Rohr and his University of South Florida colleagues Thomas R. Raffel and John M. Romansic, both faculty associates, along with Hudson and Hamish McCallum, professor of wildlife research, University of Tasmania, tested the competing theories by re-analyzing the same data used in conceiving the two ideas.
The team's findings were published in a recent issue of the Proceedings of the National Academy of Sciences. The work is funded by the National Science Foundation.
The scientists checked the first hypothesis to see whether climatic factors such as the percentage of cloud cover, narrowing difference between the lowest average daily temperature and the highest average daily temperature, and the predicted growth rate of the fungus under certain temperatures, could accurately predict extinctions.
Their statistical analysis revealed no such narrowing of temperature spans in the 1980s, when extinctions were increasing. When the difference in average daily temperatures did narrow in the 1990s, amphibian extinctions were decreasing.
Further, while the chytrid-thermal-optimum hypothesis showed high elevations as having the highest proportion of amphibian declines and the second highest proportion of amphibian extinctions, statistical analysis showed that growth rates for the fungus and cloud cover to be lowest at the highest elevation.
"While there is evidence to suggest that the chytrid fungus is killing the frogs, further research is needed before we can conclude that climate change is accelerating the spread," said Rohr, who previously was a researcher with Penn State's Center for Infectious Disease Dynamics.
A separate statistical analysis of the spread hypothesis also indicated inconsistencies between the year of amphibian declines, and the sites from where the fun
|Contact: Amitabh Avasthi|