As a result of factors such as global warming, habitat destruction, and species introduction, amphibians are declining worldwide. No one, however, has analyzed the status of polymorphic amphibian species at a national or continental scale, although some local reports exist. Our aim was to report on the loss of intraspecific heterochrony as a loss to diversity in determining the consequences of fish stocking on European populations of paedomorphic newts. Paedomorphosis is a polymorphism in which larval traits are retained in the adult stage. We surveyed 39 paedomorphic populations of the alpine ( Triturus alpestris) and palmate ( T. helveticus) newts, all but one of which initially occupied fishless ponds and lakes in France, Italy, Slovenia, Bosnia, Montenegro, and Greece. Exotic fishes were found in 44% of the studied aquatic habitats, with a 100% presence in Montenegro. At all sites paedomorphs disappeared and metamorphs declined. Only fish explained these population changes because alternative factors such as drying were not significant. More catastrophically, fish introductions occurred in habitats known to support the largest populations of newts and even some endemic subspecies. If management and legislative measures are not taken to stop fish stocking, protect paedomorphs as conservation units at national and international levels, and restore natural habitats, all the largest paedomorphic populations may disappear in the near future. Their disappearance would represent a loss of one of the rare, fascinating examples of intraspecific heterochrony. Resumen: Los anfibios están declinando mundialmente debido a causas como calentamiento global, destrucción de hábitat e introducción de especies. Sin embargo, nadie ha analizado el estatus de especies polimórficas de anfibios a una escala nacional o continental, aunque existen algunos reportes locales. Nuestro objetivo fue reportar la pérdida de heterocronía intraespecífica como una pérdida de diversidad al determinar las consecuencias del aprovisionamiento de peces sobre poblaciones europeas de tritones pedomórficos. La pedomórfosis es un polimorfismo en el que se retienen características larvarias en la etapa adulta. Muestreamos 39 poblaciones pedomórficas de los tritones Triturus alpestris y T. helveticus, que, excepto una, inicialmente habitaban charcas y lagos sin peces en Francia, . Encontramos peces exóticos en 44% de los hábitats acuáticos estudiados, con presencia de 100% en Montenegro. Los pedomorfos desaparecieron y los metamorfos declinaron en todos los sitios. Solo peces explicaron estos cambios poblacionales porque factores alternativos como desecación no fueron significativos. Más catastróficamente, las introducciones de peces ocurrieron en hábitats conocidos por sostener a las mayores poblaciones de tritones incluyendo algunas subespecies endémicas. Todas las poblaciones pedomórficas grandes pueden desaparecer en el futuro cercano si no se toman medidas de gestión y legislativas para detener el aprovisionamiento de peces, proteger a pedomorfos como...

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As with many other amphibians, Triturus species are characterized by a biphasic life cycle with abrupt changes in the cranial skeleton during metamorphosis. The post-metamorphic shape changes of the cranial skeleton were investigated using geometric morphometric techniques in six species: Triturus alpestris, T. vulgaris, T. dobrogicus, T. cristatus, T. carnifex, and T. karelinii. The comparative analysis of ontogenetic trajectories revealed that these species have a conserved developmental rate with divergent ontogenetic trajectories of the ventral skull shape that mainly reXect phylogenetic relatedness. A striking exception in the ontogenetic pattern was possibly found in T. dobrogicus, characterized by a marked increase in the developmental rate compared to the other newt species. The size-related shape changes explained a large proportion of shape change during postmetamorphic growth within each species, with marked positive allometric growth of skull elements related to foraging.

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In this article, we explore the possible influences of the developmental and functional relationships between skeletal elements on the pattern of morphological integration in the adult skull of the alpine newt. Like many tailed amphibians, the alpine newt has a biphasic life cycle, which implies the possibility that two distinct sets of constraints on development and function of the cranial skeleton may act at different times. We study how trait covariation, resulting from processes early in development, affects patterns of covariation at the adult stage. We test whether the observed patterns of integration are consistent with those predicted from three a priori hypothesized sources of integration: developmental timing, hormonally mediated growth/remodeling during metamorphosis, and developmental and functional relationships. The analyses of the covariation among the landmarks in the dorsal and ventral alpine newt craniums yield somewhat contrasting results. Our results do not indicate a clear correspondence between the observed variations in the skull shape and any of the three proposed hypotheses. No traceable reflection of hypothesized developmental relationships in the pattern of morphological integration/modularity in the adult skull indicate that covariation structure is continually restructured by overlaying variation introduced through developmental and environmental factors at different stages of development. This finding supports the recently elaborated palimpsest view of morphological integration. Also, our results indicate that the allometry-free shape data have an even higher level of morphological integration than the data that contain the allometric component of the shape variation.

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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.