Evolutionary biology of birds and their associated microbiota in the Madrean Archipelago sky islands

Abstract

Sky islands are disjunct patches of montane forested habitat in a matrix of desert, grasslands, and scrub. I investigated intraspecific evolutionary biology of two bird species—the White­‐breasted Nuthatch (Sitta carolinensis) and the Brown Creeper (Certhia americana)—in the Madrean Archipelago sky islands (Arizona, USA), a biodiversity and evolution hotspot. In addition, I explored patterns of codiversification of these two birds and their associated gut microbial communities. The two bird studies revealed different patterns of diversification within the sky islands. The White­‐breasted Nuthatch exhibits a pattern of isolation by environment, where genetic differences among populations are related to environmental differences of those localities. In contrast, the Brown Creeper has a strong genetic break between northern and southern populations, with no evidence of gene flow between lineages. When I investigated codiversification of birds and their microbial communities, I found no relationship between host genetic diversity and microbial community alpha diversity, while genetic differentiation between birds was significantly related with beta diversity between microbial communities. This dissertation provides a first step in comparative evolutionary biology of Madrean Archipelago avian taxa, and adds to the knowledge of the factors shaping microbial community diversity in wild animals.