Is the diet of a typical shredder related to the physical habitat of headwater streams in the Brazilian Cerrado?

¹ Laboratório de Ecologia de Bentos, Departamento de Biologia Geral, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Av. Antônio Carlos 6627, CP 486, CEP 31270-901, Belo Horizonte, Minas Gerais, Brazil
² Instituto Brasileiro de Geografia e Estatística, Rua Oliveira 523, CEP 30310-150, Belo Horizonte, Minas Gerais, Brazil
³ Amnis Opes Institute and Department of Fisheries & Wildlife, Oregon State University, 97331-4501, Corvallis, OR, USA
⁴ U.S. Environmental Protection Agency, Office of Research and Development, National Health and Environmental Effects Lab., Western Ecology Division, 200 SW35 Street, 97333 Corvallis, OR, USA
⁵ Departamento de Ecologia, Instituto de Ciências Biológicas, Universidade Federal de Goiás, Campus II, Samambaia CP. 131, CEP. 74001-970 Goiânia, Goiás, Brazil

^* Corresponding author: ferreirawr@gmail.com

Received: 27 December 2013
Accepted: 21 December 2014

Abstract

Macroinvertebrates are important for processing leaf detritus in temperate streams, but studies about their role in tropical streams often present conflicting results. Via digestive tract analyses, we assessed the diets of Phylloicus sp. larvae (Trichoptera: Calamoceratidae), collected from streams of two southeastern Brazil river basins (Araguari, São Francisco). We classified gut contents as coarse particulate organic matter (CPOM), fine particulate organic matter (FPOM), algae, animal tissue, vascular plant tissue and mineral material. We hypothesized that the diets of Phylloicus larvae would be related to the physical habitat of the streams (e.g., riparian vegetation, organic matter availability and morphological characteristics), larval size and river basin. Although FPOM content predominated in both basins, we found greater CPOM content in Phylloicus larvae of Upper São Francisco sites, and this food item was related to greater riparian vegetation canopy density. The FPOM content was greater in larvae of Upper Araguari sites, and this food item was correlated with greater instream brush cover. Algae, animal tissue, vascular plant tissue and mineral material were very rare in the digestive tracts, and therefore could not be explained. These results indicate the importance of riparian vegetation structure in modulating feeding habitats of macroinvertebrates. We conclude that the Phylloicus larvae had more flexibility in what they eat than we might expect based on their traditional classification as shredders. Therefore, trusting in published classifications, ignoring regional or local differences, may be inaccurate. Instead, regional studies of feeding habits are needed for accurate classifications of invertebrate taxa into trophic guilds.