Darwin’s Finch Subfossils Provide Evidence of Historic Beak Morphology
Jaden McCaffrey
Department of Biology
Faculty Supervisor: Jaime Chaves
The Galapagos Islands are known for their unique biodiversity and the evolution of Darwin's finch radiation. Darwin’s finches have been documented evolving in real-time in response to climatic events, hybridization between species, and diversifying into unique ecological niches. Darwin's finches are closely related species that differ primarily in subtle variation of overall size and shape in the body and beak. Despite the long-term focus on these islands for evolutionary studies, the Galapagos has experienced significant ecological degradation over the past 500 years. Subfossil material from before human arrival is often preserved in lava tunnel caves and can be used to document species losses on a given island. Assessment of these biodiversity losses can be studied through subfossil material from caves. To fully document what species of finches occurred in the past on Santiago and Santa Cruz Islands, we collected subfossil material from multiple cave deposits. A linear discriminant analysis (LDA) was created using extant museum specimens and then was used to predict the likelihood of identification of subfossil beaks recovered from caves. Nearly half of the subfossil beaks clustered with existing species, confirming their existence in the paleocommunity. While the other half cluster similarly outside the 95% confidence interval of any species included in the reference material. These results suggest there may be further investigation needed into extirpation, species hybridization, morphological shifts, and evolutionary shifts.