibrium.
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Affiliation(s)
- Kay Lucek
- Department of Environmental Sciences, University of Basel, Basel, Switzerland
| | - Nora Hohmann
- Department of Environmental Sciences, University of Basel, Basel, Switzerland
| | - Yvonne Willi
- Department of Environmental Sciences, University of Basel, Basel, Switzerland
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35
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Koski MH, Layman NC, Prior CJ, Busch JW, Galloway LF. Selfing ability and drift load evolve with range expansion. Evol Lett 2019; 3:500-512. [PMID: 31636942 PMCID: PMC6791181 DOI: 10.1002/evl3.136] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2019] [Revised: 08/09/2019] [Accepted: 08/11/2019] [Indexed: 12/16/2022] Open
Abstract
Colonization at expanding range edges often involves few founders, reducing effective population size. This process can promote the evolution of self-fertilization, but implicating historical processes as drivers of trait evolution is often difficult and requires an explicit model of biogeographic history. In plants, contemporary limits to outcrossing are often invoked as evolutionary drivers of self-fertilization, but historical expansions may shape mating system diversity, with leading-edge populations evolving elevated selfing ability. In a widespread plant, Campanula americana, we identified a glacial refugium in the southern Appalachian Mountains from spatial patterns of genetic drift among 24 populations. Populations farther from this refugium have smaller effective sizes and fewer rare alleles. They also displayed elevated heterosis in among-population crosses, reflecting the accumulation of deleterious mutations during range expansion. Although populations with elevated heterosis had reduced segregating mutation load, the magnitude of inbreeding depression lacked geographic pattern. The ability to self-fertilize was strongly positively correlated with the distance from the refugium and mutation accumulation-a pattern that contrasts sharply with contemporary mate and pollinator limitation. In this and other species, diversity in sexual systems may reflect the legacy of evolution in small, colonizing populations, with little or no relation to the ecology of modern populations.
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Affiliation(s)
- Matthew H Koski
- Department of Biology University of Virginia Charlottesville Virginia 22902.,Current Address: Department of Biological Sciences Clemson University Clemson SC 29631
| | - Nathan C Layman
- School of Biological Sciences Washington State University Pullman Washington 99164
| | - Carly J Prior
- School of Biological Sciences Washington State University Pullman Washington 99164
| | - Jeremiah W Busch
- School of Biological Sciences Washington State University Pullman Washington 99164
| | - Laura F Galloway
- Department of Biology University of Virginia Charlottesville Virginia 22902
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36
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Shao JW, Wang HF, Fang SP, Conti E, Chen YJ, Zhu HM. Intraspecific variation of self-incompatibility in the distylous plant Primula merrilliana. AOB PLANTS 2019; 11:plz030. [PMID: 32489575 PMCID: PMC6557196 DOI: 10.1093/aobpla/plz030] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/01/2019] [Revised: 04/16/2019] [Accepted: 05/15/2019] [Indexed: 05/09/2023]
Abstract
Heteromorphic self-incompatibility can prevent self- and intramorph fertilization while favouring intermorph mating and the maintenance of morph-ratio stability in heterostylous populations. However, variation in the expression of self-incompatibility intraspecies has seldom been assessed. Through hand pollinations and microsatellite markers, the variation in the expression of self-incompatibility and genetic diversity were studied in distylous plant Primula merrilliana. We discovered that the strength of self-incompatibility varied extensively among individuals and populations, from pronounced to weaker self-incompatibility in distylous populations, all the way to strong self-compatibility in homostylous populations. Each distylous population included self-incompatible (SI), partly self-compatible (PSC) and self-compatible (SC) individuals, with the index of self-compatibility (ISC) ranging from 0.07 to 0.68 across populations. Self-compatible populations (ISC > 0.25) were not genetically clustered but were more closely related to populations with high SI and SC individuals were mixed with SI individuals within populations. The ISC and the proportions of SC and PSC individuals were higher in peripheral than in central populations, but no decrease of genetic diversity and no deviations of floral morph ratio from isoplethy were detected in peripheral populations. Additionally, the expression of self-incompatibility was stronger in long-styled flowers than in short-styled flowers. The variation in the strength of self-incompatibility documented in P. merrilliana cautions against the estimation of ISC from a few individuals or populations in distylous species and provides a more complex and nuanced understanding of the role of self-incompatibility in heterostyly.
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Affiliation(s)
- Jian-Wen Shao
- College of Life Sciences, Anhui Normal University, Wuhu, P.R. China
- The Key Laboratory of Conservation and Employment of Biological Resources of Anhui, Wuhu, P.R. China
| | - Hui-Feng Wang
- College of Life Sciences, Anhui Normal University, Wuhu, P.R. China
| | - Su-Ping Fang
- College of Life Sciences, Anhui Normal University, Wuhu, P.R. China
| | - Elena Conti
- Department of Systematic and Evolutionary Botany and Botanic Garden, University of Zurich, Zollikerstrasse, Zurich, Switzerland
| | - Ya-Jing Chen
- College of Life Sciences, Anhui Normal University, Wuhu, P.R. China
| | - Hu-Ming Zhu
- College of Life Sciences, Anhui Normal University, Wuhu, P.R. China
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37
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Tabassum S, Leishman MR. It doesn’t take two to tango: increased capacity for self-fertilization towards range edges of two coastal invasive plant species in eastern Australia. Biol Invasions 2019. [DOI: 10.1007/s10530-019-01989-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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38
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Voillemot M, Encinas-Viso F, Pannell JR. Rapid loss of self-incompatibility in experimental populations of the perennial outcrossing plant Linaria cavanillesii. Evolution 2019; 73:913-926. [PMID: 30874301 DOI: 10.1111/evo.13721] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2018] [Accepted: 02/18/2019] [Indexed: 11/30/2022]
Abstract
Transitions from self-incompatibility to self-compatibility in angiosperms may be frequently driven by selection for reproductive assurance when mates or pollinators are rare, and are often succeeded by loss of inbreeding depression by purging. Here, we use experimental evolution to investigate the spread of self-compatibility from one such population of the perennial plant Linaria cavanillesii into self-incompatible (SI) populations that still have high inbreeding depression. We introduced self-compatible (SC) individuals at different frequencies into replicate experimental populations of L. cavanillesii that varied in access to pollinators. Our experiment revealed a rapid shift to self-compatibility in all replicates, driven by both greater seed set and greater outcross siring success of SC individuals. We discuss our results in the light of computer simulations that confirm the tendency of self-compatibility to spread into SI populations under the observed conditions. Our study illustrates the ease with which self-compatibility can spread among populations, a requisite for species-wide transitions from self-incompatibility to self-compatibility.
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Affiliation(s)
- Marie Voillemot
- Department of Ecology and Evolution, Biophore/Sorge, University of Lausanne, 1015, Lausanne, Switzerland
| | - Francisco Encinas-Viso
- Centre for Australian National Biodiversity Research, CSIRO, Canberra, ACT 2601, Australia
| | - John R Pannell
- Department of Ecology and Evolution, Biophore/Sorge, University of Lausanne, 1015, Lausanne, Switzerland
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39
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Willi Y, Fracassetti M, Zoller S, Van Buskirk J. Accumulation of Mutational Load at the Edges of a Species Range. Mol Biol Evol 2019; 35:781-791. [PMID: 29346601 DOI: 10.1093/molbev/msy003] [Citation(s) in RCA: 62] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Why species have geographically restricted distributions is an unresolved question in ecology and evolutionary biology. Here, we test a new explanation that mutation accumulation due to small population size or a history of range expansion can contribute to restricting distributions by reducing population growth rate at the edge. We examined genomic diversity and mutational load across the entire geographic range of the North American plant Arabidopsis lyrata, including old, isolated populations predominantly at the southern edge and regions of postglacial range expansion at the northern and southern edges. Genomic diversity in intergenic regions declined toward distribution edges and signatures of mutational load in exon regions increased. Genomic signatures of mutational load were highly linked to phenotypically expressed load, measured as reduced performance of individual plants and lower estimated rate of population growth. The geographic pattern of load and the connection between load and population growth demonstrate that mutation accumulation reduces fitness at the edge and helps restrict species' distributions.
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Affiliation(s)
- Yvonne Willi
- Institute of Biology, University of Neuchâtel, Neuchâtel, Switzerland.,Department of Environmental Sciences, University of Basel, Basel, Switzerland
| | - Marco Fracassetti
- Institute of Biology, University of Neuchâtel, Neuchâtel, Switzerland.,Department of Environmental Sciences, University of Basel, Basel, Switzerland
| | - Stefan Zoller
- Genetic Diversity Centre, ETH Zürich, Zürich, Switzerland
| | - Josh Van Buskirk
- Institute of Evolutionary Biology and Environmental Studies, University of Zürich, Zürich, Switzerland
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40
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Huang Q, Burd M. The Effect of Pollen Limitation on the Evolution of Mating System and Seed Size in Hermaphroditic Plants. Am Nat 2019; 193:447-457. [DOI: 10.1086/701782] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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41
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Mertens A, Brys R, Schouppe D, Jacquemyn H. The impact of floral morphology on genetic differentiation in two closely related biennial plant species. AOB PLANTS 2018; 10:ply051. [PMID: 30323915 PMCID: PMC6178171 DOI: 10.1093/aobpla/ply051] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/14/2017] [Accepted: 09/05/2018] [Indexed: 06/08/2023]
Abstract
The genetic diversity and structure of plant populations are determined by the interaction of three distinct processes: gene flow, genetic drift and natural selection. These processes are to some extent dependent on the mating system of plants, which in turn is largely determined by floral morphology and the level of herkogamy in particular. In this study, we used molecular markers to investigate the impact of floral morphology on genetic differentiation and structure in two closely related Centaurium species that display large variation in floral morphology across two distinct geographic regions in Europe (mainland Europe and the UK). Our results showed that genetic differences between regions and populations within regions were similar for both species, but that patterns of genetic structure largely depended on the observed variation in floral morphology. Populations of Centaurium erythraea showed higher genetic differentiation and clear isolation by distance (IBD) in mainland Europe, but limited IBD in the UK. Opposite patterns were found in Centaurium littorale, with higher genetic differentiation and significant IBD in populations sampled in the UK and lower genetic differentiation in Continental populations with no pattern of IBD. Overall, these results indicate that variation in floral morphology has a profound impact on structuring of genetic diversity, with populations displaying low levels of herkogamy showing the strongest patterns of genetic structuring and the reverse pattern in populations showing high levels of herkogamy.
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Affiliation(s)
- Arne Mertens
- Department of Biology, Plant Conservation and Population Biology, KU Leuven, Leuven, Belgium
| | - Rein Brys
- Research Institute for Nature and Forest, Geraardsbergen, Belgium
| | - Dorien Schouppe
- Department of Biology, Plant Conservation and Population Biology, KU Leuven, Leuven, Belgium
| | - Hans Jacquemyn
- Department of Biology, Plant Conservation and Population Biology, KU Leuven, Leuven, Belgium
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42
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Bonchev G, Willi Y. Accumulation of transposable elements in selfing populations of Arabidopsis lyrata supports the ectopic recombination model of transposon evolution. THE NEW PHYTOLOGIST 2018; 219:767-778. [PMID: 29757461 DOI: 10.1111/nph.15201] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/13/2018] [Accepted: 04/01/2018] [Indexed: 06/08/2023]
Abstract
Transposable elements (TE) can constitute a large fraction of plant genomes, yet our understanding of their evolution and fitness effect is still limited. Here we tested several models of evolution that make specific predictions about differences in TE abundance between selfing and outcrossing taxa, and between small and large populations. We estimated TE abundance in multiple populations of North American Arabidopsis lyrata differing in mating system and long-term size, using transposon insertion display on several TE families. Selfing populations had higher TE copy numbers per individual and higher TE allele frequencies, supporting models which assume that selection against TEs acts predominantly against heterozygotes via the process of ectopic recombination. In outcrossing populations differing in long-term size, the data supported neither a model of density-regulated transposition nor a model of direct deleterious effect. Instead, the population structure of TEs revealed that outcrossing populations tended to split into western and eastern groups - as previously detected using microsatellite markers - whereas selfing populations from west and east were less differentiated. This, too, agrees with the model of ectopic recombination. Overall, our results suggest that TE elements are nearly neutral except for their deleterious potential to disturb meiosis in the heterozygous state.
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Affiliation(s)
- Georgi Bonchev
- Institute of Biology, Evolutionary Botany, University of Neuchâtel, Neuchâtel, 2000, Switzerland
- Institute of Plant Physiology and Genetics, Laboratory of Genome Dynamics and Stability, Bulgarian Academy of Sciences, Sofia, 1113, Bulgaria
| | - Yvonne Willi
- Institute of Biology, Evolutionary Botany, University of Neuchâtel, Neuchâtel, 2000, Switzerland
- Department of Environmental Sciences, University of Basel, Basel, 4056, Switzerland
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43
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Sutherland BL, Quarles BM, Galloway LF. Intercontinental dispersal and whole-genome duplication contribute to loss of self-incompatibility in a polyploid complex. AMERICAN JOURNAL OF BOTANY 2018; 105:249-256. [PMID: 29578295 DOI: 10.1002/ajb2.1027] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/15/2017] [Accepted: 01/09/2018] [Indexed: 06/08/2023]
Abstract
PREMISE OF THE STUDY Angiosperm species often shift from self-incompatibility to self-compatibility following population bottlenecks. Across the range of a species, population bottlenecks may result from multiple factors, each of which may affect the geographic distribution and magnitude of mating-system shifts. We describe how intercontinental dispersal and genome duplication facilitate loss of self-incompatibility. METHODS Self and outcross pollinations were performed on plants from 24 populations of the Campanula rotundifolia polyploid complex. Populations spanned the geographic distribution and three dominant cytotypes of the species (diploid, tetraploid, hexaploid). KEY RESULTS Loss of self-incompatibility was associated with both intercontinental dispersal and genome duplication. European plants were largely self-incompatible, whereas North American plants were intermediately to fully self-compatible. Within both European and North American populations, loss of self-incompatibility increased as ploidy increased. Ploidy change and intercontinental dispersal both contributed to loss of self-incompatibility in North America, but range expansion did not affect self-incompatibility within Europe or North America. CONCLUSIONS When species are subject to population bottlenecks arising through multiple factors, each factor can contribute to self-incompatibility loss. In a widespread polyploid complex, the loss of self-incompatibility can be predicted by the cumulative effects of whole-genome duplication and intercontinental dispersal.
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Affiliation(s)
- Brittany L Sutherland
- Department of Biology, University of Virginia, P.O. Box 400328, Charlottesville, Virginia, 22904-4328, USA
| | - Brandie M Quarles
- Department of Biology, University of Virginia, P.O. Box 400328, Charlottesville, Virginia, 22904-4328, USA
| | - Laura F Galloway
- Department of Biology, University of Virginia, P.O. Box 400328, Charlottesville, Virginia, 22904-4328, USA
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44
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Wos G, Willi Y. Thermal acclimation in Arabidopsis lyrata: genotypic costs and transcriptional changes. J Evol Biol 2017; 31:123-135. [PMID: 29134788 DOI: 10.1111/jeb.13208] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2017] [Accepted: 11/07/2017] [Indexed: 02/04/2023]
Abstract
Frost and heat events can be challenging for sessile organisms that cannot escape thermal extremes. However, adverse effects of thermal stress on fitness may be reduced by pre-exposure to cold or heat, a process known as acclimation. To understand the ecological and evolutionary implications of acclimation, we investigated (1) the reduction in performance due to stress pre-exposure, (2) the magnitude of increased leaf resistance to subsequent stress, (3) the costs of acclimation and (4) the genes differing in expression due to stress pre-exposure. Plants of Arabidopsis lyrata were raised under three treatments of pre-exposure: bouts of frost, bouts of heat or constant temperature. Resistance of leaves to subsequent frost and heat stress was then measured by electrolyte leakage. RNA-seq analysis was performed to examine the genes differentially expressed between stress-pre-exposed and control plants. Pre-exposure to stress during growth decreased plant size and increased leaf resistance to subsequent stress independent of whether pre-exposure was to frost or heat. But the highest increase in leaf resistance to frost was found after pre-exposure to frost (as a trend) and in leaf resistance to heat after pre-exposure to heat. No evidence for costs of acclimation was detected. RNA-sequencing suggested that acclimation by frost and heat pre-exposure was caused by distinct mechanisms: modification of the chloroplast membrane and modification of the cell wall and membrane, respectively. Our results suggest that thermal resistance is a labile complex of traits, strongly affected by the previously experienced stress environment, with undetermined costs.
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Affiliation(s)
- G Wos
- Institute of Biology, University of Neuchâtel, Neuchâtel, Switzerland.,Department of Environmental Sciences, University of Basel, Basel, Switzerland
| | - Y Willi
- Institute of Biology, University of Neuchâtel, Neuchâtel, Switzerland.,Department of Environmental Sciences, University of Basel, Basel, Switzerland
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45
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Koski MH, Grossenbacher DL, Busch JW, Galloway LF. A geographic cline in the ability to self-fertilize is unrelated to the pollination environment. Ecology 2017; 98:2930-2939. [PMID: 28869778 DOI: 10.1002/ecy.2001] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/31/2017] [Revised: 06/22/2017] [Accepted: 08/18/2017] [Indexed: 01/14/2023]
Abstract
The reproductive assurance (RA) hypothesis predicts that the ability to autonomously self-fertilize should be favored in environments where a lack of mates or pollinators limits outcross reproduction. Because such limits to outcrossing are predicted to be most severe at range edges, elevated autonomy in peripheral populations is often attributed to RA. We test this hypothesis in 24 populations spanning the range of Campanula americana, including sampling at the range interior and three geographic range edges. We scored autonomous fruit set in a pollinator-free environment and detected clinal variation-autonomy increased linearly from the southern to the northern edge, and from the eastern to the western edge. We then address whether the cline reflects the contemporary pollination environment. We measured population size, plant density, pollinator visitation, outcross pollen limitation and RA in natural populations over two years. Most populations were pollen limited, and those that experienced higher visitation rates by bumblebees had reduced pollen limitation. Reproductive assurance, however, was generally low across populations and was unrelated to pollen limitation or autonomy. Neither pollen limitation nor RA displayed geographic clines. Finally, autonomy was not associated with pollinator visitation rates or mate availability. Thus, the data do not support the RA hypothesis; clinal variation in autonomy is unrelated to the current pollination environment. Therefore, geographic patterns of autonomy are likely the result of historical processes rather than contemporary natural selection for RA.
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Affiliation(s)
- Matthew H Koski
- Department of Biology, University of Virginia, PO Box 400328, Charlottesville, Virginia, 22904, USA
| | - Dena L Grossenbacher
- School of Biological Sciences, Washington State University, PO Box 644236, Pullman, Washington, 99164-4236, USA.,Department of Biology, California Polytechnic State University, 1 Grand Avenue, San Luis Obispo, California, 93407, USA
| | - Jeremiah W Busch
- School of Biological Sciences, Washington State University, PO Box 644236, Pullman, Washington, 99164-4236, USA
| | - Laura F Galloway
- Department of Biology, University of Virginia, PO Box 400328, Charlottesville, Virginia, 22904, USA
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46
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Carleial S, van Kleunen M, Stift M. Relatively weak inbreeding depression in selfing but also in outcrossing populations of North American Arabidopsis lyrata. J Evol Biol 2017; 30:1994-2004. [PMID: 28833878 DOI: 10.1111/jeb.13169] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2016] [Revised: 08/01/2017] [Accepted: 08/09/2017] [Indexed: 01/28/2023]
Abstract
Hermaphroditic plants can potentially self-fertilize, but most possess adaptations that promote outcrossing. However, evolutionary transitions to higher selfing rates are frequent. Selfing comes with a transmission advantage over outcrossing, but self-progeny may suffer from inbreeding depression, which forms the main barrier to the evolution of higher selfing rates. Here, we assessed inbreeding depression in the North American herb Arabidopsis lyrata, which is normally self-incompatible, with a low frequency of self-compatible plants. However, a few populations have become fixed for self-compatibility and have high selfing rates. Under greenhouse conditions, we estimated mean inbreeding depression per seed (based on cumulative vegetative performance calculated as the product of germination, survival and aboveground biomass) to be 0.34 for six outcrossing populations, and 0.26 for five selfing populations. Exposing plants to drought and inducing defences with jasmonic acid did not magnify these estimates. For outcrossing populations, however, inbreeding depression per seed may underestimate true levels of inbreeding depression, because self-incompatible plants showed strong reductions in seed set after (enforced) selfing. Inbreeding-depression estimates incorporating seed set averaged 0.63 for outcrossing populations (compared to 0.30 for selfing populations). However, this is likely an overestimate because exposing plants to 5% CO2 to circumvent self-incompatibility to produce selfed seed might leave residual effects of self-incompatibility that contribute to reduced seed set. Nevertheless, our estimates of inbreeding depression were clearly lower than previous estimates based on the same performance traits in outcrossing European populations of A. lyrata, which may help explain why selfing could evolve in North American A. lyrata.
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Affiliation(s)
- S Carleial
- Ecology, Department of Biology, University of Konstanz, Konstanz, Germany
| | - M van Kleunen
- Ecology, Department of Biology, University of Konstanz, Konstanz, Germany.,Zhejiang Provincial Key Laboratory of Plant Evolutionary Ecology and Conservation, Taizhou University, Taizhou, China
| | - M Stift
- Ecology, Department of Biology, University of Konstanz, Konstanz, Germany
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47
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Geographic variation in floral traits and the capacity of autonomous selfing across allopatric and sympatric populations of two closely related Centaurium species. Sci Rep 2017; 7:46410. [PMID: 28429781 PMCID: PMC5399455 DOI: 10.1038/srep46410] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2016] [Accepted: 03/07/2017] [Indexed: 02/02/2023] Open
Abstract
Floral traits and the relative contribution of autonomous selfing to total seed set varies geographically and is often driven by the availability and abundance of suitable pollinators and/or the presence of co-flowering relatives. In the latter case, competition for pollinator services and costs of hybridization can select for floral traits that reduce interspecific gene flow and contribute to prezygotic isolation, potentially leading to geographic variation in floral divergence between allopatric and sympatric populations. In this study, we investigated variation in floral traits and its implications on the capacity of autonomous selfing in both allopatric and sympatric populations of two closely related Centaurium species(Gentianaceae) across two distinct geographic regions(UK and mainland Europe). Although the magnitude and direction of floral differentiation varied between regions, sympatric populations were always significantly more divergent in floral traits and the capacity to self autonomously than allopatric populations. These results indicate that mating systems can vary substantially within a species and that the joint occurrence of plant species can have a major impact on floral morphology and capacity of autonomous selfing, most likely as a way to reduce the probability of interspecific interference.
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48
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Rodríguez-Verdugo A, Buckley J, Stapley J. The genomic basis of eco-evolutionary dynamics. Mol Ecol 2017; 26:1456-1464. [PMID: 28160333 DOI: 10.1111/mec.14045] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2016] [Revised: 01/22/2017] [Accepted: 01/25/2017] [Indexed: 12/30/2022]
Abstract
Recent recognition that ecological and evolutionary processes can operate on similar timescales has led to a rapid increase in theoretical and empirical studies on eco-evolutionary dynamics. Progress in the fields of evolutionary biology, genomics and ecology is greatly enhancing our understanding of rapid adaptive processes, the predictability of adaptation and the genetics of ecologically important traits. However, progress in these fields has proceeded largely independently of one another. In an attempt to better integrate these fields, the centre for 'Adaptation to a Changing Environment' organized a conference entitled 'The genomic basis of eco-evolutionary change' and brought together experts in ecological genomics and eco-evolutionary dynamics. In this review, we use the work of the invited speakers to summarize eco-evolutionary dynamics and discuss how they are relevant for understanding and predicting responses to contemporary environmental change. Then, we show how recent advances in genomics are contributing to our understanding of eco-evolutionary dynamics. Finally, we highlight the gaps in our understanding of eco-evolutionary dynamics and recommend future avenues of research in eco-evolutionary dynamics.
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Affiliation(s)
- Alejandra Rodríguez-Verdugo
- Adaptation to a Changing Environment, ETH Zürich, 8092, Zürich, Switzerland.,Department of Environmental Microbiology, Eawag, Dübendorf, Switzerland
| | - James Buckley
- Adaptation to a Changing Environment, ETH Zürich, 8092, Zürich, Switzerland
| | - Jessica Stapley
- Adaptation to a Changing Environment, ETH Zürich, 8092, Zürich, Switzerland
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49
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Pironon S, Papuga G, Villellas J, Angert AL, García MB, Thompson JD. Geographic variation in genetic and demographic performance: new insights from an old biogeographical paradigm. Biol Rev Camb Philos Soc 2016; 92:1877-1909. [DOI: 10.1111/brv.12313] [Citation(s) in RCA: 214] [Impact Index Per Article: 23.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2015] [Revised: 10/07/2016] [Accepted: 10/17/2016] [Indexed: 12/17/2022]
Affiliation(s)
- Samuel Pironon
- Instituto Pirenaico de Ecología (IPE-CSIC); Box 1005 avenida Montañana 50059 Zaragoza, Spain
| | - Guillaume Papuga
- UMR 5175 Centre d'Ecologie Fonctionnelle et Evolutive, CNRS; Box 1019 route de Mende 34090 Montpellier France
- Dipartimento di Scienze della Natura e del Territorio; Università degli Studi di Sassari; Box 21 Piazza Universitá 07100 Sassari Italy
| | - Jesús Villellas
- Department of Biology; Duke University; Box 90338 Durham NC 27708-0338 U.S.A
| | - Amy L. Angert
- Departments of Botany and Zoology; University of British Columbia; Box 4200-6270 University Boulevard, Vancouver V6T 1Z4 Canada
| | - María B. García
- Instituto Pirenaico de Ecología (IPE-CSIC); Box 1005 avenida Montañana 50059 Zaragoza, Spain
| | - John D. Thompson
- UMR 5175 Centre d'Ecologie Fonctionnelle et Evolutive, CNRS; Box 1019 route de Mende 34090 Montpellier France
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50
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Carleial S, van Kleunen M, Stift M. Small reductions in corolla size and pollen: ovule ratio, but no changes in flower shape in selfing populations of the North American Arabidopsis lyrata. Oecologia 2016; 183:401-413. [DOI: 10.1007/s00442-016-3773-4] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2016] [Accepted: 11/08/2016] [Indexed: 12/31/2022]
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