2023 124 ENV

Urbanization Affects the Morphology of Adaptive Traits in Galápagos Darwin's Finches

By: Adan Deeb

Department: Biology

Faculty Advisors: Dr. Jaime Chaves, Dr. Jack Dumbacher (California Academy of Sciences), Dr. Kiyoko Gotanda (Brock University)

Harsh environments result in the evolution of specialized traits. The Galápagos Islands of Ecuador are characterized by dramatically opposing seasons. Wet seasons result in abundant resources while dry seasons greatly limit resource availability. Limited resources force species to specialize and diversify to minimize interspecific competition. This environment has resulted in Darwin’s finches’ characteristic beak diversity. However, urbanization is rapidly changing selective pressures and affecting evolution in unprecedented ways. Previous research on Darwin’s finches in urban areas has found reduced resource specialization along with a significant preference for human foods. Nevertheless, the generality of these effects across finch species, islands, and years has not been explored. Our research investigates the predictability of the impacts of urbanization on adaptive morphological traits in Darwin’s finches across two species and two islands of the Galápagos across 6 years. We analyzed distributions of beak length, width, and depth of small (Geospiza fuliginosa) and medium (G. fortis) ground finches on San Cristóbal and Santa Cruz islands across urban and non-urban sites. Measurements were recorded for 1,717 birds in San Cristóbal and 2,516 birds in Santa Cruz from 2014-2020. Data were analyzed using Principal Component Analyses (PCA), Analyses of Variance (ANOVA), and a Phenotypic Trajectory Analysis (PTA). Results show significant morphological differences between urban and non-urban areas between and within species on both islands. Additionally, morphology responds similarly to urbanization across time, islands, and species. Our findings suggest that urbanization is a driving evolutionary force affecting species' trajectories in predictable ways.