Authors: Godfrey C. Akani, Luca Luiselli And Francesco M. Angelici

Authors: Mayuri R. Wijesinghe And P. N. Dayawansa

Authors: Gabriel Lobos And G. John Measey

Abstract: Invasive populations of Xenopus laevis are known from the UK, USA and Chile, although there is poor documentation of the latter. Currently, four administrative Regions in Chile are reported as having established populations. Fieldwork during the austral winter of 2001 was conducted in order to assess the density and diet of X. laevis populations in two localities. At one site, fewer than 30 adults were captured and a population 4 times this size was estimated. At the second site, nearly 2000 adults were trapped and a population of nearly 20000 was estimated. This yielded density estimates of 0.37 and 0.25 clawed frogs m·2 respectively. However, significant bias in the sex ratio of animals caught at each site suggests that the populations may be even larger. Stomach contents of a sub-sample of animals revealed a diet consisting primarily of zoobenthic and zooplanktonic components. Further work is required to assess the extent to which this anuran affects the biodiversity of indigenous aquatic invertebrate, fish and amphibian populations.

Keywords: African clawed frogs, exotic species, invasive amphibians, South America

Authors: Bruno Josseaume

Authors: Jerry Lea , Mandy Dyson And Tim Halliday

Abstract: The Mallorcan midwife toad (Alytes muletensis) has a very extended breeding season, and the nature of competition between larvae in the torrent pools where it breeds is likely to change across time. Larvae commonly overwinter and grow to a very large size and new hatchlings will have to compete with these overwintered larvae under varying conditions of density. The effects of density and cohort structure (i.e. the presence/absence of large overwintered tadpoles) on the growth and development of hatchling A. muletensis larvae were investigated in the laboratory using a factorial design. Large competitors, high densities and lower temperatures were all shown to suppress tadpole growth and development. Larger competitors were superior, especially the very large overwintered tadpoles. Whilst large size is advantageous, avoiding competition with overwintered tadpoles or high densities of tadpoles is probably much more important in determining size at - and timing of - metamorphosis. Because A. muletensis is an endangered species, knowledge of life history constraints can guide management of wild populations. The results are discussed in terms of potential optimal times to breed in light of the changing competitive environment.

Keywords: amphibian, anuran, competition, density effects, tadpoles

Authors: Ulrich Sinsch, Hans Schneider , Ugur Kaya And Hüseyin Arikan

Abstract: The morphometric variation among 138 water frogs collected in Turkey at twelve localities extending from the Mediterranean coast in the south to the Black Sea coast was analysed using principal component and discriminant analyses. The water frog sample was heterogeneous and included two diagnosable morphs. Comparison with specimens from the type localities of Rana bedriagae (Damascus, Syria) and R. ridibunda (Atyrau, Kazakhstan) demonstrated that the most common water frog taxon in Turkey is R. bedriagae. The second morph was restricted to Ulubey, near Ordu, and was not conspecific with either R. bedriagae or R. ridibunda. It was, however, morphometrically closer to R. bedriagae than to R. ridibunda. As we were unable to locate an extant population of frogs which resembled the preserved sample from Ulubey, the taxonomic status of these morphometrically distinct water frogs remains unresolved. The large water frogs of the Anatolian Lakes District were indistinguishable from R. bedriagae in size-adjusted shape, but their maximum size exceeded that of R. bedriagae from all other localities by about 30 mm. We therefore provisionally refer to them as R. bedriagae caralitana. Reliable taxonomic recommendations require further information on independent character complexes such as advertisement calls and allozymes.

Keywords: morphometry, Rana bedriagae, R. bedriagae caralitana, R. ridibunda, systematics