The roles of vicariance and isolation by distance in shaping biotic diversification across an ancient archipelago: evidence from a Seychelles caecilian amphibian

BMC Evolutionary Biology

article

Maddock, Simon T.¹  Pfrender, Michael E.⁵  Nussbaum, Ronald A.⁶  Day, Julia J.³  Latta, Leigh⁷  Miller, Mark⁸  Fisk, Debra L.⁹  Wilkinson, Mark²  Rocha, Sara^1,10  Gower, David J.² 

[1] Present address: Faculty of Science and Engineering, University of Wolverhampton;Department of Life Sciences;Department of Genetics, University College London;Island Biodiversity and Conservation Centre, University of Seychelles;Department of Biological Sciences, University of Notre Dame;Research Museums Center, University of Michigan;Division of Natural Sciences and Mathematics, Lewis-Clark State College;Department of Biology, Utah State University;McPherson Eye Research Institute, University of Wisconsin;Biomedical Research Center (CINBIO), University of Vigo;Galicia Sur Health Research Institute

关键词: Adaptation;    AFLPs;    Biogeography;    Caecilian;    Evolution;    Islands;    Morphology;   

DOI  :  10.1186/s12862-020-01673-w

学科分类：护理学

来源: BioMed Central

【 摘 要 】

Island systems offer excellent opportunities for studying the evolutionary histories of species by virtue of their restricted size and easily identifiable barriers to gene flow. However, most studies investigating evolutionary patterns and processes shaping biotic diversification have focused on more recent (emergent) rather than ancient oceanic archipelagos. Here, we focus on the granitic islands of the Seychelles, which are unusual among island systems because they have been isolated for a long time and are home to a monophyletic radiation of caecilian amphibians that has been separated from its extant sister lineage for ca. 65–62 Ma. We selected the most widespread Seychelles caecilian species, Hypogeophis rostratus, to investigate intraspecific morphological and genetic (mitochondrial and nuclear) variation across the archipelago (782 samples from nine islands) to identify patterns and test processes that shaped their evolutionary history within the Seychelles. Overall a signal of strong geographic structuring with distinct northern- and southern-island clusters were identified across all datasets. We suggest that these distinct groups have been isolated for ca. 1.26 Ma years without subsequent migration between them. Populations from the somewhat geographically isolated island of Frégate showed contrasting relationships to other islands based on genetic and morphological data, clustering alternatively with northern-island (genetic) and southern-island (morphological) populations. Although variation in H. rostratus across the Seychelles is explained more by isolation-by-distance than by adaptation, the genetic-morphological incongruence for affinities of Frégate H. rostratus might be caused by local adaptation over-riding the signal from their vicariant history. Our findings highlight the need of integrative approaches to investigate fine-scale geographic structuring to uncover underlying diversity and to better understand evolutionary processes on ancient, continental islands.

【 授权许可】

CC BY|CC0