How biogeographical history determines what termites are found where: first comparison of quantitative estimates of termite biomass and abundance reveals strong intercontinental differences
We have a nice new paper led by DPhil student Cecilia Dahlsjö, looking at the abundance, biomass and phylogeny of termites across the tropics, comparing three sites in Peru, Cameroon and Malaysia. Termites are social insects (essentially evolved and modified cockroaches) completely unrelated to other social insects such as ants.
The paper shows that there are large differences in termite biomass, function and diversity between the three ytopical continents driven by biogeographical history. Africa has much higher termite biomass, dominated by soil feeding termites, while the highest biomass of wood-feeding termites was in Asia. Wood feeding termites dominate in biomass in both Asia and South America. The unique fungus-growing "farming" termites are very important food wood descomposition in Africa and Asia, yet completely absent from South America ,where leaf-cutter ants have a similar fungus'growing "agriculture". The likely causes for these differences are biogeographical history.
The Termitidae probably evolved and dispersed from Africa with higher dispersal rates for wood- feeding termites compared with soil-feeding termites. Soil-feeding termites are probably more dependent on the buffered environment within tropical rain forest, which offer less fluctuation in temperature and moisture compared with non-forest habitats. Therefore, arid and semi-arid habitats such as woodland, savanna and desert would be more likely to be barriers to dispersal for those groups. Wood-feeding termites on the other hand (with the probable exception of fungus-
growing termites) are more likely to have been able to disperse across different types of barrier, including bodies of water, because of their rafting abilities. These activities are probably dependent on their harder and thicker exoskeletons, which support their foraging behaviour and therefore the likelihood of allowing dispersal across suboptimal habitat types. The biogeographical patterns of wood-feeding termites may therefore have evolved through a wider range of dispersing types than soil- feeding termites, which may have had relatively low dispersal rates. However, it seems likely that soil- feeding termites may have evolved independently from rafting wood-feeding termites on several occasions across the continents leading to the relatively depauperate humus- and soil-feeder assemblages of the non-African sites.
Macrotermitinae (fungus-growing termites) seem to have evolved in African tropical forests and although four dispersal events from Africa to South-East Asia appear to have taken place, fungus-growing termites have failed to colonize South America. Macrotermitinae are poor dispersers, as they depend on their close mutualistic relationship with Termitomyces, a fungus, which breaks down organic matter within the termite mound . Generally termites depend on the presence of the reproductive caste (king and queen), however, the species of Macrotermitinae also need spores of Termitomyces to be available in their new environment. The successful colonization of Asia but their failure to inhabit South America contributes to the diversity anomaly of functional groups across the equatorial regions.
Dahlsjö C.A.L, Catherine L. Parr, Yadvinder Malhi, Homathevi Rahman, Patrick Meir, David T. Jones and Paul Eggleton (2014). First comparison of quantitative estimates of termite biomass and abundance reveals strong intercontinental differences . Journal of Tropical Ecology, 30, pp 143-152 doi:10.1017/S0266467413000898
Yadvinder Malhi is an ecosytem ecologist and Professor of Ecosystem Science at Oxford University