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Nieto Feliner G, Criado Ruiz D, Álvarez I, Villa-Machío I. The puzzle of plant hybridisation: a high propensity to hybridise but few hybrid zones reported. Heredity (Edinb) 2023; 131:307-315. [PMID: 37884616 PMCID: PMC10673867 DOI: 10.1038/s41437-023-00654-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2023] [Revised: 10/13/2023] [Accepted: 10/13/2023] [Indexed: 10/28/2023] Open
Abstract
An interesting conundrum was recently revealed by R. Abbott when he found that the number of hybrid zones reported in the literature for plants is very low, given the propensity of plants to hybridise. In another literature survey on hybrid zones performed over the period 1970-2022, we found that the number of hybrid zones reported for vertebrates was 2.3 times greater than that reported for vascular plants, even though there are about six times more vascular plant species than vertebrates. Looking at the number of papers reporting hybrid zones, there are 4.9 times more on vertebrates than on vascular plants. These figures support the relevance of this conundrum. In this paper we aim to shed light on this question by providing a structured discussion of the causes that may underlie this conundrum. We propose six non-mutually exclusive factors, namely lack or deficit of spatial structure, lack or deficit of genetic structure, effects of hybridisation between non-closely related species, lability of plant hybrid zones over time, botanists' perception of hybridisation, and deficit of population genetic data. There does not appear to be a single factor that explains our puzzle, which applies to all cases of plants where hybridisation is detected but no hybrid zone is reported. It is argued that some plant features suggest that the puzzle is not, at least entirely, due to insufficient knowledge of the specific cases, a hypothesis that should be addressed with a wider range of empirical data across different taxonomic groups.
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Affiliation(s)
| | - David Criado Ruiz
- Real Jardín Botánico (RJB), CSIC, Plaza de Murillo 2, 28014, Madrid, Spain
| | - Inés Álvarez
- Real Jardín Botánico (RJB), CSIC, Plaza de Murillo 2, 28014, Madrid, Spain
| | - Irene Villa-Machío
- Real Jardín Botánico (RJB), CSIC, Plaza de Murillo 2, 28014, Madrid, Spain
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Villa-Machío I, Heuertz M, Álvarez I, Nieto Feliner G. Demography-driven and adaptive introgression in a hybrid zone of the Armeria syngameon. Mol Ecol 2023. [PMID: 37837272 DOI: 10.1111/mec.17167] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2022] [Revised: 09/30/2023] [Accepted: 10/04/2023] [Indexed: 10/15/2023]
Abstract
Syngameons represent networks of otherwise distinct species connected by limited gene exchange. Although most studies have focused on how species maintain their cohesiveness despite gene flow, there are additional relevant questions regarding the evolutionary dynamics of syngameons and their drivers, as well as the success of their members and the network as a whole. Using a ddRADseq approach, we analysed the genetic structure, genomic clines and demographic history of a coastal hybrid zone involving two species of the Armeria (Plumbaginaceae) syngameon in southern Spain. We inferred that a peripheral population of the sand dune-adapted A. pungens diverged from the rest of the conspecific populations and subsequently hybridized with a locally more abundant pinewood congener, A. macrophylla. Both species display extensive plastid DNA haplotype sharing. Genomic cline analysis identified bidirectional introgression, but more outlier loci with excess A. pungens than A. macrophylla ancestry, suggesting the possibility of selection for A. pungens alleles. This is consistent with the finding that the A. pungens phenotype is selected for in open habitats, and with the strong correlation found between ancestry and phenotype. Taken together, our analyses suggest an intriguing scenario in which bidirectional introgression may, on the one hand, help to avoid reduced levels of genetic diversity due to the small size and isolated location of the A. pungens range-edge population, thereby minimizing demographic risks of stochastic extinction. On the other hand, the data also suggest that introgression into A. macrophylla may allow individuals to grow in open, highly irradiated, deep sandy, salt-exposed habitats.
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Affiliation(s)
- Irene Villa-Machío
- Department of Biodiversity and Conservation, Real Jardín Botánico (RJB), CSIC, Madrid, Spain
| | | | - Inés Álvarez
- Department of Biodiversity and Conservation, Real Jardín Botánico (RJB), CSIC, Madrid, Spain
| | - Gonzalo Nieto Feliner
- Department of Biodiversity and Conservation, Real Jardín Botánico (RJB), CSIC, Madrid, Spain
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Naciri Y, Linder HP. The genetics of evolutionary radiations. Biol Rev Camb Philos Soc 2020; 95:1055-1072. [PMID: 32233014 DOI: 10.1111/brv.12598] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2018] [Revised: 03/12/2020] [Accepted: 03/17/2020] [Indexed: 02/06/2023]
Abstract
With the realization that much of the biological diversity on Earth has been generated by discrete evolutionary radiations, there has been a rapid increase in research into the biotic (key innovations) and abiotic (key environments) circumstances in which such radiations took place. Here we focus on the potential importance of population genetic structure and trait genetic architecture in explaining radiations. We propose a verbal model describing the stages of an evolutionary radiation: first invading a suitable adaptive zone and expanding both spatially and ecologically through this zone; secondly, diverging genetically into numerous distinct populations; and, finally, speciating. There are numerous examples of the first stage; the difficulty, however, is explaining how genetic diversification can take place from the establishment of a, presumably, genetically depauperate population in a new adaptive zone. We explore the potential roles of epigenetics and transposable elements (TEs), of neutral process such as genetic drift in combination with trait genetic architecture, of gene flow limitation through isolation by distance (IBD), isolation by ecology and isolation by colonization, the possible role of intra-specific competition, and that of admixture and hybridization in increasing the genetic diversity of the founding populations. We show that many of the predictions of this model are corroborated. Most radiations occur in complex adaptive zones, which facilitate the establishment of many small populations exposed to genetic drift and divergent selection. We also show that many radiations (especially those resulting from long-distance dispersal) were established by polyploid lineages, and that many radiating lineages have small genome sizes. However, there are several other predictions which are not (yet) possible to test: that epigenetics has played a role in radiations, that radiations occur more frequently in clades with small gene flow distances, or that the ancestors of radiations had large fundamental niches. At least some of these may be testable in the future as more genome and epigenome data become available. The implication of this model is that many radiations may be hard polytomies because the genetic divergence leading to speciation happens within a very short time, and that the divergence history may be further obscured by hybridization. Furthermore, it suggests that only lineages with the appropriate genetic architecture will be able to radiate, and that such a radiation will happen in a meta-population environment. Understanding the genetic architecture of a lineage may be an essential part of accounting for why some lineages radiate, and some do not.
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Affiliation(s)
- Yamama Naciri
- Plant Systematics and Biodiversity Laboratory, Department of Botany and Plant biology of the University of Geneva, 1 Chemin de l'Impératrice, CH-1292, Chambésy, Geneva, Switzerland
| | - H Peter Linder
- Department of Systematic and Evolutionary Botany, University of Zurich, Zollikerstrasse 107, CH-8008, Zurich, Switzerland
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Nieto Feliner G, Rosato M, Alegre G, San Segundo P, Rosselló JA, Garnatje T, Garcia S. Dissimilar molecular and morphological patterns in an introgressed peripheral population of a sand dune species (Armeria pungens, Plumbaginaceae). PLANT BIOLOGY (STUTTGART, GERMANY) 2019; 21:1072-1082. [PMID: 31349366 DOI: 10.1111/plb.13035] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/02/2019] [Accepted: 07/23/2019] [Indexed: 05/26/2023]
Abstract
Introgression is a poorly understood evolutionary outcome of hybridisation because it may remain largely undetected whenever it involves the transfer of small parts of the genome from one species to another. Aiming to understand the early stages of this process, a putative case from the southernmost border of the Armeria pungens range from its congener A. macrophylla is revisited following the discovery of a subpopulation that does not show phenotypic signs of introgression and resembles typical A. pungens. We analysed morphometrics, nuclear ribosomal DNA ITS and plastid DNA (trnL-trnF) sequences, genome size, 45S and 5S rDNA loci-FISH data and nrDNA IGS sequences. Within the study site, most individuals match morphologies of either of the two hybridising species, particularly the new subpopulation, with intermediate phenotypes being scarce. This pattern does not fully fit molecular evidence revealing two ITS ribotypes co-occurring intragenomically in most plants from the study site and one single plastid haplotype. Genome size and structural features of the IGS sequences both indicate that A. pungens from the study site is genetically more similar to its sympatric congener than to the remainder of its conspecifics. Introgression of A. macrophylla into A. pungens and plastid capture explain all the evidence analysed. However, important features to understand the origin and fate of the introgressed population, such as the degree and direction of introgression, which are important for understanding early stages of hybridisation in plants with low reproductive barriers, should be addressed with new data.
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Affiliation(s)
| | - M Rosato
- Jardín Botánico, ICBIBE-Unidad Asociada CSIC, Universidad de Valencia, Valencia, Spain
| | - G Alegre
- Institut Botànic de Barcelona (IBB-CSIC-ICUB), Barcelona, Catalonia, Spain
| | | | - J A Rosselló
- Jardín Botánico, ICBIBE-Unidad Asociada CSIC, Universidad de Valencia, Valencia, Spain
| | - T Garnatje
- Institut Botànic de Barcelona (IBB-CSIC-ICUB), Barcelona, Catalonia, Spain
| | - S Garcia
- Institut Botànic de Barcelona (IBB-CSIC-ICUB), Barcelona, Catalonia, Spain
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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.
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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
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Return flight to the Canary Islands – The key role of peripheral populations of Afrocanarian blue tits (Aves: Cyanistes teneriffae) in multi-gene reconstructions of colonization pathways. Mol Phylogenet Evol 2013; 67:458-67. [DOI: 10.1016/j.ympev.2013.02.010] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2012] [Revised: 02/04/2013] [Accepted: 02/11/2013] [Indexed: 11/18/2022]
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Schneider JV, Schulte K, Aguilar JF, Huertas ML. Molecular evidence for hybridization and introgression in the neotropical coastal desert-endemic Palaua (Malveae, Malvaceae). Mol Phylogenet Evol 2011; 60:373-84. [DOI: 10.1016/j.ympev.2011.05.010] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2010] [Revised: 05/05/2011] [Accepted: 05/13/2011] [Indexed: 01/20/2023]
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