title: Presumable incipient hybrid speciation of door snails in previously glaciated areas in the Caucasus.
abstract: Homoploid hybrid speciation, speciation by hybridization without a change in chromosome number, may be the result of an encounter of closely related species in a habitat that is different from that usually occupied by these species. In the northwestern Caucasus the land snail species Micropontica caucasica and M. circassica form two distinct entities with little admixture at low and intermediate altitudes. However, at higher altitudes in the Lagonaki plateau, which were repeatedly glaciated, Micropontica populations with intermediate characters occur. Admixture analyses based on AFLP data demonstrated that the populations from the Lagonaki plateau are homoploid hybrids that now form a cluster separate from the parental species. The Lagonaki populations are characterized by a mtDNA haplotype clade that has been found in the parental species only once. The fixation of this haplotype clade in most hybrid populations suggests that these haplotypes are better adapted to the cooler conditions in high altitude habitats and have replaced the haplotypes of the parental species in a selective sweep. The fixation of a presumably adaptive mitochondrial haplotype clade in the Lagonaki populations is an important step towards speciation under the differential fitness species concept.
authors.affiliation: Center of Natural History, Zoological Museum, University of Hamburg, Martin-Luther-King-Platz 3, 20146 Hamburg, Germany; Institute of Evolutionary Biology and Environmental Studies, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland.
authors.forename: Eva L
authors.initials: EL
authors.lastname: Koch
authors.affiliation: Center of Natural History, Zoological Museum, University of Hamburg, Martin-Luther-King-Platz 3, 20146 Hamburg, Germany.
authors.forename: Marco T
authors.initials: MT
authors.lastname: Neiber
authors.affiliation: Center of Natural History, Zoological Museum, University of Hamburg, Martin-Luther-King-Platz 3, 20146 Hamburg, Germany; Universität Duisburg-Essen, Universitätsstraße 5, 45141 Essen, Germany.
authors.forename: Frank
authors.initials: F
authors.lastname: Walther
authors.affiliation: Center of Natural History, Zoological Museum, University of Hamburg, Martin-Luther-King-Platz 3, 20146 Hamburg, Germany. Electronic address: hausdorf@zoologie.uni-hamburg.de.
authors.forename: Bernhard
authors.initials: B
authors.lastname: Hausdorf
mesh_terms: D000064:Acclimatization / Q000235:genetics; D000531:Altitude; D054458:Amplified Fragment Length Polymorphism Analysis; D000818:Animals; D004272:DNA, Mitochondrial / Q000235:genetics; D017753:Ecosystem; D049810:Genetic Speciation; D006239:Haplotypes; D006824:Hybridization, Genetic; D046448:Ice Cover; D012908:Snails / Q000145:classification* / Q000235:genetics*
chemical_list: D004272:DNA, Mitochondrial
keywords: AFLP; Homoploid hybrid speciation; Land snails; Phylogeography; Pleistocene