Les populations néoténiques de Triturus helveticus des Causses et du Bas-Languedoc. I. Répartition et caractéristiques

Abstract

Neoteny is common in some populations of Palmate newts Triturus helveticus of Southern France. Population samples have been collected from 117 pools, at three different seasons of the year. Percentages of neotenic individuals have been calculated for 29 of these pools where neotenic newts were found. Neoteny is not evenly distributed over the whole study area. It is more prevalent in the S.E. part of the Causse du Larzac and in the Causse de Blandas, than in the coastal plains of Languedoc. On the “causses” (arid limestone tablelands), neoteny only occurs among palmate newts, no neotenic individual having ever been found among the sympatric Triturus marmoratus population. Morphological differences between neotenic and normal populations of Triturus helveticus are described. None of them is consistent enough to allow sub-specific status to be given to the neotenic population. Breeding takes place later in the season among the Larzac population and the duration of the aquatic phase of the yearly cycle is also longer in the plateau population than among the newts of the coastal plains. All these differences, morphological as well as biological, disappear when the newts are kept in laboratory conditions. Metamorphosis occurs normally when the progeny of both newt populations are bred in the laboratory. However mortality is much higher among the progeny of neotenic females, during their first three months of life.