Field Work




1998 IRIAN JAYA (FREEPORT) RAP: THE ANTS

Roy R. Snelling
Natural History Museum of Los Angeles County
Los Angeles, California
email antmanrs@nhm.org

SUMMARY

     Two sites were surveyed for ants over a two week period at each. The first of these sites was the lowland secondary forest at Siewa Base Camp (ca. 200 ft. el.); the second site was in montane primary rainforest at Wapoga (ca. 3400-3800 ft.). Traditional methods were employed in collecting samples of these insects. In all, 223 individual samples were collected. At Siewa 108 species in 45 genera were recovered; Wapoga yielded 85 species in 38 genera.

INTRODUCTION

     Ants and other social insects (bees, wasps, termites) comprise a signification portion of the total animal biomass in any tropical ecosystem. They are numerically abundant and are taxonomically more diverse than another other group of social organisms. And, since many are specialized predotors, they may prove useful indicators of the ecological health of any given area.

DISCUSSION & RESULTS

     The site at the PT. Freeport Siewa Base Camp is in an area of lowland rainforest that had been intensively logged two years before my visit; a few primary trees remain, but the area is mostly dense second growth forest, with little ground litter. Ants were hand collected from standing vegetation and fallen (or cut) tree trunks; loose bark was pulled off and ants collected from under the bark as well as from rotting trunks and branches. Samples were also collected from under mass and in the root masses of epiphytes. Additional samples were taken of foraging ants in ground litter and from under objects on the ground. Finally, Winkler bags were used to extract ants and other arthropods from leaf litter.

     These same techniques were employed at the Wapoga site, an area of montane primary rainforest. Wapoga was a cooler - and wetter - site than Siewa and ant diversity, both in genera and species, appears to be less than at Siewa.

     Preliminary results of my collections are listed in Table 1, showing the species present at both sites. Twenty-eight genera were present at both sites, but only 19 species were shared. I have only begun the task of species level identification, but several undescribed species are present in the samples, as well as a number of significant range extensions.

     Although my original assessment was that the faunas of both sites are depauperate, such may not, in fact, be true. At Lakekamu, PNG, over 250 ant species were collected in about 9 weeks of effort. During the first two weeks at Lakekamu a total of 109 species was collected from 111 samples. These results closely parallel those obtained at both Siewa and Wapoga, suggesting that these faunas might well prove much richer were more time available for survey work.

     There were some interesting "gaps" in the samples. For example, the rare ponerine genus Myopias, was well represented at Lakekamu, another lowland forest site, and at Wapoga. No species were found at Siewa. Similarly, the genus Crematogaster, an often dominant element in tropical forests, appears to be absent at Wapoga. At both sites the species-rich arboreal genus Polyrhachis was much less diverse than I had expected.

     This is an area of considerable interest to me and I would hope that further surveys can be conducted to determine the true extent of the diversity of the ant fauna, as well as assess its relationships to the Melanesian fauna further east and with the Indonesian fauna to the west. It would be useful, too, to conduct surveys in lowland primary forest adjacent to secondary forest in order to provide a base-line for determining the impact of logging on ant faunas. Such survey work should require a minimum time of two months at each site, but my experience at Lakekamu suggests that three months would be better.

TABLE 1. PT. FREEPORT ANTS: SIEWA AND WAPOGA CAMPS