Evolutionary history of the Kelp Gull (Larus dominicanus) in the southern hemisphere supported by multilocus evidence

Abstract

The high dispersal ability of seabirds and the absence of geographical barriers has led to high gene flow and reduced population differentiation. Nevertheless, some species with philopatric behavior have restricted gene flow among colonies, revealing a strong population structure. Gulls show widespread colonial behavior, and are long-lived species, which make them a good model for understanding evolutionary processes in seabirds. Previous genetic studies on the Kelp Gull (Larus dominicanus) have revealed low genetic variability in mitochondrial markers but relatively high genetic variation in a nuclear marker. These observations can be explained by the occurrence of a selective sweep on mtDNA, population genetic bottlenecks or a recent origin of the species. We used microsatellite data to further investigate these hypotheses, mainly by testing for bottleneck events. Low genetic variability (H o = 0.276–0.570) was detected in Kelp Gulls. However, population genetic structure was observed among regions (Chile, Argentina and Brazil), and between continents (South America and Antarctica). The population of the Kelp Gull in South America may have differentiated due to isolation by distance (r = 0.7273, p = 0.0013), whereas the population in the Antarctic seems to be isolated by non-physical barriers. Bottleneck events were detected in 6 out of 14 colonies studied. These colonies are at the limits of the distribution of the Kelp Gull, and thus experience harsh survival conditions. We believe that the Kelp Gull has a complex history in the southern hemisphere, with a recent origin, followed by bottlenecks and then population expansion. Thus, the genetic diversity found in Kelp Gull is similar to that observed for other species of Laridae.