Background
The authors write that "climate change has been proposed as a driver of amphibian declines," but they note that this hypothesis has been largely displaced by a competing theory built around the observation that the pathogen Batrachochytrium dendrobatidis (Bd) has been "associated with amphibian declines throughout the world (Berger et al., 1998; Briggs et al., 2005; Lips et al., 2006)" in a manner indicative of an introduced and subsequently-spreading epidemic disease. And in an attempt to shed more light on this important subject, they conducted a study of the recent collapse of anuran species richness and abundance in the Upper Manu National Park of Southeastern Peru.

What was done
Catenazzi et al. surveyed frogs in the Peruvian Andes in montane forests along a steep elevation gradient (1200-3700 m), using visual encounter surveys to sample stream-dwelling and arboreal species and leaf-litter plots to sample terrestrial-breeding species, in order to compare species richness and abundance among the wet seasons of 1999, 2008 and 2009.

What was learned
The U.S. and Peruvian researchers found there had been "a dramatic decline in species richness of amphibians" -- a mean decline of 38% in the area of their study over the ten-year period -- with stream-breeding species being "disproportionally represented among the missing taxa in 2008 and 2009." Of this result, they say that it "is consistent with observations in other Neotropical (Lips, 1998) and Australian (Laurance et al., 1996; Williams and Hero, 1998) sites where the species richness and abundance of frogs have declined or frogs have been extirpated," while noting that "declines in these other areas are unequivocally linked to the introduction of Bd to naïve amphibian populations (Berger et al., 1998; Lips et al., 2006)."

In addition, they say their results show that "the geographic and elevational distribution of Bd extends to southern Peru," noting that this extent is consistent with Lips et al.'s (2008) hypothesis that Bd is spreading southward in a wave from a Bd introduction site in southwestern Ecuador. Alternatively, they suggest that the Bd introduction site could be Cusco, which "receives more visitors than any other tourist destination in Peru." And, noting that "frogs originating from many streams, ponds and lakes of the Bolivian-Peruvian Altiplano are sold live in the city for human consumption," they suggest that this frog trade "could facilitate the spread of Bd over large areas in southern Peru."

What it means
Given the above observations, plus the fact that "Bd occurs in a wide range of land-cover types and microclimates," Catenazzi et al. say "it is unclear how climate change would increase the rate of spread or the virulence of such an opportunistic pathogen in frog populations," and they thus conclude that it hasn't.

References
Berger, L., Speare, R., Daszak, P., Green, D.E., Cunningham, A.A., Goggin, C.L., Slocombe, R., Ragan, M.A., Hyatt, A.D., McDonald, K.R., Hine, H.B., Lips, K.R., Marantelli, G. and Parkes, H. 1998. Chytridiomycosis causes amphibian mortality associated with population declines in the rainforests of Australia and Central America. Proceedings of the National Academy of Sciences USA 95: 9031-9036.

Briggs, C.J., Vredenburg, V., Knapp, R.A. and Rachowicz, L.J. 2005. Investigating the population-level effects of chytridiomycosis, an emerging infectious disease of amphibians. Ecology 86: 3149-3159.

Laurance, W.F., McDonald, K.R. and Speare, R. 1996. Epidemic disease and the catastrophic decline of Australian rain forest frogs. Conservation Biology 10: 406-413.

Lips, K.R. 1998. Decline of a tropical montane amphibian fauna. Conservation Biology 12: 106-117.

Lips, K.R., Brem, F., Brenes, R., Reeve, J.D., Alford, R.A., Voyles, J., Carey, C., Livo, L., Pressier, A.P. and Collins, J.P. 2006. Emerging infectious disease and the loss of biodiversity in a Neotropical amphibian community. Proceedings of the National Academy of Sciences USA 103: 3165-3170.

Williams, S.E. and Hero, J.-M. 1998. Rainforest frogs of the Australian wet tropics: Guild classification and the ecological similarity of declining species. Proceedings of the Royal Society of London B 265: 597-602.