Diversification mechanisms in Sub-Saharan Africa have long attracted research interest with varying support for either allopatric or parapatric models of speciation. However, studies have seldom been performed across the entire continent, a scale which could elucidate the relative importance of allopatric and parapatric models of divergence. To shed light on continental-scale patterns of African biogeography and diversification, we investigated the historical demography of a bird with a continent-wide distribution in Sub-Saharan Africa, the Yellow-rumped Tinkerbird, Pogoniulus bilineatus. We sampled populations from across the continent and using genomic data, assessed genetic diversity, structure, and differentiation, reconstructed the phylogeny, and performed alternative demographic model selection between neighbouring clade pairs. We uncovered substantial genetic structure and differentiation patterns which corroborated the phylogenetic topology. Structure was chiefly influenced by the arid corridor, a postulated biogeographical barrier in Sub-Saharan Africa. Moreover, peak genetic diversities coincided with postulated refugial areas while demographic reconstructions between genetic lineages supported allopatric models consistent with the Pleistocene Forest Refuge hypothesis. However, within lineages, divergence with gene flow was supported. Continent-wide patterns of diversification involve an integration of both allopatric and parapatric mechanisms, with a role for both periods of divergence in isolation and across ecological gradients. Furthermore, our study emphasises the importance of the arid corridor as a primary biogeographical feature across which diversification occurs, yet one that has hitherto received scant attention regarding its importance in avian diversification in Sub-Saharan Africa.

California’s Channel Islands are home to two endemic mammalian carnivores: island foxes (Urocyon littoralis) and island spotted skunks (Spilogale gracilis amphiala). Although it is rare for two insular terrestrial carnivores to coexist, these known competitors persist on both Santa Cruz Island and Santa Rosa Island. We hypothesized that examination of their gut microbial communities would provide insight into the factors that enable this coexistence, as microbial symbionts often reflect host evolutionary history and contemporary ecology. Using rectal swabs collected from island foxes and island spotted skunks sampled across both islands, we generated 16S rRNA amplicon sequencing data to characterize their gut microbiomes. While island foxes and island spotted skunks both harbored the core mammalian microbiome, host species explained the largest proportion of variation in the dataset. We further identified intraspecific variation between island populations, with greater differentiation observed between more specialist island spotted skunk populations compared to more generalist island fox populations. This pattern may reflect differences in resource utilization following fine-scale niche differentiation. It may further reflect evolutionary differences regarding the timing of intraspecific separation. Considered together, this study contributes to the growing catalog of wildlife microbiome studies, with important implications for understanding how eco-evolutionary processes enable the coexistence of terrestrial carnivores – and their microbiomes – in island environments.

Due to a population bottleneck, northern elephant seals (Mirounga angustirostris ) have very low genetic diversity, making them ideal model organisms for assessing the impact of genetic and non-genetic factors on the gut microbiome. In our study, we were especially interested in the role of sex given the northern elephant seal’s extreme sexual dimorphism. We investigated 54 northern elephant seal pups that were rescued from along the California coastline and brought to The Marine Mammal Center, a rehabilitation facility. Using a metabarcoding approach, we characterized microbial communities shortly after admission to the facility and found that both sex and geographic origin explained microbial variation. We detected significant differences in microbial class and order composition between sexes. We further analyzed paired samples from 24 seals at two time points, shortly after admission to the rehabilitation facility and a month post-acclimation in the facility. Between these two time points, microbial diversity increased, likely due to changes in diet. While there was an overall convergence of microbiome composition in a shared environment over time, remaining differences in microbial composition were explained by sex and host genetics.