Environmental Influences on the Arboreal Nesting Termite Community in New Guinean Coconut Plantations

Abstract

Three species of arboreal nesting termites common in New Guinean coconut plantations: Microcerotermes biroi (Desneux), Nasutitermes princeps (Desneux), and Nasutitermes novarumhebridarum (N. and K. Holmgren), are in competition with each other. This work evaluated the influence of environmental factors on this community. We compared the arboreal nesting termite distribution, abundance, and colony size in the following 3 types of coconut plantation: (1) open plantations with tall trees (=25 m) at low density (≤100 trees per hectare); (2) standard plantations with medium size trees (=13 m) at standard density (100–180 trees per hectare); (3) dense plantations (180–300 trees per hectare) with medium size or mixed size trees (13–25 m). The overall proportion of coconut trees occupied byarboreal termites increased from 25% in open plantations to 56% in standard or dense plantations. M. biroi was less abundant in open plantations than in standard or dense ones, whereas N. princeps was scarcest in standard plantations. N. novarumhebridarum occupied =2% of the trees in all plantation types, but showed a clear preference for dead trees. Nest volumes of all species and colony territories were larger in dense plantations, especially for N. princeps . Data on nest thermoregulation suggest that M. biroi is the most affected by sun exposure, which could constitute a limiting factor in open plantations. N. princeps incipient colonies would be particularly hindered by competition with first established colonies of M. biroi in standard plantations. Large territories of N. princeps in dense plantations suggest that this species is especially favored by high tree densities, allowing easy colony expansion by galleries or satellite nests and reproduction by budding. We propose that arboreal termite community structure is mainly shaped by microclimatic conditions and food availability in open plantations, and by interspecific competition in denser habitats, although the incidence of other factors, such as predation or intraspecific competition, remains to be studied.