The Ant Species Richness and Diversity of a Primary Lowland Rain Forest, the Pasoh Forest Reserve, West-Malaysia

Abstract

We present results of an inventory of the ant fauna from all strata at Pasoh Forest Reserve (Pasoh FR), Malaysia, with special emphasis on the diversity of leaf-litter inhabiting ants. A variety of sampling methods were used including the “Winkler-Moczarski eclector”, the “Berlese-Tullgren method”, “pitfall traps” and “hand collection”. We collected a total of 489 ant species belonging to 76 genera and 9 subfamilies. The Myrmicinae was the most species rich subfamily with 40.7% of the species collected, followed by Formicinae with 28.2%, Ponerinae 18.0%, Dolichoderinae 5.9%, Cerapachyinae 2.9%; Aenictinae 2.5%, Pseudomyrmecinae 1.4%, Dorylinae 0.2% and Leptanillinae 0.2%. The most species-rich genera were Camponotus with 50 species, Polyrhachis with 45 species and Pheidole with 38 species. Of 475 ant species for which capture sites were recorded approximately 71% of the species seemed to be restricted to one stratum. Nesting sites were recorded for 199 species: 49.7% nested exclusively on the ground, 47.2% in vegetation and only 3% could be found in both. The species accumulation curves showed no tendency toward saturation (e.g. for Berlese and pitfall collections). In regard to all methods, 36% of the species were single captures and 54% single or double captures. In a detailed study on the diversity of ground leaf-litter inhabiting ants we extracted 120 species belonging to 49 genera and 5 subfamilies by using the Winkler-Moczarski eclector. The resulting species accumulation curves of three sample area sizes show no tendency toward saturation, but give a different prognosis of species richness expected at a given sampling site. The ß-diversity values calculated by the S0rensen quotient were 52.7 ± 7.68% comparing nine 25 m² plots compared to nine 9 m² plots 43.0 ± 8.18%. Our study gave evidence that the sample area size may greatly influence the results on the degree of diversity. Nevertheless, the ground leaf-litter ß-diversity in Pasoh FR is high which is supported by the collection of many rare species and only a small number of species with high abundance. In conclusion the unsaturated species accumulation curves, the large number of rare species and the distinct vertical stratification suggest that there are many more species to be found at Pasoh FR. There are many microhabitats we did not reach. Species foraging only by night are underestimated and the same is probably true for arboreal species. In conclusion our data revealed that the Pasoh FR has to be regarded as one of the most species rich places known in the world, as far as ants are concerned.