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Philopatry drives genetic differentiation in an island archipelago: comparative population genetics of Galapagos Nazca boobies ( S ula granti ) and great frigatebirds ( F regata minor )

2012; Wiley; Volume: 2; Issue: 11 Linguagem: Inglês

10.1002/ece3.386

2045-7758

Iris I. Levin, Patricia G. Parker,

Identification and Quantification in Food

Abstract Seabirds are considered highly mobile, able to fly great distances with few apparent barriers to dispersal. However, it is often the case that seabird populations exhibit strong population genetic structure despite their potential vagility. Here we show that G alapagos N azca booby ( S ula granti ) populations are substantially differentiated, even within the small geographic scale of this archipelago. On the other hand, G alapagos great frigatebird ( F regata minor ) populations do not show any genetic structure. We characterized the genetic differentiation by sampling five colonies of both species in the G alapagos archipelago and analyzing eight microsatellite loci and three mitochondrial genes. Using an F ‐statistic approach on the multilocus data, we found significant differentiation between nearly all island pairs of N azca booby populations and a B ayesian clustering analysis provided support for three distinct genetic clusters. Mitochondrial DNA showed less differentiation of N azca booby colonies; only N azca boobies from the island of D arwin were significantly differentiated from individuals throughout the rest of the archipelago. Great frigatebird populations showed little to no evidence for genetic differentiation at the same scale. Only two island pairs (Darwin – Wolf, N. Seymour – Wolf) were significantly differentiated using the multilocus data, and only two island pairs had statistically significant φ ST values (N. Seymour – Darwin, N. Seymour – Wolf) according to the mitochondrial data. There was no significant pattern of isolation by distance for either species calculated using both markers. Seven of the ten N azca booby migration rates calculated between island pairs were in the south or southeast to north or northwest direction. The population differentiation found among G alapagos N azca booby colonies, but not great frigatebird colonies, is most likely due to differences in natal and breeding philopatry.