David E. Bignell

Termites: Evolution, Sociality, Symbioses, Ecology

Contributors. Acknowledgements. Preface. Taxonomy and Phylogeny of Termites S. Kambhampati, P. Eggleton. Global Patterns of Termite Diversity P. Eggleton. Characterizing the Ancestors: Paedomorphosis and Termite Evolution C.A. Nalepa, C. Bandi. Early Fossil History of the Termites B.L. Thorne, D.A. Grimaldi, K. Krishna. Diversity and Evolution of Caste Patterns Y. Roisin. Termite Nests: Architecture, Regulation and Defence C. Noirot, J.P.E.C. Darlington. Behavior and Ecology of Foraging in Termites J.F.A. Traniello, R.H. Leuthold. Theories on the Sociality of Termites M. Higashi, N. Yamamura, T. Abe. Introduction to the Symbiosis D.E. Bignell. Ecology of Prokaryotic Microbes in the Guts of Wood and Litter-Feeding Termites J.A. Breznak. Soil-Feeding Termites: Biology, Microbial Associations and Digestive Mechanisms A. Brauman, D.E. Bignell, I. Tayasu. Intracellular Symbiosis in Termites C. Bandi, L. Sacchi. Symbiotic Associations with Protists T. Inoue, O. Kitade, T. Yoshimura, I. Yamaoka. Symbiosis with Fungi C. Rouland-Lefevre. Energy Metabolism in the Termite and its Gut Microbiota M. Slaytor. Population Dynamics of Termites M. LePage, J.P.E.C. Darlington. Termites in Ecosystems D.E. Bignell, P. Eggleton. Global Impact of Termites on the Carbon Cycle and Atmospheric Trace Gases A. Sugimoto, D.E. Bignell, J.A. MacDonald. Termites as Pests of Buildings Nan-Yao Su, R.H. Scheffrahn. Index.

Termites in Ecosystems

Termite assemblages are considered as complex systems containing species with several modes of feeding and nesting, which have a major though not necessarily dominant role in decomposition and C mineralization processes, and which influence soil properties and structure. Sampling methods for species richness, abundance and biomass and the estimation of food consumption rates are reviewed; transect methods are recommended for biodiversity surveys as they are efficient and have acceptable accuracy. Biases introduced by sampling methods which focus on mounds only and by consumption assays based on baits lead to underestimates of assemblage diversity, abundance and ecological impact. The range of abundance and biomass of termites in major ecosystems and biogeographical regions is discussed and representative data are tabulated. In savanna systems, the turnover of organic matter by termites is roughly comparable to that of mammalian herbivores and bush fires, and as much as 20% of C mineralization may be directly attributed to termites. In forests, absolute C fluxes through populations are generally larger, owing to higher termite biomass, but the relative contribution to C turnover is less. Functional group heterogeneity rather than species richness per se is considered the key link between termite biodiversity and ecosystem functions.

Global decomposition experiment shows soil animal impacts on decomposition are climate-dependent

Climate and litter quality are primary drivers of terrestrial decomposition and, based on evidence from multisite experiments at regional and global scales, are universally factored into global decomposition models. In contrast, soil animals are considered key regulators of decomposition at local scales but their role at larger scales is unresolved. Soil animals are consequently excluded from global models of organic mineralization processes. Incomplete assessment of the roles of soil animals stems from the difficulties of manipulating invertebrate animals experimentally across large geographic gradients. This is compounded by deficient or inconsistent taxonomy. We report a global decomposition experiment to assess the importance of soil animals in C mineralization, in which a common grass litter substrate was exposed to natural decomposition in either control or reduced animal treatments across 30 sites distributed from 43°S to 68°N on six continents. Animals in the mesofaunal size range were recovered from the litter by Tullgren extraction and identified to common specifications, mostly at the ordinal level. The design of the trials enabled faunal contribution to be evaluated against abiotic parameters between sites. Soil animals increase decomposition rates in temperate and wet tropical climates, but have neutral effects where temperature or moisture constrain biological activity. Our findings highlight that faunal influences on decomposition are dependent on prevailing climatic conditions. We conclude that (1) inclusion of soil animals will improve the predictive capabilities of region- or biome-scale decomposition models, (2) soil animal influences on decomposition are important at the regional scale when attempting to predict global change scenarios, and (3) the statistical relationship between decomposition rates and climate, at the global scale, is robust against changes in soil faunal abundance and diversity.

Biology of Termites: A Modern Synthesis

Biology of Termites, a Modern Synthesis brings together the major advances in termite biology, phylogenetics, social evolution and biogeography made in the decade since Abe et al Termites: Evolution, Sociality, Symbioses, Ecology became the standard modern reference work on termite science. Building on the success of the Kluwer book, David Bignell, Yves Roisin and Nathan Lo have brought together in the new volume most of the worlds leading experts on termite taxonomy, behaviour, genetics, caste differentiation, physiology, microbiology, mound architecture, distribution and control. Very strong evolutionary and developmental themes run through the individual chapters, fed by new data streams from molecular sequencing, and for the first time it is possible to compare the social organisation of termites with that of the social Hymenoptera, focusing on caste determination, population genetics, cooperative behaviour, nest hygiene and symbioses with microorganisms. New chapters have been added on termite pheromones, termites as pests of agriculture and on destructive invasive species, and new molecular and cladistic frameworks are presented for clarifying taxonomy, especially in the higher termites which dominate many tropical ecosystems. Applied entomologists, developmental and evolutionary biologists, microbial ecologists, sociobiologists and tropical agriculture specialists will all benefit from the new insights provided by this work.

Gut content analysis and a new feeding group classification of termites

1. Gut content analysis of termites was undertaken using microscopical techniques. The 46 study species covered the entire range of taxonomic and feeding forms within the Order.

The species richness of termites (Isoptera) under differing levels of forest disturbance in the Mbalmayo Forest Reserve, southern Cameroon

Five forest plots of differing disturbance levels were sampled qualitatively for termites in the Mbalmayo Forest Reserve, southern Cameroon, using 100 m belt transects. Results showed a large reduction in species richness in two severely disturbed plots compared with a Near Primary plot, but little difference in two less disturbed regenerating plots; there is some evidence for a slight increase in species richness in the regenerating plots. Soil-feeders predominate in the primary and regenerating plots, but are greatly reduced in the severely disturbed plots. Wood-feeders appear to be more resilient to disturbance than soil-feeders, although their species richness is low in the most disturbed plots. The Termitinae are the dominant taxonomic group in the Near Primary plot, the Apicotermitinae in the less disturbed regenerating plots and the Macrotermitinae in the clear felled areas. There appears to be no secondary invasion of plots by savanna-associated species, and the small apparent increase in species richness in the less disturbed regenerating plots appears to be due to the influx of forest species usually associated with natural gaps.

Nitrogen and carbon isotope ratios in termites: an indicator of trophic habit along the gradient from wood-feeding to soil-feeding

1. Nitrogen and carbon stable‐isotope ratios (δ15N and δ13C) of body tissues, mound/nest materials and dietary substrates were determined in termite species with differing trophic habits, sampled from the Mbalmayo Forest Reserve, southern Cameroon.

On the elevated intestinal pH of higher termites (Isoptera: Termitidae)

SummaryThe pH of the gut contents was measured in 52 species of higher termites (Termitidae), representing 36 genera in all four subfamilies. A statistically significant trend was shown from lower termites with low mean gut pH through to the Termitinae with higher mean gut pHs. Elevation of the pH occurred principally in the first and third proctodaeal segments, reaching values as high as 10.5 in 8 soil-feeding genera and 1 wood-feeding genus of Termitinae. Elevation of gut pH within the Termitidae appears to be independent of the general nature of the feeding substrate.

Introduction to Symbiosis

Termite symbioses are characterized as obligate nutritional mutualisms between the insect host and various microorganisms drawn from three domains: Archaea, Eubacteria, and Eucarya (protozoans and fungi). In many cases the precise nature of the exchanges is unknown, and further, there is no evidence that any termite is completely dependent on symbionts for cellulose degradation. Intestinal microbes, and where appropriate, fungal associates may have other roles such as nitrogen fixation, nitrogen enrichment of the diet, pyruvate metabolism or the metabolism or acetogenic reduction of CO2. The general design of the termite gut and morphological variations within different taxa and feeding groups, particularly those of the midgut and hidgut, are reviewed, with emphasis on the intestine as a bioreactor accommodating diverse organisms, many of which are as yet uncultured. The sparse current knowledge of secretion, absorption and motility in the alimentary canal is summarized, but attention is also drawn to new insights into the physiology and functioning of the gut community which arise from the demonstration of both radial and longitudinal gradients of oxygen and hydrogen ion concentrations in the lumen. Historical and contemporary methods of investigating termite symbioses are compared, with the conclusion that the symbioses are still relatively little understood.

Carbon flux and diversity of nematodes and termites in Cameroon forest soils

Theoretically, there are three principal ways in which ecosystem processes might respond to reductions in species richness. These theories are reviewed, and then considered in the context of a study of the diversity of soil nematodes and termites in near-primary forest sites at Mbalmayo, Cameroon, and the contribution made by these two taxa to carbon fluxes (CO2 and CH4) from the forest floor. Nematode abundances average 2.04 × 106 m-2, and termites between 2933 and 6957 m-2. The site is the most species-rich yet investigated for both groups anywhere in the world, so that a very large number of species contribute to carbon fluxes. We speculate about how much ‘redundancy’ might be built into the functioning of both assemblages, and point out the enormous difficulties of resolving such questions, and of producing such detailed species-inventories.