Effects of Density on Batrachochytrium dendrobatidis Transmission in Mountain Yellow-legged Frogs (Rana muscosa)

Lara Rachowicz

Resource Management and Science,

Yosemite National Park, Yosemite, CA

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ABSTRACT

RACHOWICZ, LARA1,2*, and CHERIE BRIGGS2
1Resources Management and Science, Yosemite National Park, Yosemite, CA, lara_rachowicz@nps.gov; 2Dept. of Integrative Biology, Univ. of California, Berkeley, CA.

Effects of Density on Batrachochytrium dendrobatidis Transmission in Mountain Yellow-legged Frogs (Rana muscosa).

An emerging infectious disease of amphibians, chytridiomycosis, caused by the fungal pathogen Batrachochytrium dendrobatidis, recently has been implicated in population declines and possible extinctions throughout the world, including in protected areas. B. dendrobatidis zoospores, the infectious stage of the fungus, infect keratinized cells found in the mouthparts of anuran tadpoles and the skin of postmetamorphic individuals. Here, we examined the form of the transmission function of this pathogen in the mountain yellow-legged frog (Rana muscosa) by performing laboratory and field experiments. We then used a maximum likelihood approach to determine what form of the transmission function is best supported by the experimental data. We also investigated what impact crowding might have had on transmission. In the laboratory and in some natural environments, we detected a significant positive relationship in the proportion of R. muscosa tadpole hosts that became infected after a few weeks of B. dendrobatidis exposure with increasing numbers of previously infected R. muscosa tadpoles added to their local environment.