Abstract

BackgroundBased 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.ResultsFor 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.ConclusionsWe 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.

Highlights

  • Based on extensive mitochondrial DNA 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

  • These include (i) herring gulls breeding in the Palearctic (European herring gull, L. argentatus) with subspecies argentatus, and argenteus, (ii) herring gulls breeding in the Nearctic (American herring gull, L. smithsonianus), (iii) yellow-legged gulls from the Atlantic (L. michahellis atlantis) and the Mediterranean (L. m. michahellis), (iv) Caspian gull (L. cachinnans), (v) lesser black-backed gull (L. fuscus) with subspecies fuscus and graellsii, (vi) glaucous gull (L. hyperboreus) from its Nearctic and Palearctic breeding range, and (vii) great black-backed gull (L. marinus), from its Nearctic and Palearctic breeding range

  • Mitochondrial phylogeography Based on the concatenated mitochondrial DNA (mtDNA)-hypervariable region 1 (HVR1) and cytochrome B (cytB) sequences of 369 large white headed gull individuals (109 selected argentatus and 260 individuals of six other species; Table 1) a median joining network was drawn (Figure 2)

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Summary

Introduction

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. With ongoing gene flow this process will be delayed and it is unclear to what extent gene flow must be reduced - or is still allowed - in order for speciation to be “complete” [2,3]. It was Ernst Mayr [4], who proposed that reproductive. Mayr and others envisioned all taxa of the circumpolar chain to be connected by gene flow, while herring gulls and lesser black-backed gull (L. fuscus) in Europe, the hypothetical endpoints of the ring, have reached full reproductive isolation and coexist as distinct species [4,9]

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