Climate change and outbreaks of amphibian chytridiomycosis in a montane area of Central Spain; is there a link?

Abstract

Amphibian species are declining at an alarming rate on a global scale in large part owing to an infectious disease caused by the chytridiomycete fungus, Batrachochytrium dendrobatidis. This disease of amphibians has recently emerged within Europe, but knowledge of its effects on amphibian assemblages remains poor. Importantly, little is known about the environmental envelope that is associated with chytridiomycosis in Europe and the potential for climate change to drive future disease dynamics. Here, we use long-term observations on amphibian population dynamics in the Peñalara Natural Park, Spain, to investigate the link between climate change and chytridiomycosis. Our analysis shows a significant association between change in local climatic variables and the occurrence of chytridiomycosis within this region. Specifically, we show that rising temperature is linked to the occurrence of chytrid-related disease, consistent with the chytrid-thermal-optimum hypothesis. We show that these local variables are driven by general circulation patterns, principally the North Atlantic Oscillation. Given that B. dendrobatidis is known to be broadly distributed across Europe, there is now an urgent need to assess the generality of our finding and determine whether climate-driven epidemics may be expected to impact on amphibian species across the wider region.

Figure 1

(a) Yearly and (b) monthly variation in the climatic characteristics of an alpine area of the Sierra de Guadarrama. Sample size is 12 months for each year and 28 years for each month. Values represented are mean±1 s.e. Within grey areas are included the years of observed chytridiomycosis infection in the amphibian populations of Peñalara area. For significance of differences among years and months, see table 1.

Figure 2

Variation in the number of days (ordinate) with maximum temperatures higher than several temperature values (abscissa) in the time-interval 15 July to 15 September. Two time periods are compared according to lack (1976–1996) or presence (1997–2003) of chytridiomycosis. The grey area denotes significant differences in the t-tests comparing these two time periods (p<0.05).

Figure 3

Yearly mean surface temperature anomalies for the station (dashed line) along with annual land air and sea surface temperature anomalies (solid line).

Figure 4

Composite maps of the 850 GHA for the first three PCs when their value is (a) higher than half of the s.d. and (b) lower than minus half of the s.d. ‘X’ denotes the geographical location of the study area.