Study of Coregonus populations in the zone of intergradation between the vendace and least cisco: the role of the environment in speciation

Phylogenetic analysis using mitochondrial and nuclear DNA markers showed that the Least Cisco gradually spread from Siberia to Europe until the last glaciation. This was accompanied by gradual replacement of "typically Siberian" gene variants with "typically European" ones. Morphological traits also changed as the species expanded, the changes in the body proportions being apparently adaptive. They are likely to reflect the transition of the cisco from the semi-anadromous life history type to the lacustrine type, which is more characteristic of the European form. Thus, the speciation of the vendace is clearly adaptive, at least with respect to some traits. It should be noted, however, that the results of this study raise doubt as to whether the vendace has entirely diverged from the Least Cisco, and the speciation has completed.