Termites of the subfamily Macrotermitinae (Termitidae) live in an obligate mutualistic symbiosis
with fungi of the genus Termitomyces (basidiomycetes). Fungus-growing termites are restricted to
the Old-World tropics, with the highest diversity in African tropical rain forests. This habitat has also
been reconstructed as the centre of origin [16], likely just before the expansion of the savannah, about
31 Ma [17]. Entering the symbiosis has allowed the fungi to overcome highly unfavorable seasonal conditions (e.g., temperature fluctuations and low moisture), and the termites to exploit complex plant
substrates (e.g., lignocellulose). The current habitat of fungus-growing termites ranges from rain
forest to savannah. Whereas species numbers of fungus-growing termites are highest in rainforest
habitats [17,18], their relative contribution to ecosystem decomposition is highest in savannahs, with
up to 20% of all carbon mineralization attributed to fungus-growing termites [19]. The highest estimate
on their contribution to carbon mineralization, 90%, relates to their activity in a very arid habitat [20].
The transition to fungiculture in both partners has occurred only once, with no reversals to free-living
states of any of the two partners [13].