Characterizing Trichoptera trophic structure in rivers under contrasting land use in Patagonia, Argentina

BRAND, C.; MISERENDINO, M. L.

Bialowieza

Simposio; 13th International Symposium on Trichoptera; 2009

Lodz University, Lodz, Polonia

Trichoptera is a widely distributed and diversified group in Andean Patagonia (Subandean Patagonic Province), this group exhibits a wide array of functional adaptations to exploit the available food resources. It is well known that changes in the relative abundance of functional feeding groups (FFG) occur when the distribution of energetic resources (organic matter) is altered. In order to determine the functional structure variation among rivers subjected to different land uses, we selected three disturbance types (exotic plantation, pastures and logging) and native forest as reference. Three sites were assessed for each land use type (n=12) seasonally (every three months) and 6 samples with a Surber net (0.09 m-2 and 250 pore size) were taken. Larvae obtained were identified to the lesser possible taxonomic level, counted and assigned to a FFG using available references, knowledge of feeding modes and analysis of gut contents. A total of 33 species were identified belonging to 13 families. Mean annual densities of Trichoptera were comprised between 131 ind.m-2 to 4231 ind.m-2. Pasture sites had three to four times higher density than the rest of the uses, and observed differences were statistically significant only for pine and native forest (T-test(df=22) p