How close is microhabitat and diet association in aquatic ecomorphotypes? A test with tadpoles of syntopic species

Abstract

Tadpoles are important components of food webs at aquatic ecosystems; however, their trophic roles remain understudied compared to fish. Morphology indicates general aspects of tadpole diets (e.g., food size), but a fine association between preferred microhabitats and diet composition remained to be tested. We tested whether syntopic tadpoles differed in microhabitat use and in diet composition according to food availability in different microhabitats. We also tested whether types of microhabitats were consistent in food availability or if food availability would vary among streams. Considering volumes of different food groups ingested, the diets of tadpoles could be partly explained by the microhabitats where they were sampled, but not by streams or even species. Considering number of items of each food group, the diet of tadpoles varied according to stream, microhabitat, and species. Volumes of items of each food group differed among microhabitats, but not among streams. All the studied species could be classified as primary consumers based on the dominance of algae (especially Zygnematophyceae and Bacillariophyceae) in their diets. Patterns of food consumption of tadpoles were complex and responded to variables at a very fine spatial scale, suggesting that they may be sensitive even to small alterations in stream dynamics.