Comparisons of niche diversification in an upland neotropical stream food web pre- and post- frog extinction

Background/Question/Methods . This study was part of the TADS (Tropical Amphibian Declines in Streams) project. We examined niche diversification among macroinvertebrates and tadpoles in an upland stream in Panama. We used C-N stable isotope biplots. Results/Conclusions . There was clear separation in isotope niche space among insect species within given functional feeding groups, suggesting that food partitioning is occurring at fine scales. For example, two insect grazer species Petrophila (Lepidoptera) and Thraulodes (Ephemeroptera) had completely non-overlapping C-N isotope niches. Dramatic declines in tadpole abundance occurred for all frog species in our study stream during our study as a result of a fungal pathogen, with concomitant changes in the relative abundance of macroinvertebrate species such as Petrophila (increases) and Thraulodes (decreases). Tadpoles of some frog species (e.g, Rana warszewitschii and Centrolene sp.) were still present in the stream at greatly reduced numbers five months after the major decline. Conclusions. This provided us with the opportunity to compare C-N niche spaces of these remaining frog species and dominant insect taxa before and after an amphibian decline.