31 Oral - Platform Session #3 Speciation, Hybridization, and Introgression
Thursday June 09, 10:00 AM - 10:15 AM

Authors:
Erik Enbody ^1,2; C. Grace Sprehn ¹; Ashley T. Sendell-Pierce1 ¹; Carl-Johan Rubin ¹; B. Rosemary Grant ³; Peter Grant ³; Leif Andersson ^1,4,5

Affiliations:
1) Department of Medical Biochemistry and Microbiology, Uppsala University, Uppsala, Sweden; 2) Department of Biomolecular Engineering, University of California Santa Cruz, CA, USA; 3) Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ 08544, USA; 4) Department of Veterinary Integrative Biosciences, Texas A&M University, College Station, USA; 5) Department of Animal Breeding and Genetics, Swedish University of Agricultural Sciences, Uppsala, Sweden

Keywords:
Speciation & hybridization

Molecular data provides a powerful opportunity to study the historical processes that have led to speciation and the evolution of phenotypic diversity, but rarely is it linked to contemporary observations of population change. Here, we link long-term trends in natural selection and hybridization in an iconic adaptive radiation, the Galápagos finches, to their molecular drivers by whole-genome sequencing of an entire island community. Specifically, we sequenced every finch alive on Daphne Island in the Galápagos Islands between the years 1983 and 2012 (Geospiza, n = 3,957). We show that hybridization has had dramatic effects on the genetic ancestry of three species, leading to large shifts in population-wide ancestry coefficients over the course of the study period. We identify six loci of large phenotypic effect that together explain as much as 70% of beak morphology variation; a key ecological trait in this group that has facilitated speciation. We next use individual-level haplotype data to track the frequency of causal alleles through time. In doing so, we show that allele frequency shifts in G. fortis at loci contributing to beak size track a decline in beak size over time in this species. We next show evidence for introgression of these loci leaving lasting footprints on morphology over the time period and discuss evidence for introgression between two species via a third conduit species. Our community-based investigation identifies several important genetic loci governing beak traits that have been subject to natural selection. They are transferred between species through introgressive hybridization and may reflect a general mechanism for how gene exchange is contributing to biodiversity.