Emerging infectious disease and the loss of biodiversity in a Neotropical amphibian community

Abstract

Pathogens rarely cause extinctions of host species, and there are few examples of a pathogen changing species richness and diversity of an ecological community by causing local extinctions across a wide range of species. We report the link between the rapid appearance of a pathogenic chytrid fungus Batrachochytrium dendrobatidis in an amphibian community at El Copé, Panama, and subsequent mass mortality and loss of amphibian biodiversity across eight families of frogs and salamanders. We describe an outbreak of chytridiomycosis in Panama and argue that this infectious disease has played an important role in amphibian population declines. The high virulence and large number of potential hosts of this emerging infectious disease threaten global amphibian diversity.

Fig. 1.

Map of Central America, with sites of published population declines; lines represent date and location of reported declines (36).

Fig. 2.

Mortality rates for riparian and terrestrial transects, calculated as the proportion of dead frogs in all captures for both night and day transects (1998–2005). No dead animals were found on transects until October 4, 2004, at which time mortality increased until January, 2005, by which time abundance was significantly reduced.

Fig. 3.

Amphibian densities and statistical models for riparian and terrestrial transects (1998–2005). By using a segmented linear model for the riparian transects, we found a highly significant difference (θ₂) in slope (t = −24.44, df = 486, P < 0.0001), with the estimated time of change (α) being September 4, 2004 (95% confidence interval, September 1–6). We could fit a linear model to only the terrestrial transects (see text for details). Diurnal transects were significantly lower in density than nocturnal ones (t = −13.05, df = 486, P < 0.0001 for riparian transects; t = −9.11, df = 212, P < 0.0001 for terrestrial transects).

Fig. 4.

Species richness and statistical models for riparian and terrestrial transects (1998–2005). By using the segmented linear model for the riparian transects, we found a highly significant difference (θ₂) in slope (t = −6.97, df = 486, P < 0.0001), with the estimated time of change (α) being October 22, 2004 (95% confidence interval, October 11–November 3, 2004). We could fit a linear model to only the terrestrial transects (see text for details). Diurnal transects were significantly lower in density than nocturnal transects (t = −21.33, df = 486, P < 0.0001 for riparian transects; t = −6.14, df = 212, P < 0.0001 for terrestrial transects).