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Habitat-linked genetic variation supports microgeographic adaptive divergence in an island-endemic bird species

2022 , Cheek, R.G. , Forester, B.R. , Salerno, Patricia E. , Trumbo, D.R. , Langin, K.M. , Chen, N. , Scott Sillett, T. , Morrison, S.A. , Ghalambor, C.K. , Chris Funk, W.

We investigated the potential mechanisms driving habitat-linked genetic divergence within a bird species endemic to a single 250-km2 island. The island scrub-jay (Aphelocoma insularis) exhibits microgeographic divergence in bill morphology across pine–oak ecotones on Santa Cruz Island, California (USA), similar to adaptive differences described in mainland congeners over much larger geographic scales. To test whether individuals exhibit genetic differentiation related to habitat type and divergence in bill length, we genotyped over 3000 single nucleotide polymorphisms in 123 adult island scrub-jay males from across Santa Cruz Island using restriction site-associated DNA sequencing. Neutral landscape genomic analyses revealed that genome-wide genetic differentiation was primarily related to geographic distance and differences in habitat composition. We also found 168 putatively adaptive loci associated with habitat type using multivariate redundancy analysis while controlling for spatial effects. Finally, two genome-wide association analyses revealed a polygenic basis to variation in bill length with multiple loci detected in or near genes known to affect bill morphology in other birds. Our findings support the hypothesis that divergent selection at microgeographic scales can cause adaptive divergence in the presence of ongoing gene flow. © 2022 The Authors. Molecular Ecology published by John Wiley & Sons Ltd.

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Near-shore island lizard fauna shaped by a combination of human-mediated and natural dispersal

2023 , Salerno, Patricia E. , Chan L.M. , Pauly G.B. , Funk W.C. , Robertson J.M.

Aim: Island biotas provide opportunities to study colonization and adaptation to novel environments. Islands, especially near-shore islands, may have a long record of human habitation such that some lineages result from human-assisted introductions. Here, we combine phylogenetic analyses with fossil data and historical specimen records to reconstruct colonization histories, characterize among-island divergence and assess the role of humans in shaping the evolutionary history of lizards inhabiting a near-shore island archipelago. Location: Channel Islands and adjacent mainland of California, United States. Taxa: Western fence lizard (Sceloporus occidentalis), southern alligator lizard (Elgaria multicarinata), common side-blotched lizard (Uta stansburiana). Methods: We sequenced mitochondrial DNA (ND1, cyt-b) from each of three lizard species, covering their entire island distributions plus the adjacent mainland. For each, we estimated diversity within and among each island, obtained maximum likelihood bootstrapped phylogenies, constructed haplotype networks and tested for population expansion. We used museum specimen records and microfossil evidence to infer colonization scenarios. Results: Sceloporus occidentalis is characterized by a single island-colonization event, and exhibits the deepest divergences from mainland relatives and the highest among-island divergence. Elgaria multicarinata and Uta stansburiana each have at least three distinct colonization events, with fossil and historical data indicating that some of these occurred after humans arrived to the islands. Main Conclusions: The evolution of Channel Island lineages for two lizard taxa has been mediated by ancient and contemporary anthropogenic activity, while the evolution of the third is shaped by natural dispersal and vicariance caused by sea-level rise. Genetic divergence corroborates the treatment of S. occidentalis as an endemic island species, Sceloporus becki. The unique histories of these three taxa are synthesized with other Channel Island lineages highlighting that taxa inhabiting islands with long histories of human activity should be carefully studied to assess the role of people in facilitating colonization and subsequent gene flow. © 2022 John Wiley & Sons Ltd.

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Hunting alters viral transmission and evolution in a large carnivore

2022 , Fountain-Jones N.M. , Kraberger S. , Gagne R.B. , Gilbertson M.L.J. , Trumbo D.R. , Charleston M. , Salerno, Patricia E. , Chris Funk W. , Crooks K. , Logan K. , Alldredge M. , Dellicour S. , Baele G. , Didelot X. , VandeWoude S. , Carver S. , Craft M.E.

Hunting can fundamentally alter wildlife population dynamics but the consequences of hunting on pathogen transmission and evolution remain poorly understood. Here, we present a study that leverages a unique landscape-scale quasi-experiment coupled with pathogen-transmission tracing, network simulation and phylodynamics to provide insights into how hunting shapes feline immunodeficiency virus (FIV) dynamics in puma (Puma concolor). We show that removing hunting pressure enhances the role of males in transmission, increases the viral population growth rate and increases the role of evolutionary forces on the pathogen compared to when hunting was reinstated. Changes in transmission observed with the removal of hunting could be linked to short-term social changes while the male puma population increased. These findings are supported through comparison with a region with stable hunting management over the same time period. This study shows that routine wildlife management can have impacts on pathogen transmission and evolution not previously considered. © 2022, The Author(s), under exclusive licence to Springer Nature Limited.