Rainforest frogs of the Australian Wet Tropics: guild classification and the ecological similarity of declining species

Anthropogenic environmental change and the emergence of infectious diseases in wildlife

By using the criteria that define emerging infectious diseases (EIDs) of humans, we can identify a similar group of EIDs in wildlife. In the current review we highlight an important series of wildlife EIDs: amphibian chytridiomycosis; diseases of marine invertebrates and vertebrates and two recently-emerged viral zoonoses, Nipah virus disease and West Nile virus disease. These exemplify the varied etiology, pathogenesis, zoonotic potential and ecological impact of wildlife EIDs. Strikingly similar underlying factors drive disease emergence in both human and wildlife populations. These are predominantly ecological and almost entirely the product of human environmental change. The implications of wildlife EIDs are twofold: emerging wildlife diseases cause direct and indirect loss of biodiversity and add to the threat of zoonotic disease emergence. Since human environmental changes are largely responsible for their emergence, the threats wildlife EIDs pose to biodiversity and human health represent yet another consequence of anthropogenic influence on ecosystems. We identify key areas where existing expertise in ecology, conservation biology, wildlife biology, veterinary medicine and the impact of environmental change would augment programs to investigate emerging diseases of humans, and we comment on the need for greater medical and microbiological input into the study of wildlife diseases.

Colonization of high-elevation lakes by long-toed salamanders (Ambystoma macrodactylum) after the extinction of introduced trout populations

We surveyed high-elevation lakes for long-toed salamander (Ambystoma macrodactylum) larvae and trout in the northern Bitterroot Mountains of Montana, U.S.A., in 1978, 1997, and 1998. Our objectives were to (i) test whether trout exclude salamander populations; (ii) determine whether lakes in which trout have gone extinct have since been colonized by salamanders; and (iii) estimate the rates of population extinction and colonization in lakes never stocked with trout. In agreement with previous work on the interactions between trout and long-toed salamanders, trout effectively excluded salamander populations from lakes. Somewhat surprisingly, however, salamanders managed to colonize lakes after the extinction of trout populations despite evidence of low levels of interpopulation dispersal in these salamander populations. In lakes never stocked with trout there was no evidence of a decline in salamander populations; 2 of these lakes were colonized and no populations went extinct.

Emerging infectious diseases and amphibian population declines

We review recent research on the pathology, ecology, and biogeography of two emerging infectious wildlife diseases, chytridiomycosis and ranaviral disease, in the context of host-parasite population biology. We examine the role of these diseases in the global decline of amphibian populations and propose hypotheses for the origins and impact of these panzootics. Finally, we discuss emerging infectious diseases as a global threat to wildlife populations.