Beth Shapiro (Santa Cruz)
Thu 12 Nov 2015, 16:00 - 17:00
Ashworth Laboratories (LT1)

If you have a question about this talk, please contact: Darren Obbard (dobbard)

The passenger pigeon was once the most abundant bird in North America, with flocks that, during the early and middle 19th century, were estimated to comprise up to three billion individuals. Less than 100 years later, however, passenger pigeons were extinct.  Why passenger pigeons disappeared so quickly remains an open question. Over-exploitation by humans has been the favored hypothesis. Using genetic data from passenger pigeon remains, it was recently reported that passenger pigeon population sizes fluctuated dramatically over relatively short time frames. Based on this interpretation, the recent extinction may have been initiated by a natural population decline. To test this hypothesis and explore the genomic consequences of rapid population decline, we sequenced and assembled high-quality genomes from five passenger pigeons and two band-tailed pigeons (the closest living relative of passenger pigeons) and mitochondrial genomes from 41 passenger pigeons. Our mitochondrial data indicate that passenger pigeon populations were growing exponentially at the time of their extinction and not in a period of decline. The nuclear genomic data reveal a striking, bimodal genomic pattern of genetic diversity with regions of extremely high and low diversity organized in distinct segments across the genome. We hypothesize that this pattern is a consequence of a long-term extremely large effective population size and consequent dominance of natural selection as an evolutionary force.