Biogeography and ecology of paedomorphosis in Triturus alpestris (Amphibia, Caudata)

Abstract

Aim Paedomorphosis is an evolutionary change in which larval structures are retained in adult animals. In newts and salamanders, this heterochronic process is widely represented and concerns the retention of gill slits. We want to ®nd out whether ecological and geographical determinants may be associated with paedomorphosis in the Alpine newt Triturus alpestris.Location Europe.Methods Determination of the main characteristics of all known aquatic sites containing paedomorphic Alpine newt individuals.Results Although metamorphs are common in Europe, paedomorphs are only found at the southern margin of the geographical range of the species: mainly in Italy and in the Balkans. They were recorded in eighty-seven aquatic sites. No single trend was outlined for the analysed ecological parameters of the aquatic and terrestrial habitats (e.g. altitude, maximum water depth, drying and presence of forest).Main conclusions Contrary to the ®rst models of paedomorphosis, the main traits of aquatic and terrestrial habitat do not explain the occurrence of paedomorphs in natural populations. Although they were found in favourable aquatic habitats surrounded by hostile terrestrial landscapes, they also exist in temporary waters located at proximity of appropriate terrestrial environments. These results support models predicting paedomorphosis in varied environments, but require complementary investigations on the costs and bene®ts of the alternative ontogenetic pathways. On the other hand, the southern limitation of the heterochronic phenomenon suggests a genetic basis for paedomorphosis in the studied species.

Life cycle polyphenism as a factor affecting ecological divergence within Notophthalmus viridescens

“…This association between polyphenic expression and habitat characteristics has been suggested in ambystomatid salamanders in North America (Rose and Armentrout 1976;ShaVer 1984;Semlitsch and Gibbons 1985;Ryan and Semlitsch 1998). On the other hand, ecological parameters of aquatic and terrestrial environments do not explain the patterns of polyphenic expression in alpine newt, Triturus alpestris (Denoël et al 2001a). Resource competition within populations likely explains maintenance of life cycle polyphenism in this species (Denoël and Joly 2001;Denoël et al 2004).…”

Trophic specialisations in alternative heterochronic morphs

“…One lake is located in southern France (La Cabane,4424 The three populations are composed of syntopic paedomorphic and metamorphic newts (Denol et al 2001a). In paedomorphic newts, the gill slits are open and support three pairs of external gills.…”

Patterns of morphometric variation in the alpine newt (Mesotriton alpestris) at the southern limit of its distribution: environmental correlates

“…For example, predation on newts could be intensive in large ponds, while in smaller ponds predation could be limited or even absent because most of the time the newts are the major predators (e.g. Cooke & Frazer 1976;Giacoma et al 1988;Bringsøe 1994;Denoël et al 2001). It has been reported that intensive predation on Appendix I.…”