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Vertebrates host complex microbiomes that impact their physiology. In many taxa, including colourful wood-warblers, gut microbiome similarity decreases with evolutionary distance. This may suggest that as host populations diverge, so do their microbiomes, because of either tight coevolutionary dynamics, or differential environmental influences, or both. Hybridization is common in wood-warblers, but the effects of evolutionary divergence on the microbiome during secondary contact are unclear. Here, we analyse gut microbiomes in two geographically disjunct hybrid zones between blue-winged warblers (Vermivora cyanoptera) and golden-winged warblers (Vermivora chrysoptera). We performed 16S faecal metabarcoding to identify species-specific bacteria and test the hypothesis that host admixture is associated with gut microbiome disruption. Species identity explained a small amount of variation between microbiomes in only one hybrid zone. Co-occurrence of species-specific bacteria was rare for admixed individuals, yet microbiome richness was similar among admixed and parental individuals. Unexpectedly, we found several bacteria that were more abundant among admixed individuals with a broader deposition of carotenoid-based plumage pigments. These bacteria are predicted to encode carotenoid biosynthesis genes, suggesting birds may take advantage of pigments produced by their gut microbiomes. Thus, host admixture may facilitate beneficial symbiotic interactions which contribute to plumage ornaments that function in sexual selection.
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The extent of introgression between incipient Clarkia species is determined by temporal environmental variation and mating system
Introgression is pervasive across the tree of life but varies across taxa, geography, and genomic regions. However, the factors modulating this variation and how they may be affected by global change are not well understood. Here, we used 200 genomes and a 15-y site-specific environmental dataset to investigate the effects of environmental variation and mating system divergence on the magnitude of introgression between a recently diverged outcrosser-selfer pair of annual plants in the genusClarkia. These sister taxa diverged very recently and subsequently came into secondary sympatry where they form replicated contact zones. Consistent with observations of other outcrosser-selfer pairs, we found that introgression was asymmetric between taxa, with substantially more introgression from the selfer to the outcrosser. This asymmetry was caused by a bias in the direction of initial F1 hybrid formation and subsequent backcrossing. We also found extensive variation in the outcrosser’s admixture proportion among contact zones, which was predicted nearly entirely by interannual variance in spring precipitation. Greater fluctuations in spring precipitation resulted in higher admixture proportions, likely mediated by the effects of spring precipitation on the expression of traits that determine premating reproductive isolation. Climate-driven hybridization dynamics may be particularly affected by global change, potentially reshaping species boundaries and adaptation to novel environments.
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- PAR ID:
- 10568123
- Publisher / Repository:
- pnas.org
- Date Published:
- Journal Name:
- Proceedings of the National Academy of Sciences
- Volume:
- 121
- Issue:
- 12
- ISSN:
- 0027-8424
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1073/pnas.2316008121
