Diversity and community composition of the ground and lower canopy foraging worker ants in the Gilimale forest

Abstract

Ants are a very important group of insects in the forests of Sri Lanka and their microhabitats vary from ground to the canopy. Worker ants on the ground and lower canopy of two sites in the Gilimale forest were sampled by several methods in April, June and August 2004. Worker ants were sampled along a 100 m transect in each site by the baited traps (honey and canned fish), manual collection, soil and litter sieving (Time unit method) and Winkler extraction. Branch clipping, beating and, five honey baited traps hanged at a height of 15 - 20 feet were used to sample ants on three Symplocos bractealis (Wal Bombu) and three Schumacheria castaneifolia (Kekiriwara) trees in April. Fifteen honey baited traps were hung on three of the each tree species in June. In August, five traps baited with honey, canned fish, desiccated coconut, ground peanut or paddy seeds (variety BG 11)) were hung on the same trees. Pitfall traps and baits on trees were set to collect ants that forage at dusk and the night. Worker ants were identified with the assistance of Bolton (1994) and the reference collection at the Department of Zoology, University of Kelaniya. Worker ants belonging to nine subfamilies and thirty five taxa (H = Ópi logpi = 2.56), Aenictus sp. (0.26%), Aneuretus simoni Emery (2.5%), Amblyopone sp. (0.15%), Anochetus (0.1%), Aphaenogaster sp. (25%), Calyptomyrmex sp. (0.3%), Camponotus sp. (4.7%), Cataulacus sp. (0.05%), Crematogaster sp. (9.4%), Cryptopone sp. (0.26%), Dolichoderus sp. (0.56%), Hypoponera sp. (0.1%), Leptanilla sp. (0.26%), Leptomyrmex sp. (1%), Leptogenys sp. (0.7%), Lophomyrmex sp. (0.26%), Meranoplus bicolor (0.77%), Monomorium sp. (1.1%), Myrmicaria sp. (10.4%), Odontomachus simillimus Smith (0.15%), Oligomyrmex sp. (13.4%), Paratrechina sp. (2.%), Pheidole sp. (4.5%), Pheidologeton sp. (8.4%), Polyrhachis sp. (1.2%), Ponera sp. (0.36%), Solenopsis sp. 1 (0.26%), Strumigenys sp. (0.05%), Tapinoma melanocephalum Forel (0.3%), Tapinoma indicum Forel (0.2%), Technomyrmex albipes Emery (2%), Technomyrmex bicolor Emery (2%), Tetramorium sp.1 (4.3%), Tetramorium bicarinatum Mayr (3.2%) and Tetraponera allaborans (0.05%) were recorded from the ground samples. Ten taxa (H = 1.73) of worker ants that belonging to Dolichoderinae, Formicinae and Myrmicinae, Aphaenogaster sp. (8%), Camponotus sp. (17%), Cataulacus sp. (1%), Crematogaster sp. (5%), Leptomyrmex sp. (1%), Myrmicaria sp. (1%), Polyrhachis sp. (8%), Solenopsis sp. 2 (12%), Technomyrmex albipes Emery (43%) and Tetramorium sp. 2 (4%) were identified from the lower canopy. Solenopsis sp. 2 and Tetramorium sp. 2 were observed only on the trees. Worker ants belonging to five subfamilies and fifteen morphospecies were observed in the night traps. Species Richness values recorded from both ground and the canopy in April, June and August were not significantly different (Chi-square, p > 0.05) and reached 24, 25 and 24, respectively. Presence or absence of some taxa and the proportional abundance of dominant taxa varied on the three occasions. Leptomyrmex sp. forages on the ground as well as on trees and is a new record from Sri Lanka.