Diversity of Trichoptera emergence and their longitudinal distribution along streams in central Palawan, the Philippines

Abstract

Trichoptera emergences were cumulatively collected from two rivers in central Palawan over 11 months by use of specially modified emergence traps. The quantitative samples were identified at species level. Fifty morphospecies, of which fifteen have been recently newly described, are recognized. The highest species diversity was found in pristine headwater streams. Leptoceridae were most speciose with eleven Oecetis spp., four Leptocerus spp., two Adicella spp., and one species each of Tagalopsyche, Triaenodes, and Triplectides. Highest abundances were observed for Ecnomus cabayugani (Ecnomidae), Dipseudopsis digitata, and Hyalopsyche winkleri (Dipseudopsidae) which contributed alone 34% of the annual emergence. A mid-stream site where mayflies were mainly absent had the highest Trichoptera emergence, brackish water sites the lowest. Many species in Palawan (44% of the taxa) were recorded at a single locality, suggesting that they are stenoecious and that the real number of species on the island might be distinctly higher. This is the first study ever covering quantitative and species-level Trichoptera emergence data for a longitudinal river course.