Author's personal copy High prevalence of infection in tadpoles increases vulnerability to fungal pathogen in high-Andean amphibians Alessandro Catenazzi a,⇑ , Rudolf von May b , Vance T. Vredenburg a a Department of Biology, San Francisco State University, San Francisco, CA 94132, USA b Museum of Vertebrate Zoology, University of California, Berkeley, CA 94720, USA article info Article history: Received 18 September 2012 Received in revised form 16 November 2012 Accepted 19 November 2012 Keywords: Batrachochytrium dendrobatidis Chytridiomycosis Telmatobius jelskii Peru Andes Streams Infection prevalence Epizootic Larval stage abstract The amphibian pathogen Batrachochytrium dendrobatidis (Bd) is causing population declines and species extirpations worldwide. Montane amphibians in tropical and temperate regions are especially vulnerable to chytridiomycosis. High-elevation amphibian assemblages typically include few species, so that epizo- otics should be limited once high frog mortality hinders transmission of the pathogen. We hypothesized that tadpoles of a high-elevation frog in the Peruvian Andes, Telmatobius jelskii, could function as reser- voir for Bd in Andean streams. We postulated that, for tadpoles to function as an efficient reservoir of Bd, they should inhabit streams over extended periods of time, and have high prevalence of Bd. We surveyed streams between 2400 and 4850 m in the wet and dry seasons of 2010, where we captured, swabbed and determined the developmental stage of 458 tadpoles. We found that cohorts of tadpoles overlap contin- uously in these streams, as a consequence of multiple breeding events throughout the year. Prevalence of Bd among tadpoles averaged 53.1% (95% confidence interval: 49.8–56.3%); 8 out of 13 streams inhabited by T. jelskii had a prevalence greater than 50%. Prevalence of Bd was also higher during the dry season and increased with the age of the tadpoles. Our results support the hypothesis that the year-long presence of infected tadpoles in streams makes high-Andean Telmatobius frogs especially vulnerable to chytridiomy- cosis. The genus is already extirpated in Ecuador, and has been observed to decline rapidly in Peru, Bolivia and Argentina. Conservation strategies to mitigate the impact of Bd on populations of Telmatobius should consider aquatic life-stages. Ó 2012 Elsevier Ltd. All rights reserved. 1. Introduction High elevation amphibians are threatened by chytridiomycosis, an emergent and highly virulent disease caused by the fungus Batra- chochytrium dendrobatidis (Bd; Berger et al., 1998; Kilpatrick et al., 2010; Vredenburg et al., 2010). Bd epizootic events, which cause population declines and extirpations, have been documented in montane areas in California (Vredenburg et al., 2010), the Andes in Peru (Catenazzi et al., 2011; Seimon et al., 2007), and the Pyrenees and similar regions of the Iberian peninsula (Walker et al., 2010). The devastating impact of chytridiomycosis on montane amphibi- ans is puzzling for a number of reasons. The optimal growth for Bd in culture is reportedly 15–25 °C(Piotrowski et al., 2004; Wood- hams et al., 2008). These temperatures seldom occur at high eleva- tion, even in tropical regions. The persistence of Bd in populations of highly vulnerable hosts is especially intriguing, because amphibian species richness at high-elevations is low, which limits the number of alternative hosts. During a chytridiomycosis outbreak, the high mortality of infected host frogs should quickly reduce transmission, and therefore reduce the risks of future outbreaks and epizootics (Anderson and May, 1979). Therefore, in order to persist Bd requires an alternative host or an environmental reservoir. In contrast to adults, chytridiomycosis is not lethal to tadpoles of most species (Blaustein et al., 2005). Bd infects the keratinized mouthparts of tad- poles (Fellers et al., 2001), and infected tadpoles can be recognized by their abnormal and depigmented oral disks (Knapp and Morgan, 2006; Vredenburg and Summers, 2001). The larval stages of montane amphibians often spend extended periods of time in water before completing metamorphosis, and frequently over-winter in temperate regions (Bosch and Marti- nez-Solano, 2006; Bosch et al., 2001; Briggs et al., 2010). Under- standing the link between amphibian larval development and Bd epidemiology is crucial for designing strategies to reduce the im- pact of this disease on potentially susceptible species (Bosch and Martinez-Solano, 2006; Briggs et al., 2010; Conradie et al., 2011). Here we explore the hypothesis that long-lived tadpoles function as reservoirs for Bd in populations of high-Andean frogs. We inves- tigated whether tadpoles of Telmatobius jelskii continuously occupy aquatic habitats throughout the year, and denoted their Bd infec- 0006-3207/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.biocon.2012.11.023 ⇑ Corresponding author. Address: Department of Biology, San Francisco State University, 1600 Holloway Ave., San Francisco, CA 94132, USA. Tel.: +1 (305) 396 2626. E-mail address: acatenazzi@gmail.com (A. Catenazzi). Biological Conservation 159 (2013) 413–421 Contents lists available at SciVerse ScienceDirect Biological Conservation journal homepage: www.elsevier.com/locate/biocon