Introgressive hybridization in herring gulls

Next Monday, Paulette will present a paper on the evolutionary history of three closely related species of Herring Gull: Larus argenteus, L. hyperboreus, L. marinus. A previous study showed that each of these species presented a biphyletic pattern based on mitochondrial markers, suggesting introgression events provoked by recent hybridization. In this paper, the authors studied the evolutionary history of these species, specifically analyzing the introgression events using both mtDNA and RLFP. Thanks Paulette.

From Sternkopf V, Liebers-Helbig D, Ritz MS, Zhang J, Helbig AJ, de Knijff P (2010) BMC Evolutionary Biology 10:348

Title: Introgressive hybridization and the evolutionary history of the herring gull complex revealed by mitochondrial and nuclear DNA

Abstract

Background: Based on extensive mitochondrial DNA (mtDNA) sequence data, we previously showed that the model of speciation among species of herring gull (Larus argentatus) complex was not that of a ring species, but most likely due more complex speciation scenario’s. We also found that two species, herring gull and glaucous gull (L. hyperboreus) displayed an unexpected biphyletic distribution of their mtDNA haplotypes. It was evident that mtDNA sequence data alone were far from sufficient to obtain a more accurate and detailed insight into the demographic processes that underlie speciation of this complex, and that extensive autosomal genetic analysis was warranted.

Results: For this reason, the present study focuses on the reconstruction of the phylogeographic history of a limited number of gull species by means of a combined approach of mtDNA sequence data and 230 autosomal amplified fragment length polymorphism (AFLP) loci. At the species level, the mtDNA and AFLP genetic data were largely congruent. Not only for argentatus and  hyperboreus, but also among a third species, great black-backed gull (L. marinus) we observed two distinct groups of mtDNA sequence haplotypes. Based on the AFLP data we were also able to detect distinct genetic subgroups among the various argentatus, hyperboreus, and marinus populations, supporting our initial hypothesis that complex demographic scenario’s underlie speciation in the herring gull complex.

Conclusions: We present evidence that for each of these three biphyletic gull species, extensive mtDNA introgression could have taken place among the various geographically distinct subpopulations, or even among current species. Moreover, based on a large number of autosomal AFLP loci, we found evidence for distinct and complex demographic scenario’s for each of the three species we studied. A more refined insight into the exact phylogeographic history within the herring gull complex is still impossible, and requires detailed autosomal sequence information, a topic of our future studies.