Meeting Abstract
27.2 Monday, Jan. 5 Growth and development of stream tadpoles in relation to drainage network position CATENAZZI, A*; KUPFERBERG, S; University of California, Berkeley; University of California, Berkeley acatenazzi@gmail.com
An open question in amphibian ecology is the extent to which distribution and abundance of populations are determined by the performance of early life stages. Monitoring of the stream-breeding Foothill Yellow-legged frog (Rana boylii) in northern California suggests that variation in larval survival induces population fluctuations. Although frogs use all lotic habitats at the Angelo Reserve, oviposition occurs only in wide, sun-lit channels. We focused on 4 streams varying in primary productivity and temperature. Egg mass censuses indicate a dense population in the S. Fk. Eel River, which is intermediate in watershed size (130 km2) and temperature, a smaller population in warm Tenmile Ck. (180 km2) and no reproduction in cooler tributaries, Elder and Fox (16.8 and 2.6 km2). To understand the consequences of thermal regime and food requirements to frog recruitment, we reared tadpoles in enclosures in these streams. In half of the enclosures, we supplemented ambient epilithic periphyton with macroalgae epiphytized by nutritious Epithemia spp. diatoms. Survival to metamorphosis in the Eel was higher with algal supplements (46 7%) than it was with ambient periphyton (26 8%), and significantly lower in other locations. Although cool temperatures greatly lengthened the larval period, food supplements allowed some individuals to reach metamorphosis in the small tributaries. With food, the first metamorphs appeared in the two warm sites at day 69, but not until day 111 and 118 in cooler streams. Regardless of algal supplementation, tadpoles grew to larger size at the Eel and Tenmile, contrary to the expectation that tadpoles grow to larger size at lower temperatures. Our results suggest that the distribution of frogs in the drainage network is explained by factors affecting early life stages, such as food availability and water temperature.
