Abstract
The Oja River (La Rioja, Spain), belonging to the Ebro River Basin (NE Spain), encloses 3 different fluvial types (Mediterranean siliceous mountain, Mediterranean calcareous mountain and Humid calcareous mountain rivers) that give rise to a great diversity in the fauna of aquatic macroinvertebrates.
During the years 2003−2009 benthic macroinvertebrates (aquatic stages and adults) were sampled in 7 sites along the river (3 in siliceous stretches, 1 in humid calcareous stretch and 3 in calcareous stretches) in different seasons.
We have found 54 Trichoptera taxa, belonging to 31 genera and 16 families. Hydropsychidae (10 species), Limnephilidae (7 species) and Rhyacophilidae (7 species) were the dominant families. Most of the species have wide European distribution (50%), with the Iberian endemic species (22%) and Central and Western European species (18%) being the 2nd and 3rd groups in importance.
The presence of some relict species in headwaters [Thremma gallicum McLachlan, Larcasia partita Navas and Odontocerum albicorne (Scopoli)] support the inclusion of this geographical area (Sierra de la Demanda, Iberian System Mountains) in the list of European pre-Pleistocene refuges for the Trichoptera fauna.