1
|
James ME, Allsopp RN, Groh JS, Kaur A, Wilkinson MJ, Ortiz-Barrientos D. Uncovering the genetic architecture of parallel evolution. Mol Ecol 2023; 32:5575-5589. [PMID: 37740681 DOI: 10.1111/mec.17134] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2023] [Revised: 07/31/2023] [Accepted: 08/07/2023] [Indexed: 09/25/2023]
Abstract
Identifying the genetic architecture underlying adaptive traits is exceptionally challenging in natural populations. This is because associations between traits not only mask the targets of selection but also create correlated patterns of genomic divergence that hinder our ability to isolate causal genetic effects. Here, we examine the repeated evolution of components of the auxin pathway that have contributed to the replicated loss of gravitropism (i.e. the ability of a plant to bend in response to gravity) in multiple populations of the Senecio lautus species complex in Australia. We use a powerful approach which combines parallel population genomics with association mapping in a Multiparent Advanced Generation Inter-Cross (MAGIC) population to break down genetic and trait correlations to reveal how adaptive traits evolve during replicated evolution. We sequenced auxin and shoot gravitropism-related gene regions in 80 individuals from six natural populations (three parallel divergence events) and 133 individuals from a MAGIC population derived from two of the recently diverged natural populations. We show that artificial tail selection on gravitropism in the MAGIC population recreates patterns of parallel divergence in the auxin pathway in the natural populations. We reveal a set of 55 auxin gene regions that have evolved repeatedly during the evolution of the species, of which 50 are directly associated with gravitropism divergence in the MAGIC population. Our work creates a strong link between patterns of genomic divergence and trait variation contributing to replicated evolution by natural selection, paving the way to understand the origin and maintenance of adaptations in natural populations.
Collapse
Affiliation(s)
- Maddie E James
- School of Biological Sciences, The University of Queensland, St Lucia, Queensland, Australia
- Australian Research Council Centre of Excellence for Plant Success in Nature and Agriculture, The University of Queensland, St Lucia, Queensland, Australia
| | - Robin N Allsopp
- School of Biological Sciences, The University of Queensland, St Lucia, Queensland, Australia
| | - Jeffrey S Groh
- School of Biological Sciences, The University of Queensland, St Lucia, Queensland, Australia
| | - Avneet Kaur
- School of Biological Sciences, The University of Queensland, St Lucia, Queensland, Australia
- Australian Research Council Centre of Excellence for Plant Success in Nature and Agriculture, The University of Queensland, St Lucia, Queensland, Australia
| | - Melanie J Wilkinson
- School of Biological Sciences, The University of Queensland, St Lucia, Queensland, Australia
- Australian Research Council Centre of Excellence for Plant Success in Nature and Agriculture, The University of Queensland, St Lucia, Queensland, Australia
| | - Daniel Ortiz-Barrientos
- School of Biological Sciences, The University of Queensland, St Lucia, Queensland, Australia
- Australian Research Council Centre of Excellence for Plant Success in Nature and Agriculture, The University of Queensland, St Lucia, Queensland, Australia
| |
Collapse
|
2
|
Cornet C, Noret N, Van Rossum F. Pollinator sharing between reproductively isolated genetic lineages of Silene nutans. FRONTIERS IN PLANT SCIENCE 2022; 13:927498. [PMID: 36340351 PMCID: PMC9634645 DOI: 10.3389/fpls.2022.927498] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/24/2022] [Accepted: 09/22/2022] [Indexed: 06/16/2023]
Abstract
High reciprocal pollination specialization leading to pollinator isolation can prevent interspecific pollen transfer and competition for pollinators. Sharing pollinators may induce mating costs, but it may also increase pollination services and pollen dispersal and offer more resources to pollinators, which may be important in case of habitat fragmentation leading to pollination disruption. We estimated pollen dispersal and pollinator isolation or sharing between two reproductively isolated genetic lineages of Silene nutans (Caryophyllaceae), which are rare and occur in parapatry in southern Belgium, forming two edaphic ecotypes. As inter-ecotypic crosses may lead to pollen wastage and inviable progeny, pollinator isolation might have evolved between ecotypes. Silene nutans is mainly pollinated by nocturnal moths, including nursery pollinators, which pollinate and lay their eggs in flowers, and whose caterpillars feed on flowers and seeds. Pollinator assemblages of the two ecotypes are largely unknown and inter-ecotypic pollen flows have never been investigated. Fluorescent powdered dyes were used as pollen analogues to quantify intra- and inter-ecotypic pollen transfers and seeds were germinated to detect chlorotic seedlings resulting from inter-ecotypic pollination. Nocturnal pollinators were observed using infrared cameras on the field, and seed-eating caterpillars were collected and reared to identify nursery pollinator species. No pollinator isolation was found: we detected long-distance (up to 5 km) inter-ecotypic dye transfers and chlorotic seedlings, indicating inter-ecotypic fertilization events. The rare moth Hadena albimacula, a nursery pollinator specialized on S. nutans, was found on both ecotypes, as well as adults visiting flowers (cameras recordings) as seed-eating caterpillars. However, S. nutans populations harbor different abundance and diversity of seed predator communities, including other rare nursery pollinators, suggesting a need for distinct conservation strategies. Our findings demonstrate the efficiency of moths, especially of nursery pollinators, to disperse pollen over long distances in natural landscapes, so to ensure gene flow and population sustainability of the host plant. Seed-predator specificities between the two reproductively isolated genetic lineages of S. nutans, and pollinator sharing instead of pollinator isolation when plants occur in parapatry, suggest that conservation of the host plant is also essential for sustaining (rare) pollinator and seed predator communities.
Collapse
Affiliation(s)
- Camille Cornet
- Laboratoire d’Ecologie végétale et Biogéochimie, Université libre de Bruxelles, Brussels, Belgium
| | - Nausicaa Noret
- Laboratoire d’Ecologie végétale et Biogéochimie, Université libre de Bruxelles, Brussels, Belgium
| | - Fabienne Van Rossum
- Laboratoire d’Ecologie végétale et Biogéochimie, Université libre de Bruxelles, Brussels, Belgium
- Research Department, Meise Botanic Garden, Meise, Belgium
- Service général de l’Enseignement supérieur et de la Recherche scientifique, Fédération Wallonie-Bruxelles, Brussels, Belgium
| |
Collapse
|
3
|
Christie K, Fraser LS, Lowry DB. The strength of reproductive isolating barriers in seed plants: Insights from studies quantifying premating and postmating reproductive barriers over the past 15 years. Evolution 2022; 76:2228-2243. [PMID: 35838076 PMCID: PMC9796645 DOI: 10.1111/evo.14565] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2021] [Revised: 06/23/2022] [Accepted: 06/30/2022] [Indexed: 01/22/2023]
Abstract
Speciation is driven by the evolution of reproductive isolating barriers that reduce, and ultimately prevent, substantial gene flow between lineages. Despite its central role in evolutionary biology, the process can be difficult to study because it proceeds differently among groups and may occur over long timescales. Due to this complexity, we typically rely on generalizations of empirical data to describe and understand the process. Previous reviews of reproductive isolation (RI) in flowering plants have suggested that prezygotic or extrinsic barriers generally have a stronger effect on reducing gene flow compared to postzygotic or intrinsic barriers. Past conclusions have rested on relatively few empirical estimates of RI; however, RI data have become increasingly abundant over the past 15 years. We analyzed data from recent studies quantifying multiple pre- and postmating barriers in plants and compared the strengths of isolating barriers across 89 taxa pairs using standardized RI metrics. Individual prezygotic barriers were on average stronger than individual postzygotic barriers, and the total strength of prezygotic RI was approximately twice that of postzygotic RI. These findings corroborate that ecological divergence and extrinsic factors, as opposed to solely the accumulation of genetic incompatibilities, are important to speciation and the maintenance of species boundaries in plants. Despite an emphasis in the literature on asymmetric postmating and postzygotic RI, we found that prezygotic barriers acted equally asymmetrically. Overall, substantial variability in the strengths of 12 isolating barriers highlights the great diversity of mechanisms that contribute to plant diversification.
Collapse
Affiliation(s)
- Kyle Christie
- Department of Plant BiologyMichigan State UniversityEast LansingMichigan48824,Department of Biological SciencesNorthern Arizona UniversityFlagstaffArizona86011
| | - Linnea S. Fraser
- Department of Plant BiologyMichigan State UniversityEast LansingMichigan48824
| | - David B. Lowry
- Department of Plant BiologyMichigan State UniversityEast LansingMichigan48824
| |
Collapse
|
4
|
Thompson KA, Schluter D. Heterosis counteracts hybrid breakdown to forestall speciation by parallel natural selection. Proc Biol Sci 2022; 289:20220422. [PMID: 35506223 PMCID: PMC9065978 DOI: 10.1098/rspb.2022.0422] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
In contrast to ecological speciation, where reproductive isolation evolves as a consequence of divergent natural selection, speciation by parallel natural selection has been less thoroughly studied. To test whether parallel evolution drives speciation, we leveraged the repeated evolution of benthic and limnetic ecotypes of threespine stickleback fish and estimated fitness for pure crosses and within-ecotype hybrids in semi-natural ponds and in laboratory aquaria. In ponds, we detected hybrid breakdown in both ecotypes but this was counterbalanced by heterosis and the strength of post-zygotic isolation was nil. In aquaria, we detected heterosis in limnetic crosses and breakdown in benthic crosses, which is suggestive of process- and ecotype-specific environment-dependence. In ponds, heterosis and breakdown were three times greater in limnetic crosses than in benthic crosses, contrasting the prediction that the fitness consequences of hybridization should be greater in crosses among more derived ecotypes. Consistent with a primary role for stochastic processes, patterns differed among crosses between populations from different lakes. Yet, the observation of qualitatively similar patterns of heterosis and hybrid breakdown for both ecotypes when averaging the lake pairs indicates that the outcome of hybridization is repeatable in a general sense.
Collapse
Affiliation(s)
- Ken A. Thompson
- Department of Zoology and Biodiversity Research Centre, University of British Columbia, Vancouver, British Columbia, Canada
| | - Dolph Schluter
- Department of Zoology and Biodiversity Research Centre, University of British Columbia, Vancouver, British Columbia, Canada
| |
Collapse
|
5
|
Koski MH, Galloway LF, Busch JW. Hybrid breakdown is elevated near the historical cores of a species' range. Proc Biol Sci 2022; 289:20220070. [PMID: 35291839 PMCID: PMC8924771 DOI: 10.1098/rspb.2022.0070] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
New species form when they become reproductively isolated. A classic model of speciation posits that derived mutations appear in isolated populations and reduce fitness when combined in hybrids. While these Bateson-Dobzhansky-Muller incompatibilities are known to accumulate as populations diverge over time, they may also reflect the amount of standing genetic variation within populations. We analysed the fitness of F2 hybrids in crosses between 24 populations of a plant species (Campanula americana) with broad variation in standing genetic variation and genetic differentiation driven by post-glacial range expansions. Hybrid breakdown varied substantially and was strongest between populations near the historical cores of the species range where within-population genetic diversity was high. Nearly half of the variation in hybrid breakdown was predicted by the combined effects of standing genetic variation within populations, their pairwise genetic differentiation and differences in the climates they inhabit. Hybrid breakdown was enhanced between populations inhabiting distinct climates, likely reflecting local adaptation. Results support that the mutations causing hybrid breakdown, the raw material for speciation, are more common in long-inhabited areas of the species range. Genetic diversity harboured in refugial areas is thus an important source of incompatibilities critical to the speciation process.
Collapse
Affiliation(s)
- Matthew H. Koski
- Department of Biological Sciences, Clemson University, 134 Long Hall, Clemson, SC 29634, USA
| | - Laura F. Galloway
- Department of Biology, University of Virginia, PO Box 400328, Charlottesville, VA 22904, USA
| | - Jeremiah W. Busch
- School of Biological Sciences, Washington State University, PO Box 644236, Pullman, WA 99164, USA
| |
Collapse
|
6
|
Carscadden KA, Doak DF, Emery NC. Climate Variation Influences Flowering Time Overlap in a Pair of Hybridizing Montane Plants. WEST N AM NATURALIST 2022. [DOI: 10.3398/064.082.0112] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Affiliation(s)
- Kelly A. Carscadden
- Department of Ecology and Evolutionary Biology, University of Colorado Boulder, 1900 Pleasant St., Boulder, CO 80309
| | - Daniel F. Doak
- Department of Ecology and Evolutionary Biology, University of Colorado Boulder, 1900 Pleasant St., Boulder, CO 80309
| | - Nancy C. Emery
- Department of Ecology and Evolutionary Biology, University of Colorado Boulder, 1900 Pleasant St., Boulder, CO 80309
| |
Collapse
|
7
|
Mino M, Tezuka T, Shomura S. The hybrid lethality of interspecific F 1 hybrids of Nicotiana: a clue to understanding hybrid inviability-a major obstacle to wide hybridization and introgression breeding of plants. MOLECULAR BREEDING : NEW STRATEGIES IN PLANT IMPROVEMENT 2022; 42:10. [PMID: 37309322 PMCID: PMC10248639 DOI: 10.1007/s11032-022-01279-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/04/2021] [Accepted: 01/23/2022] [Indexed: 06/14/2023]
Abstract
Reproductive isolation poses a major obstacle to wide hybridization and introgression breeding of plants. Hybrid inviability in the postzygotic isolation barrier inevitably reduces hybrid fitness, consequently causing hindrances in the establishment of novel genotypes from the hybrids among genetically divergent parents. The idea that the plant immune system is involved in the hybrid problem is applicable to the intra- and/or interspecific hybrids of many different taxa. The lethality characteristics and expression profile of genes associated with the hypersensitive response of the hybrids, along with the suppression of causative genes, support the deleterious epistatic interaction of parental NB-LRR protein genes, resulting in aberrant hyper-immunity reactions in the hybrid. Moreover, the cellular, physiological, and biochemical reactions observed in hybrid cells also corroborate this hypothesis. However, the difference in genetic backgrounds of the respective hybrids may contribute to variations in lethality phenotypes among the parental species combinations. The mixed state in parental components of the chaperone complex (HSP90-SGT1-RAR1) in the hybrid may also affect the hybrid inviability. This review article discusses the facts and hypothesis regarding hybrid inviability, alongside the findings of studies on the hybrid lethality of interspecific hybrids of the genus Nicotiana. A possible solution for averting the hybrid problem has also been scrutinized with the aim of improving the wide hybridization and introgression breeding program in plants.
Collapse
Affiliation(s)
- Masanobu Mino
- Graduate School of Life and Environmental Sciences, Kyoto Prefectural University, 1-5 Hangi-cho, Shimogamo, Sakyo-ku, Kyoto, 606-8522 Japan
- Present Address: Graduate School of Life and Environmental Sciences, Osaka Prefecture University, 1-1 Gakuen-cho, Naka-ku Sakai, Osaka, 599-8531 Japan
| | - Takahiro Tezuka
- Present Address: Graduate School of Life and Environmental Sciences, Osaka Prefecture University, 1-1 Gakuen-cho, Naka-ku Sakai, Osaka, 599-8531 Japan
| | - Sachiko Shomura
- Graduate School of Life and Environmental Sciences, Kyoto Prefectural University, 1-5 Hangi-cho, Shimogamo, Sakyo-ku, Kyoto, 606-8522 Japan
| |
Collapse
|
8
|
Adaptive divergence in shoot gravitropism creates hybrid sterility in an Australian wildflower. Proc Natl Acad Sci U S A 2021; 118:2004901118. [PMID: 34789571 PMCID: PMC8617494 DOI: 10.1073/pnas.2004901118] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/02/2021] [Indexed: 11/18/2022] Open
Abstract
New species originate as populations become reproductively isolated from one another. Despite recent progress in uncovering the genetic basis of reproductive isolation, it remains unclear whether intrinsic reproductive barriers, such as hybrid sterility, can evolve as a by-product of local adaptation to contrasting environments. Here, we show that differences in a plant’s response to the pull of gravity have repeatedly evolved amongst coastal populations of an Australian wildflower, thus implicating a role of natural selection in their evolution. We found a strong genetic association between variation in this adaptive trait and hybrid sterility, suggesting that intrinsic reproductive barriers contribute to the origin of new species as populations adapt to heterogeneous environments. Natural selection is responsible for much of the diversity we see in nature. Just as it drives the evolution of new traits, it can also lead to new species. However, it is unclear whether natural selection conferring adaptation to local environments can drive speciation through the evolution of hybrid sterility between populations. Here, we show that adaptive divergence in shoot gravitropism, the ability of a plant’s shoot to bend upwards in response to the downward pull of gravity, contributes to the evolution of hybrid sterility in an Australian wildflower, Senecio lautus. We find that shoot gravitropism has evolved multiple times in association with plant height between adjacent populations inhabiting contrasting environments, suggesting that these traits have evolved by natural selection. We directly tested this prediction using a hybrid population subjected to eight rounds of recombination and three rounds of selection in the field. Our experiments revealed that shoot gravitropism responds to natural selection in the expected direction of the locally adapted population. Using the advanced hybrid population, we discovered that individuals with extreme differences in gravitropism had more sterile crosses than individuals with similar gravitropic responses, which were largely fertile, indicating that this adaptive trait is genetically correlated with hybrid sterility. Our results suggest that natural selection can drive the evolution of locally adaptive traits that also create hybrid sterility, thus revealing an evolutionary connection between local adaptation and the origin of new species.
Collapse
|
9
|
Zalmat AS, Sotola VA, Nice CC, Martin NH. Genetic structure in Louisiana Iris species reveals patterns of recent and historical admixture. AMERICAN JOURNAL OF BOTANY 2021; 108:2257-2268. [PMID: 34618352 DOI: 10.1002/ajb2.1758] [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: 03/08/2021] [Revised: 08/10/2021] [Accepted: 08/18/2021] [Indexed: 06/13/2023]
Abstract
PREMISE When divergent lineages come into secondary contact, reproductive isolation may be incomplete, thus providing an opportunity to investigate how speciation is manifested in the genome. The Louisiana Irises (Iris, series Hexagonae) comprise a group of three or more ecologically and reproductively divergent lineages that can produce hybrids where they come into contact. We estimated standing genetic variation to understand the current distribution of population structure in the Louisiana Irises. METHODS We used genotyping-by-sequencing techniques to sample the genomes of Louisiana Iris species across their ranges. We sampled 20 populations (n = 632 individuals) across 11,249 loci and used Entropy and PCA models to assess population genetic data. RESULTS We discovered evidence for interspecific gene flow in parts of the range. Our analysis revealed patterns of population structure at odds with widely accepted nominal taxonomy. We discovered undescribed hybrid populations, designated as belonging to the I. brevicaulis lineage. Iris nelsonii shared significant ancestry with only one of the purported parent species, I. fulva, evidence inconsistent with a hybrid origin. CONCLUSIONS This study provides several key findings important to the investigation of standing genetic variation in the Louisiana Iris species complex. Compared to the other nominal species, I. brevicaulis contains a large amount of genetic diversity. In addition, we discovered a previously unknown hybrid zone between I. brevicaulis and I. hexagona along the Texas coast. Finally, our results do not support the long-standing hypothesis that I. nelsonii has mixed ancestry from three parental taxa.
Collapse
Affiliation(s)
- Alexander S Zalmat
- Department of Biology, Texas State University, San Marcos, Texas, 78666-0202, USA
| | - V Alex Sotola
- Department of Genetics, University of Georgia, Athens, Georgia, 30602-7223, USA
| | - Chris C Nice
- Department of Biology, Texas State University, San Marcos, Texas, 78666-0202, USA
| | - Noland H Martin
- Department of Biology, Texas State University, San Marcos, Texas, 78666-0202, USA
- Director of the Population and Conservation Biology Program, Department of Biology, Texas State University, San Marcos, Texas, 78666-0202, USA
| |
Collapse
|
10
|
James ME, Arenas-Castro H, Groh JS, Allen SL, Engelstädter J, Ortiz-Barrientos D. Highly Replicated Evolution of Parapatric Ecotypes. Mol Biol Evol 2021; 38:4805-4821. [PMID: 34254128 PMCID: PMC8557401 DOI: 10.1093/molbev/msab207] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Parallel evolution of ecotypes occurs when selection independently drives the evolution of similar traits across similar environments. The multiple origins of ecotypes are often inferred based on a phylogeny that clusters populations according to geographic location and not by the environment they occupy. However, the use of phylogenies to infer parallel evolution in closely related populations is problematic because gene flow and incomplete lineage sorting can uncouple the genetic structure at neutral markers from the colonization history of populations. Here, we demonstrate multiple origins within ecotypes of an Australian wildflower, Senecio lautus. We observed strong genetic structure as well as phylogenetic clustering by geography and show that this is unlikely due to gene flow between parapatric ecotypes, which was surprisingly low. We further confirm this analytically by demonstrating that phylogenetic distortion due to gene flow often requires higher levels of migration than those observed in S. lautus. Our results imply that selection can repeatedly create similar phenotypes despite the perceived homogenizing effects of gene flow.
Collapse
Affiliation(s)
- Maddie E James
- School of Biological Sciences, The University of Queensland,St. Lucia, QLD, Australia
| | - Henry Arenas-Castro
- School of Biological Sciences, The University of Queensland,St. Lucia, QLD, Australia
| | - Jeffrey S Groh
- School of Biological Sciences, The University of Queensland,St. Lucia, QLD, Australia
| | - Scott L Allen
- School of Biological Sciences, The University of Queensland,St. Lucia, QLD, Australia
| | - Jan Engelstädter
- School of Biological Sciences, The University of Queensland,St. Lucia, QLD, Australia
| | | |
Collapse
|
11
|
James ME, Wilkinson MJ, Bernal DM, Liu H, North HL, Engelstädter J, Ortiz-Barrientos D. Phenotypic and genotypic parallel evolution in parapatric ecotypes of Senecio. Evolution 2021; 75:3115-3131. [PMID: 34687472 PMCID: PMC9299460 DOI: 10.1111/evo.14387] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2021] [Revised: 10/08/2021] [Accepted: 10/12/2021] [Indexed: 12/11/2022]
Abstract
The independent and repeated adaptation of populations to similar environments often results in the evolution of similar forms. This phenomenon creates a strong correlation between phenotype and environment and is referred to as parallel evolution. However, we are still largely unaware of the dynamics of parallel evolution, as well as the interplay between phenotype and genotype within natural systems. Here, we examined phenotypic and genotypic parallel evolution in multiple parapatric Dune‐Headland coastal ecotypes of an Australian wildflower, Senecio lautus. We observed a clear trait‐environment association in the system, with all replicate populations having evolved along the same phenotypic evolutionary trajectory. Similar phenotypes have arisen via mutational changes occurring in different genes, although many share the same biological functions. Our results shed light on how replicated adaptation manifests at the phenotypic and genotypic levels within populations, and highlight S. lautus as one of the most striking cases of phenotypic parallel evolution in nature.
Collapse
Affiliation(s)
- Maddie E James
- School of Biological Sciences, The University of Queensland, St. Lucia, QLD, 4072, Australia.,Australian Research Council Centre of Excellence for Plant Success in Nature and Agriculture, The University of Queensland, St Lucia, QLD, 4072, Australia
| | - Melanie J Wilkinson
- School of Biological Sciences, The University of Queensland, St. Lucia, QLD, 4072, Australia.,Australian Research Council Centre of Excellence for Plant Success in Nature and Agriculture, The University of Queensland, St Lucia, QLD, 4072, Australia
| | - Diana M Bernal
- School of Biological Sciences, The University of Queensland, St. Lucia, QLD, 4072, Australia.,Current Address: Biousos Neotropicales S.A.S, Bogotá, Colombia
| | - Huanle Liu
- School of Biological Sciences, The University of Queensland, St. Lucia, QLD, 4072, Australia.,Current Address: Centre for Genomic Regulation, The Barcelona Institute of Science and Technology, Barcelona, 08003, Spain
| | - Henry L North
- School of Biological Sciences, The University of Queensland, St. Lucia, QLD, 4072, Australia.,Current Address: Department of Zoology, University of Cambridge, Cambridge, CB2 3EJ, United Kingdom
| | - Jan Engelstädter
- School of Biological Sciences, The University of Queensland, St. Lucia, QLD, 4072, Australia
| | - Daniel Ortiz-Barrientos
- School of Biological Sciences, The University of Queensland, St. Lucia, QLD, 4072, Australia.,Australian Research Council Centre of Excellence for Plant Success in Nature and Agriculture, The University of Queensland, St Lucia, QLD, 4072, Australia
| |
Collapse
|
12
|
Moran BM, Payne C, Langdon Q, Powell DL, Brandvain Y, Schumer M. The genomic consequences of hybridization. eLife 2021; 10:e69016. [PMID: 34346866 PMCID: PMC8337078 DOI: 10.7554/elife.69016] [Citation(s) in RCA: 78] [Impact Index Per Article: 26.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2021] [Accepted: 07/09/2021] [Indexed: 12/29/2022] Open
Abstract
In the past decade, advances in genome sequencing have allowed researchers to uncover the history of hybridization in diverse groups of species, including our own. Although the field has made impressive progress in documenting the extent of natural hybridization, both historical and recent, there are still many unanswered questions about its genetic and evolutionary consequences. Recent work has suggested that the outcomes of hybridization in the genome may be in part predictable, but many open questions about the nature of selection on hybrids and the biological variables that shape such selection have hampered progress in this area. We synthesize what is known about the mechanisms that drive changes in ancestry in the genome after hybridization, highlight major unresolved questions, and discuss their implications for the predictability of genome evolution after hybridization.
Collapse
Affiliation(s)
- Benjamin M Moran
- Department of Biology, Stanford UniversityStanfordUnited States
- Centro de Investigaciones Científicas de las Huastecas “Aguazarca”HidalgoMexico
| | - Cheyenne Payne
- Department of Biology, Stanford UniversityStanfordUnited States
- Centro de Investigaciones Científicas de las Huastecas “Aguazarca”HidalgoMexico
| | - Quinn Langdon
- Department of Biology, Stanford UniversityStanfordUnited States
| | - Daniel L Powell
- Department of Biology, Stanford UniversityStanfordUnited States
- Centro de Investigaciones Científicas de las Huastecas “Aguazarca”HidalgoMexico
| | - Yaniv Brandvain
- Department of Ecology, Evolution & Behavior and Plant and Microbial Biology, University of MinnesotaMinneapolisUnited States
| | - Molly Schumer
- Department of Biology, Stanford UniversityStanfordUnited States
- Centro de Investigaciones Científicas de las Huastecas “Aguazarca”HidalgoMexico
- Hanna H. Gray Fellow, Howard Hughes Medical InstituteStanfordUnited States
| |
Collapse
|
13
|
Abstract
Pollen-pistil interactions serve as important prezygotic reproductive barriers that play a critical role in mate selection in plants. Here, we highlight recent progress toward understanding the molecular basis of pollen-pistil interactions as reproductive isolating barriers. These barriers can be active systems of pollen rejection, or they can result from a mismatch of required male and female factors. In some cases, the barriers are mechanistically linked to self-incompatibility systems, while others represent completely independent processes. Pollen-pistil reproductive barriers can act as soon as pollen is deposited on a stigma, where penetration of heterospecific pollen tubes is blocked by the stigma papillae. As pollen tubes extend, the female transmitting tissue can selectively limit growth by producing cell wall-modifying enzymes and cytotoxins that interact with the growing pollen tube. At ovules, differential pollen tube attraction and inhibition of sperm cell release can act as barriers to heterospecific pollen tubes.
Collapse
Affiliation(s)
- Amanda K Broz
- Department of Biology, Colorado State University, Fort Collins, Colorado 80523-1878, USA; ,
| | - Patricia A Bedinger
- Department of Biology, Colorado State University, Fort Collins, Colorado 80523-1878, USA; ,
| |
Collapse
|
14
|
Keller B, Ganz R, Mora-Carrera E, Nowak MD, Theodoridis S, Koutroumpa K, Conti E. Asymmetries of reproductive isolation are reflected in directionalities of hybridization: integrative evidence on the complexity of species boundaries. THE NEW PHYTOLOGIST 2021; 229:1795-1809. [PMID: 32761901 DOI: 10.1111/nph.16849] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/28/2020] [Accepted: 07/23/2020] [Indexed: 05/26/2023]
Abstract
The complex nature of species boundaries has been a central topic in evolutionary biology ever since Darwin. Despite numerous separate studies on reproductive isolation and hybridization, their relationship remains underinvestigated. Are the strengths and asymmetries of reproductive barriers reflected in the extent and directionalities of interspecific genetic exchange? We combined field, experimental, and molecular data to quantify strengths and asymmetries of sympatric reproductive barriers and hybridization between florally heteromorphic primroses. We also assessed whether generalist pollinators discriminate between different floral cues and contribute to reproductive isolation, a long-debated topic. Sympatric reproductive isolation is high but incomplete, and most phenotypic intermediates are genetic F1 hybrids, whereas backcrosses are rare, revealing low interspecific gene flow. Species integrity rests on multiple barriers, but ethological isolation is among the strongest, demonstrating that even generalist pollinators crucially contribute to the maintenance of species boundaries. Furthermore, reproductive barriers are weaker for Primula veris and short-styled plants, results corroborated by molecular data. Thus, in florally heteromorphic systems, both species- and morph-dependent asymmetries affect permeability of species boundaries. Our study illustrates how the interactions between complex floral syndromes and pollinators shape species boundaries in unique, previously undescribed ways.
Collapse
Affiliation(s)
- Barbara Keller
- Department of Systematic and Evolutionary Botany, University of Zurich, Zollikerstrasse 107, Zurich, 8008, Switzerland
| | - Rita Ganz
- Department of Systematic and Evolutionary Botany, University of Zurich, Zollikerstrasse 107, Zurich, 8008, Switzerland
| | - Emiliano Mora-Carrera
- Department of Systematic and Evolutionary Botany, University of Zurich, Zollikerstrasse 107, Zurich, 8008, Switzerland
| | - Michael D Nowak
- Department of Systematic and Evolutionary Botany, University of Zurich, Zollikerstrasse 107, Zurich, 8008, Switzerland
| | - Spyros Theodoridis
- Department of Systematic and Evolutionary Botany, University of Zurich, Zollikerstrasse 107, Zurich, 8008, Switzerland
| | - Konstantina Koutroumpa
- Department of Systematic and Evolutionary Botany, University of Zurich, Zollikerstrasse 107, Zurich, 8008, Switzerland
| | - Elena Conti
- Department of Systematic and Evolutionary Botany, University of Zurich, Zollikerstrasse 107, Zurich, 8008, Switzerland
| |
Collapse
|
15
|
DiVittorio CT, Singhal S, Roddy AB, Zapata F, Ackerly DD, Baldwin BG, Brodersen CR, Búrquez A, Fine PVA, Padilla Flores M, Solis E, Morales-Villavicencio J, Morales-Arce D, Kyhos DW. Natural selection maintains species despite frequent hybridization in the desert shrub Encelia. Proc Natl Acad Sci U S A 2020; 117:33373-33383. [PMID: 33318178 PMCID: PMC7776959 DOI: 10.1073/pnas.2001337117] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2020] [Accepted: 11/03/2020] [Indexed: 01/01/2023] Open
Abstract
Natural selection is an important driver of genetic and phenotypic differentiation between species. For species in which potential gene flow is high but realized gene flow is low, adaptation via natural selection may be a particularly important force maintaining species. For a recent radiation of New World desert shrubs (Encelia: Asteraceae), we use fine-scale geographic sampling and population genomics to determine patterns of gene flow across two hybrid zones formed between two independent pairs of species with parapatric distributions. After finding evidence for extremely strong selection at both hybrid zones, we use a combination of field experiments, high-resolution imaging, and physiological measurements to determine the ecological basis for selection at one of the hybrid zones. Our results identify multiple ecological mechanisms of selection (drought, salinity, herbivory, and burial) that together are sufficient to maintain species boundaries despite high rates of hybridization. Given that multiple pairs of Encelia species hybridize at ecologically divergent parapatric boundaries, such mechanisms may maintain species boundaries throughout Encelia.
Collapse
Affiliation(s)
- Christopher T DiVittorio
- Department of Integrative Biology, University of California, Berkeley, CA 94720;
- TruBreed Technologies, Oakland, CA 94609
| | - Sonal Singhal
- Department of Biology, California State University - Dominguez Hills, Carson, CA 90747;
| | - Adam B Roddy
- School of the Environment, Yale University, New Haven, CT 06511
- Institute of Environment, Department of Biological Sciences, Florida International University, Miami, FL 33199
| | - Felipe Zapata
- Department of Ecology and Evolutionary Biology, University of California, Los Angeles, CA 90095
| | - David D Ackerly
- Department of Integrative Biology, University of California, Berkeley, CA 94720
- Jepson Herbarium, University of California, Berkeley, CA 94720
- Department of Environmental Science, Policy, and Management, University of California, Berkeley, CA 94720
| | - Bruce G Baldwin
- Department of Integrative Biology, University of California, Berkeley, CA 94720
- Jepson Herbarium, University of California, Berkeley, CA 94720
| | | | - Alberto Búrquez
- Instituto de Ecología, Universidad Autónoma de México, Sonora, 83000 Hermosillo, México
| | - Paul V A Fine
- Department of Integrative Biology, University of California, Berkeley, CA 94720
| | - Mayra Padilla Flores
- Department of Biology, California State University - Dominguez Hills, Carson, CA 90747
| | - Elizabeth Solis
- Department of Biology, California State University - Dominguez Hills, Carson, CA 90747
| | | | - David Morales-Arce
- Benito Juárez s/n, Colonia Barrio La Punta, Bahia Asunción, 23960 Baja California Sur, México
| | - Donald W Kyhos
- Department of Plant Biology, University of California, Davis, CA 95616
| |
Collapse
|
16
|
Leal BSS, Brandão MM, Palma-Silva C, Pinheiro F. Differential gene expression reveals mechanisms related to habitat divergence between hybridizing orchids from the Neotropical coastal plains. BMC PLANT BIOLOGY 2020; 20:554. [PMID: 33302865 PMCID: PMC7731501 DOI: 10.1186/s12870-020-02757-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/08/2020] [Accepted: 11/25/2020] [Indexed: 06/10/2023]
Abstract
BACKGROUND Closely related hybridizing species are ideal systems for identifying genomic regions underlying adaptive divergence. Although gene expression plays a central role in determining ecologically-based phenotypic differences, few studies have inferred the role of gene expression for adaptive divergence in Neotropical systems. In this study, we conduct genome-wide expression analysis alongside soil elemental analysis in sympatric and allopatric populations of Epidendrum fulgens and E. puniceoluteum (Orchidaceae), which occur in contrasting adjacent habitats in the Neotropical coastal plains. RESULTS These species were highly differentiated by their gene expression profiles, as determined by 18-21% of transcripts. Gene ontology (GO) terms associated with reproductive processes were enriched according to comparisons between species in both allopatric and sympatric populations. Species showed differential expression in genes linked to salt and waterlogging tolerance according to comparisons between species in sympatry, and biological processes related to environmental stimulus appeared as representative among those transcripts associated with edaphic characteristics in each sympatric zone. Hybrids, in their turn, were well differentiated from E. fulgens, but exhibited a similar gene expression profile to flooding-tolerant E. puniceolutem. When compared with parental species, hybrids showed no transcripts with additive pattern of expression and increased expression for almost all transgressive transcripts. CONCLUSIONS This study sheds light on general mechanisms promoting ecological differentiation and assortative mating, and suggests candidate genes, such as those encoding catalase and calcium-dependent protein kinase, underling adaptation to harsh edaphic conditions in the Neotropical coastal plains. Moreover, it demonstrates that differential gene expression plays a central role in determining ecologically-based phenotypic differences among co-occurring species and their hybrids.
Collapse
Affiliation(s)
| | - Marcelo Mendes Brandão
- Centro de Biologia Molecular e Engenharia Genética, Universidade Estadual de Campinas, Campinas, SP, 13083-862, Brazil
| | - Clarisse Palma-Silva
- Departamento de Biologia Vegetal, Universidade Estadual de Campinas, Campinas, SP, 13083-862, Brazil
| | - Fabio Pinheiro
- Departamento de Biologia Vegetal, Universidade Estadual de Campinas, Campinas, SP, 13083-862, Brazil
| |
Collapse
|
17
|
Choi JY, Purugganan M, Stacy EA. Divergent Selection and Primary Gene Flow Shape Incipient Speciation of a Riparian Tree on Hawaii Island. Mol Biol Evol 2020; 37:695-710. [PMID: 31693149 PMCID: PMC7038655 DOI: 10.1093/molbev/msz259] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
A long-standing goal of evolutionary biology is to understand the mechanisms underlying the formation of species. Of particular interest is whether or not speciation can occur in the presence of gene flow and without a period of physical isolation. Here, we investigated this process within Hawaiian Metrosideros, a hypervariable and highly dispersible woody species complex that dominates the Hawaiian Islands in continuous stands. Specifically, we investigated the origin of Metrosideros polymorpha var. newellii (newellii), a riparian ecotype endemic to Hawaii Island that is purportedly derived from the archipelago-wide M. polymorpha var. glaberrima (glaberrima). Disruptive selection across a sharp forest-riparian ecotone contributes to the isolation of these varieties and is a likely driver of newellii's origin. We examined genome-wide variation of 42 trees from Hawaii Island and older islands. Results revealed a split between glaberrima and newellii within the past 0.3-1.2 My. Admixture was extensive between lineages within Hawaii Island and between islands, but introgression from populations on older islands (i.e., secondary gene flow) did not appear to contribute to the emergence of newellii. In contrast, recurrent gene flow (i.e., primary gene flow) between glaberrima and newellii contributed to the formation of genomic islands of elevated absolute and relative divergence. These regions were enriched for genes with regulatory functions as well as for signals of positive selection, especially in newellii, consistent with divergent selection underlying their formation. In sum, our results support riparian newellii as a rare case of incipient ecological speciation with primary gene flow in trees.
Collapse
Affiliation(s)
- Jae Young Choi
- Center for Genomics and Systems Biology, Department of Biology, New York University, New York, NY
| | - Michael Purugganan
- Center for Genomics and Systems Biology, Department of Biology, New York University, New York, NY.,Center for Genomics and Systems Biology, NYU Abu Dhabi Research Institute, New York University Abu Dhabi, Abu Dhabi, United Arab Emirates
| | - Elizabeth A Stacy
- School of Life Sciences, University of Nevada, Las Vegas, Las Vegas, NV
| |
Collapse
|
18
|
Walter GM, Richards TJ, Wilkinson MJ, Blows MW, Aguirre JD, Ortiz‐Barrientos D. Loss of ecologically important genetic variation in late generation hybrids reveals links between adaptation and speciation. Evol Lett 2020; 4:302-316. [PMID: 32774880 PMCID: PMC7403682 DOI: 10.1002/evl3.187] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2019] [Revised: 06/02/2020] [Accepted: 06/11/2020] [Indexed: 12/13/2022] Open
Abstract
Adaptation to contrasting environments occurs when advantageous alleles accumulate in each population, but it remains largely unknown whether these same advantageous alleles create genetic incompatibilities that can cause intrinsic reproductive isolation leading to speciation. Identifying alleles that underlie both adaptation and reproductive isolation is further complicated by factors such as dominance and genetic interactions among loci, which can affect both processes differently and obscure potential links between adaptation and speciation. Here, we use a combination of field and glasshouse experiments to explore the connection between adaptation and speciation while accounting for dominance and genetic interactions. We created a hybrid population with equal contributions from four contrasting ecotypes of Senecio lautus (Asteraceae), which produced hybrid genomes both before (F1 hybrid generation) and after (F4 hybrid generation) recombination among the parental ecotypes. In the glasshouse, plants in the second generation (F2 hybrid generation) showed reduced fitness as a loss of fertility. However, fertility was recovered in subsequent generations, suggesting that genetic variation underlying the fitness reduction was lost in subsequent generations. To quantify the effects of losing genetic variation at the F2 generation on the fitness of later generation hybrids, we used a reciprocal transplant to test for fitness differences between parental ecotypes, and F1 and F4 hybrids in all four parental habitats. Compared to the parental ecotypes and F1 hybrids, variance in F4 hybrid fitness was lower, and lowest in habitats that showed stronger native-ecotype advantage, suggesting that stronger natural selection for the native ecotype reduced fitness variation in the F4 hybrids. Fitness trade-offs that were present in the parental ecotypes and F1 hybrids were absent in the F4 hybrid. Together, these results suggest that the genetic variation lost after the F2 generation was likely associated with both adaptation and intrinsic reproductive isolation among ecotypes from contrasting habitats.
Collapse
Affiliation(s)
- Greg M. Walter
- School of Biological SciencesUniversity of QueenslandBrisbane4072Australia
- Current address: School of Biological SciencesMonash UniversityMelbourne3800Australia
| | - Thomas J. Richards
- Department of Ecology and GeneticsUppsala UniversityUppsalaSE‐752 36Sweden
| | | | - Mark W. Blows
- School of Biological SciencesUniversity of QueenslandBrisbane4072Australia
| | - J. David Aguirre
- School of Natural and Computational SciencesMassey UniversityAuckland0745New Zealand
| | | |
Collapse
|
19
|
Walter GM, Abbott RJ, Brennan AC, Bridle JR, Chapman M, Clark J, Filatov D, Nevado B, Ortiz-Barrientos D, Hiscock SJ. Senecio as a model system for integrating studies of genotype, phenotype and fitness. THE NEW PHYTOLOGIST 2020; 226:326-344. [PMID: 31951018 DOI: 10.1111/nph.16434] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/19/2019] [Accepted: 12/17/2019] [Indexed: 05/24/2023]
Abstract
Two major developments have made it possible to use examples of ecological radiations as model systems to understand evolution and ecology. First, the integration of quantitative genetics with ecological experiments allows detailed connections to be made between genotype, phenotype, and fitness in the field. Second, dramatic advances in molecular genetics have created new possibilities for integrating field and laboratory experiments with detailed genetic sequencing. Combining these approaches allows evolutionary biologists to better study the interplay between genotype, phenotype, and fitness to explore a wide range of evolutionary processes. Here, we present the genus Senecio (Asteraceae) as an excellent system to integrate these developments, and to address fundamental questions in ecology and evolution. Senecio is one of the largest and most phenotypically diverse genera of flowering plants, containing species ranging from woody perennials to herbaceous annuals. These Senecio species exhibit many growth habits, life histories, and morphologies, and they occupy a multitude of environments. Common within the genus are species that have hybridized naturally, undergone polyploidization, and colonized diverse environments, often through rapid phenotypic divergence and adaptive radiation. These diverse experimental attributes make Senecio an attractive model system in which to address a broad range of questions in evolution and ecology.
Collapse
Affiliation(s)
- Greg M Walter
- School of Biological Sciences, University of Bristol, Bristol, BS8 1TQ, UK
| | - Richard J Abbott
- School of Biology, University of St Andrews, St Andrews, Fife, KY16 9TH, UK
| | - Adrian C Brennan
- School of Biological and Biomedical Sciences, University of Durham, Durham, DH1 3LE, UK
| | - Jon R Bridle
- School of Biological Sciences, University of Bristol, Bristol, BS8 1TQ, UK
| | - Mark Chapman
- School of Biological Sciences, University of Southampton, Southampton, SO17 1BJ, UK
| | - James Clark
- Department of Plant Sciences, University of Oxford, Oxford, OX1 3RB, UK
| | - Dmitry Filatov
- Department of Plant Sciences, University of Oxford, Oxford, OX1 3RB, UK
| | - Bruno Nevado
- Department of Plant Sciences, University of Oxford, Oxford, OX1 3RB, UK
| | | | - Simon J Hiscock
- Department of Plant Sciences, University of Oxford, Oxford, OX1 3RB, UK
| |
Collapse
|
20
|
Matsumoto TK, Miyazaki Y, Sueyoshi M, Senda Y, Yamada K, Hirobe M. Pre-pollination barriers between two sympatric Arisaema species in northern Shikoku Island, Japan. AMERICAN JOURNAL OF BOTANY 2019; 106:1612-1621. [PMID: 31729010 DOI: 10.1002/ajb2.1389] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/23/2019] [Accepted: 10/01/2019] [Indexed: 06/10/2023]
Abstract
PREMISE The genus Arisaema (Araceae) has rapidly diversified in Japan, and multiple species often coexist in the field. Although Japanese Arisaema species hybridize from artificial crossing, hybrid individuals are rare in mixed populations; suggesting the presence of effective pre-pollination barriers. We examined the following reproductive barriers between A. sikokianum and A. tosaense: habitat, phenology, and pollinator isolations. METHODS Habitat isolation was examined by interspecific comparisons of microhabitat conditions at a mixed site and of altitude at the sampling site of herbarium specimens. Phenological isolation was evaluated by comparing seasonal transition in apparent spathe condition and frequency of insect visitation. Pollinator isolation was examined by comparing floral visitor assemblages between the two Arisaema species. To avoid overestimation of pollinator isolation due to seasonal changes in insect assemblages, we also compared visitor assemblages between natural and late-flowering A. sikokianum, where the latter was experimentally introduced and blooming with a natural A. tosaense population. RESULTS Microhabitat conditions and sampling elevations of herbarium specimens overlapped between the two Arisaema species. At the population level, A. sikokianum and A. tosaense flowered for 39 and 52 days, respectively, with 13 days overlap. Insect visitation in A. sikokianum decreased before the seasonal overlap. Floral visitor assemblages differed between the two Arisaema species, while the difference between natural and late-flowering A. sikokianum was less distinct. CONCLUSIONS Phenological and pollinator isolation contribute to reproductive isolation between the two Arisaema species and should enable the two species to coexist in this area.
Collapse
Affiliation(s)
- Tetsuya K Matsumoto
- Graduate School of Environmental and Life Science, Okayama University, Tsushima-Naka 1-1-1, Kita-ku, Okayama, 700-8530, Japan
| | - Yuko Miyazaki
- Graduate School of Environmental and Life Science, Okayama University, Tsushima-Naka 1-1-1, Kita-ku, Okayama, 700-8530, Japan
| | - Masahiro Sueyoshi
- Center for Biodiversity, Forestry and Forest Products Research Institute, 1 Matsunosato, Tsukuba, 305-8687, Japan
| | - Yoshihiro Senda
- Hiwa Museum for Natural History, Hiwa 1119-1, Hiwa, Shôbara, 727-0301, Japan
| | - Kazuhiro Yamada
- Graduate School of Environmental and Life Science, Okayama University, Tsushima-Naka 1-1-1, Kita-ku, Okayama, 700-8530, Japan
| | - Muneto Hirobe
- Graduate School of Environmental and Life Science, Okayama University, Tsushima-Naka 1-1-1, Kita-ku, Okayama, 700-8530, Japan
| |
Collapse
|
21
|
Christie K, Strauss SY. Reproductive isolation and the maintenance of species boundaries in two serpentine endemic Jewelflowers. Evolution 2019; 73:1375-1391. [PMID: 31152435 DOI: 10.1111/evo.13767] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2019] [Revised: 04/28/2019] [Accepted: 05/03/2019] [Indexed: 12/30/2022]
Abstract
Speciation occurs when reproductive barriers substantially reduce gene flow between lineages. Understanding how specific barriers contribute to reproductive isolation offers insight into the initial forces driving divergence and the evolutionary and ecological processes responsible for maintaining diversity. Here, we quantified multiple pre- and post-pollination isolating barriers in a pair of closely related California Jewelflowers (Streptanthus, Brassicaceae) living in an area of sympatry. S. breweri and S. hesperidis are restricted to similar serpentine habitats; however, populations are spatially isolated at fine-scales and rarely co-occur in intermixed stands. Several intrinsic postzygotic barriers were among the strongest we quantified, yet, postzygotic barriers currently contribute little to overall reproductive isolation due to the cumulative strength of earlier-acting extrinsic barriers, including spatial isolation, and flowering time and pollinator differences. Data from multiple years suggest that pre-pollination barriers may have different strengths depending on annual environmental conditions. Similarly, crossing data suggest that the strength of intrinsic isolation may vary among different population pairs. Estimates of total reproductive isolation in S. breweri and S. hesperidis are robust to uncertainty and variability in individual barrier strength estimates, demonstrating how multiple barriers can act redundantly to prevent gene flow between close relatives living in sympatry.
Collapse
Affiliation(s)
- Kyle Christie
- UC Davis Department of Evolution and Ecology, and Center for Population Biology, University of California, One Shields Avenue, Davis, California, 95616
| | - Sharon Y Strauss
- UC Davis Department of Evolution and Ecology, and Center for Population Biology, University of California, One Shields Avenue, Davis, California, 95616
| |
Collapse
|
22
|
Burge DO, Parker VT, Mulligan M, Sork VL. Influence of a climatic gradient on genetic exchange between two oak species. AMERICAN JOURNAL OF BOTANY 2019; 106:864-878. [PMID: 31216071 DOI: 10.1002/ajb2.1315] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/05/2018] [Accepted: 03/27/2019] [Indexed: 06/09/2023]
Abstract
PREMISE In plant groups with limited intrinsic barriers to gene flow, it is thought that environmental conditions can modulate interspecific genetic exchange. Oaks are known for limited barriers to gene flow among closely related species. Here, we use Quercus as a living laboratory in which to pursue a fundamental question in plant evolution: Do environmental gradients restrict or promote genetic exchange between species? METHODS We focused on two North American oaks, the rare Quercus dumosa and the widespread Q. berberidifolia. We sampled intensively along a contact zone in California, USA. We sequenced restriction site-associated DNA markers and measured vegetative phenotype. We tested for genetic exchange, the association with climate, and the effect on phenotype. RESULTS There is evidence for genetic exchange between the species. Admixed plants are found in areas of intermediate climate, while less admixed plants are found at the extremes of the climatic gradient. Genetic and phenotypic patterns are out of phase in the contact zone; some plants display the phenotype of one species but are genetically associated with another. CONCLUSIONS Our results support the hypothesis that a strong climatic gradient can promote genetic exchange between species. The overall weak correlation between genotype and phenotype in the contact zone between the species suggests that genetic exchange can lead to the breakdown of trait combinations used to define species. This incongruency predicts ongoing problems for conservation of Q. dumosa, with implications for conservation of other oaks.
Collapse
Affiliation(s)
- Dylan O Burge
- Department of Ecology and Evolutionary Biology, University of California, Box 957239, Los Angeles, California, 90095-7239, USA
- 554 Vallombrosa Avenue, P.O. Box 418, Chico, California, 95927, USA
| | - V Thomas Parker
- San Francisco State University, 1600 Holloway Avenue, San Francisco, California, 94132, USA
| | - Margaret Mulligan
- San Diego Natural History Museum, Balboa Park, 1788 El Prado, San Diego, California, 92101, USA
| | - Victoria L Sork
- Department of Ecology and Evolutionary Biology, University of California, Box 957239, Los Angeles, California, 90095-7239, USA
| |
Collapse
|
23
|
Richards TJ, Ortiz‐Barrientos D, McGuigan K. Natural selection drives leaf divergence in experimental populations of Senecio lautus under natural conditions. Ecol Evol 2019; 9:6959-6967. [PMID: 31380026 PMCID: PMC6662321 DOI: 10.1002/ece3.5263] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2019] [Revised: 04/21/2019] [Accepted: 04/23/2019] [Indexed: 11/11/2022] Open
Abstract
Leaf morphology is highly variable both within and between plant species. This study employs a combination of common garden and reciprocal transplant experiments to determine whether differences in leaf shape between Senecio lautus ecotypes has evolved as an adaptive response to divergent ecological conditions.We created a synthetic population of hybrid genotypes to segregate morphological variation between three ecotypes and performed reciprocal transplants where this hybrid population was transplanted into the three adjacent native environments. We measured nine leaf morphology traits across the experimental and natural populations at these sites.We found significant divergence in multivariate leaf morphology toward the native character in each environment, suggesting environmental conditions at each site exert selective pressure that results in a phenotypic shift toward the local phenotype of the wild populations.These associations suggest that differences in leaf morphology between S. lautus ecotypes have arisen as a result of divergent selection on leaf shape or associated traits that confer an adaptive advantage in each environment, which has led to the formation of morphologically distinct ecotypes.
Collapse
Affiliation(s)
- Thomas J. Richards
- School of Biological Sciences St LuciaUniversity of QueenslandSt LuciaQueenslandAustralia
- Department of Plant BiologySwedish University of Agricultural SciencesLinnean Center for Plant BiologyUppsalaSweden
| | | | - Katrina McGuigan
- School of Biological Sciences St LuciaUniversity of QueenslandSt LuciaQueenslandAustralia
| |
Collapse
|
24
|
Sobel JM, Stankowski S, Streisfeld MA. Variation in ecophysiological traits might contribute to ecogeographic isolation and divergence between parapatric ecotypes of
Mimulus aurantiacus. J Evol Biol 2019; 32:604-618. [DOI: 10.1111/jeb.13442] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2016] [Revised: 03/06/2019] [Accepted: 03/11/2019] [Indexed: 12/11/2022]
Affiliation(s)
- James M. Sobel
- Department of Biological Sciences Binghamton University (SUNY) Binghamton New York
| | - Sean Stankowski
- Institute of Ecology and Evolution University of Oregon Eugene Oregon
| | | |
Collapse
|
25
|
Jacquemyn H, Waud M, Brys R. Mycorrhizal divergence and selection against immigrant seeds in forest and dune populations of the partially mycoheterotrophic Pyrola rotundifolia. Mol Ecol 2018; 27:5228-5237. [PMID: 30427084 DOI: 10.1111/mec.14940] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2018] [Revised: 10/17/2018] [Accepted: 10/24/2018] [Indexed: 11/29/2022]
Abstract
Plant populations occupying different habitats may diverge from each other over time and gradually accumulate genetic and morphological differences, ultimately resulting in ecotype or even species formation. In plant species that critically rely on mycorrhizal fungi, differences in mycorrhizal communities can contribute to ecological isolation by reducing or even inhibiting germination of immigrant seeds. In this study, we investigated whether the mycorrhizal communities available in the soil and associating with the roots of seedlings and adult plants of the partially mycoheterotrophic Pyrola rotundifolia differed between populations growing in sand dunes and forests. In addition, reciprocal germination experiments were performed to test whether native seeds showed higher germination than immigrant seeds. Our results showed that the mycorrhizal communities differed significantly between forest and dune populations, and that within populations seedlings and adults also associated with different mycorrhizal communities. In both forest and dune populations, mycorrhizal communities were dominated by members of the Thelephoraceae, but dune populations showed a higher incidence of members of the Inocybaceae, whereas forest populations showed a high abundance of members of the Russulaceae. Reciprocal germination experiments showed that native seeds showed a higher germination success than immigrant seeds and this effect was most pronounced in dune populations. Overall, these results demonstrate that plants of P. rotundifolia growing in dune and forest habitats associate with different mycorrhizal communities and that reduced germination of non-native seeds may contribute to reproductive isolation. We conclude that selection against immigrants may constitute an important reproductive barrier at early stages of the speciation process.
Collapse
Affiliation(s)
- Hans Jacquemyn
- Department of Biology, Plant Conservation and Population Biology, KU Leuven, Leuven, Belgium
| | - Michael Waud
- Department of Biology, Plant Conservation and Population Biology, KU Leuven, Leuven, Belgium
| | - Rein Brys
- Research Institute for Forest and Nature, Geraardsbergen, Belgium
| |
Collapse
|
26
|
Bertel C, Rešetnik I, Frajman B, Erschbamer B, Hülber K, Schönswetter P. Natural selection drives parallel divergence in the mountain plant Heliosperma pusillum
s.l. OIKOS 2018. [DOI: 10.1111/oik.05364] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Affiliation(s)
- Clara Bertel
- Dept. of Botany; Univ. of Innsbruck, Sternwartestraße 15; AT-6020 Innsbruck Austria
| | | | - Božo Frajman
- Dept. of Botany; Univ. of Innsbruck, Sternwartestraße 15; AT-6020 Innsbruck Austria
| | - Brigitta Erschbamer
- Dept. of Botany; Univ. of Innsbruck, Sternwartestraße 15; AT-6020 Innsbruck Austria
| | - Karl Hülber
- Dept of Botany and Biodiversity Research; Univ. of Vienna; Vienna Austria
| | - Peter Schönswetter
- Dept. of Botany; Univ. of Innsbruck, Sternwartestraße 15; AT-6020 Innsbruck Austria
| |
Collapse
|
27
|
Cahenzli F, Bonetti C, Erhardt A. Divergent strategies in pre- and postzygotic reproductive isolation between two closely related Dianthus species. Evolution 2018; 72:1851-1862. [PMID: 30003537 DOI: 10.1111/evo.13556] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2018] [Accepted: 07/02/2018] [Indexed: 10/28/2022]
Abstract
Quantifying the relative contribution of multiple isolation barriers to gene flow between recently diverged species is essential for understanding speciation processes. In parapatric populations, local adaptation is thought to be a major contributor to the evolution of reproductive isolation. However, extrinsic postzygotic barriers assessed in reciprocal transplant experiments are often neglected in empirical assessments of multiple isolation barriers. We analyzed multiple isolation barriers between two closely related species of the plant genus Dianthus, a genus characterized by the most rapid species diversification in plants reported so far. Although D. carthusianorum L. and D. sylvestris Wulf. can easily be hybridized in crossing experiments, natural hybrids are rare. We found that in parapatry, pollinator-mediated prezygotic reproductive isolation barriers are important for both D. carthusianorum (0.761) and D. sylvestris (0.468). In contrast to D. carthusianorum, high hybrid viability in D. sylvestris (-0.491) was counteracted by strong extrinsic postzygotic isolation (0.900). Our study highlights the importance of including reciprocal transplant experiments for documenting extrinsic postzygotic isolation and demonstrates clearly divergent strategies and hence asymmetric pre- and postzygotic reproductive isolation between closely related species. It also suggests that pollinator-mediated and ecological isolation could have interacted in synergistic ways, further stimulating rapid speciation in Dianthus.
Collapse
Affiliation(s)
- Fabian Cahenzli
- Forschungsinstitut für biologischen Landbau (FiBL), Department of crop Sciences, Ackerstrasse 113, CH-5070, Frick, Switzerland
| | - Christophe Bonetti
- Department of Environmental Sciences, Section Conservation Biology (NLU), University of Basel, St. Johanns-Vorstadt 10, CH-4056, Basel, Switzerland
| | - Andreas Erhardt
- Department of Environmental Sciences, Botany, University of Basel, Schönbeinstrasse 6, CH-4056, Basel, Switzerland
| |
Collapse
|
28
|
Walter GM, Wilkinson MJ, Aguirre JD, Blows MW, Ortiz-Barrientos D. Environmentally induced development costs underlie fitness tradeoffs. Ecology 2018; 99:1391-1401. [PMID: 29856491 DOI: 10.1002/ecy.2234] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/27/2017] [Revised: 02/05/2018] [Accepted: 03/19/2018] [Indexed: 11/07/2022]
Abstract
Local adaptation can lead to genotype-by-environment interactions, which can create fitness tradeoffs in alternative environments, and govern the distribution of biodiversity across geographic landscapes. Exploring the ecological circumstances that promote the evolution of fitness tradeoffs requires identifying how natural selection operates and during which ontogenetic stages natural selection is strongest. When organisms disperse to areas outside their natural range, tradeoffs might emerge when organisms struggle to reach key life history stages, or alternatively, die shortly after reaching life history stages if there are greater risks of mortality associated with costs to developing in novel environments. We used multiple populations from four ecotypes of an Australian native wildflower (Senecio pinnatifolius) in reciprocal transplants to explore how fitness tradeoffs arise across ontogeny. We then assessed whether the survival probability for plants from native and foreign populations was contingent on reaching key developmental stages. We found that fitness tradeoffs emerged as ontogeny progressed when native plants were more successful than foreign plants at reaching seedling establishment and maturity. Native and foreign plants that failed to reach seedling establishment died at the same rate, but plants from foreign populations died quicker than native plants after reaching seedling establishment, and died quicker regardless of whether they reached sexual maturity or not. Development rates were similar for native and foreign populations, but changed depending on the environment. Together, our results suggest that natural selection for environment-specific traits early in life history created tradeoffs between contrasting environments. Plants from foreign populations were either unable to develop to seedling establishment, or they suffered increased mortality as a consequence of reaching seedling establishment. The observation of tradeoffs together with environmentally dependent changes in development rate suggest that foreign environments induce organisms to develop at a rate different from their native habitat, incurring consequences for lifetime fitness and population divergence.
Collapse
Affiliation(s)
- Greg M Walter
- School of Biological Sciences, University of Queensland, St. Lucia, Queensland, 4072, Australia
| | - Melanie J Wilkinson
- School of Biological Sciences, University of Queensland, St. Lucia, Queensland, 4072, Australia
| | - J David Aguirre
- School of Biological Sciences, University of Queensland, St. Lucia, Queensland, 4072, Australia.,Institute of Natural and Mathematical Sciences, Massey University, Auckland, 0745, New Zealand
| | - Mark W Blows
- School of Biological Sciences, University of Queensland, St. Lucia, Queensland, 4072, Australia
| | - Daniel Ortiz-Barrientos
- School of Biological Sciences, University of Queensland, St. Lucia, Queensland, 4072, Australia
| |
Collapse
|
29
|
Ferris KG, Willis JH. Differential adaptation to a harsh granite outcrop habitat between sympatric
Mimulus
species. Evolution 2018; 72:1225-1241. [DOI: 10.1111/evo.13476] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2017] [Revised: 02/20/2018] [Accepted: 02/28/2018] [Indexed: 12/11/2022]
Affiliation(s)
- Kathleen G. Ferris
- Department of Biology Duke University 125 Science Drive Durham North Carolina 27705
- Current Address: Center for Population Biology, 2320 Storer Hall University of California Davis One Shields Avenue Davis California 95616
| | - John H. Willis
- Department of Biology Duke University 125 Science Drive Durham North Carolina 27705
| |
Collapse
|
30
|
Christie K, Strauss SY. Along the speciation continuum: Quantifying intrinsic and extrinsic isolating barriers across five million years of evolutionary divergence in California jewelflowers. Evolution 2018; 72:1063-1079. [DOI: 10.1111/evo.13477] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2017] [Accepted: 02/27/2018] [Indexed: 12/11/2022]
Affiliation(s)
- Kyle Christie
- Department of Evolution and Ecology and Center for Population Biology University of California One Shields Avenue Davis California 95616
| | - Sharon Y. Strauss
- Department of Evolution and Ecology and Center for Population Biology University of California One Shields Avenue Davis California 95616
| |
Collapse
|
31
|
Walter GM, Aguirre JD, Blows MW, Ortiz-Barrientos D. Evolution of Genetic Variance during Adaptive Radiation. Am Nat 2018; 191:E108-E128. [PMID: 29570402 DOI: 10.1086/696123] [Citation(s) in RCA: 42] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Genetic correlations between traits can concentrate genetic variance into fewer phenotypic dimensions that can bias evolutionary trajectories along the axis of greatest genetic variance and away from optimal phenotypes, constraining the rate of evolution. If genetic correlations limit adaptation, rapid adaptive divergence between multiple contrasting environments may be difficult. However, if natural selection increases the frequency of rare alleles after colonization of new environments, an increase in genetic variance in the direction of selection can accelerate adaptive divergence. Here, we explored adaptive divergence of an Australian native wildflower by examining the alignment between divergence in phenotype mean and divergence in genetic variance among four contrasting ecotypes. We found divergence in mean multivariate phenotype along two major axes represented by different combinations of plant architecture and leaf traits. Ecotypes also showed divergence in the level of genetic variance in individual traits and the multivariate distribution of genetic variance among traits. Divergence in multivariate phenotypic mean aligned with divergence in genetic variance, with much of the divergence in phenotype among ecotypes associated with changes in trait combinations containing substantial levels of genetic variance. Overall, our results suggest that natural selection can alter the distribution of genetic variance underlying phenotypic traits, increasing the amount of genetic variance in the direction of natural selection and potentially facilitating rapid adaptive divergence during an adaptive radiation.
Collapse
|
32
|
Deschepper P, Brys R, Fortuna MA, Jacquemyn H. Analysis of spatial genetic variation reveals genetic divergence among populations of Primula veris associated to contrasting habitats. Sci Rep 2017; 7:8847. [PMID: 28821787 PMCID: PMC5562905 DOI: 10.1038/s41598-017-09154-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2017] [Accepted: 07/24/2017] [Indexed: 12/01/2022] Open
Abstract
Genetic divergence by environment is a process whereby selection causes the formation of gene flow barriers between populations adapting to contrasting environments and is often considered to be the onset of speciation. Nevertheless, the extent to which genetic differentiation by environment on small spatial scales can be detected by means of neutral markers is still subject to debate. Previous research on the perennial herb Primula veris has shown that plants from grassland and forest habitats showed pronounced differences in phenology and flower morphology, suggesting limited gene flow between habitats. To test this hypothesis, we sampled 33 populations of P. veris consisting of forest and grassland patches and used clustering techniques and network analyses to identify sets of populations that are more connected to each other than to other sets of populations and estimated the timing of divergence. Our results showed that spatial genetic variation had a significantly modular structure and consisted of four well-defined modules that almost perfectly coincided with habitat features. Genetic divergence was estimated to have occurred about 114 generations ago, coinciding with historic major changes in the landscape. Overall, these results illustrate how populations adapting to different environments become structured genetically within landscapes on small spatial scales.
Collapse
Affiliation(s)
- Pablo Deschepper
- Division of Plant Ecology and Systematics, Biology Department, University of Leuven, Leuven, Belgium.
| | - Rein Brys
- Research Institute for Forest and Nature, Gaverstraat 4, B-9500, Geraardsbergen, Belgium
| | - Miguel A Fortuna
- Department of Evolutionary Biology and Environmental Studies. University of Zurich, Zurich, Switzerland
| | - Hans Jacquemyn
- Division of Plant Ecology and Systematics, Biology Department, University of Leuven, Leuven, Belgium
| |
Collapse
|
33
|
Jacquemyn H, Kort HD, Broeck AV, Brys R. Immigrant and extrinsic hybrid seed inviability contribute to reproductive isolation between forest and dune ecotypes of Epipactis helleborine
(Orchidaceae). OIKOS 2017. [DOI: 10.1111/oik.04329] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Affiliation(s)
- Hans Jacquemyn
- Dept of Biology; Plant Conservation and Population Biology; BE-3001 Leuven Belgium
| | - Hanne De Kort
- Dept of Biology; Plant Conservation and Population Biology; BE-3001 Leuven Belgium
- Station d'Ecologie Théorique et Expérimentale du CNRS, Centre National de la Recherche Scientifique; Moulis France
| | | | - Rein Brys
- Research Inst. for Forest and Nature; Geraardsbergen Belgium
| |
Collapse
|
34
|
Roda F, Walter GM, Nipper R, Ortiz‐Barrientos D. Genomic clustering of adaptive loci during parallel evolution of an Australian wildflower. Mol Ecol 2017; 26:3687-3699. [DOI: 10.1111/mec.14150] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2015] [Revised: 03/07/2017] [Accepted: 04/03/2017] [Indexed: 12/11/2022]
Affiliation(s)
- Federico Roda
- School of Biological Sciences The University of Queensland St. Lucia QLD Australia
- Harvard University Boston MA USA
| | - Greg M. Walter
- School of Biological Sciences The University of Queensland St. Lucia QLD Australia
| | | | | |
Collapse
|
35
|
Favre A, Widmer A, Karrenberg S. Differential adaptation drives ecological speciation in campions (Silene): evidence from a multi-site transplant experiment. THE NEW PHYTOLOGIST 2017; 213:1487-1499. [PMID: 27775172 DOI: 10.1111/nph.14202] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/07/2016] [Accepted: 08/12/2016] [Indexed: 06/06/2023]
Abstract
In order to investigate the role of differential adaptation for the evolution of reproductive barriers, we conducted a multi-site transplant experiment with the dioecious sister species Silene dioica and S. latifolia and their hybrids. Crosses within species as well as reciprocal first-generation (F1 ) and second-generation (F2 ) interspecific hybrids were transplanted into six sites, three within each species' habitat. Survival and flowering were recorded over 4 yr. At all transplant sites, the local species outperformed the foreign species, reciprocal F1 hybrids performed intermediately and F2 hybrids underperformed in comparison to F1 hybrids (hybrid breakdown). Females generally had slightly higher cumulative fitness than males in both within- and between-species crosses and we thus found little evidence for Haldane's rule acting on field performance. The strength of selection against F1 and F2 hybrids as well as hybrid breakdown increased with increasing strength of habitat adaptation (i.e. the relative fitness difference between the local and the foreign species) across sites. Our results suggest that differential habitat adaptation led to ecologically dependent post-zygotic reproductive barriers and drives divergence and speciation in this Silene system.
Collapse
Affiliation(s)
- Adrien Favre
- Plant Ecological Genetics, ETH Zurich, Institute of Integrative Biology, Universitätstrasse 16, 8092, Zurich, Switzerland
- Department of Molecular Evolution and Plant Systematics & Herbarium (LZ), Institute of Biology, University of Leipzig, Johannisallee 21-23, 04103, Leipzig, Germany
| | - Alex Widmer
- Plant Ecological Genetics, ETH Zurich, Institute of Integrative Biology, Universitätstrasse 16, 8092, Zurich, Switzerland
| | - Sophie Karrenberg
- Plant Ecological Genetics, ETH Zurich, Institute of Integrative Biology, Universitätstrasse 16, 8092, Zurich, Switzerland
- Department of Ecology and Genetics, Plant Ecology and Evolution, Uppsala University, Norbyvägen 18 D, 752 36, Uppsala, Sweden
| |
Collapse
|
36
|
Bertel C, Hülber K, Frajman B, Schönswetter P. No evidence of intrinsic reproductive isolation between two reciprocally non-monophyletic, ecologically differentiated mountain plants at an early stage of speciation. Evol Ecol 2016. [DOI: 10.1007/s10682-016-9867-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
|
37
|
Yardeni G, Tessler N, Imbert E, Sapir Y. Reproductive isolation between populations of Iris atropurpurea is associated with ecological differentiation. ANNALS OF BOTANY 2016; 118:971-982. [PMID: 27436798 PMCID: PMC5055820 DOI: 10.1093/aob/mcw139] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/09/2016] [Revised: 05/13/2016] [Accepted: 05/23/2016] [Indexed: 05/28/2023]
Abstract
Background and Aims Speciation is often described as a continuous dynamic process, expressed by different magnitudes of reproductive isolation (RI) among groups in different levels of divergence. Studying intraspecific partial RI can shed light on mechanisms underlying processes of population divergence. Intraspecific divergence can be driven by spatially stochastic accumulation of genetic differences following reduced gene flow, resulting in increased RI with increased geographical distance, or by local adaptation, resulting in increased RI with environmental difference. Methods We tested for RI as a function of both geographical distance and ecological differentiation in Iris atropurpurea, an endemic Israeli coastal plant. We crossed plants in the Netanya Iris Reserve population with plants from 14 populations across the species' full distribution, and calculated RI and reproductive success based on fruit set, seed set and fraction of seed viability. Key Results We found that total RI was not significantly associated with geographical distance, but significantly increased with ecological distance. Similarly, reproductive success of the crosses, estimated while controlling for the dependency of each component on the previous stage, significantly reduced with increased ecological distance. Conclusions Our results indicate that the rise of post-pollination reproductive barriers in I. atropurpurea is more affected by ecological differentiation between populations than by geographical distance, supporting the hypothesis that ecological differentiation is predominant over isolation by distance and by reduced gene flow in this species. These findings also affect conservation management, such as genetic rescue, in the highly fragmented and endangered I. atropurpurea.
Collapse
Affiliation(s)
- Gil Yardeni
- The Botanical Garden, Department of Molecular Biology and Ecology of Plants, Tel Aviv University, Ramat Aviv, Tel Aviv 69978, Israel
| | - Naama Tessler
- Department of Biology, University of Haifa, Oranim, Tivon, Israel
| | - Eric Imbert
- Institut des Sciences de l’Evolution CNRS, IRD, University Montpellier 2, Montpellier, France
| | | |
Collapse
|
38
|
Keller B, de Vos JM, Schmidt‐Lebuhn AN, Thomson JD, Conti E. Both morph- and species-dependent asymmetries affect reproductive barriers between heterostylous species. Ecol Evol 2016; 6:6223-44. [PMID: 27648239 PMCID: PMC5016645 DOI: 10.1002/ece3.2293] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2016] [Revised: 06/03/2016] [Accepted: 06/07/2016] [Indexed: 12/13/2022] Open
Abstract
The interaction between floral traits and reproductive isolation is crucial to explaining the extraordinary diversity of angiosperms. Heterostyly, a complex floral polymorphism that optimizes outcrossing, evolved repeatedly and has been shown to accelerate diversification in primroses, yet its potential influence on isolating mechanisms remains unexplored. Furthermore, the relative contribution of pre- versus postmating barriers to reproductive isolation is still debated. No experimental study has yet evaluated the possible effects of heterostyly on pre- and postmating reproductive mechanisms. We quantify multiple reproductive barriers between the heterostylous Primula elatior (oxlip) and P. vulgaris (primrose), which readily hybridize when co-occurring, and test whether traits of heterostyly contribute to reproductive barriers in unique ways. We find that premating isolation is key for both species, while postmating isolation is considerable only for P. vulgaris; ecogeographic isolation is crucial for both species, while phenological, seed developmental, and hybrid sterility barriers are also important in P. vulgaris, implicating sympatrically higher gene flow into P. elatior. We document for the first time that, in addition to the aforementioned species-dependent asymmetries, morph-dependent asymmetries affect reproductive barriers between heterostylous species. Indeed, the interspecific decrease of reciprocity between high sexual organs of complementary floral morphs limits interspecific pollen transfer from anthers of short-styled flowers to stigmas of long-styled flowers, while higher reciprocity between low sexual organs favors introgression over isolation from anthers of long-styled flowers to stigmas of short-styled flowers. Finally, intramorph incompatibility persists across species boundaries, but is weakened in long-styled flowers of P. elatior, opening a possible backdoor to gene flow through intramorph pollen transfer between species. Therefore, patterns of gene flow across species boundaries are likely affected by floral morph composition of adjacent populations. To summarize, our study highlights the general importance of premating isolation and newly illustrates that both morph- and species-dependent asymmetries shape boundaries between heterostylous species.
Collapse
Affiliation(s)
- Barbara Keller
- Department of Systematic and Evolutionary BotanyUniversity of ZürichZollikerstrasse 1078008ZürichSwitzerland
| | - Jurriaan M. de Vos
- Department of Ecology and Evolutionary BiologyBrown University80 Waterman StreetBox G‐WProvidenceRhode Island02912USA
- Present address: Comparative Plant and Fungal Biology DepartmentRoyal Botanic GardensKewRichmondSurreyTW9 3AE UK
| | | | - James D. Thomson
- Ecology and Evolutionary Biology DepartmentUniversity of Toronto25 Harbord St.TorontoOntarioM5S 3G5Canada
| | - Elena Conti
- Department of Systematic and Evolutionary BotanyUniversity of ZürichZollikerstrasse 1078008ZürichSwitzerland
| |
Collapse
|
39
|
Ostevik KL, Andrew RL, Otto SP, Rieseberg LH. Multiple reproductive barriers separate recently diverged sunflower ecotypes. Evolution 2016; 70:2322-2335. [PMID: 27479368 DOI: 10.1111/evo.13027] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2016] [Revised: 06/12/2016] [Accepted: 06/27/2016] [Indexed: 01/17/2023]
Abstract
Measuring reproductive barriers between groups of organisms is an effective way to determine the traits and mechanisms that impede gene flow. However, to understand the ecological and evolutionary factors that drive speciation, it is important to distinguish between the barriers that arise early in the speciation process and those that arise after speciation is largely complete. In this article, we comprehensively test for reproductive isolation between recently diverged (<10,000 years bp) dune and nondune ecotypes of the prairie sunflower, Helianthus petiolaris. We find reproductive barriers acting at multiple stages of hybridization, including premating, postmating-prezygotic, and postzygotic barriers, despite the recent divergence. Barriers include extrinsic selection against immigrants and hybrids, a shift in pollinator assemblage, and postpollination assortative mating. Together, these data suggest that multiple barriers can be important for reducing gene flow in the earliest stages of speciation.
Collapse
Affiliation(s)
- Katherine L Ostevik
- Department of Botany, University of British Columbia, Vancouver, British Columbia, Canada.
| | - Rose L Andrew
- School of Environmental and Rural Science, University of New England, Armidale, New South Wales, Australia
| | - Sarah P Otto
- Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada
| | - Loren H Rieseberg
- Department of Botany, University of British Columbia, Vancouver, British Columbia, Canada.,Department of Biology, Indiana University, Bloomington, Indiana
| |
Collapse
|
40
|
Richards TJ, Walter GM, McGuigan K, Ortiz‐Barrientos D. Divergent natural selection drives the evolution of reproductive isolation in an Australian wildflower. Evolution 2016; 70:1993-2003. [DOI: 10.1111/evo.12994] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2015] [Revised: 05/20/2016] [Accepted: 05/25/2016] [Indexed: 12/11/2022]
Affiliation(s)
- Thomas J. Richards
- School of Biological Sciences University of Queensland St. Lucia QLD Australia
| | - Greg M. Walter
- School of Biological Sciences University of Queensland St. Lucia QLD Australia
| | - Katrina McGuigan
- School of Biological Sciences University of Queensland St. Lucia QLD Australia
| | | |
Collapse
|
41
|
Walter GM, Wilkinson MJ, James ME, Richards TJ, Aguirre JD, Ortiz‐Barrientos D. Diversification across a heterogeneous landscape. Evolution 2016; 70:1979-92. [DOI: 10.1111/evo.13009] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2015] [Accepted: 07/05/2016] [Indexed: 12/11/2022]
Affiliation(s)
- Greg M. Walter
- School of Biological Sciences University of Queensland St. Lucia QLD 4072 Australia
| | - Melanie J. Wilkinson
- School of Biological Sciences University of Queensland St. Lucia QLD 4072 Australia
| | - Maddie E. James
- School of Biological Sciences University of Queensland St. Lucia QLD 4072 Australia
| | - Thomas J. Richards
- School of Biological Sciences University of Queensland St. Lucia QLD 4072 Australia
| | - J. David Aguirre
- School of Biological Sciences University of Queensland St. Lucia QLD 4072 Australia
- Institute of Natural and Mathematical Sciences Massey University Auckland 0745 New Zealand
| | | |
Collapse
|
42
|
Baack E, Melo MC, Rieseberg LH, Ortiz-Barrientos D. The origins of reproductive isolation in plants. THE NEW PHYTOLOGIST 2015; 207:968-84. [PMID: 25944305 DOI: 10.1111/nph.13424] [Citation(s) in RCA: 187] [Impact Index Per Article: 20.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/09/2015] [Accepted: 03/16/2015] [Indexed: 05/23/2023]
Abstract
Reproductive isolation in plants occurs through multiple barriers that restrict gene flow between populations, but their origins remain uncertain. Work in the past decade has shown that postpollination barriers, such as the failure to form hybrid seeds or sterility of hybrid offspring, are often less strong than prepollination barriers. Evidence implicates multiple evolutionary forces in the origins of reproductive barriers, including mutation, stochastic processes and natural selection. Although adaptation to different environments is a common element of reproductive isolation, genomic conflicts also play a role, including female meiotic drive. The genetic basis of some reproductive barriers, particularly flower colour influencing pollinator behaviour, is well understood in some species, but the genetic changes underlying many other barriers, especially pollen-stylar interactions, are largely unknown. Postpollination barriers appear to accumulate at a faster rate in annuals compared with perennials, due in part to chromosomal rearrangements. Chromosomal changes can be important isolating barriers in themselves but may also reduce the recombination of genes contributing to isolation. Important questions for the next decade include identifying the evolutionary forces responsible for chromosomal rearrangements, determining how often prezygotic barriers arise due to selection against hybrids, and establishing the relative importance of genomic conflicts in speciation.
Collapse
Affiliation(s)
- Eric Baack
- Department of Biology, Luther College, Decorah, IA, 52101, USA
| | - Maria Clara Melo
- School of Biological Sciences, The University of Queensland, St Lucia, QLD, 4072, Australia
| | - Loren H Rieseberg
- Department of Botany, University of British Columbia, Vancouver, BC, V6T 1Z4, Canada
- Department of Biology, Indiana University, Bloomington, IN, 47405, USA
| | | |
Collapse
|