Macrotermes

Abstract: Termites normally rely on gut symbionts to decompose organic matter but the Macrotermitinae domesticated Termitomyces fungi to produce their own food. This transition was accompanied by a shift in the composition of the gut microbiota, but the complementary roles of these bacteria in the symbiosis have remained enigmatic. We obtained high-quality annotated draft genomes of the termite Macrotermes natalensis, its Termitomyces symbiont, and gut metagenomes from workers, soldiers, and a queen. We show that members from 111 of the 128 known glycoside hydrolase families are represented in the symbiosis, that Termitomyces has the genomic capacity to handle complex carbohydrates, and that worker gut microbes primarily contribute enzymes for final digestion of oligosaccharides. This apparent division of labor is consistent with the Macrotermes gut microbes being most important during the second passage of comb material through the termite gut, after a first gut passage where the crude plant substrate is inoculated with Termitomyces asexual spores so that initial fungal growth and polysaccharide decomposition can proceed with high efficiency. Complex conversion of biomass in termite mounds thus appears to be mainly accomplished by complementary cooperation between a domesticated fungal monoculture and a specialized bacterial community. In sharp contrast, the gut microbiota of the queen had highly reduced plant decomposition potential, suggesting that mature reproductives digest fungal material provided by workers rather than plant substrate.

Abstract: Foraging behavior has evolved in concert with termite life types, some species feeding on the wood in which they live and others harvesting food that is separate from the nest The nutritional value of food sources appears to be critically important to colony foundation by alates as well as food selection by workers Termite foraging is often a collective process in which groups of individuals search in organized patterns for new food sources and communicate their location by the use of sternal gland pheromones to other colony members Division of labor between soldiers and workers and among workers is observed in the foraging activities of some rhinotermitids and in many species of higher termites Soldiers function chiefly in the defense of workers, but may also explore new areas for food and recuit workers to newly discovered resources Workers collect and process food, but may also defend foraging territory The degree of caste polyethism seems to be correlated with termite ecology, and division of labor is most elaborate in fungus-growing termites such as Macrotermes Many aspects of termite foraging, such as the measurement of task efficiency, the role of individuals and analysis of mechanisms of collective action require additional study

Abstract: The flux of CH4 and CO2 from termite nests into the atmosphere has been measured in a broad-leafed-type savannah in South Africa. Measurements were carried out on nests of species of six genera, i.e., Hodotermes, Macrotermes, Odontotermes, Trinervitermes, Cubitermes, and Amitermes. The flux rates of CH4 relative to the flux rate of CO2 in terms of carbon obtained for the individual species showed ratios of 2.9×10-3, 7.0×10-4, 6.7×10-5, 8.7×10-3, 2.0×10-3 and 4.2×10-3, respectively. Using data published on the assimulation efficiencies of termites, the flux of carbon as CH4 accounts for 6.0×10-5 to 2.6×10-3 of the carbon ingested which results in a global CH4 emission by termites of 2 to 5×1012 g/yr. Methane is decomposed in the soil with average decomposition rates of 52 μg/m2/h. The annual CH4 consumption in the tropics and subtropics is estimated to be 21×1012 g which exceeds the CH4 emission rate by termites.

Abstract: Objectives: To (1) assess the strength of evidence for the role of termites in vegetation heterogeneity in African savannas, and (2) identify the mechanisms by which termites induce such heterogeneity. Location: African savannas. Methods: We conducted a review of the literature, a meta-analysis and qualitative systems analysis to identify mechanisms to explain the observed patterns. Results: The review provided evidence for termite-induced heterogeneity in floristic composition and vegetation patterning in savannas across Africa. Termites induced vegetation heterogeneity directly or indirectly through their nest-building and foraging activities, associated nutrient cycling and their interaction with mammalian herbivores and fire. The literature reviewed indicated that termite mounds essentially act as islands of fertility, which are responsible for ecosystem-level spatial heterogeneity in savannas. This was supported by the meta-analysis, which demonstrated that mounds of Ancistrotermes, Macrotermes, Odontotermes (family Macrotermitinae), Cubitermes (family Termitinae) and Trinervitermes (Nasutitermitinae) are significantly enriched in clay (75%), carbon (16%), total nitrogen (42%), calcium (232%), potassium (306%) and magnesium (154%) compared to the surrounding savanna soil. Conclusions: Termite activity is one of the major factors that induce vegetation patterning in African savannas. The implications of this are discussed and research questions for future studies and modelling efforts are indicated.