Urbanization erodes niche segregation in Darwin's finches

Abstract

Urbanization is influencing patterns of biological evolution in ways that are only beginning to be explored. One potential effect of urbanization is in modifying ecological resource distributions that underlie niche differences and that thus promote and maintain species diversification. Few studies have assessed such modifications, or their potential evolutionary consequences, in the context of ongoing adaptive radiation. We study this effect in Darwin's finches on the Galápagos Islands, by quantifying feeding preferences and diet niche partitioning across sites with different degrees of urbanization. We found higher finch density in urban sites and that feeding preferences and diets at urban sites skew heavily toward human food items. Furthermore, we show that finches at urban sites appear to be accustomed to the presence of people, compared with birds at sites with few people. In addition, we found that human behavior via the tendency to feed birds at non‐urban but tourist sites is likely an important driver of finch preferences for human foods. Site differences in diet and feeding behavior have resulted in larger niche breadth within finch species and wider niche overlap between species at the urban sites. Both factors effectively minimize niche differences that would otherwise facilitate interspecies coexistence. These findings suggest that both human behavior and ongoing urbanization in Galápagos are starting to erode ecological differences that promote and maintain adaptive radiation in Darwin's finches. Smoothing of adaptive landscapes underlying diversification represents a potentially important yet underappreciated consequence of urbanization. Overall, our findings accentuate the fragility of the initial stages of adaptive radiation in Darwin's finches and raise concerns about the fate of the Galápagos ecosystems in the face of increasing urbanization.

Urban herring gulls use human behavioural cues to locate food

“…7: 191959 on anthropogenic food can be harmful for wildlife (e.g. [46,47]). A more comprehensive understanding of the cues that cause wild animals to engage in interactions with humans is likely to be key in developing preventative measures that not only reduce negative encounters for humans but also potentially lessen the impact of anthropogenic items on wild animal populations.…”

Human activity can influence the gut microbiota of Darwin's finches in the Galapagos Islands

“…The Galapagos currently hosts 225,000 tourists each year and is home to ~30,000 permanent residents (Walsh & Mena, ). Consequently, in areas with the presence of humans (e.g., towns and areas with high human visitation rates), the natural habitat and diet of endemic species, such as Darwin's finches, have been altered (de León et al., ). In turn, changes in the natural and unnatural diet of Darwin's finches has affected selection on their bill size and shape (Hendry et al., ; de León, Podos, Gardezi, Herrel, & Hendry, ; de León et al., ) and thus might also affect their gut microbiota.…”

“…We focused on localities that were studied by de León et al. () because the authors showed that Darwin's finches, such as small and medium ground finches, in areas with human presence preferrentially consumed human‐based food (i.e., crisps, biscuits and rice) over their natural foods salt bush ( Cryptocarpus pyriformis ), smooth‐stemmed tournefortia ( Tournefortia psilostachya ) and thorn shrub ( Scutia spicata ); in contrast, finches in areas without human presence did not forage on human‐based food when given the option. Because diet can influence gut microbiota, we hypothesized that measures of the gut bacterial communities, such as diversity, relative abundance of taxa, and community structure and membership, would differ across a gradient of human disturbance.…”

Local extirpation is pervasive among populations of Galápagos endemic tomatoes

“…Urbanization has had numerous evolutionary and ecological consequences on the Galápagos (De Leon et al, 2018; Hendry et al, 2006; Sequeira et al, 2016; Tanner Perry, 2007), indicating that human-induced habitat disruption is one of the foremost threats to biodiversity on the islands (Pizzitutti et al, 2017; Quiroga, 2018). Our findings similarly suggest that urbanization has played an important role in the loss of endemic CHS and GAL populations.…”