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Urbanization can influence many environmental factors that can affect the condition, immunity, and gut microbiota of birds. Over the past several decades, the Galápagos Islands of Ecuador have experienced increasing human activity, which has led to recent changes in the morphology, gut microbiota, and immunity of Darwin’s finches. However, these traits have not been characterized before the exponential growth of human population size and tourist visitation rates, i.e., before 2009. The goal of this study was to determine the effect of land use on the fecal microbiota, immune response, and body measurements of Darwin’s finches in 2008, at a time of rapidly increasing human activity on the islands. Specifically, we compared fecal microbiota (bacterial diversity, community structure and membership, and relative abundance of bacterial taxa), proxies of immunity (lysozyme activity and haptoglobin, complement antibody, and natural antibody levels), and body measurements (body mass and condition, tarsus length) across undeveloped, agricultural, and urban areas for medium ground finches (Geospiza fortis) and small ground finches (G. fuliginosa). Lysozyme activity was lower and observed bacterial species richness was higher in urban areas compared to non-urban areas across both finch species. In medium ground finches, four genera (Methylobacterium-Methylorubrum, Escherichia-Shigella, Brucella, and Citrobacter spp.) were higher in urban areas compared to undeveloped areas. In small ground finches, Paucibacter, Achromobacter, Delftia, Stenotrophomonas, and Brucella spp. had higher relative abundances in undeveloped and agricultural areas whereas the genus Cutibacterium was more abundant in finches from urban and agricultural areas than in finches from undeveloped areas. Medium ground finches were smaller in undeveloped areas compared to the other two areas, but body mass of small ground finches did not differ across areas. Our results suggest that human activity can have an impact on immune measures and gut microbiota of Darwin’s finches. 

Invasive parasites are a major threat to biodiversity worldwide, so understanding the factors that control them is necessary to improve the health of affected host species. In the Galápagos Islands, the invasive nest ectoparasite, the avian vampire fly (Philornis downsi), is causing up to 100% mortality in nestling Darwin’s finches. However, urban finch nests have fewer flies than non-urban finch nests. One explanation is that finches incorporate cigarette butts into their nests, which can decrease nest parasite abundance for other bird species. For our study, we exposed larval flies to cigarette tobacco-treated (concentrated or diluted) or untreated cotton, then characterized pupation success, pupal deformities and success, and adult fly eclosure success and size. The influence of moisture on the effect of tobacco treatment on fly health was also determined. Flies reared in the tobacco treatments as larvae had lower pupation success, larger pupal volume, and a higher prevalence of pupal deformities compared to control flies, regardless of moisture treatment. Furthermore, we found that tobacco-treated flies had lower eclosure success. In fact, very few tobacco-treated flies survived to adulthood. We also collected finch nests and quantified the prevalence and mass of cigarette butts and abundance of flies in the nests. Although most urban finch nests contain cigarette butts (73%), the mass of cigarette butts was very low and did not correlate with fly abundance. Compared to past studies, finch nests require ten times as many cigarette butts to affect fly survival. Although tobacco can negatively affect vampire flies, finches likely do not incorporate enough cigarette butts to affect fly fitness. 

Divergent natural selection should lead to adaptive radiation—that is, the rapid evolution of phenotypic and ecological diversity originating from a single clade. The drivers of adaptive radiation have often been conceptualized through the concept of “adaptive landscapes,” yet formal empirical estimates of adaptive landscapes for natural adaptive radiations have proven elusive. Here, we use a 17-year dataset of Darwin’s ground finches (Geospiza spp.) at an intensively studied site on Santa Cruz (Galápagos) to estimate individual apparent lifespan in relation to beak traits. We use these estimates to model a multi-species fitness landscape, which we also convert to a formal adaptive landscape. We then assess the correspondence between estimated fitness peaks and observed phenotypes for each of five phenotypic modes (G. fuliginosa, G. fortis [small and large morphotypes], G. magnirostris, and G. scandens). The fitness and adaptive landscapes show 5 and 4 peaks, respectively, and, as expected, the adaptive landscape was smoother than the fitness landscape. Each of the five phenotypic modes appeared reasonably close to the corresponding fitness peak, yet interesting deviations were also documented and examined. By estimating adaptive landscapes in an ongoing adaptive radiation, our study demonstrates their utility as a quantitative tool for exploring and predicting adaptive radiation. 

Abstract The termterroiris used in viticulture to emphasize how the biotic and abiotic characteristics of a local site influence grape physiology and thus the properties of wine. In ecology and evolution, such terroir (i.e., the effect of space or “site”) is expected to play an important role in shaping phenotypic traits. Just how important is the pure spatial effect of terroir (e.g., differences between sites that persist across years) in comparison to temporal variation (e.g., differences between years that persist across sites), and the interaction between space and time (e.g., differences between sites change across years)? We answer this question by analyzing beak and body traits of 4388 medium ground finches (Geospiza fortis) collected across 10 years at three locations in Galápagos. Analyses of variance indicated that phenotypic variation was mostly explained by site for beak size (η² = 0.42) and body size (η² = 0.43), with a smaller contribution for beak shape (η² = 0.05) and body shape (η² = 0.12), but still higher compared to year and site‐by‐year effects. As such, the effect of terroir seems to be very strong in Darwin's finches, notwithstanding the oft‐emphasized interannual variation. However, these results changed dramatically when we excluded data from Daphne Major, indicating that the strong effect of terroir was mostly driven by that particular population. These phenotypic results were largely paralleled in analyses of environmental variables (rainfall and vegetation indices) expected to shape terroir in this system. These findings affirm the evolutionary importance of terroir, while also revealing its dependence on other factors, such as geographical isolation.