Recent genetic analysis of the largest collection of Bd isolates from around the globe (because Bd is now found in all continents) shows that Bd is older, definitively (much) older than mass amphibian population crashes, and has a complex population structure. What does this tell us? Many things in fact, but the fact I find most relevant to conservation is that Bd may have been exerting selective pressure on a number of amphibian species, possibly for a long time. Exerting a selective pressure means, in genetic terms, that individuals with certain alleles had a greater survival than individuals that had not. In population terms it means that populations might had quite severe reductions, followed by rebounds when individuals carrying the selected for alleles became the norm in the population. It also means that naive populations (that is, populations that have not yet encountered Bd) will undergo a strong selection that will either select for infection resistance (if the necessary genetic variation is present). Alternatively these naive populations will have a great risk of going extinct. We know in fact that Bd is causing mass mortalities of many amphibian species around the globe, and we know that a number of these species just disappeared. We know next to nothing about the genetics of amphibians, so there is no way we can understand what is happening, in genetic terms, on the host side of the equation.
The observations above give me a strong 'take home message': unless we start to work in earnest on amphibian genetics and genomics, all the work done on Bd will not be enough to stop and revert amphibian populations declines. Because virulence is a property of the host/parasite interaction, we must be able to understand *both* Bd and amphibian population genetic structure to properly understand the potential virulence of each Bd/amphibian interaction. This understanding is necessary to model population crash dynamics in the wild, and to have a hope to rescue amphibian populations in the first place. Only genetic tools will allow us to test the hypothesis that Bd has been a selective force for some amphibian species for thousands of years, and only genetic tools will allow us to understand the genetics of adaptation to such selective pressure.
All the above is, in practice, a lot of work, expensive, time consuming. With the world economy circling around the drain, governments are brutally cutting research funds for biology and conservation. This is too bad, for so many reasons, and because we are running out of time to save many amphibian species. Amphibian genetics is a prefect case of basic research with a direct, clearly identifiable goal that will have potential benefit for the taxpayer. If the urgency of this issue and the obvious potential benefits of tackling it are not enough to get people to invest on amphibian genetics now, all I can say is that we might as well have frog legs for dinner.