Habitat Partitioning in Facultatively Paedomorphic Populations of Palmate Newts Triturus helveticus

摘要

The life cycle of newts of the genus Triturus is characterized by an aquatic larval stage, followed by a succession of transitions between the aquatic and terrestrial habitats. Water remains essential because it is the place for reproduction (1). However, in some populations, the terrestrial component is eliminated. The larvae acquire sexual maturity before metamorphosis, and then retain their gills and gill slits. This alternative path of development is paedomorphosis. In most cases, only a part of the population follows the paedo-morphic ontogenetic pathway, while the other part normally metamorphoses (facultative paedomorphosis) (2). Habitat is an essential key in the persistence of facultative paedomorphosis in natural populations of newts and salamanders. Laboratory experiments have shown that more larvae become paedo-morphic in permanent waters than in temporary waters (3). In drying ponds, larvae and paedomorphs are constrained either to die or to metamorphose into the terrestrial morph. However, when other aquatic habitats are in proximity, they can survive by migrating without losing their larval attributes (4). Heterogeneous habitats composed of permanent and temporary habitats are usually differently used by the two morphs. Both paedomorphs and metamorphs breed in permanent ponds, but only the metamorphs are able to use drying ponds to forage on transient energetic resources (5).