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Abstract In nature, small populations are often of concern because of limited genetic diversity, which underlies adaptive potential in the face of environmental change. Assessing patterns of genetic variation within co-distributed species sampled across varied landscapes can therefore illuminate their capacity to persist over time. We sequenced new genome-wide sequence data (double-digest restriction site-associated DNA sequencing) for four frog species (Anaxyrus terrestris, Hyla cinerea, Hyla squirella, and Rana sphenocephala) sampled from two barrier islands and the adjacent mainland of northern Florida. We calculated genomic diversity metrics and analysed spatial patterns of genomic variation for each species. We found higher genomic diversity within mainland individuals compared to island individuals for all species, suggesting a consistent effect of small island area on diversity across species. Three species (all but A. terrestris) showed significant signatures of isolation by distance, and some clustering analyses indicated separation of island and mainland individuals within species. We identified subtle differences in the strength of these patterns among species, with the strongest genetic differentiation observed in R. sphenocephala. Finally, we found evidence of recent migration between island and mainland populations for all species, which likely explains the limited genetic structure observed and contributes to the persistence of these small populations.
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An assemblage-level comparison of genetic diversity and population genetic structure between island and mainland ant populations
Abstract Island biotas provide unparalleled opportunities to examine evolutionary processes. Founder effects and bottlenecks, e.g., typically decrease genetic diversity in island populations, while selection for reduced dispersal can increase population structure. Given that support for these generalities mostly comes from single-species analyses, assemblage-level comparisons are needed to clarify how (i) colonization affects the gene pools of interacting insular organisms, and (ii) patterns of genetic differentiation vary within assemblages of organisms. Here, we use genome-wide sequence data from ultraconserved elements (UCEs) to compare the genetic diversity and population structure of mainland and island populations of nine ant species in coastal southern California. As expected, island populations (from Santa Cruz Island) had lower expected heterozygosity and Watterson’s theta compared to mainland populations (from the Lompoc Valley). Island populations, however, exhibited smaller genetic distances among samples, indicating less population subdivision. Within the focal assemblage, pairwise Fst values revealed pronounced interspecific variation in mainland-island differentiation, which increases with gyne body size. Our results reveal population differences across an assemblage of interacting species and illuminate general patterns of insularization in ants. Compared to single-species studies, our analysis of nine conspecific population pairs from the same island-mainland system offers a powerful approach to studying fundamental evolutionary processes.
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- PAR ID:
- 10546135
- Publisher / Repository:
- Oxford University Press
- Date Published:
- Journal Name:
- Evolution
- Volume:
- 78
- Issue:
- 10
- ISSN:
- 0014-3820
- Format(s):
- Medium: X Size: p. 1685-1698
- Size(s):
- p. 1685-1698
- Sponsoring Org:
- National Science Foundation
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