ABSTRACT
Unlike the over 200 years long history of research on the symbiosis between fungus-growing termites and Termitomyces fungi (Wilson, 1971), the research history of the termite egg mimicking fungi is only 10 years. To date, termite balls have been found in five Reticulitermes species. Climatic factors play much more important roles in restricting the distribution of termite ball fungi than do geographic distances and phylogeny of host termites. Phylogenetic analysis illustrated that termite ball fungi isolated from different termite species were all very similar, with no significant molecular differences among host species or geographic locations. The evidences to date indicate long-distance gene flow and horizontal transmission of the termite ball fungi. This seems impossible to explain without spore formation, although inducing spore formation in laboratory conditions has so far not succeeded. It is most likely that this fungus has a free-living sexual stage independent of termites. Evidences for the strict morphological and chemical egg-mimicry by the termite ball fungi were provided. The net outcome of the interaction seems most likely to be negative for termites. In contrast, the termite ball fungus profits from this interaction by receiving competitor-free habitat in termite nests and protection from termites. Thus it can be concluded that termite balls parasitically mimic termite eggs to be harbored in termite nests.
