Michelle De Jesús Ortiz
University of Puerto Rico in Humacao
Urb. Estancias del Golf #379
Ponce, P.R. 00731
(787)448-2718; miche_dejesus@hotmail.com

Freshwater stream invertebrates often prefer consuming conditioned leaf litter by fungi and other microorganisms. This study differed from previous research on freshwater stream invertebrates by addressing possible differences in palatability between leaves conditioned by white-rot basidiomycete vs. brown-rot. We used both an in situ trial and a microcosm experiment to determine through paired trials whether conditioning by white- vs. non-white-rot influences palatability of leaf litter to stream invertebrates. We compared leaf area and mass loss of leaf discs of two leaf species (high lignin, Inga vera; low lignin, Manilkara bidentata) conditioned either by a white-rot, Collybia johnstonii vs. paired discs cut from the same leaves with brown-rot that are exposed to freshwater invertebrates. Using paired t-tests, both percent mass loss and percent leaf area loss were greater in white- than in brown-rot in the microcosms. However, only mass loss was significantly faster in the stream by the white-rot of I. vera. The preference towards white-rot and a high lignin conditioned leaf was consistent with our main hypothesis. Thus, the preferences in the stream were apparently based on an interaction of the type of rot with leaf species, and may also reflect responses from mixtures of leaf shredders with differing preferences.