The Herring Gull complex (Larus argentatue-fuscus-cachinnans) as a model group for recent holarctic vertebrate radiations

• Applicant: Dr. Dorit Liebers-Helbig
• Subject Area: Evolution and Systematics of Plants and Fungi
• Term: from 2004 to 2011
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 5424229

Under what circumstances speciation in sexually reproducing animals can occur without geographical disjunction is still controversial. According to the ring species model, a reproductive barrier may arise through 'isolation-by-distance' when peripheral populations of a species meet after expanding around some uninhabitable barrier. The classical example for this kind of speciation is the Herring Gull (Larus argentatus) complex with a circumpolar distribution in the northern hemisphere. An analysis of mtDNA variation among 21 gull taxa indicated that members of this complex differentiated largely in allopatry following multiple vicariance and long-distance colonization events, not primarily through isolation-by-distance. Extant taxa are the result of a recent (late Pleistocene) radiation within which two ancestral lineages were originally separated in a North Atlantic and a continental Eurasian refugium. Contrary to the ring species model, I found no mitochondrial genetic evidence for a closure of the circumpo lar ring through colonization of Europe by North American Herring Gulls. I now intend to use nuclear markers (AFLP & SNP genotyping, intron sequences) as an independent (biparentally inherited) source of genetic information to be compared with the mitochondrial (maternally inherited) phylogeography. These markers will also serve to test the apparent biphyletic origin of two species (argentatus, hyperboreus) as well as the unexpected position of L. marinus within (rather than as an outgroup to) the complex. Concentrating on markers on the large sex (Z) chromosome I hope to identify loci linked to post-zygotic isolation factors which should be the first to differentiate between incipient species and may bring us closer to an understanding of molecular-genetic mechanisms of speciation.

• DFG Programme: Priority Programmes
• Subproject of: SPP 1127: Radiations - Origins of Biological Diversity