1
|
Van Drunen WE, Friedman J. Autopolyploid establishment depends on life-history strategy and the mating outcomes of clonal architecture. Evolution 2022; 76:1953-1970. [PMID: 35861365 DOI: 10.1111/evo.14582] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2021] [Revised: 06/21/2022] [Accepted: 07/11/2022] [Indexed: 01/22/2023]
Abstract
Polyploidy is a significant component in the evolution of many taxa, particularly plant groups. However, new polyploids face substantial fitness disadvantages due to a lack of same-cytotype mates, and the factors promoting or preventing polyploid establishment in natural populations are often unclear. We develop spatially explicit agent-based simulation models to test the hypothesis that a perennial life history and clonal propagation facilitate the early stages of polyploid establishment and persistence. Our models show that polyploids are more likely to establish when they have longer life spans than diploids, especially when self-fertilization rates are high. Polyploids that combine sexual and clonal reproduction can establish across a wide range of life histories, but their success is moderated by clonal strategy. By tracking individuals and mating events, we reveal that clonal architecture has a substantial impact on the spatial structure of the mixed diploid-polyploid population during polyploid establishment: altering patterns of mating within or between cytotypes via geitonogamous self-fertilization, the mechanisms through which polyploid establishment proceeds, and the final composition of the polyploid population. Overall, our findings provide novel insight into the role of clonal structure in modulating the complex relationship between polyploidy, perenniality, and clonality and offer testable predictions for future empirical work.
Collapse
Affiliation(s)
- Wendy E Van Drunen
- Department of Biology, University of Toronto Mississauga, Mississauga, ON, L5L 1C6, Canada.,Biology Department, Queen's University, Kingston, ON, K7L 3N6, Canada
| | - Jannice Friedman
- Biology Department, Queen's University, Kingston, ON, K7L 3N6, Canada
| |
Collapse
|
2
|
Toll K, Lowry DB. Frequency-dependent hybridization contributes to habitat segregation in monkeyflowers. Am Nat 2022; 199:743-757. [DOI: 10.1086/719381] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
|
3
|
Matsumoto TK, Hirobe M, Sueyoshi M, Miyazaki Y. Selective pollination by fungus gnats potentially functions as an alternative reproductive isolation among five Arisaema species. ANNALS OF BOTANY 2021; 127:633-644. [PMID: 33263745 PMCID: PMC8052922 DOI: 10.1093/aob/mcaa204] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/24/2020] [Accepted: 12/01/2020] [Indexed: 05/10/2023]
Abstract
BACKGROUND AND AIMS Interspecific difference in pollinators (pollinator isolation) is important for reproductive isolation in flowering plants. Species-specific pollination by fungus gnats has been discovered in several plant taxa, suggesting that they can contribute to reproductive isolation. Nevertheless, their contribution has not been studied in detail, partly because they are too small for field observations during flower visitation. To quantify their flower visitation, we used the genus Arisaema (Araceae) because the pitcher-like spathe of Arisaema can trap all floral visitors. METHODS We evaluated floral visitor assemblage in an altitudinal gradient including five Arisaema species. We also examined interspecific differences in altitudinal distribution (geographic isolation) and flowering phenology (phenological isolation). To exclude the effect of interspecific differences in altitudinal distribution on floral visitor assemblage, we established ten experimental plots including the five Arisaema species in high- and low-altitude areas and collected floral visitors. We also collected floral visitors in three additional sites. Finally, we estimated the strength and contribution of these three reproductive barriers using a unified formula for reproductive isolation. KEY RESULTS Each Arisaema species selectively attracted different fungus gnats in the altitudinal gradient, experimental plots and additional sites. Altitudinal distribution and flowering phenology differed among the five Arisaema species, whereas the strength of geographic and phenological isolations were distinctly weaker than those in pollinator isolation. Nevertheless, the absolute contribution of pollinator isolation to total reproductive isolation was weaker than geographic and phenological isolations, because pollinator isolation functions after the two early-acting barriers in plant life history. CONCLUSIONS Our results suggest that selective pollination by fungus gnats potentially contributes to reproductive isolation. Since geographic and phenological isolations can be disrupted by habitat disturbance and interannual climate change, the strong and stable pollinator isolation might compensate for the weakened early-acting barriers as an alternative reproductive isolation among the five Arisaema species.
Collapse
Affiliation(s)
- Tetsuya K Matsumoto
- Graduate School of Environmental and Life Science, Okayama University, Kita-ku, Okayama, Japan
- For correspondence. E-mail
| | - Muneto Hirobe
- Graduate School of Environmental and Life Science, Okayama University, Kita-ku, Okayama, Japan
| | - Masahiro Sueyoshi
- Center for Biodiversity, Forestry and Forest Products Research Institute, Tsukuba, Japan
| | - Yuko Miyazaki
- Graduate School of Environmental and Life Science, Okayama University, Kita-ku, Okayama, Japan
| |
Collapse
|
4
|
The rapid dissolution of dioecy by experimental evolution. Curr Biol 2021; 31:1277-1283.e5. [PMID: 33472050 DOI: 10.1016/j.cub.2020.12.028] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2020] [Revised: 12/10/2020] [Accepted: 12/18/2020] [Indexed: 11/20/2022]
Abstract
Evolutionary transitions from hermaphroditism to dioecy have been common in flowering plants,1,2 but recent analysis also points to frequent reversions from dioecy to hermaphroditism.2-4 Here, we use experimental evolution to expose a mechanism for such reversions, validating an explanation for the scattered phylogenetic distribution of dioecy. We removed males from dioecious populations of the wind-pollinated plant Mercurialis annua and allowed natural selection to act on the remaining females that occasionally produced male flowers; such "leaky" sex expression is common in both males and females of dioecious plants.5 Over the course of four generations, females evolved a 23-fold increase in average male flower production. This phenotypic masculinization of females coincided with the evolution of partial self-fertilization, high average seed set in the continued absence of males, and a capacity to sire progeny when males were re-introduced into their populations. Our study thus validates a mechanism for the rapid dissolution of dioecy and the evolution of functional hermaphroditism under conditions that may frequently occur during periods of low population density, repeated colonization, or range expansion.6,7 Our results illustrate the power of natural selection, acting in replicated experimental populations, to bring about transitions in the mating behavior of plants.
Collapse
|
5
|
Bianconi ME, Dunning LT, Curran EV, Hidalgo O, Powell RF, Mian S, Leitch IJ, Lundgren MR, Manzi S, Vorontsova MS, Besnard G, Osborne CP, Olofsson JK, Christin PA. Contrasted histories of organelle and nuclear genomes underlying physiological diversification in a grass species. Proc Biol Sci 2020; 287:20201960. [PMID: 33171085 PMCID: PMC7735283 DOI: 10.1098/rspb.2020.1960] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
C4 photosynthesis evolved multiple times independently in angiosperms, but most origins are relatively old so that the early events linked to photosynthetic diversification are blurred. The grass Alloteropsis semialata is an exception, as this species encompasses C4 and non-C4 populations. Using phylogenomics and population genomics, we infer the history of dispersal and secondary gene flow before, during and after photosynthetic divergence in A. semialata. We further analyse the genome composition of individuals with varied ploidy levels to establish the origins of polyploids in this species. Detailed organelle phylogenies indicate limited seed dispersal within the mountainous region of origin and the emergence of a C4 lineage after dispersal to warmer areas of lower elevation. Nuclear genome analyses highlight repeated secondary gene flow. In particular, the nuclear genome associated with the C4 phenotype was swept into a distantly related maternal lineage probably via unidirectional pollen flow. Multiple intraspecific allopolyploidy events mediated additional secondary genetic exchanges between photosynthetic types. Overall, our results show that limited dispersal and isolation allowed lineage divergence, with photosynthetic innovation happening after migration to new environments, and pollen-mediated gene flow led to the rapid spread of the derived C4 physiology away from its region of origin.
Collapse
Affiliation(s)
- Matheus E Bianconi
- Department of Animal and Plant Sciences, University of Sheffield, Western Bank, Sheffield S10 2TN, UK
| | - Luke T Dunning
- Department of Animal and Plant Sciences, University of Sheffield, Western Bank, Sheffield S10 2TN, UK
| | - Emma V Curran
- Department of Animal and Plant Sciences, University of Sheffield, Western Bank, Sheffield S10 2TN, UK
| | - Oriane Hidalgo
- Comparative Plant and Fungal Biology, Royal Botanic Gardens, Kew, Richmond, Surrey TW9 3AB, UK
| | - Robyn F Powell
- Comparative Plant and Fungal Biology, Royal Botanic Gardens, Kew, Richmond, Surrey TW9 3AB, UK
| | - Sahr Mian
- Comparative Plant and Fungal Biology, Royal Botanic Gardens, Kew, Richmond, Surrey TW9 3AB, UK
| | - Ilia J Leitch
- Comparative Plant and Fungal Biology, Royal Botanic Gardens, Kew, Richmond, Surrey TW9 3AB, UK
| | - Marjorie R Lundgren
- Department of Animal and Plant Sciences, University of Sheffield, Western Bank, Sheffield S10 2TN, UK
| | - Sophie Manzi
- Laboratoire Evolution and Diversité Biologique (EDB UMR5174), Université de Toulouse III - Paul Sabatier, CNRS, IRD, 118 route de Narbonne, 31062 Toulouse, France
| | - Maria S Vorontsova
- Comparative Plant and Fungal Biology, Royal Botanic Gardens, Kew, Richmond, Surrey TW9 3AB, UK
| | - Guillaume Besnard
- Laboratoire Evolution and Diversité Biologique (EDB UMR5174), Université de Toulouse III - Paul Sabatier, CNRS, IRD, 118 route de Narbonne, 31062 Toulouse, France
| | - Colin P Osborne
- Department of Animal and Plant Sciences, University of Sheffield, Western Bank, Sheffield S10 2TN, UK
| | - Jill K Olofsson
- Department of Animal and Plant Sciences, University of Sheffield, Western Bank, Sheffield S10 2TN, UK
| | - Pascal-Antoine Christin
- Department of Animal and Plant Sciences, University of Sheffield, Western Bank, Sheffield S10 2TN, UK
| |
Collapse
|
6
|
Schley RJ, Pennington RT, Pérez-Escobar OA, Helmstetter AJ, de la Estrella M, Larridon I, Sabino Kikuchi IAB, Barraclough TG, Forest F, Klitgård B. Introgression across evolutionary scales suggests reticulation contributes to Amazonian tree diversity. Mol Ecol 2020; 29:4170-4185. [PMID: 32881172 DOI: 10.1111/mec.15616] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2020] [Revised: 08/14/2020] [Accepted: 08/17/2020] [Indexed: 01/03/2023]
Abstract
Hybridization has the potential to generate or homogenize biodiversity and is a particularly common phenomenon in plants, with an estimated 25% of plant species undergoing interspecific gene flow. However, hybridization in Amazonia's megadiverse tree flora was assumed to be extremely rare despite extensive sympatry between closely related species, and its role in diversification remains enigmatic because it has not yet been examined empirically. Using members of a dominant Amazonian tree family (Brownea, Fabaceae) as a model to address this knowledge gap, our study recovered extensive evidence of hybridization among multiple lineages across phylogenetic scales. More specifically, using targeted sequence capture our results uncovered several historical introgression events between Brownea lineages and indicated that gene tree incongruence in Brownea is best explained by reticulation, rather than solely by incomplete lineage sorting. Furthermore, investigation of recent hybridization using ~19,000 ddRAD loci recovered a high degree of shared variation between two Brownea species that co-occur in the Ecuadorian Amazon. Our analyses also showed that these sympatric lineages exhibit homogeneous rates of introgression among loci relative to the genome-wide average, implying a lack of selection against hybrid genotypes and persistent hybridization. Our results demonstrate that gene flow between multiple Amazonian tree species has occurred across temporal scales, and contrasts with the prevailing view of hybridization's rarity in Amazonia. Overall, our results provide novel evidence that reticulate evolution influenced diversification in part of the Amazonian tree flora, which is the most diverse on Earth.
Collapse
Affiliation(s)
- Rowan J Schley
- Royal Botanic Gardens, Kew, Richmond, UK.,Department of Life Sciences, Imperial College London, Ascot, Berkshire, London, UK
| | - R Toby Pennington
- Geography, University of Exeter, Exeter, UK.,Royal Botanic Garden Edinburgh, Edinburgh, UK
| | | | - Andrew J Helmstetter
- Institut de Recherche pour le Développement (IRD), UMR-DIADE, Montpellier, France
| | - Manuel de la Estrella
- Departamento de Botánica, Ecología y Fisiología Vegetal, Facultad de Ciencias, Universidad de Córdoba, Córdoba, Spain
| | - Isabel Larridon
- Royal Botanic Gardens, Kew, Richmond, UK.,Systematic and Evolutionary Botany Lab, Department of Biology, Ghent University, K.L, Gent, Belgium
| | | | - Timothy G Barraclough
- Department of Life Sciences, Imperial College London, Ascot, Berkshire, London, UK.,Department of Zoology, University of Oxford, Oxford, UK
| | | | | |
Collapse
|
7
|
Nishida S, Takakura KI, Naiki A, Nishida T. Habitat partitioning in native Geranium species through reproductive interference. ANNALS OF BOTANY 2020; 125:651-661. [PMID: 31900487 PMCID: PMC7102965 DOI: 10.1093/aob/mcz210] [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: 05/20/2019] [Accepted: 12/30/2019] [Indexed: 06/10/2023]
Abstract
BACKGROUND AND AIMS Heterospecific pollen transfer may reduce the fitness of recipient species, a phenomenon known as reproductive interference. A theoretical study has predicted that distributions of species pairs affected by reproductive interference may be syntopic under negligible reproductive interference, sympatric but with partitioning at small spatial scale (i.e. allotopic) under weak interference, or exclusive when reproductive interference is strong. Verifying these predictions is essential for evaluation of the applicability of reproductive interference as a general assembly rule of biological communities. The aim of this study was to test these predictions in two sympatrically distributed wild Geranium species, G. thunbergii and G. wilfordii. METHODS To measure the effect of reproductive interference, the associations between the relative abundance of the counterpart species and seed set in the focal species, and seed set reduction following mixed pollination, were analysed. The possibility of hybridization with viable offspring was examined by genotyping plants in the field and after mixed pollination. Fertility of putative hybrids was based on their seed set and the proportion of pollen grains with apertural protrusions. A transect study was conducted to examine spatial partitioning, and possible influences of environmental conditions (canopy openness and soil moisture content) on partitioning between the species were analysed. KEY RESULTS Neither abundance of the counterpart species nor heterospecific pollen deposition significantly affected seed set in the focal species, and hybridization between species was almost symmetrical. Putative hybrids had low fertility. The two species were exclusively distributed at small scale, although environmental conditions were not significantly different between them. CONCLUSIONS The allotopy of the two species may be maintained by relatively weak reproductive interference through bidirectional hybridization. Re-evaluation of hybridization may allow ongoing or past reproductive interference to be recognized and provide insight into the distributional relationships between the interacting plants.
Collapse
Affiliation(s)
- Sachiko Nishida
- Nagoya University Museum, Furo-cho, Chikusa-ku, Nagoya, Japan
| | - Koh-Ichi Takakura
- School of Environmental Science, University of Shiga Prefecture, Yasaka-cho, Hikone, Japan
| | - Akiyo Naiki
- Iriomote Station, Tropical Biosphere Research Center, University of the Ryukyus, Taketomi-cho, Yaeyama-gun, Japan
| | - Takayoshi Nishida
- School of Environmental Science, University of Shiga Prefecture, Yasaka-cho, Hikone, Japan
| |
Collapse
|
8
|
Siopa C, Dias MC, Castro M, Loureiro J, Castro S. Is selfing a reproductive assurance promoting polyploid establishment? Reduced fitness, leaky self-incompatibility and lower inbreeding depression in neotetraploids. AMERICAN JOURNAL OF BOTANY 2020; 107:526-538. [PMID: 32144761 DOI: 10.1002/ajb2.1441] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/11/2019] [Accepted: 01/14/2020] [Indexed: 06/10/2023]
Abstract
PREMISE Newly formed polyploids face significant obstacles to persistence and population establishment because of fitness costs of intercytotype mating. Selfing provides the opportunity to escape mate limitation, enabling production of new individuals and increasing the likelihood of fixation of new polyploid lineages. Still, association between self-compatibility and polyploidy is not always clear. We compared self-incompatibility and inbreeding depression in neotetraploids and their diploid progenitor to explore the direct effects of whole genome duplications on self-incompatibility and the implications of ploidy-driven changes for polyploid establishment. METHODS Outcross and self-pollinations were performed in diploids and synthetic neotetraploids of Jasione maritima var. maritima, and reproductive success was measured through fruit and seed production and seed germination. Self- and outcross offspring were grown under controlled conditions, and plant performance was measured through several fitness parameters. RESULTS Neotetraploids showed an overall lower performance than diploids. Reproductive success was negatively affected by selfing in both cytotypes. However, greater variation in the expression of self-incompatibility was observed in neotetraploids; additionally, developmental and physiological parameters were not affected by selfing on neotetraploids, with an overall similar fitness of outcrossed and selfed individuals, resulting in lower inbreeding depression indexes. CONCLUSIONS Neotetraploids might have benefited from selfing at initial stages after their formation. Genome duplications resulted in leaky self-incompatibility, enabling the production of offspring under minority cytotype disadvantage with similar fitness as outcrossed offspring. Our results support theoretical assumptions that selfing might be important for neopolyploid establishment, although changes in self-incompatibility might not be abrupt.
Collapse
Affiliation(s)
- Catarina Siopa
- Centre for Functional Ecology, Department of Life Sciences, University of Coimbra, 3000-456, Coimbra, Portugal
| | - Maria C Dias
- Centre for Functional Ecology, Department of Life Sciences, University of Coimbra, 3000-456, Coimbra, Portugal
| | - Mariana Castro
- Centre for Functional Ecology, Department of Life Sciences, University of Coimbra, 3000-456, Coimbra, Portugal
| | - João Loureiro
- Centre for Functional Ecology, Department of Life Sciences, University of Coimbra, 3000-456, Coimbra, Portugal
| | - Sílvia Castro
- Centre for Functional Ecology, Department of Life Sciences, University of Coimbra, 3000-456, Coimbra, Portugal
| |
Collapse
|
9
|
Hornych O, Ekrt L, Riedel F, Koutecký P, Košnar J. Asymmetric hybridization in Central European populations of the Dryopteris carthusiana group. AMERICAN JOURNAL OF BOTANY 2019; 106:1477-1486. [PMID: 31634425 DOI: 10.1002/ajb2.1369] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/03/2019] [Accepted: 08/30/2019] [Indexed: 06/10/2023]
Abstract
PREMISE Hybridization is a key process in plant speciation. Despite its importance, there is no detailed study of hybridization rates in fern populations. A proper estimate of hybridization rates is needed to understand factors regulating hybridization. METHODS We studied hybridization in the European Dryopteris carthusiana group, represented by one diploid and two tetraploid species and their hybrids. We sampled ~100 individuals per population in 40 mixed populations of the D. carthusiana group across Europe. All plants were identified by measuring genome size (DAPI staining) using flow cytometry. To determine the maternal parentage of hybrids, we sequenced the chloroplast region trnL-trnF of all taxa involved. RESULTS We found hybrids in 85% of populations. Triploid D. ×ambroseae occurred in every population that included both parent species and is most abundant when the parent species are equally abundant. By contrast, tetraploid D. ×deweveri was rare (15 individuals total) and triploid D. ×sarvelae was absent. The parentage of hybrid taxa is asymmetric. Despite expectations from previous studies, tetraploid D. dilatata is the predominant male parent of its triploid hybrid. CONCLUSIONS This is a thorough investigation of hybridization rates in natural populations of ferns. Hybridization rates differ greatly even among closely related fern taxa. In contrast to angiosperms, our data suggest that hybridization rates are highest in balanced parent populations and support the notion that some ferns possess very weak barriers to hybridization. Our results from sequencing cpDNA challenge established notions about the correlation of ploidy level and mating tendencies.
Collapse
Affiliation(s)
- Ondřej Hornych
- Faculty of Science, University of South Bohemia, Branišovská 1760, České Budějovice, CZ-37005, Czech Republic
| | - Libor Ekrt
- Faculty of Science, University of South Bohemia, Branišovská 1760, České Budějovice, CZ-37005, Czech Republic
| | - Felix Riedel
- Botanischer Garten der Universität Potsdam, Maulbeerallee 3, Potsdam, D-14469, Germany
- Arboretum der Humboldt-Universität zu Berlin, Späthstrasse 80/81, Berlin, D-12437, Germany
| | - Petr Koutecký
- Faculty of Science, University of South Bohemia, Branišovská 1760, České Budějovice, CZ-37005, Czech Republic
| | - Jiří Košnar
- Faculty of Science, University of South Bohemia, Branišovská 1760, České Budějovice, CZ-37005, Czech Republic
| |
Collapse
|
10
|
Pickup M, Brandvain Y, Fraïsse C, Yakimowski S, Barton NH, Dixit T, Lexer C, Cereghetti E, Field DL. Mating system variation in hybrid zones: facilitation, barriers and asymmetries to gene flow. THE NEW PHYTOLOGIST 2019; 224:1035-1047. [PMID: 31505037 PMCID: PMC6856794 DOI: 10.1111/nph.16180] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/14/2019] [Accepted: 08/19/2019] [Indexed: 05/11/2023]
Abstract
Plant mating systems play a key role in structuring genetic variation both within and between species. In hybrid zones, the outcomes and dynamics of hybridization are usually interpreted as the balance between gene flow and selection against hybrids. Yet, mating systems can introduce selective forces that alter these expectations; with diverse outcomes for the level and direction of gene flow depending on variation in outcrossing and whether the mating systems of the species pair are the same or divergent. We present a survey of hybridization in 133 species pairs from 41 plant families and examine how patterns of hybridization vary with mating system. We examine if hybrid zone mode, level of gene flow, asymmetries in gene flow and the frequency of reproductive isolating barriers vary in relation to mating system/s of the species pair. We combine these results with a simulation model and examples from the literature to address two general themes: (1) the two-way interaction between introgression and the evolution of reproductive systems, and (2) how mating system can facilitate or restrict interspecific gene flow. We conclude that examining mating system with hybridization provides unique opportunities to understand divergence and the processes underlying reproductive isolation.
Collapse
Affiliation(s)
- Melinda Pickup
- Institute of Science and Technology AustriaAm Campus 1Klosterneuburg3400Austria
| | - Yaniv Brandvain
- Department of Plant and Microbial BiologyUniversity of Minnesota1500 Gortner AveSt Paul, MinneapolisMN55108USA
| | - Christelle Fraïsse
- Institute of Science and Technology AustriaAm Campus 1Klosterneuburg3400Austria
| | - Sarah Yakimowski
- Department of BiologyQueen's University116 Barrie StKingstonONK7L 3N6Canada
| | - Nicholas H. Barton
- Institute of Science and Technology AustriaAm Campus 1Klosterneuburg3400Austria
| | - Tanmay Dixit
- Department of ZoologyUniversity of CambridgeDowning StreetCambridgeCB2 3EJUK
| | - Christian Lexer
- Department of Botany and Biodiversity ResearchFaculty of Life SciencesUniversity of ViennaA‐1030ViennaAustria
| | - Eva Cereghetti
- Institute of Science and Technology AustriaAm Campus 1Klosterneuburg3400Austria
| | - David L. Field
- Department of Botany and Biodiversity ResearchFaculty of Life SciencesUniversity of ViennaA‐1030ViennaAustria
- School of ScienceEdith Cowan University270 Joondalup DriveJoondalupWestern Australia6027Australia
| |
Collapse
|
11
|
Ma WJ, Santos del Blanco L, Pannell JR. A new biological species in the Mercurialis annua polyploid complex: functional divergence in inflorescence morphology and hybrid sterility. ANNALS OF BOTANY 2019; 124:165-178. [PMID: 31098610 PMCID: PMC6676388 DOI: 10.1093/aob/mcz058] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/07/2018] [Accepted: 03/27/2019] [Indexed: 06/09/2023]
Abstract
BACKGROUND AND AIMS Polyploidy has played a major role in the origin of new plant species, probably because of the expansion of polyploid populations in the species' ecological niche, and because reproductive isolation can be established between a new polyploid population and its diploid progenitor species. It is well established that most polyploid species are polyphyletic, with multiple independent origins, and that polyploid genomes may undergo rapid change after their duplication and hybridization associated with their origin. We considered whether multiple independent origins and rapid genomic change might lead to reproductive isolation between polyploid populations of the same ploidy but with potentially different evolutionary histories. METHODS We tested our hypothesis by assessing differences in DNA content and morphology, the evolution of reproductive isolation, and the phylogenetic placement of two broadly sympatric hexaploid lineages of the wind-pollinated annual plant Mercurialis annua hitherto regarded as populations of the same species. KEY RESULTS The two hexaploid lineages of M. annua have slightly divergent DNA content, and distinct inflorescence morphology. They also fall into largely different clades of a chloroplast phylogeny and are reproductively isolated from one another. CONCLUSIONS The distinct evolutionary histories of the two hexaploid lineages of M. annua have contributed to the remarkable reproductive diversity of the species complex. It seems likely that reproductive interference between them will eventually lead to the displacement of one lineage by the other via pollen swamping. Thus, whereas polyploidization can contribute to speciation, diversification might also be compromised by reproductive interference.
Collapse
Affiliation(s)
- Wen-Juan Ma
- Department of Ecology and Evolution, University of Lausanne, Lausanne, Switzerland
| | | | - John R Pannell
- Department of Ecology and Evolution, University of Lausanne, Lausanne, Switzerland
| |
Collapse
|
12
|
Marques I, Loureiro J, Draper D, Castro M, Castro S. How much do we know about the frequency of hybridisation and polyploidy in the Mediterranean region? PLANT BIOLOGY (STUTTGART, GERMANY) 2018; 20 Suppl 1:21-37. [PMID: 28963818 DOI: 10.1111/plb.12639] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/22/2017] [Accepted: 09/25/2017] [Indexed: 06/07/2023]
Abstract
Natural hybridisation and polyploidy are currently recognised as drivers of biodiversity, despite early scepticism about their importance. The Mediterranean region is a biodiversity hotspot where geological and climatic events have created numerous opportunities for speciation through hybridisation and polyploidy. Still, our knowledge on the frequency of these mechanisms in the region is largely limited, despite both phenomena are frequently cited in studies of Mediterranean plants. We reviewed information available from biodiversity and cytogenetic databases to provide the first estimates of hybridisation and polyploidy frequency in the Mediterranean region. We also inspected the most comprehensive modern Mediterranean Flora (Flora iberica) to survey the frequency and taxonomic distribution of hybrids and polyploids in Iberian Peninsula. We found that <6% of Mediterranean plants were hybrids, although a higher frequency was estimated for the Iberian Peninsula (13%). Hybrids were concentrated in few families and in even fewer genera. The overall frequency of polyploidy (36.5%) was comparable with previous estimates in other regions; however our estimates increased when analysing the Iberian Peninsula (48.8%). A surprisingly high incidence of species harbouring two or more ploidy levels was also observed (21.7%). A review of the available literature also showed that the ecological factors driving emergence and establishment of new entities are still poorly studied in the Mediterranean flora, although geographic barriers seem to play a major role in polyploid complexes. Finally, this study reveals several gaps and limitations in our current knowledge about the frequency of hybridisation and polyploidy in the Mediterranean region. The obtained estimates might change in the future with the increasing number of studies; still, rather than setting the complete reality, we hope that this work triggers future studies on hybridisation and polyploidy in the Mediterranean region.
Collapse
Affiliation(s)
- I Marques
- Department of Agricultural and Environmental Sciences, High Polytechnic School of Huesca, University of Zaragoza, Huesca, Spain
| | - J Loureiro
- Centre for Functional Ecology, Department of Life Sciences, University of Coimbra, Coimbra, Portugal
| | - D Draper
- Centro de Ecologia, Evolução e Alterações Ambientais (cE3c), Universidade de Lisboa, Lisbon, Portugal
- UBC Botanical Garden & Centre for Plant Research, and Department of Botany, University of British Columbia, Vancouver, Canada
| | - M Castro
- Centre for Functional Ecology, Department of Life Sciences, University of Coimbra, Coimbra, Portugal
| | - S Castro
- Centre for Functional Ecology, Department of Life Sciences, University of Coimbra, Coimbra, Portugal
- Botanic Garden of the University of Coimbra, Coimbra, Portugal
| |
Collapse
|
13
|
Muñoz-Pajares AJ, Perfectti F, Loureiro J, Abdelaziz M, Biella P, Castro M, Castro S, Gómez JM. Niche differences may explain the geographic distribution of cytotypes in Erysimum mediohispanicum. PLANT BIOLOGY (STUTTGART, GERMANY) 2018; 20 Suppl 1:139-147. [PMID: 28741843 DOI: 10.1111/plb.12605] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/05/2017] [Accepted: 07/18/2017] [Indexed: 05/26/2023]
Abstract
Polyploidisation has played an important role in plant diversification, and variation in ploidy level may be found not only between species of the same genus, but also within a single species. Although establishing the adaptive significance of polyploidy to explain the geographic distribution of cytotypes is challenging, the occurrence of different cytotypes in different ecological niches may suggest an adaptive role of genome duplication. We studied the adaptive significance of the geographic distribution of cytotypes across the entire distribution range of the endemic Erysimum mediohispanicum (Brassicaceae). For that, we have used climate variables, population elevation and soil properties to model ecological niches for the different cytotypes. In addition, we analysed the effect that ploidy level has on the floral phenotype. We found a clear geographic pattern in the distribution of cytotypes, with diploid individuals occurring in the southernmost part of the distribution range, while tetraploids were found in the northern area. A contact (mosaic) zone between both cytotypes was identified, but diploids and tetraploids occur in sympatry in only one population (although in a highly unbalanced proportion). Gene flow between different cytotypes seems to be negligible, as evident from an almost complete absence of triploids and other minority cytotypes. Niches occupied by both cytotypes showed subtle, but significant differences, even in the contact zone. Precipitation was higher in regions occupied by tetraploid individuals, which present wider corolla tubes and thinner but taller stalks than diploids. Our findings highlight the potential role of polyploidy in the ecological adaptation of E. mediohispanicum to both abiotic factors and biotic interactions.
Collapse
Affiliation(s)
- A J Muñoz-Pajares
- Plant Biology, CIBIO/InBio, Centro de Investigação em Biodiversidade e Recursos Genéticos, Laboratório Associado, Universidade do Porto, Vairão, Portugal
- Departamento de Genetica, Universidad de Granada, Granada, Spain
| | - F Perfectti
- Departamento de Genetica, Universidad de Granada, Granada, Spain
| | - J Loureiro
- Centre for Functional Ecology, Department of Life Sciences, University of Coimbra, Coimbra, Portugal
| | - M Abdelaziz
- Departamento de Genetica, Universidad de Granada, Granada, Spain
| | - P Biella
- Departamento de Ecologıa, Universidad de Granada, Granada, Spain
- Department of Zoology, Faculty of Science, University of South Bohemia, České Budějovice, Czech Republic
- Institute of Entomology, Biology Centre of the Academy of Sciences of the Czech Republic, České Budějovice, Czech Republic
| | - M Castro
- Centre for Functional Ecology, Department of Life Sciences, University of Coimbra, Coimbra, Portugal
| | - S Castro
- Centre for Functional Ecology, Department of Life Sciences, University of Coimbra, Coimbra, Portugal
| | - J M Gómez
- Departamento de Ecologıa, Universidad de Granada, Granada, Spain
- Estación Experimental de Zonas Aridas (EEZA-CSIC), Almería, Spain
| |
Collapse
|
14
|
Wielstra B, Burke T, Butlin RK, Arntzen JW. A signature of dynamic biogeography: enclaves indicate past species replacement. Proc Biol Sci 2017; 284:20172014. [PMID: 29187631 PMCID: PMC5740283 DOI: 10.1098/rspb.2017.2014] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2017] [Accepted: 10/30/2017] [Indexed: 11/12/2022] Open
Abstract
Understanding how species have replaced each other in the past is important to predicting future species turnover. While past species replacement is difficult to detect after the fact, the process may be inferred from present-day distribution patterns. Species with abutting ranges sometimes show a characteristic distribution pattern, where a section of one species range is enveloped by that of the other. Such an enclave could indicate past species replacement: when a species is partly supplanted by a competitor, but a population endures locally while the invading species moves around and past it, an enclave forms. If the two species hybridize and backcross, the receding species is predicted to leave genetic traces within the expanding one under a scenario of species replacement. By screening dozens of genes in hybridizing crested newts, we uncover genetic remnants of the ancestral species, now inhabiting an enclave, in the range of the surrounding invading species. This independent genetic evidence supports the past distribution dynamics we predicted from the enclave. We suggest that enclaves provide a valuable tool in understanding historical species replacement, which is important because a major conservation concern arising from anthropogenic climate change is increased species replacement in the future.
Collapse
Affiliation(s)
- B Wielstra
- Department of Animal and Plant Sciences, University of Sheffield, Sheffield S10 2TN, UK
- Department of Ecology and Evolutionary Biology, University of California, Los Angeles, CA 90095, USA
- Naturalis Biodiversity Center, PO Box 9517, Leiden, 2300 RA, The Netherlands
| | - T Burke
- Department of Animal and Plant Sciences, University of Sheffield, Sheffield S10 2TN, UK
| | - R K Butlin
- Department of Animal and Plant Sciences, University of Sheffield, Sheffield S10 2TN, UK
- Department of Marine Sciences, University of Gothenburg, Gothenburg 405 30, Sweden
| | - J W Arntzen
- Naturalis Biodiversity Center, PO Box 9517, Leiden, 2300 RA, The Netherlands
| |
Collapse
|
15
|
Dormontt EE, Prentis PJ, Gardner MG, Lowe AJ. Occasional hybridization between a native and invasive Senecio species in Australia is unlikely to contribute to invasive success. PeerJ 2017; 5:e3630. [PMID: 28828245 PMCID: PMC5562138 DOI: 10.7717/peerj.3630] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2017] [Accepted: 07/11/2017] [Indexed: 11/29/2022] Open
Abstract
Background Hybridization between native and invasive species can facilitate introgression of native genes that increase invasive potential by providing exotic species with pre-adapted genes suitable for new environments. In this study we assessed the outcome of hybridization between native Senecio pinnatifolius var. pinnatifolius A.Rich. (dune ecotype) and invasive Senecio madagascariensis Poir. to investigate the potential for introgression of adaptive genes to have facilitated S. madagascariensis spread in Australia. Methods We used amplified fragment length polymorphisms (141 loci) and nuclear microsatellites (2 loci) to genotype a total of 118 adults and 223 seeds from S. pinnatifolius var.pinnatifolius and S. madagascariensis at one allopatric and two shared sites. We used model based clustering and assignment methods to establish whether hybrid seed set and mature hybrids occur in the field. Results We detected no adult hybrids in any population. Low incidence of hybrid seed set was found at Lennox Head where the contact zone overlapped for 20 m (6% and 22% of total seeds sampled for S. pinnatifolius var. pinnatifolius and S. madagascariensis respectively). One hybrid seed was detected at Ballina where a gap of approximately 150 m was present between species (2% of total seeds sampled for S. madagascariensis). Conclusions We found no evidence of adult hybrid plants at two shared sites. Hybrid seed set from both species was identified at low levels. Based on these findings we conclude that introgression of adaptive genes from S. pinnatifolius var. pinnatifolius is unlikely to have facilitated S. madagascariensis invasions in Australia. Revisitation of one site after two years could find no remaining S. pinnatifolius var. pinnatifolius, suggesting that contact zones between these species are dynamic and that S. pinnatifolius var. pinnatifolius may be at risk of displacement by S. madagascariensis in coastal areas.
Collapse
Affiliation(s)
- Eleanor E Dormontt
- The Environment Institute, School of Biological Sciences, University of Adelaide, Adelaide, South Australia, Australia
| | - Peter J Prentis
- Institute for Future Environments, School of Earth, Environmental and Biological Sciences, Queensland University of Technology, Brisbane, Queensland, Australia
| | - Michael G Gardner
- School of Biological Sciences, Flinders University of South Australia, Adelaide, South Australia, Australia
| | - Andrew J Lowe
- The Environment Institute, School of Biological Sciences, University of Adelaide, Adelaide, South Australia, Australia
| |
Collapse
|
16
|
Čertner M, Fenclová E, Kúr P, Kolář F, Koutecký P, Krahulcová A, Suda J. Evolutionary dynamics of mixed-ploidy populations in an annual herb: dispersal, local persistence and recurrent origins of polyploids. ANNALS OF BOTANY 2017; 120:303-315. [PMID: 28398545 PMCID: PMC5737363 DOI: 10.1093/aob/mcx032] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/21/2016] [Accepted: 03/08/2017] [Indexed: 05/18/2023]
Abstract
Background and Aims Despite the recent wealth of studies targeted at contact zones of cytotypes in various species, some aspects of polyploid evolution are still poorly understood. This is especially the case for the frequency and success rate of spontaneous neopolyploidization or the temporal dynamics of ploidy coexistence, requiring massive ploidy screening and repeated observations, respectively. To fill this gap, an extensive study of spatio-temporal patterns of ploidy coexistence was initiated in the widespread annual weed Tripleurospermum inodorum (Asteraceae). Methods DNA flow cytometry along with confirmatory chromosome counts was employed to assess ploidy levels of 11 018 adult individuals and 1263 ex situ germinated seedlings from 1209 Central European populations. The ploidy screening was conducted across three spatial scales and supplemented with observations of temporal development of 37 mixed-ploidy populations. Key Results The contact zone between the diploid and tetraploid cytotypes has a diffuse, mosaic-like structure enabling common cytotype coexistence from the within-population to the landscape level. A marked difference in monoploid genome size between the two cytotypes enabled the easy distinction of neotetraploid mutants from long-established tetraploids. Neotetraploids were extremely rare (0·03 %) and occurred solitarily. Altogether five ploidy levels (2 x -6 x ) and several aneuploids were discovered; the diversity in nuclear DNA content was highest in early ontogenetic stages (seedlings) and among individuals from mixed-ploidy populations. In spite of profound temporal oscillations in cytotype frequencies in mixed-ploidy populations, both diploids and tetraploids usually persisted up to the last census. Conclusions Diploids and tetraploids commonly coexist at all spatial scales and exhibit considerable temporal stability in local ploidy mixtures. Mixed-ploidy populations containing fertile triploid hybrids probaby act as effective generators of cytogenetic novelty and may facilitate inter-ploidy gene flow. Neopolyploid mutants were incapable of local establishment.
Collapse
Affiliation(s)
- Martin Čertner
- Department of Botany, Faculty of Science, Charles University, Benátská 2, CZ-128 00 Prague, Czech Republic
- Institute of Botany, The Czech Academy of Sciences, Zámek 1, CZ-252 43 Průhonice, Czech Republic
| | - Eliška Fenclová
- Department of Botany, Faculty of Science, Charles University, Benátská 2, CZ-128 00 Prague, Czech Republic
| | - Pavel Kúr
- Department of Botany, Faculty of Science, Charles University, Benátská 2, CZ-128 00 Prague, Czech Republic
- Department of Botany, Faculty of Science, University of South Bohemia, Branišovská 1760, CZ-370 05 České Budějovice, Czech Republic
| | - Filip Kolář
- Department of Botany, Faculty of Science, Charles University, Benátská 2, CZ-128 00 Prague, Czech Republic
- Institute of Botany, The Czech Academy of Sciences, Zámek 1, CZ-252 43 Průhonice, Czech Republic
- National Centre for Biosystematics, Natural History Museum, University of Oslo, NO-0318 Oslo, Norway
| | - Petr Koutecký
- Department of Botany, Faculty of Science, University of South Bohemia, Branišovská 1760, CZ-370 05 České Budějovice, Czech Republic
| | - Anna Krahulcová
- Institute of Botany, The Czech Academy of Sciences, Zámek 1, CZ-252 43 Průhonice, Czech Republic
| | - Jan Suda
- Department of Botany, Faculty of Science, Charles University, Benátská 2, CZ-128 00 Prague, Czech Republic
- Institute of Botany, The Czech Academy of Sciences, Zámek 1, CZ-252 43 Průhonice, Czech Republic
| |
Collapse
|
17
|
Rostgaard Nielsen L, Brandes U, Dahl Kjaer E, Fjellheim S. Introduced Scotch broom (Cytisus scoparius) invades the genome of native populations in vulnerable heathland habitats. Mol Ecol 2016; 25:2790-804. [DOI: 10.1111/mec.13666] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2015] [Revised: 03/21/2016] [Accepted: 04/12/2016] [Indexed: 11/27/2022]
Affiliation(s)
- Lene Rostgaard Nielsen
- Department of Geosciences and Natural Resource Management; University of Copenhagen; Rolighedsvej 23 Frederiksberg C 1958 Denmark
| | - Ursula Brandes
- Department of Plant Sciences; Norwegian University of Life Sciences; Ås NO-1432 Norway
| | - Erik Dahl Kjaer
- Department of Geosciences and Natural Resource Management; University of Copenhagen; Rolighedsvej 23 Frederiksberg C 1958 Denmark
| | - Siri Fjellheim
- Department of Plant Sciences; Norwegian University of Life Sciences; Ås NO-1432 Norway
| |
Collapse
|
18
|
Glotzbecker GJ, Walters DM, Blum MJ. Rapid movement and instability of an invasive hybrid swarm. Evol Appl 2016; 9:741-55. [PMID: 27330551 PMCID: PMC4908461 DOI: 10.1111/eva.12371] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2015] [Accepted: 02/08/2016] [Indexed: 12/15/2022] Open
Abstract
Unstable hybrid swarms that arise following the introduction of non‐native species can overwhelm native congeners, yet the stability of invasive hybrid swarms has not been well documented over time. Here, we examine genetic variation and clinal stability across a recently formed hybrid swarm involving native blacktail shiner (Cyprinella venusta) and non‐native red shiner (C. lutrensis) in the Upper Coosa River basin, which is widely considered to be a global hot spot of aquatic biodiversity. Examination of phenotypic, multilocus genotypic, and mitochondrial haplotype variability between 2005 and 2011 revealed that the proportion of hybrids has increased over time, with more than a third of all sampled individuals exhibiting admixture in the final year of sampling. Comparisons of clines over time indicated that the hybrid swarm has been rapidly progressing upstream, but at a declining and slower pace than rates estimated from historical collection records. Clinal comparisons also showed that the hybrid swarm has been expanding and contracting over time. Additionally, we documented the presence of red shiner and hybrids farther downstream than prior studies have detected, which suggests that congeners in the Coosa River basin, including all remaining populations of the threatened blue shiner (Cyprinella caerulea), are at greater risk than previously thought.
Collapse
Affiliation(s)
| | - David M Walters
- U.S. Geological Survey Fort Collins Science Center Fort Collins CO USA
| | - Michael J Blum
- Department of Ecology and Evolutionary BiologyTulane UniversityNew OrleansLAUSA; Tulane - Xavier Center for Bioenvironmental ResearchTulane UniversityNew OrleansLAUSA
| |
Collapse
|
19
|
Genetic characterization of hybridization between native and invasive bittersweet vines (Celastrus spp.). Biol Invasions 2015. [DOI: 10.1007/s10530-015-0926-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
|
20
|
Cinget B, de Lafontaine G, Gérardi S, Bousquet J. Integrating phylogeography and paleoecology to investigate the origin and dynamics of hybrid zones: insights from two widespread North American firs. Mol Ecol 2015; 24:2856-70. [DOI: 10.1111/mec.13194] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2014] [Revised: 04/02/2015] [Accepted: 04/08/2015] [Indexed: 12/20/2022]
Affiliation(s)
- Benjamin Cinget
- Canada Research Chair in Forest and Environmental Genomics; Centre for Forest Research and Institute for Systems and Integrative Biology; Université Laval; 1030 Avenue de la Médecine Québec QC Canada G1V0A6
| | - Guillaume de Lafontaine
- Canada Research Chair in Forest and Environmental Genomics; Centre for Forest Research and Institute for Systems and Integrative Biology; Université Laval; 1030 Avenue de la Médecine Québec QC Canada G1V0A6
| | - Sébastien Gérardi
- Canada Research Chair in Forest and Environmental Genomics; Centre for Forest Research and Institute for Systems and Integrative Biology; Université Laval; 1030 Avenue de la Médecine Québec QC Canada G1V0A6
| | - Jean Bousquet
- Canada Research Chair in Forest and Environmental Genomics; Centre for Forest Research and Institute for Systems and Integrative Biology; Université Laval; 1030 Avenue de la Médecine Québec QC Canada G1V0A6
| |
Collapse
|
21
|
Balao F, Casimiro-Soriguer R, García-Castaño JL, Terrab A, Talavera S. Big thistle eats the little thistle: does unidirectional introgressive hybridization endanger the conservation of Onopordum hinojense? THE NEW PHYTOLOGIST 2015; 206:448-458. [PMID: 25401776 DOI: 10.1111/nph.13156] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/09/2014] [Accepted: 09/28/2014] [Indexed: 06/04/2023]
Abstract
Hybridization is known to have a creative role in plant evolution. However, it can also have negative effects on parental species. Onopordum is a large genus whose species frequently hybridize. In the Southwest Iberian Peninsula, the rare O. hinojense co-occurs with the widely distributed O. nervosum, and hybrids between these two taxa have been described as O. × onubense. In this study we determine the extinction risk in a hybrid zone, both for hybrids and parentals, using analyses of morphological and cytogenetic traits as well as genetic markers and demographic models. To investigate the introgression process we used amplified fragment length polymorphism (AFLP) markers, Bayesian analyses and genome scan methods. Morphology, genome size and molecular markers confirmed homoploid hybridization and also indicated unidirectional backcrossing of F₁ hybrids with O. nervosum, which is likely to swamp O. hinojense, the parental with lower pollen size and a very low fruit set (8%). Genome scan methods revealed several loci significantly deviating from neutrality. Finally, our demographic modeling indicated that the higher fitness of O. nervosum threats the survival of O. hinojense by demographic swamping. Our study provides strong new evidence for a scenario of rapid extinction by unidirectional introgression and demographic swamping. The multifaceted approach used here sheds new light on the role of introgression in plant extinctions.
Collapse
Affiliation(s)
- Francisco Balao
- Departamento de Biología Vegetal y Ecología, Facultad de Biología, Universidad de Sevilla, Apdo. 1095, 41080, Sevilla, Spain
- Department of Systematic and Evolutionary Botany, University of Vienna, Rennweg 14, 1030, Austria
| | - Ramón Casimiro-Soriguer
- Departamento de Biología Vegetal y Ecología, Facultad de Biología, Universidad de Sevilla, Apdo. 1095, 41080, Sevilla, Spain
- Departmento de Biología, CASEM, Universidad de Cádiz, Campus Río San Pedro, E-11510, Puerto Real, Spain
| | - Juan Luis García-Castaño
- Departamento de Biología Vegetal y Ecología, Facultad de Biología, Universidad de Sevilla, Apdo. 1095, 41080, Sevilla, Spain
| | - Anass Terrab
- Departamento de Biología Vegetal y Ecología, Facultad de Biología, Universidad de Sevilla, Apdo. 1095, 41080, Sevilla, Spain
- Department of Systematic and Evolutionary Botany, University of Vienna, Rennweg 14, 1030, Austria
| | - Salvador Talavera
- Departamento de Biología Vegetal y Ecología, Facultad de Biología, Universidad de Sevilla, Apdo. 1095, 41080, Sevilla, Spain
| |
Collapse
|
22
|
Russell JRW, Pannell JR. Sex determination in dioecious Mercurialis annua and its close diploid and polyploid relatives. Heredity (Edinb) 2015; 114:262-71. [PMID: 25335556 PMCID: PMC4815579 DOI: 10.1038/hdy.2014.95] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2014] [Revised: 08/04/2014] [Accepted: 08/11/2014] [Indexed: 11/09/2022] Open
Abstract
Separate sexes have evolved on numerous independent occasions from hermaphroditic ancestors in flowering plants. The mechanisms of sex determination is known for only a handful of such species, but, in those that have been investigated, it usually involves alleles segregating at a single locus, sometimes on heteromorphic sex chromosomes. In the genus Mercurialis, transitions between combined (hermaphroditism) and separate sexes (dioecy or androdioecy, where males co-occur with hermaphrodites rather than females) have occurred more than once in association with hybridisation and shifts in ploidy. Previous work has pointed to an unusual 3-locus system of sex determination in dioecious populations. Here, we use crosses and genotyping for a sex-linked marker to reject this model: sex in diploid dioecious M. annua is determined at a single locus with a dominant male-determining allele (an XY system). We also crossed individuals among lineages of Mercurialis that differ in their ploidy and sexual system to ascertain the extent to which the same sex-determination system has been conserved following genome duplication, hybridisation and transitions between dioecy and hermaphroditism. Our results indicate that the male-determining element is fully capable of determining gender in the progeny of hybrids between different lineages. Specifically, males crossed with females or hermaphrodites always generate 1:1 male:female or male:hermaphrodite sex ratios, respectively, regardless of the ploidy levels involved (diploid, tetraploid or hexaploid). Our results throw further light on the genetics of the remarkable variation in sexual systems in the genus Mercurialis. They also illustrate the almost identical expression of sex-determining alleles in terms of sexual phenotypes across multiple divergent backgrounds, including those that have lost separate sexes altogether.
Collapse
Affiliation(s)
- J R W Russell
- Department of Plant Sciences, University of Oxford, Oxford, UK
| | - J R Pannell
- Department of Ecology and Evolution, University of Lausanne, Biophore Building, Lausanne, Switzerland
| |
Collapse
|
23
|
Wang N, Borrell JS, Bodles WJA, Kuttapitiya A, Nichols RA, Buggs RJA. Molecular footprints of the Holocene retreat of dwarf birch in Britain. Mol Ecol 2014; 23:2771-82. [PMID: 24762172 PMCID: PMC4237149 DOI: 10.1111/mec.12768] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2014] [Revised: 04/19/2014] [Accepted: 04/21/2014] [Indexed: 01/17/2023]
Abstract
Past reproductive interactions among incompletely isolated species may leave behind a trail of introgressed alleles, shedding light on historical range movements. Betula pubescens is a widespread native tetraploid tree species in Britain, occupying habitats intermediate to those of its native diploid relatives, B. pendula and B. nana. Genotyping 1134 trees from the three species at 12 microsatellite loci, we found evidence of introgression from both diploid species into B. pubescens, despite the ploidy difference. Surprisingly, introgression from B. nana, a dwarf species whose present range is highly restricted in northern, high-altitude peat bogs, was greater than introgression from B. pendula, which is morphologically similar to B. pubescens and has a substantially overlapping range. A cline of introgression from B. nana was found extending into B. pubescens populations far to the south of the current B. nana range. We suggest that this genetic pattern is a footprint of a historical decline and/or northwards shift in the range of B. nana populations due to climate warming in the Holocene. This is consistent with pollen records that show a broader, more southerly distribution of B. nana in the past. Ecological niche modelling predicts that B. nana is adapted to a larger range than it currently occupies, suggesting additional factors such as grazing and hybridization may have exacerbated its decline. We found very little introgression between B. nana and B. pendula, despite both being diploid, perhaps because their distributions in the past have rarely overlapped. Future conservation of B. nana may partly depend on minimization of hybridization with B. pubescens, and avoidance of planting B. pendula near B. nana populations.
Collapse
Affiliation(s)
- Nian Wang
- School of Biological and Chemical Sciences, Queen Mary University of London, London, E1 4NS, UK
| | | | | | | | | | | |
Collapse
|
24
|
Pannell JR, Eppley SM, Dorken ME, Berjano R. Regional variation in sex ratios and sex allocation in androdioecious Mercurialis annua. J Evol Biol 2014; 27:1467-77. [PMID: 24618014 DOI: 10.1111/jeb.12352] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2013] [Revised: 02/03/2014] [Accepted: 02/03/2014] [Indexed: 11/29/2022]
Abstract
In androdioecious metapopulations, where males co-occur with hermaphrodites, the absence of males from certain populations or regions may be explained by locally high selfing rates, high hermaphrodite outcross siring success (e.g. due to high pollen production by hermaphrodites), or to stochastic processes (e.g. the failure of males to invade populations or regions following colonization or range expansion by hermaphrodites). In the Iberian Peninsula and Morocco, the presence of males with hermaphrodites in the wind-pollinated androdioecious plant Mercurialis annua (Euphorbiaceae) varies both among populations within relatively small regions and among regions, with some regions lacking males from all populations. The species is known to have expanded its range into the Iberian Peninsula from a southern refugium. To account for variation in male presence in M. annua, we test the following hypotheses: (1) that males are absent in areas where plant densities are lower, because selfing rates should be correspondingly higher; (2) that males are absent in areas where hermaphrodites produce more pollen; and (3) that males are absent in areas where there is an elevated proportion of populations in which plant density and hermaphrodite pollen production disfavour their invasion. We found support for predictions two and three in Morocco (the putative Pleistocene refugium for M. annua) but no support for any hypothesis in Iberia (the expanded range). Our results are partially consistent with a hypothesis of sex-allocation equilibrium for populations in Morocco; in Iberia, the absence of males from large geographical regions is more consistent with a model of sex-ratio evolution in a metapopulation with recurrent population turnover. Our study points to the role of both frequency-dependent selection and contingencies imposed by colonization during range expansions and in metapopulations.
Collapse
Affiliation(s)
- J R Pannell
- Department of Ecology and Evolution, University of Lausanne, Lausanne, Switzerland
| | | | | | | |
Collapse
|
25
|
Weller SG, Sakai AK, Culley TM, Duong L, Danielson RE. Segregation of male-sterility alleles across a species boundary. J Evol Biol 2014; 27:429-36. [PMID: 24417506 DOI: 10.1111/jeb.12312] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2013] [Accepted: 11/26/2013] [Indexed: 11/29/2022]
Abstract
Hybrid zones may serve as bridges permitting gene flow between species, including alleles influencing the evolution of breeding systems. Using greenhouse crosses, we assessed the likelihood that a hybrid zone could serve as a conduit for transfer of nuclear male-sterility alleles between a gynodioecious species and a hermaphroditic species with very rare females in some populations. Segregation patterns in progeny of crosses between rare females of hermaphroditic Schiedea menziesii and hermaphroditic plants of gynodioecious Schiedea salicaria heterozygous at the male-sterility locus, and between female S. salicaria and hermaphroditic plants from the hybrid zone, were used to determine whether male-sterility was controlled at the same locus in the parental species and the hybrid zone. Segregations of females and hermaphrodites in approximately equal ratios from many of the crosses indicate that the same nuclear male-sterility allele occurs in the parent species and the hybrid zone. These rare male-sterility alleles in S. menziesii may result from gene flow from S. salicaria through the hybrid zone, presumably facilitated by wind pollination in S. salicaria. Alternatively, rare male-sterility alleles might result from a reversal from gynodioecy to hermaphroditism in S. menziesii, or possibly de novo evolution of male sterility. Phylogenetic analysis indicates that some species of Schiedea have probably evolved separate sexes independently, but not in the lineage containing S. salicaria and S. menziesii. High levels of selfing and expression of strong inbreeding depression in S. menziesii, which together should favour females in populations, argue against a reversal from gynodioecy to hermaphroditism in S. menziesii.
Collapse
Affiliation(s)
- S G Weller
- Department of Ecology and Evolutionary Biology, University of California Irvine, Irvine, CA, USA
| | | | | | | | | |
Collapse
|
26
|
Sonnleitner M, Weis B, Flatscher R, García PE, Suda J, Krejčíková J, Schneeweiss GM, Winkler M, Schönswetter P, Hülber K. Parental ploidy strongly affects offspring fitness in heteroploid crosses among three cytotypes of autopolyploid Jacobaea carniolica (Asteraceae). PLoS One 2013; 8:e78959. [PMID: 24265735 PMCID: PMC3827125 DOI: 10.1371/journal.pone.0078959] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2013] [Accepted: 09/17/2013] [Indexed: 11/25/2022] Open
Abstract
Reproductive interactions among cytotypes in their contact zones determine whether these cytotypes can co-exist and form stable contact zones or not. In autopolyploids, heteroploid cross-compatibilities might depend on parental ploidy, but tests of this hypothesis in autopolyploid systems with more than two ploidies are lacking. Here, we study Jacobaea carniolica, which comprises diploid, tetraploid, and hexaploid individuals regularly forming contact zones. Seeds obtained from in situ cross-pollinations within and among cytotypes were subjected to DNA flow cytometry and greenhouse germination experiments. Hybrid fitness and parental effects on hybrid fitness were tested with regression models comparing fitness parameters of early life stages. Irrespective of the direction of crosses, seed viability and seedling survival in diploid-polyploid crosses were substantially lower than in tetraploid-hexaploid crosses. In contrast, seedling growth traits indicated neither transgressive character expression nor any selection against hybrid offspring. Congruent with a model of genome dosage effects, these traits differed between reciprocal crosses, especially of diploids and tetraploids, where trait values resembled those of the maternal parent. The strong effect of parental ploidy on offspring fitness in heteroploid crosses may cause contact zones involving exclusively polyploid cytotypes to be less stable over longer terms than those involving diploids and polyploids.
Collapse
Affiliation(s)
- Michaela Sonnleitner
- Department of Systematic and Evolutionary Botany, University of Vienna, Vienna, Austria
- Department of Conservation Biology, Vegetation Ecology and Landscape Ecology, University of Vienna, Vienna, Austria
| | - Birgit Weis
- Department of Systematic and Evolutionary Botany, University of Vienna, Vienna, Austria
| | - Ruth Flatscher
- Department of Systematic and Evolutionary Botany, University of Vienna, Vienna, Austria
- Institute of Botany, University of Innsbruck, Innsbruck, Austria
| | - Pedro Escobar García
- Department of Systematic and Evolutionary Botany, University of Vienna, Vienna, Austria
| | - Jan Suda
- Department of Botany, Faculty of Science, Charles University, Prague, Czech Republic
- Institute of Botany, Academy of Sciences of the Czech Republic, Průhonice, Czech Republic
| | - Jana Krejčíková
- Department of Botany, Faculty of Science, Charles University, Prague, Czech Republic
- Institute of Botany, Academy of Sciences of the Czech Republic, Průhonice, Czech Republic
| | - Gerald M. Schneeweiss
- Department of Systematic and Evolutionary Botany, University of Vienna, Vienna, Austria
| | - Manuela Winkler
- Department of Systematic and Evolutionary Botany, University of Vienna, Vienna, Austria
| | | | - Karl Hülber
- Department of Conservation Biology, Vegetation Ecology and Landscape Ecology, University of Vienna, Vienna, Austria
- Vienna Institute for Nature Conservation & Analyses, Vienna, Austria
| |
Collapse
|
27
|
Roy JS, O’Connor D, Green DM. Oscillation of an anuran hybrid zone: morphological evidence spanning 50 years. PLoS One 2013; 7:e52819. [PMID: 23300785 PMCID: PMC3530495 DOI: 10.1371/journal.pone.0052819] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2012] [Accepted: 11/23/2012] [Indexed: 11/19/2022] Open
Abstract
Background The hybrid zone between the primarily forest-dwelling American toad, Anaxyrus americanus, and the prairie-adapted Canadian toad, A. hemiophrys, in southeastern Manitoba is known to have shifted its position during the past 50 years. Hybrid zones are areas of interbreeding between species and their movement across a landscape should reflect their underlying dynamics and environmental change. However, empirical demonstrations of hybrid zone movements over long periods of time are rare. This hybrid zone is dominated by individuals of intermediate morphology and genetic composition. We sought to determine if it had continued to move and if that movement was associated with shifts in habitat, as predicted. Methodology/Principle Findings We used variation in the toads’ most diagnostic morphological feature, the separation between their interorbital cranial crests, to determine the geographic position of the hybrid zone center at four times between 1960 and 2009 using maximum likelihood methods. The hybrid zone center moved west by 38 km over 19 years and then east again by 10 km over the succeeding 29 years. The position of the hybrid zone did not track either the direction or the magnitude of movement of the forest-prairie habitat transition over the same time period. Conclusions/Significance This is the first reported evidence of oscillation in the position of a hybrid zone. The back and forth movement indicates that neither species maintains a selective advantage over the other in the long term. However, the movement of the hybrid zone was not bounded by the breadth of the habitat transition. Its oscillation suggests that the hybrid zone is better described as being elastically tethered to the habitat transition.
Collapse
Affiliation(s)
| | - David O’Connor
- Redpath Museum, McGill University, Montréal, Québec, Canada
| | - David M. Green
- Redpath Museum, McGill University, Montréal, Québec, Canada
- * E-mail:
| |
Collapse
|
28
|
Genome sequence of dwarf birch (Betula nana) and cross-species RAD markers. Mol Ecol 2012; 22:3098-111. [DOI: 10.1111/mec.12131] [Citation(s) in RCA: 113] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2012] [Revised: 10/12/2012] [Accepted: 10/17/2012] [Indexed: 12/17/2022]
|
29
|
Manzaneda AJ, Rey PJ, Bastida JM, Weiss-Lehman C, Raskin E, Mitchell-Olds T. Environmental aridity is associated with cytotype segregation and polyploidy occurrence in Brachypodium distachyon (Poaceae). THE NEW PHYTOLOGIST 2012; 193:797-805. [PMID: 22150799 PMCID: PMC3257369 DOI: 10.1111/j.1469-8137.2011.03988.x] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
• The ecological and adaptive significance of plant polyploidization is not well understood and no clear pattern of association between polyploid frequency and environment has emerged. Climatic factors are expected to predict cytotype distribution. However, the relationship among climate, cytotype distribution and variation of abiotic stress tolerance traits has rarely been examined. • Here, we use flow cytometry and root-tip squashes to examine the cytotype distribution in the temperate annual grass Brachypodium distachyon in 57 natural populations distributed across an aridity gradient in the Iberian Peninsula. We further investigate the link between environmental aridity, ploidy, and variation of drought tolerance and drought avoidance (flowering time) traits. • Distribution of diploids (2n = 10) and allotetraploids (2n = 30) in this species is geographically structured throughout its range in the Iberian Peninsula, and is associated with aridity gradients. Importantly, after controlling for geographic and altitudinal effects, the link between aridity and polyploidization occurrence persisted. Water-use efficiency varied between ploidy levels, with tetraploids being more efficient in the use of water than diploids under water-restricted growing conditions. • Our results indicate that aridity is an important predictor of polyploid occurrence in B. distachyon, suggesting a possible adaptive origin of the cytotype segregation.
Collapse
Affiliation(s)
- Antonio J. Manzaneda
- Departamento Biología Animal, Biología Vegetal y Ecología, Universidad de Jaén, Paraje las Lagunillas s/n, 23071, Jaén, Spain
- Institute for Genome Sciences and Policy, Department of Biology, Duke University, PO Box 90338, Durham, North Carolina 27708, USA
| | - Pedro J. Rey
- Departamento Biología Animal, Biología Vegetal y Ecología, Universidad de Jaén, Paraje las Lagunillas s/n, 23071, Jaén, Spain
| | - Jesús M. Bastida
- Departamento Biología Animal, Biología Vegetal y Ecología, Universidad de Jaén, Paraje las Lagunillas s/n, 23071, Jaén, Spain
| | - Christopher Weiss-Lehman
- Institute for Genome Sciences and Policy, Department of Biology, Duke University, PO Box 90338, Durham, North Carolina 27708, USA
| | - Evan Raskin
- Institute for Genome Sciences and Policy, Department of Biology, Duke University, PO Box 90338, Durham, North Carolina 27708, USA
| | - Thomas Mitchell-Olds
- Institute for Genome Sciences and Policy, Department of Biology, Duke University, PO Box 90338, Durham, North Carolina 27708, USA
| |
Collapse
|
30
|
Govindarajulu R, Hughes CE, Alexander PJ, Bailey CD. The complex evolutionary dynamics of ancient and recent polyploidy in Leucaena (Leguminosae; Mimosoideae). AMERICAN JOURNAL OF BOTANY 2011; 98:2064-76. [PMID: 22130273 DOI: 10.3732/ajb.1100260] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
PREMISE OF THE STUDY The evolutionary history of Leucaena has been impacted by polyploidy, hybridization, and divergent allopatric species diversification, suggesting that this is an ideal group to investigate the evolutionary tempo of polyploidy and the complexities of reticulation and divergence in plant diversification. METHODS Parsimony- and ML-based phylogenetic approaches were applied to 105 accessions sequenced for six sequence characterized amplified region-based nuclear encoded loci, nrDNA ITS, and four cpDNA regions. Hypotheses for the origin of tetraploid species were inferred using results derived from a novel species tree and established gene tree methods and from data on genome sizes and geographic distributions. RESULTS The combination of comprehensively sampled multilocus DNA sequence data sets and a novel methodology provide strong resolution and support for the origins of all five tetraploid species. A minimum of four allopolyploidization events are required to explain the origins of these species. The origin(s) of one tetraploid pair (L. involucrata/L. pallida) can be equally explained by two unique allopolyploidizations or a single event followed by divergent speciation. CONCLUSIONS Alongside other recent findings, a comprehensive picture of the complex evolutionary dynamics of polyploidy in Leucaena is emerging that includes paleotetraploidization, diploidization of the last common ancestor to Leucaena, allopatric divergence among diploids, and recent allopolyploid origins for tetraploid species likely associated with human translocation of seed. These results provide insights into the role of divergence and reticulation in a well-characterized angiosperm lineage and into traits of diploid parents and derived tetraploids (particularly self-compatibility and year-round flowering) favoring the formation and establishment of novel tetraploids combinations.
Collapse
|
31
|
Vandepitte K, Jacquemyn H, Roldán-Ruiz I, Honnay O. The consequences of mating over a range of parental genetic similarity in a selfing allopolyploid plant species. J Evol Biol 2011; 24:2750-8. [PMID: 21955301 DOI: 10.1111/j.1420-9101.2011.02390.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
In diploids, F(1) offspring performance is expected to increase with increasing genetic dissimilarity between the parents until an optimum is reached because outbreeding mitigates inbreeding depression and maximizes heterosis. However, many flowering plant species are derived through allopolyploidization, i.e. interspecific hybridization with genome doubling. This mode of plant speciation can be expected to considerably alter the consequences of inbreeding and outbreeding. We investigated the F1 fitness consequences of mating over a range of (genetic) distances in the allohexaploid plant species Geum urbanum. Offspring was raised under controlled conditions (632 plants). The performance of outcrossed progeny was not significantly better than that of their selfed half-siblings and did not increase with parental genetic dissimilarity (0-0.83). Our findings support low, if any, inbreeding depression and heterosis. We attribute this to the peculiar state of quasi-permanent heterozygosity in allopolyploids and frequent selfing.
Collapse
Affiliation(s)
- K Vandepitte
- Laboratory of Plant Ecology, Biology Department, K.U. Leuven, Heverlee, Belgium.
| | | | | | | |
Collapse
|
32
|
Wallace LE, Culley TM, Weller SG, Sakai AK, Kuenzi A, Roy T, Wagner WL, Nepokroeff M. Asymmetrical gene flow in a hybrid zone of Hawaiian Schiedea (Caryophyllaceae) species with contrasting mating systems. PLoS One 2011; 6:e24845. [PMID: 21949765 PMCID: PMC3176226 DOI: 10.1371/journal.pone.0024845] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2011] [Accepted: 08/22/2011] [Indexed: 01/21/2023] Open
Abstract
Asymmetrical gene flow, which has frequently been documented in naturally occurring hybrid zones, can result from various genetic and demographic factors. Understanding these factors is important for determining the ecological conditions that permitted hybridization and the evolutionary potential inherent in hybrids. Here, we characterized morphological, nuclear, and chloroplast variation in a putative hybrid zone between Schiedea menziesii and S. salicaria, endemic Hawaiian species with contrasting breeding systems. Schiedea menziesii is hermaphroditic with moderate selfing; S. salicaria is gynodioecious and wind-pollinated, with partially selfing hermaphrodites and largely outcrossed females. We tested three hypotheses: 1) putative hybrids were derived from natural crosses between S. menziesii and S. salicaria, 2) gene flow via pollen is unidirectional from S. salicaria to S. menziesii and 3) in the hybrid zone, traits associated with wind pollination would be favored as a result of pollen-swamping by S. salicaria. Schiedea menziesii and S. salicaria have distinct morphologies and chloroplast genomes but are less differentiated at the nuclear loci. Hybrids are most similar to S. menziesii at chloroplast loci, exhibit nuclear allele frequencies in common with both parental species, and resemble S. salicaria in pollen production and pollen size, traits important to wind pollination. Additionally, unlike S. menziesii, the hybrid zone contains many females, suggesting that the nuclear gene responsible for male sterility in S. salicaria has been transferred to hybrid plants. Continued selection of nuclear genes in the hybrid zone may result in a population that resembles S. salicaria, but retains chloroplast lineage(s) of S. menziesii.
Collapse
Affiliation(s)
- Lisa E Wallace
- Department of Biological Sciences, Mississippi State University, Mississippi State, Mississippi, United States of America.
| | | | | | | | | | | | | | | |
Collapse
|
33
|
Hesse E, Pannell JR. Sexual dimorphism in a dioecious population of the wind-pollinated herb Mercurialis annua: the interactive effects of resource availability and competition. ANNALS OF BOTANY 2011; 107:1039-45. [PMID: 21385775 PMCID: PMC3080628 DOI: 10.1093/aob/mcr046] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/30/2009] [Revised: 05/11/2009] [Accepted: 01/26/2011] [Indexed: 05/23/2023]
Abstract
BACKGROUND AND AIMS Male-biased sex allocation commonly occurs in wind-pollinated hermaphroditic plants, and is often positively associated with size, notably in terms of height. Currently, it is not well established whether a corresponding pattern holds for dioecious plants: do males of wind-pollinated species exhibit greater reproductive allocation than females? Here, sexual dimorphism is investigated in terms of life history trade-offs in a dioecious population of the wind-pollinated ruderal herb Mercurialis annua. METHODS The allocation strategies of males and females grown under different soil nutrient availability and competitive (i.e. no, male or female competitor) regimes were compared. KEY RESULTS Male reproductive allocation increased disproportionately with biomass, and was greater than that of females when grown in rich soils. Sexual morphs differentially adjusted their reproductive allocation in response to local environmental conditions. In particular, males reduced their reproductive allocation in poor soils, whereas females increased theirs, especially when competing with another female rather than growing alone. Finally, males displayed smaller above-ground vegetative sizes than females, but neither nutrient availability nor competition had a strong independent effect on relative size disparities between the sexes. CONCLUSIONS Selection appears to favour plasticity in reproductive allocation in dioecious M. annua, thereby maintaining a relatively constant size hierarchy between sexual morphs. In common with other dioecious species, there seems to be little divergence in the niches occupied by males and females of M. annua.
Collapse
Affiliation(s)
- Elze Hesse
- Department of Plant Sciences, University of Oxford, South Parks Road, Oxford, UK.
| | | |
Collapse
|
34
|
Castro S, Münzbergová Z, Raabová J, Loureiro J. Breeding barriers at a diploid–hexaploid contact zone in Aster amellus. Evol Ecol 2010. [DOI: 10.1007/s10682-010-9439-5] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
|
35
|
Gay L, Crochet PA, Bell DA, Lenormand T. COMPARING CLINES ON MOLECULAR AND PHENOTYPIC TRAITS IN HYBRID ZONES: A WINDOW ON TENSION ZONE MODELS. Evolution 2008; 62:2789-806. [PMID: 18752618 DOI: 10.1111/j.1558-5646.2008.00491.x] [Citation(s) in RCA: 126] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Laurène Gay
- CEFE-CNRS, UMR 5175, 1919 route de Mende, F-34293 Montpellier cedex 5, France.
| | | | | | | |
Collapse
|
36
|
Dorken ME, Pannell JR. Density-dependent regulation of the sex ratio in an annual plant. Am Nat 2008; 171:824-30. [PMID: 18429672 DOI: 10.1086/587524] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Sex ratios are subject to strong frequency-dependent selection regulated by the mating system and the relative male versus female investment. In androdioecious plant populations, where males co-occur with hermaphrodites, the sex ratio depends on the rate of self-fertilization by hermaphrodites and on the relative pollen production of males versus hermaphrodites. Here, we report evolutionary changes in the sex ratio from experimental mating arrays of the androdioecious plant Mercurialis annua. We found that the progeny sex ratio depended strongly on density, with fewer males in the progeny of plants grown under low density. This occurred in part because of a plastic adjustment in pollen production by hermaphrodites, which produced more pollen when grown at low density than at high density. Our results provide support for the prediction that environmental conditions govern sex ratios through their effects on the relative fertility of unisexual versus hermaphrodite individuals.
Collapse
Affiliation(s)
- Marcel E Dorken
- Department of Plant Sciences, South Parks Road, University of Oxford, Oxford OX1 3RB, United Kingdom.
| | | |
Collapse
|
37
|
Kimball S. Links between floral morphology and floral visitors along an elevational gradient in aPenstemonhybrid zone. OIKOS 2008. [DOI: 10.1111/j.0030-1299.2008.16573.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
|
38
|
Jacquemyn H, Brys R. Density-dependent mating and reproductive assurance in the temperate forest herb Paris quadrifolia (Trilliaceae). AMERICAN JOURNAL OF BOTANY 2008; 95:294-298. [PMID: 21632354 DOI: 10.3732/ajb.95.3.294] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
In animal-pollinated plants, autonomous selfing provides reproductive assurance under conditions of infrequent pollinator visits or a lack of mates, but few data are available for wind-pollinated species or species with combined insect and wind-pollination, for which it is often assumed that pollen availability does not limit reproduction. In this study, the capacity of autonomous selfing was investigated in the temperate forest herb Paris quadrifolia, and an emasculation experiment was performed under natural field conditions to investigate the contribution of autonomous selfing to total seed set across a continuous gradient of densities of flowering conspecifics. In the absence of wind or pollinators, autonomous selfing was observed through anthers approaching stigmas at the end of flowering and the capacity for autonomous pollination was about 0.34. Under natural conditions, considerable outcross pollination was observed, but the proportion of ovules successfully fertilized significantly decreased with decreasing density of conspecifics when flowers were emasculated, but not when flowers were left intact. These results indicate that autonomous selfing resulted in reproductive assurance (RA = 0.16) and thus support the hypothesis that autonomous selfing can also provide reproductive assurance in wind-pollinated species.
Collapse
Affiliation(s)
- Hans Jacquemyn
- Division Plant Ecology and Systematics, University of Leuven, Arenbergpark 31, B-3001 Heverlee, Belgium
| | | |
Collapse
|
39
|
Burgess KS, Morgan M, Husband BC. Interspecific seed discounting and the fertility cost of hybridization in an endangered species. THE NEW PHYTOLOGIST 2007; 177:276-284. [PMID: 17944826 DOI: 10.1111/j.1469-8137.2007.02244.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Hybrid fertilizations can have negative demographic effects on taxa by usurping ovules that would otherwise give rise to nonhybrid offspring. The consequent reduction in conspecific matings may be exaggerated in rare taxa and constitutes a fertility cost that has rarely been quantified. Here, the effect of interspecific mating was estimated on the fecundity of locally rare red mulberry (Morus rubra), which hybridizes with introduced white mulberry (Morus alba) and red yen white hybrids. First, the asymmetry in pollen production among red, white and hybrid mulberry in two sympatric populations was quantified. The fertility cost of hybridization was then assessed experimentally by estimating seed production and rates of interspecific mating in red mulberry trees from plots where white and hybrid mulberry trees were selectively removed. On average, the percentage of mulberry pollen per plot produced by red mulberry (8%) was significantly lower than the mean for white and hybrid mulberry combined (92%). Experimentally removing white and hybrid mulberry increased the siring fertility of red mulberry by 14% but produced no change in seed set. Results indicate that seeds of red mulberry, ordinarily sired by conspecific pollen, are being discounted through fertilization of ovules by heterospecific pollen, which may contribute to local decline of red mulberry.
Collapse
Affiliation(s)
- Kevin S Burgess
- Department of Botany, University of Guelph, Guelph, Ontario N1G 2W1, Canada
- Present address: Department of Ecology & Evolutionary Biology, University of Toronto, 25 Willcocks Street, Toronto, Ontario M5S 3B2, Canada
| | - Martin Morgan
- School of Biological Sciences, Washington State University, PO Box 644236, Pullman, WA 99164-4236, USA
| | - Brian C Husband
- Department of Botany, University of Guelph, Guelph, Ontario N1G 2W1, Canada
| |
Collapse
|
40
|
Eppley SM, Pannell JR. DENSITY-DEPENDENT SELF-FERTILIZATION AND MALE VERSUS HERMAPHRODITE SIRING SUCCESS IN AN ANDRODIOECIOUS PLANT. Evolution 2007; 61:2349-59. [PMID: 17711472 DOI: 10.1111/j.1558-5646.2007.00195.x] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Models of mating-system evolution emphasize the importance of frequency-dependent interactions among mating partners. It is also known that outcross siring success and the selfing rate in self-compatible hermaphrodites can be density dependent. Here, we use array experiments to show that the mating system (i.e., the outcrossing rate) and the siring success of morphs with divergent sex allocation strategies are both density dependent and frequency dependent in androdioecious populations of the wind-pollinated, annual plant Mercurialis annua. In particular, the outcrossing rate is a decreasing function of the mean interplant distance, regulated by a negative exponential pollen fall-off curve. Our results indicate that pollen dispersed from a male inflorescence are over 60% more likely to sire outcrossed progeny than equivalent pollen dispersed from hermaphrodites, likely due to the fact that males, but not hermaphrodites, disperse their pollen from erect inflorescence stalks. Because of this difference, and because males of M. annua produce much more pollen than hermaphrodites, the presence of males in the experimental arrays reduced both the selfing rate and the outcross siring success of hermaphrodites. We use our results to infer a density threshold below which males are unable to persist with hermaphrodites but above which they can invade hermaphroditic populations. We discuss our findings in the context of a metapopulation model, in which males can only persist in well-established populations but are excluded from small, sparse populations, for example, in the early stages of colonization.
Collapse
Affiliation(s)
- Sarah M Eppley
- Department of Plant Sciences, University of Oxford, Oxford, UK.
| | | |
Collapse
|
41
|
Abstract
Hybrid zones are 'natural laboratories' for studying the origin, maintenance and demise of species. Theory predicts that hybrid zones can move in space and time, with significant consequences for both evolutionary and conservation biology, though such movement is often perceived as rare. Here, a review of empirical studies of moving hybrid zones in animals and plants shows 23 examples with observational evidence for movement, and a further 16 where patterns of introgression in molecular markers could be interpreted as signatures of movement. The strengths and weaknesses of methods used for detecting hybrid zone movement are discussed, including long-term replicated sampling, historical surveys, museum/herbarium collections, patterns of relictual populations and introgression of genetic markers into an advancing taxon. Factors governing hybrid zone movement are assessed in the light of the empirical studies, including environmental selection, competition, asymmetric hybridization, dominance drive, hybrid fitness, human activity and climate change. Hybrid zone movement means that untested assumptions of stability in evolutionary studies on hybrid zone can lead to mistaken conclusions. Movement also means that conservation effort aimed at protecting against introgression could unwittingly favour an invading taxon. Moving hybrid zones are of wide interest as examples of evolution in action and possible indicators of environmental change. More long-term experimental studies are needed that incorporate reciprocal transplants, hybridization experiments and surveys of molecular markers and population densities on a range of scales.
Collapse
|
42
|
Abstract
The parapatric distribution of genetically divergent lineages in hybrid zones can be maintained by ecological differences (dispersal-independent 'ecotonal' hybrid zones), by frequency- and density-dependent interference when they intermingle and mate (dispersal-dependent 'tension' hybrid zones), or by both processes acting together. One potentially important ecological factor that has received little theoretical attention is gradients in habitat disturbance. Such gradients may be particularly important in contact zones in which the interacting lineages differ in their sexual system (e.g., self-fertile versus obligately outcrossing) because self-fertility promotes the colonization of open patches. Here we use a spatially explicit metapopulation model to examine the dynamics of a dispersal-dependent ecotonal hybrid zone across a gradient in the rate of habitat disturbance, where competing lineages differ in their sexual system. We found that self-fertility promoted the maintenance of one lineage over its outcrossing counterpart at high extinction rates, predominantly because self-fertility confers reproductive assurance. Additionally, greater seed and pollen production promoted a lineage's persistence by reducing the seed fertility of its counterpart through hybridization. Our results draw attention to the joint effects of ecological and endogenous selection in regulating the location of hybrid zones. Our study also casts new light on the maintenance of the parapatric distribution of incompatible lineages of Spanish populations of the plant Mercurialis annua. In particular, we expect the rate of movement of a contact zone in eastern Spain to increase as it moves further south, contrary to earlier predictions.
Collapse
Affiliation(s)
- M E Dorken
- Department of Plant Sciences, University of Oxford, Oxford, UK.
| | | |
Collapse
|
43
|
Prentis PJ, White EM, Radford IJ, Lowe AJ, Clarke AR. Can hybridization cause local extinction: a case for demographic swamping of the Australian native Senecio pinnatifolius by the invasive Senecio madagascariensis? THE NEW PHYTOLOGIST 2007; 176:902-912. [PMID: 17850249 DOI: 10.1111/j.1469-8137.2007.02217.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
Hybridization between native and invasive species can have several outcomes, including enhanced weediness in hybrid progeny, evolution of new hybrid lineages and decline of hybridizing species. Whether there is a decline of hybridizing species largely depends on the relative frequencies of parental taxa and the viability of hybrid progeny. Here, the individual- and population-level consequences of hybridization between the Australian native Senecio pinnatifolius and the exotic Senecio madagascariensis were investigated with amplified fragment length polymorphism (AFLP) markers, and this information was used to estimate the annual loss of viable seeds to hybridization. A high frequency (range 8.3-75.6%) of hybrids was detected in open pollinated seeds of both species, but mature hybrids were absent from sympatric populations. A hybridization advantage was observed for S. madagascariensis, where significantly more progeny than expected were sired based on proportional representation of the two species in sympatric populations. Calculations indicated that S. pinnatifolius would produce less viable seed than S. madagascariensis, if hybridization was frequency dependent and S. madagascariensis reached a frequency of between 10 and 60%. For this native-exotic species pair, prezygotic isolating barriers are weak, but low hybrid viability maintains a strong postzygotic barrier to introgression. As a result of asymmetric hybridization, S. pinnatifolius would appear to be under threat if S. madagascariensis increases numerically in areas of contact.
Collapse
Affiliation(s)
- P J Prentis
- School of Natural Resource Sciences, QUT, GPO Box 2434, Brisbane 4001, Qld, Australia
- School of Environmental and Earth Sciences, University of Adelaide, Adelaide, SA 5005, Australia
| | - E M White
- School of Natural Resource Sciences, QUT, GPO Box 2434, Brisbane 4001, Qld, Australia
- Alan Fletcher Research Station, Department of Natural Resources, Mines and Water and CRC for Australian Weed Management, PO Box 36, Sherwood 4075, Qld, Australia
| | - I J Radford
- Department of Environment and Conservation, PO Box 942, Kununurra, WA 6743, Australia
| | - A J Lowe
- School of Environmental and Earth Sciences, University of Adelaide, Adelaide, SA 5005, Australia
| | - A R Clarke
- School of Natural Resource Sciences, QUT, GPO Box 2434, Brisbane 4001, Qld, Australia
| |
Collapse
|
44
|
Obbard DJ, Harris SA, Buggs RJA, Pannell JR. HYBRIDIZATION, POLYPLOIDY, AND THE EVOLUTION OF SEXUAL SYSTEMS IN MERCURIALIS (EUPHORBIACEAE). Evolution 2006. [DOI: 10.1111/j.0014-3820.2006.tb00524.x] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
|
45
|
Abstract
Contrasts between related diploid and polyploid taxa can serve as windows into the evolution of sexual systems. A recent study of a moving diploid-polyploid contact zone explores this topic in novel ways.
Collapse
Affiliation(s)
- Christian Lexer
- Jodrell Laboratory, Royal Botanic Gardens, Kew, Richmond, Surrey TW9 3DS, UK.
| | | |
Collapse
|
46
|
Obbard DJ, Harris SA, Buggs RJA, Pannell JR. HYBRIDIZATION, POLYPLOIDY, AND THE EVOLUTION OF SEXUAL SYSTEMS IN MERCURIALIS (EUPHORBIACEAE). Evolution 2006. [DOI: 10.1554/06-104.1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
|