Evaluating the links between climate, disease spread, and amphibian declines

Area of Science:

• Ecology
• Zoology
• Environmental Science

Background:

• Amphibians face a high extinction risk, with the chytrid fungus Batrachochytrium dendrobatidis (Bd) identified as a major driver of global declines.
• Two primary hypotheses, the chytrid-thermal-optimum and spatiotemporal-spread hypotheses, attempt to explain Bd-driven amphibian extinctions, with differing roles for climate change.

Purpose of the Study:

• To rigorously test the chytrid-thermal-optimum and spatiotemporal-spread hypotheses regarding amphibian extinctions in the genus Atelopus.
• To determine if climate factors like cloud cover and temperature convergence predict Atelopus extinctions and if spatial patterns exist in extinction timing.

Main Methods:

• Evaluated the predictive power of cloud cover, temperature convergence, and Bd growth optima on Atelopus extinctions.
• Assessed spatial structure in extinction timing without assuming Bd emergence details.
• Correlated Atelopus extinctions with mean tropical air temperature and other regional variables.

Main Results:

• Spatial structure in Atelopus spp. extinctions was detected, but its cause remains unclear, necessitating further molecular study of Bd.
• A robust multi-decade correlation between Atelopus extinctions and prior year tropical air temperature was confirmed.
• Evidence for a causal link between temperature and extinctions was weak, with variables like regional banana and beer production being stronger predictors.

Conclusions:

• Findings largely contradicted the chytrid-thermal-optimum hypothesis.
• While climate change may influence amphibian declines, a direct causal link to Bd-driven extinctions requires more substantial evidence.
• The drivers of Atelopus extinctions are complex and may involve factors beyond climate and Bd spread alone.