Termite Communities Research Articles

Structure and Dynamics of the Arboreal Termite Community in New Guinean Coconut Plantations21

ABSTRACTWhereas ant mosaics have been widely recognized and described in tropical ecosystems, data on space partitioning among arboreal termite colonies are rudimentary. During a long term field study in New Guinea, the distribution of arboreal termite species in coconut plantations as well as the extent and dynamics of competition between them were investigated. The three dominant species, Mirrocerotermes biroi, Nasutitermes princeps and N. novarumhebridarum, feed on the same items but never exploit the same tree. The resulting distribution pattern is a mosaic with two peculiarities. First, some extended areas around N. princeps colonies appear unexploited, as this species practices interference competition on a wide scale, defending large territories inter‐ and intra‐specifically. Second, interspecific relations are asymmetrical. In some plantations, large colonies of N. princeps expand their territory by destroying colonies of M. biroi, but when the pressure of N. princeps is relaxed, dense populations of colonies of M. biroi can recolonize the trees in a few years’ time. Territorial boundaries may thus change relatively fast. N. novarumhebridarum often colonizes dead trees and interferes less with the other species. These facts are consistent with each species’ reproductive investment strategy. Hypotheses are proposed to explain how the dominant species can coexist, even in long established plantations.

Termite species richness in fire-prone and fire-protected dry deciduous dipterocarp forest in Doi Suthep-Pui National Park, northern Thailand

Fire is prevalent in the dry deciduous forests of south-east Asia, the majority of fires being man-made (Stott 1988). In Thailand, the 10-19% estimated extent of annual burning of dry deciduous dipterocarp forest (1984-1986 data on total estimated area burned each year; Settarak et al. 1987) is thought to be a severe under-estimate (Kanjanavanit 1992). The interaction of fire and termites is poorly known for Asian ecosystems, but African studies show they have complementary roles in the removal of wood and leaf litter (Collins 1981, Trapnell et al. 1976). Termites are the dominant arthropod decomposers in tropical forests (Collins 1983) and savannas (Collins 1981, Holt 1987), and are important mediators of carbon flux (Jones 1990, Lawton et al. 1996). Furthermore, these functions are dependent on the species assemblage structure of the termite community (Lawton et al. 1996). To date, the only study of the effects of fire on termite species richness and abundance is from Australia (Abensperg-Traun & Milewski 1995). Here, a preliminary survey of species richness of termites in fireprotected and fire-prone deciduous forest in northern Thailand is presented. The study suggests that the fungus-growing Macrotermitinae have a greater species richness, under certain seasonal fire regimes, compared to those in areas under complete fire protection. Species richness estimates were made for two dry deciduous dipterocarp forest sites: A, fire-protected and; B, unprotected, fire-prone, in Doi Suthep-Pui National Park, near Chiang Mai, northern Thailand. Site A covered a 10 ha

The Effects of Habitat Fragmentation and Livestock-Grazing on Animal Communities in Remnants of Gimlet Eucalyptus salubris Woodland in the Western Australian Wheatbelt. I. Arthropods

The effects of habitat fragmentation (remnant biogeographic characteristics) and livestock activity (grazing, trampling) on arthropod communities were examined within 26 remnants of gimlet Eucalyptus salubris woodland in the central wheatbelt of Western Australia. Significant correlations between remnant biogeographic variables were between remnant area and connectivity (+ ve, P < 0001), and between connectivity and distance from the study remnant to the nearest patch of native vegetation (- ve, P < 0.001). Remnant disturbance indices (sheep faecal pellet density, percentage cover of weeds) were significantly correlated with remnant biogeographic characteristics (P < 0.01). Small and poorly connected remnants showed significantly higher intensities of disturbance than larger and better connected remnants. When disturbance indices were used to categorize study remnants into groups with high, moderate or low disturbance, remnants with high intensities of disturbance had significantly less lichen, litter and shrub cover. Highly disturbed remnants were associated with : fewer scorpion species, lower termite and ant diversity (Shannon-Wiener); a lower abundance of scorpions, termites and mygalomorph spiders; more beetle species and higher beetle diversity, and greater abundance of earwigs and beetles. Cockroach, earwig and ant species richness showed no significant response to disturbance. Species richness of termites, and the abundance of lycosid and idiopid (mygalomorph) spiders, isopods, cockroaches and ants, was highest under moderate disturbance. Significant biogeographic covariates were area (abundance of araneaomorph spiders, 'associated subordinate' and 'opportunistic' ants; richness of carabid, scarabid and 'other' beetle species, subordinate and opportunistic ants), connectivity (richness of termites, scarabid beetles) and distance to the nearest native vegetation (richness of 'dominant' ants). When disturbance and biogeographic effects were combined, total termite richness, and the richness of termite functional groups, declined markedly in highly disturbed, small and poorly connected remnants. Termite communities in relatively undisturbed remnants were more similar in species composition to communities in moderately disturbed quadrats than to communities in highly disturbed quadrats. Community similarity values for ants and beetles were similar across the study quadrats with different degrees of disturbance. Arthropod communities were also examined by canonical variate analyses across remnants with different degrees of disturbance, using total abundance and richness, and abundance and richness of predators (scorpions, spiders, carabid beetles, ants) and detritivores/herbivores (termites, isopods, earwigs, cockroaches, weevil and scarab beetles). Effective site separation into the three disturbance categories was found for abundance and richness of all arthropods, and for predators alone. Abundance and richness of detritivores/herbivores separated into two groups of sites: high disturbance sites, and sites with low or moderate disturbance with no separation. In stepwise regression analyses, lichen cover, weed cover and sheep faecal pellet density were the most significant indicators of faunal abundance, richness and diversity. Remnant biogeographic variables explained a low percentage of variation in faunal characteristics. Habitat disturbance was the major influence on the arthropod communities, with remnant biogeographic factors consistently explaining low variations in the abundance or diversity of the fauna. The implications of our findings for the management of remnant vegetation are discussed.

Intraspecific interactions in a community of arboreal nesting termites (Isoptera: Termitidae)

In coconut plantations of northern New Guinea, the arboreal nesting termite community comprises three species:Nasutitermes princeps, N. novarumhebridarum, andMicrocerotermes biroi. In orde to assess the importance of intraspecific interactions in this community, we conducted pairwise encounters between batches of individuals in the laboratory and between entire nest populations in seminantural conditions. Three levels of agonism were defined in laboratory bioassays: anagonism, moderate agonism, and strong agonism. Anagonism was observed during all control tests with homocolonical groups and in some tests with allocolonial groups of all species. Moderate agonism included initial aggressiveness that subsequently faded out, and initially passive encounters where aggression progressively built up and led to fighting. Strong agonism corresponded to initial aggressiveness and fighting. Results obtained in alboratory bioassays were consistent with bioassays in seminatural conditions. WhenNasutitermes colonies were anagonists in laboratory bioassays, their foraging trails merged without aggression in field tests.N. princeps nests that were moderately agonistic in laboratory tests fought and either continued to avoid each other or finally joined after elimination of the most aggressive individuals. The most aggressiveM. biroi andN. princeps colonies fought and their foraging trails diverged afterward. Direct attacks on alien nests were winnessed inM. biroi. In all species, anagonism occurred in 21–34% of the combinations tested, between either geographically close or distantcolonies. An exeption was a group of 112 anagonist nests ofN. princeps, which most probably constituted a supercolony. The level of agonism betweenNasutitermes colonies was constant during the wet and dry season. Termite colonies excluded each other, both intra- and interspecifically, from the coconut trees, and their territories seem distributed in a mosaic pattern. Agonism between colonies may result in the elimination of the weakest colonies or in trail divergence, maintaining this mosaic. In cotrast, lack of agonism between some colonies suggests the possibility of colony fusion and gene exchanges without nuptial flights.

Reproductive mechanisms and dynamics of habitat colonization inMicrocerotermes biroi(Isoptera: Termitidae)

Abstract.1. Previous studies on the arboreal termite community in coconut plantations of northern New Guinea showed thatMicrocerotermes biroiis the most abundant species, despite the fighting superiority of two competitor speciesNasutitermes princepsandN.novarumhebridarum.In this study we tested the hypothesis that the success ofM.biroiis due to its efficiency at colonizing new habitats following nuptial flights.2. We demonstrated experimentally the ability ofM.biroicolonies to replace their reproductives when removed, or to produce reproductives in satellite nests when isolated from the remainder of the colony. Replacement reproductives were always neotenics, derived from nymphs or workers.3. Despite the ability of neotenics to differentiate within their home colonies, 84% of field colonies were headed by dealated imagos. This value constitutes a minimum estimate of the proportion of field colonies founded independently by imagos after the nuptial flight.4. The monitoring of a young plantation during the first 31/2 years of its colonization by arboreal nesting termites revealed its invasion byM.biroi, which colonized 63% of the trees while neitherNasutitermesspecies appeared.5. Our results demonstrate thatM.biroiis actually a pioneer species, able to invade a new habitat by means of nuptial flights. They outline the importance of each species' reproductive strategy in shaping the arboreal‐nesting termite community.

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

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.

Effects of habitat fragmentation on Amazonian termite communities

ABSTRACTIntuitively, termites would seem to be a very suitable group to illustrate effects of ecosystem fragmentation. Being detritivores, they do not control directly the rate at which their resources are available, nor do they restrict the ability of the resources to regenerate. Consequently, termites do not mask the ecosystem depletion caused by fragmentation. With this in mind, we compared the communities of termites in undisturbed Amazonian forest with those of two isolated fragments nearby, aiming to show that the differences observed may have resulted from habitat fragmentation. Dissimilarities between communities in the undisturbed forest suggest natural patchiness in their distribution, which could lead to misinterpretation of the effects of fragmentation. Continuous forest had higher species richness and fewer rare species than the fragments. Guild structure in the forest was biased towards soil-feeding termites, which are subterranean and soft bodied, and therefore more sensitive to variation in microclimate. In the fragments, litterfeeders and species intermediate between soil-feeding and wood-feeding types were numerically more important. Habitats in the forest were more equally used than in the fragments, suggesting habitat unsuitability increased with fragmentation. It is suggested that the community composition of the fragments is a result of the intrinsic patchiness of the original forest and deterministic and stochastic extinctions caused by fragmentation. The need for manipulative experiments to test such ideas is discussed.

The effects of sheep‐grazing on the subterranean termite fauna (Isoptera) of the Western Australian wheatbelt

Abstract The majority of existing remnants of wandoo Eucalyptus capillosa woodland in the Western Australian wheatbelt have been grazed by sheep for several decades and are often visibly degraded. A pilot survey was conducted into the effects of sheep on vegetation and soil variables, and the abundance, diversity and species frequency of occurrence of subterranean termite communities. Ten 1/4 ha study plots were used for paired grazed/ungrazed comparisons. Ungrazed plots had more litter mass (dry weight), leaf and woody litter, canopy cover (%) and soil moisture (moisture content &lt;1.2% across study plots); grazed plots had a higher percentage of bare ground. Termites were as abundant, and as diverse, in grazed as in ungrazed plots, and were equally often sampled in the soil and surface wood. Termite species eating sound wood, decayed wood/debris and grass were sampled equally often, and were of equal diversity in sheep‐grazed as in ungrazed plots. The mounds of Drepanotermes tamminensis were more abundant in grazed plots. These findings indicate that prolonged sheep grazing in remnants of wandoo woodland of the Western Australian wheatbelt has had no detrimental or beneficial effect on its subterranean termites.

The structure of termite communities in the Australian tropics

AbstractThe distributions of 50 species of termites across five habitat types in Kakadu National Park are described. Open forests are richest in species and monsoon forests are species‐poor. The greatest diversity of termites is associated with infertile soils and is probably related to the enhanced role of termites in these nutrientimpoverished sites. Only the richness of livewood feeders is associated with disturbance in the form of water buffalo impact. Few relationships with physical characteristics of the soil were apparent. Comparisons between continents suggest that lower termites are richer in Australia than on other continents. There are fewer species of soil‐feeding termites, but only two of the four subfamilies of the higher termites (Termitidae) are present in Australia. There appears to be a complementary distribution of areas of high diversity of termites and native herbivorous mammals. This may be due to the ability of termites and other invertebrate groups to exploit low fertility systems and has profound implications for the size structure of the vertebrate community.

Termite Community Composition and Mound Characteristics in Two Grassland Formations in Central Brazil

Termite Community Composition and Mound Characteristics in Two Grassland Formations in Central Brazil

Changes in the composition and activities of termite communities in relation to changing rainfall.

The foraging activities of termites were measured at nine sites distributed along a rainfall gradient in Tsavo National Park, Kenya. Dead wood disappearance (D, g m-2a-1) was mainly attributable to termites and was related to rainfall (R, mm a-1) by the equation [Formula: see text] Foraging activity was highest during rainy seasons and declined to low levels during the long dry season. The number of species increased with increasing rainfall while the importance of fungus growing Macrotermitinae declined.

Studies on a Wood-Feeding Termite Community in Ghana, West Africa

Following the partial clearance of farm scrub some termite species became locally extinct or scarcer, some were not affected, whilst others were adversely affected but became re-established and increased their activity. Wood-feeding termites in the moist semi-deciduous forest zone of Ghana consume about 0.2 kg m-2 yr-1 of woody material. This weight accounts for about 20 percent of the litter fall or about 8 to 10 percent of the annual primary production of the deciduous forest and a rather greater proportion of the lower production of more open sites. There is a spatial heterogeneity in the species distribution. Although water, clay, silt and sand contents of soil, and temperature, sunshine, and sunflecks were measured, the only significant correlations are of these parameters with Microtermes subhyalinus, which is more frequent in the moister areas with higher silt and lower sand content, and also shows a temperature preference. The lack of significance in correlation and principal component analyses is attributed to the observations being made away from the unknown location of the underground nest, and the ability of termites partially to modify their environment. The several coexisting wood-feeding species show slight micro-environment preferences leading to some spatial separation, and also show a series of size differences. The species show different responses to potential food resources, some apparently preferentially attacking wood in which fungal decomposition has begun and others not. TERMITES (Isoptera) are an important component of the fauna of tropical soils. Their efficiency in utilizing many food sources has meant that some species have become pests of crops or timber, and a few species have attacked a great variety of manmade materials. Because of their economic importance, the majority of studies of tropical termites have concentrated on the pest species and their control. The species known to attack crops have been reviewed by Harris (1961, 1969), whilst Sands (1960) has reviewed the species destroying timber and crops in West Africa. Further, Harris (1970) has listed all the species known to attack structural timbers, whilst Small et al. (1960) have described the effect of termites upon West African timbers. There have been relatively few studies on the populations of tropical termites. The relations between termites and soil have been reviewed by Lee and Wood (1971), though much of their detailed work was undertaken in Australia where the Macrotermitinae, the termites with perhaps the greatest population density in Africa, are absent. A general review of African termites is given by Bouillon (1970). Sands (1965b) attempted to sample subterranean termite populations during studies on the effect of human interference with vegetation communities in the West African savanna. However, later Sands (1972) drew attention to the extreme difficulty of obtaining estimates of the population density of truly subterranean, as opposed to moundbuilding, termite species. The work described here gives an indirect estimate of the population size and impact of a woodfeeding termite community, the majority of whose members are subterranean. These studies were undertaken during the development of a termite test site, mainly designed for conducting 'graveyard'-type tests. The Ghanaian Council for Scientific and Industrial Research wished the site to be developcd in an area of farm scrub near the village of Fumesua, about 10 km east of Kumasi (6?40'N, 1?35'W), in the Ashanti Region of Ghana. Since no previous work has been undertaken on the termite fauna of the area, the present study was designed to cover the first year of the creation of the test site, prior to any tests being carried out. It was thought important to know the ecological characteristics of the termites potentially able to attack the test samples, and the community structure of the termites that might be killed by chemical treatments of soil or wood.

Bio-Politics

MR. MORLEY ROBERTS'S study of the social organism, as he admits and indeed proclaims, is based on analogy, specifically on the thesis that the communities of bees, ants and termites, and therefore also human societies, resemble organisms. “Whatever the groups, the laws of organic development which produce order, form, interdependence, and differentiation are everywhere the same.” Hence, studies in the pathology of single animals can be applied to the functions of social and national groups. “Where protoplasmic units, however simple or complex, work together in symbiosis or communal life, they can best be considered as organisms, and as such liable to the diseases and disorders which change or destroy them.” He is not afraid of carrying his analogies to an extreme. For example: “After what was said earlier on immunity, students of medicine will have no difficulty in thinking that sarcoma, or malignant revolt of various connective tissue elements, may be nearly matched by a revolt of the police.”