The Longevity of Colonies of Fungus-Growing Termites and the Stability of the Symbiosis

Abstract

The agricultural mutualistic symbiosis between macrotermitine termites and Termitomyces fungi is obligate for both partners. The termites provide a protective growth environment for the fungus by cultivating it inside their colony and providing it with foraged plant material. The termites use the fungus for plant substrate degradation, and the production of asexual fruiting bodies for nourishment and re-inoculation of the fungus garden. The termite colony can reach an age of up to several decades, during which time it is believed that a single fungal monoculture is asexually propagated by the offspring of a single founding royal pair. The termite-fungus mutualism has a long evolutionary history dating back more than 30 million years. Both on the time-scale of a termite colony lifespan and that of the mutualistic symbiosis, questions arise about stability. We address the physical stability of the mound, the termite colony and the monoculture fungal garden during a colony’s lifetime. On the long-term evolutionary scale, we address the stability of the symbiosis, where horizontal transmission of the symbiotic fungus raises the question of how the mutualistic interaction between host and symbiont persists over generations.

Can Differences in Symbiont Transmission Mode Explain the Abundance and Distribution of Fungus-Growing Termites in West Africa?

“…However, there is still conflict between host and symbiont in associations with horizontal transmission, for instance, as the fungus is selected to spread independently from its host colony by producing mushrooms with sexual spores that can be picked up by other colonies (Vreeburg et al, 2020;Wisselink et al, 2020). These mushrooms have a high biomass (Yorou et al,FIGURE 5 | Boxplots of the relative abundances of fungus-growing termite species with horizontal vs. vertical transmission in the savannah and forest across different anthropogenic disturbance regimes.…”

Comparative Genomic and Metabolomic Analysis of Termitomyces Species Provides Insights into the Terpenome of the Fungal Cultivar and the Characteristic Odor of the Fungus Garden of Macrotermes natalensis Termites

“…Macrotermes natalensis , a fungus-growing termite species, has undergone an obligate mutualistic interaction with species of the basidiomycete genus Termitomyces . This fungus is maintained as a monoculture and is used as the primary food source by the termite colony ( 1 , 2 ). Fungus-farming M. natalensis colonies have developed high levels of social complexity with polymorphism and division of labor across castes, similar to other nonfarming insect species.…”

“…1 ) ( 3 – 7 ). Termitomyces species mostly grow as fungal mycelium on the predigested plant biomass (fungus comb), thereby decomposing the lignocellulose-rich biomass, and occasionally differentiate into fungal nodules ( 1 , 7 ). While the ecology and biology of social termites is well described, our current understandings of the molecular mechanisms that drive and orchestrate the sophisticated organization of the agricultural insect society remain fragmented ( 8 ).…”

Spatial patterns and life histories of Macrotermes michaelseni termite mounds reflect intraspecific competition: insights of a temporal comparison spanning 12 years

“…As mentioned above, the available data lack sufficient temporal and spatial data of mound activity. Only one study on M. subhyalinus Rambur (1842) evaluated the activity of mounds over a decade (Mugendi 2020), hence the presumable lifespan of a Macrotermes queen (Keller 1998, Wisselink et al 2020). Other studies of Macrotermes mounds did not mention longer time periods than 2–6.5 years (Pomeroy 1976, 2005a, b2005b, Collins 1981, Lepage 1984).…”