Temporal distribution of Ephemeroptera, Plecoptera and Trichoptera (EPT) adults at a tropical forest stream: response to seasonal variations

Temporal changes in Ephemeroptera, Plecoptera and Trichoptera (EPT) abundance were investigated monthly from January to December 2008 at a tropical forest stream of Tupah River (TR) at Gunung Jerai Forest Reserve, Malaysia. A total of 1,689 adult individuals belong to 16 families of EPT were collected from TR. EPT populations peaked in May, June and December. Mean EPT abundance was significantly different among months (Kruskal–Wallis test, P < 0.05). Among the three orders, Trichoptera had the most diverse community with eight families reported, followed by Ephemeroptera (six families) and Plecoptera (two families). The family Baetidae was the most abundant ephemeropteran. Meanwhile, caddisfly families Hydropsychidae, Leptoceridae and Lepidostomatidae were abundant at TR. However, plecopterans were mainly represented by Perlidae. There was significant difference in abundance (t = 4.863, P < 0.05) and diversity (t = 7.857, P < 0.05) of EPT adults between dry and wet seasons. Interestingly, abundance of EPT adults was higher in the dry season compared to the wet season. Consequently, seasonality impact on abundance of EPT adults at TR was obvious. The adult population of Trichoptera was dominant during the dry season. However, adults of Ephemeroptera were abundant during the wet season.