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Abstract Studying how genetic variation is structured across space, and how it relates to divergence in phenotypic traits relevant to reproductive isolation, is important for our overall understanding of the speciation process. We used reduced-representation genomic data (ddRAD-seq) to examine patterns of genetic variation across the full distribution of an Andean warbler species complex (Myioborus ornatus–melanocephalus), which includes a known hybrid zone between two strikingly different plumage forms. Genetic structure largely reflects geographic variation in head plumage, some of which corresponds to major topographic barriers in the Andes. We also found evidence of isolation by distance shaping genetic patterns across the group’s broad latitudinal range. We found thatchrysopsandbairdi, two taxa with marked plumage differences that have a known hybrid zone, were characterized by low overall genetic divergence. Based on our cline analyses of both plumage and genomic hybrid indices, this hybrid zone extends for approximately 250 km, where advanced generation hybrids are likely most common. We also identified a slight difference in the centers of the plumage and genomic clines, potentially suggesting the asymmetric introgression ofchrysops-like plumage traits. By studying genetic variation in a phenotypically complex group distributed across a topographically complex area, which includes a hybrid zone, we were able to show how both geographic features and potentially sexually selected plumage traits may play a role in species formation in tropical mountains
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Evidence of introgression, ecological divergence and adaptation in Asterias sea stars
Abstract Hybrid zones are important windows into the evolutionary dynamics of populations, revealing how processes like introgression and adaptation structure population genomic variation. Importantly, they are useful for understanding speciation and how species respond to their environments. Here, we investigate two closely related sea star species,Asterias rubensandA. forbesi, distributed along rocky European and North American coastlines of the North Atlantic, and use genome‐wide molecular markers to infer the distribution of genomic variation within and between species in this group. Using genomic data and environmental niche modelling, we document hybridization occurring between northern New England and the southern Canadian Maritimes. We investigate the factors that maintain this hybrid zone, as well as the environmental variables that putatively drive selection within and between species. We find that the two species differ in their environmental niche breadth;Asterias forbesidisplays a relatively narrow environmental niche while conversely,A. rubenshas a wider niche breadth. Species distribution models accurately predict hybrids to occur within environmental niche overlap, thereby suggesting environmental selection plays an important role in the maintenance of the hybrid zone. Our results imply that the distribution of genomic variation in North Atlantic sea stars is influenced by the environment, which will be crucial to consider as the climate changes.
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- Award ID(s):
- 1737091
- PAR ID:
- 10468887
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- Molecular Ecology
- Volume:
- 32
- Issue:
- 20
- ISSN:
- 0962-1083
- Format(s):
- Medium: X Size: p. 5541-5557
- Size(s):
- p. 5541-5557
- Sponsoring Org:
- National Science Foundation
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