Fungus Finds Frogs, Frogs Croak

Frogs have been having a tough time of it lately. While there are likely many contributing factors to the global frog decline, one known cause of frog dieoff is a fungal pathogen: Batrachochytrium dendrobatidis. Unfortunately, little is known about how this aquatic fungus kills frogs or how the disease was originated and spread.

However, Dr. Jess Morgan and colleagues published in PNAS (open access article) this week a study aimed at answering the latter questions. Specifically, the authors investigated Batrachochytrium populations in the Sierra Nevada Mountains and sampled the genetic diversity. A clonal population structure with few genotypes indicates that the fungus is new to the region as it hasn’t had time to accumulate mutations. Conversely, should the disease be endemic, there should be many distinct genotypes. Without giving too much of the punchline away, the authors find evidence for an epidemic spread, though certain locations have populations that are recombining.  Any migration of the fungus may even be human assisted.  It will be interesting to see how the disease is controlled and the authors raise a good point here: distribution of resistant sporangia may make it easy for the organism to spread and remain dormant.  As a result, this may be a particularly tough disease to control.