Italian crested newts (Triturus carnifex) in the Basin of Geneva:: Distribution and genetic interactions with autochthonous species

Three surveys in the Basin of Geneva (Switzerland and adjacent France) reveal a decline of crested newts, from 22 known populations in 1975, to 11 in 1987, and to seven in 1997. Using morphological and genetic markers, 16 out of 18 populations are identified as (allochthonous) T. carnifex or mixed populations of T. carnifex-T. cristatus. Syntopic populations are characterized by the incomplete mixing of genotypes. The presence of the genes of T. cristatus in T. carnifex demonstrates past hybridization events. Two populations are identified as (autochthonous) T. cristatus: its presence is now restricted to the northeastern fringe of the Basin. Identification of preserved material indicates that the introduction of T carnifex took place early this century. The data imply that over 30-40 generations, T. carnifex has established itself ill the Basin of Geneva at the expense of T. cristatus. No significant change in the relative distribution of the two species was observed from 1987-1997, and we conclude that the recent spread of T. carnifex has been non-existent or slow.