Authors: Jim P. Foster And Trevor J . C. Beebee

Abstract: In the UK, research has improved our understanding of amphibian popul ations, their habitats, threats and the effectiveness of conservation measures. The greatest research effort has been directed to the protected and declining species, notably Triturus cristatus, Bufa calamita and Rana lessonae. However, several challenges arise when attempting to employ research findings as a tool to shape policy. Wild populations and threats to them are not often simple systems that invite straightforward investigation. Extrapolating from small studies to more comprehensive appl i cation can also generate problems, especially with widespread species. The standards of confidence commonly used in science may not be directly transferable to conservation policy, as in conservation it is often desirable to apply the precautionary principle. When constructing policies, it is important to be realistic about the constraints that may be imposed due to factors beyond the control of conservation agencies and researchers, notably those of a legislative or socioeconomic nature. There is a need for conservation practitioners to engage more closely with scientists, with a view to identifying the current knowledge gaps that hinder the achievement of conservation gains. The increasing success of B. calamita reintroductions provides an excellent illustration of such an application of scientific knowledge.

Keywords: crested newt, natterjack toad, population ecology, research

Authors: P. Daszak, A. Strieby, A. A. Cunningham, J. E. Longcore , C. C. Brown2 And D. Porter

Abstract: To test the susceptibility of bullfrogs (Rana catesbeiana) to amphibian chytridiomycosis, groups of captive bred, recently metamorphosed bullfrogs were inoculated with zoospores of Batrachochytrium dendrobatidis, the causative agent of chytridiomycosis, and assayed for clinical and pathological signs of infection. A novel technique for counting B. dendrobatidis zoospore inocula is described. Inoculation regimes varied from single exposures of 1-10 million zoospores per animal to inocula of 10 million zoospores per animal per day for a 31 day period. Twenty-five to fifty percent of each inoculated cohort was histological ly positive for B. dendrobatidis on necropsy. However, lesions were focal, small with relatively little thickening of the keratinized epidermis and no clinical signs of chytridiomycosis were observed. Only one animal died during the experiment, due to cardiac puncture procedure. A fungal isolate used in these experiments was inoculated onto four metamorphosed poison dart frogs (Dendrobates tinctorius) to test whether B. dendrobatidis had become attenuated following repeated passage in culture. All four animals died within 30. days with severe chytridiomycosis, whereas two uninfected controls survived, demonstrating that the fungus had not become attenuated. These results provide the first experimental evidence that bullfrogs can be infected by B. dendrobatidis, but are relatively resistant to the disease chytridiomycosis, which is lethal to many other amphibian species. By demonstrating that R. catesbeiana is likely to be an efficient carrier of this pathogen, our experimental data add weight to the hypothesis that this host species is important in the spread of chytridiomycosis, particularly by commercial activities.

Keywords: amphibian decline, Batrachochytrium dendrobatidis, chytrid fungus, frog

Authors: Håkan Tegelström And Per Sjögren-gulve

Abstract: The isolated Swedish metapopulation of pool frogs (Rana lessonae) was not discovered until the 1940s and is classified as "vulnerable" in conservation terms. Swedish pool frogs are now known from 96 localities along the Baltic coast of east-central Sweden, and differ from Central European conspecifics in terms of col oration and low allozyme heterozygosity. Using mini- and microsatellite DNA fingerprinting and allozyme electrophoresis, we studied genetic differentiation among pool frogs from Poland, Latvia, Russia, and Sweden. Allozyme variability was partitioned equally within and among the populations (F _ST = 0.50). Both allozyme and DNA fingerprint analyses indicated that Swedish frogs were most similar to Latvian ones. The average similarity in DNA fingerprints among Swedish populations was of the same order as the similarity within the Polish, Latvian or Russian populations. Pool frogs from opposite ends of the Swedish distribution, however, were as different from one another as they were from continental conspecifics. Our results complement and corroborate the evidence from other studies, suggesting that there is a "northern clade" of Swedish, Norwegian and British pool frogs, and that the Swedish pool frogs constitute a relict population rather than being descendants from a recent introduction by humans.

Keywords: DNA fingerprinting, enzyme electrophoresis, green frogs

Authors: James P . Collins, Jesse L. Brunner, James K. Jancovjch And Danna M. Schock

Abstract: Pathogens are among the suspected causes of declining amphibian populations, but studying infectious diseases in small, threatened populations is ethically and experimentally questionable. Progress on understanding amphibian diseases requires model host-pathogen systems with populations large enough for robust experimental designs that do not threaten the amphibian host with extinction. We report on viral genomics, persistence, and host-pathogen dynamics of a model system we are u sing for studying an amphibian disease: tiger salamanders (Ambystoma tigrinum) and Ambystoma tigrinum virus (ATV). ATV is a large, cytoplasmic, double-stranded DNA virus that causes systemic infections in individuals and recurrent epidemics in tiger salamander populations in western North America. The A TV genome is now completely sequenced, which is an important step toward understanding viral pathogenesis. Further, because tiger salamanders and the closely related axolotl have a long history as model organisms for developmental genetics, the genetics, development, and physiology of these species are known at levels that can support detailed studies of the host-virus interaction. Salamanders b ecome infected with ATV via direct contact, feeding on infected tissues, and by immersion in water containing virus particles. There is no evidence of long-term persistence of ATV in the environment outside of sal amanders: the virus becomes quickly undetectable in pond water and dry mud, and no other syntopic hosts are known. ATV is usually lethal within 2-3 weeks of infection, although some salamanders lose overt symptoms of infection, including papules and lesions, and survive. In one laboratory experiment A TV was re-isolated from 40% of these survivors, which then transmitted the disease to uninfected.salamanders. Chronic infections also occur in field populations and appear to be the means by which A TV persists between epidemics. The tiger salamander-A TV system offers us a model for studying the host-pathogen interactions thought to be threatening some amphibian populations with extinction .

Keywords: amphibian declines, conservation, ATV, ranaviruses,

Authors: Jean-marc Hero And Clare Morrison

Abstract: Amphibian declines have been reported from around the world. H ere we examine life history and distributional characteristics of Australian frogs listed as threatened under the IUCN Global Amphibian Assessment guidelines, and compare these results to available information on threatened amphibians around the world. Forty of 213 Australian frog species (18.8%) are currently recognised as threatened. While eight species are listed as Vulnerable due to small or restricted populations alone (VU D2), the remaining 32 species are associated with population declines. Threatened species are concentrated in upland areas (41% of all upland species are threatened, while only 8% of lowland species are threatened). Twenty-eight of the 40 threatened species (70%) primarily occur in upland areas while only 42 of the 1 73 non-threatened species (24.3%) occur in upland areas. Restricted geographic range is characteristic of 31 of 40 threatened/declining species (77.5%). However, 41 non-threatened species (23.7%) also have restricted geographic ranges. Latitudinal position is not strongly associated with the degree of threat. Threatened species are strongly associated with specific reproductive habitats: 80% of species occurring in montane wetlands and 58% of species breeding in wet forest streams are threatened. For 22 of the 40 (55%) threatened species, known threats do not adequately explain the extent of decline. Habitat modification is the foremost threatening process associated with declines in 20 of the 40 threatened species (50%), including 11 of 12 threatened lowland species (91.7%). Chytrid fungus is notably associated with declines for five species and a potential contributor for an additional nine species (35% of threatened species). However, the chytrid has also been detected in an additional 33 non-threatened species (19%). Minor threats associated with threatened species include fire and global changes in weather patterns. Phylogenetic relationships of Australian frogs are poorly resolved, and there are no strong associations between phylogeny and declines within knovn1 taxonomic groups. A notable exception are frogs of the myobatrachid genus Taudactylus where five of the six species are threatened. Global patterns are difficult to assess, however, as declines are strongly associated with species that are primarily distributed in upland areas. Chytrid fungus has been found in both declining and non-declining species throughout Australia, and while its role as an emerging infectious disease is currently under investigation (in Australia, New Zealand, Spain, South Africa, Costa Rica, Ecuador and the USA), little is known about its distribution and prevalence in other countries.

Keywords: altitude, amphibians, geographic range, IUCN, life history, status

Authors: Benedikt R. Schmidt

Abstract: Most data used in the study of the demography, dynamics, distributions, diversity, and declines of amphibians are count data that are not adjusted for detection probabilities, which are generally variable and l ow. Such unadjusted count data are unreliable for understanding amphibian ecology, amphibian declines, or when developing conservation and management strategies. In the future, detection probabilities should be estimated and counts adjusted accordingly. This could be achieved by using capture-mark-recapture, distance sampling or novel Bayesian methods.

Keywords: conservation, detection probability, population census, survey methods

Authors: Richard A. Griffiths And Tim R. Halliday