Abstract

Fungus-growing termites (Isoptera: Macrotermitinae) dominate African savannah ecosystems where they play important roles in ecosystem functioning. Their ecological dominance in these ecosystems has been attributed to living in an ectosymbiosis with fungi of the genus Termitomyces (Lyophyllaceae). Evolutionary theory predicts that the transmission mode of a symbiont determines cooperation and conflict between host and symbiont with vertical transmission (co-transmission of host and symbiont offspring to the next generation) leading to less conflict than horizontal transmission (symbionts are acquired by the host from the environment). Thus, one can hypothesize associations with vertical transmission to be ecological more successful than those with horizontal transmission. We tested this by analyzing whether there is an association between transmission mode and fungus-growing termite species abundance and distribution in West-African savannah and forest ecosystems. We used data from a total of 78 study sites comprising protected National Parks as well as anthropogenically disturbed ecosystems, covering Benin, Côte d'Ivoire, and Togo. Our results showed that, in contrast to expectation, species with horizontal symbiont transmission were more common. We encountered more often species with horizontal than vertical transmission. This result might be due to the fact that only five out of the 25 identified fungus-growing termite species had vertical transmission. Yet, species with horizontal transmission also had higher relative abundances within study sites than those with vertical transmission. Thus, transmission mode is unlikely to explain abundance differences between fungus-growing termite species.

Highlights

  • Fungus-growing termites (Isoptera: Macrotermitinae) thrive in African savannah ecosystems where they often make up more than 50% of termites’ species diversity and the large majority of termites (e.g., Hausberger et al, 2011; Hausberger and Korb, 2015, 2016; Schyra et al, 2019a; and reference therein) and where they play pivotal roles in ecosystem functioning (e.g., Bignell and Eggleton, 2000; and references therein)

  • The analysis revealed that transmission mode had a strong and significant effect on the relative abundance of a species (Table 1) with species with horizontal transmission having higher abundances within study sites than species with vertical transmission (Figure 6)

  • While the results for the encounter frequencies have been biased by the fact that there were more species with horizontal than vertical transmission, this effect was accounted for in the relative abundance analyses across species (Figure 4) and when including species identity in the generalized linear mixed model (GLMM) (Figure 6)

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Summary

Introduction

Fungus-growing termites (Isoptera: Macrotermitinae) thrive in African savannah ecosystems where they often make up more than 50% of termites’ species diversity and the large majority of termites (e.g., Hausberger et al, 2011; Hausberger and Korb, 2015, 2016; Schyra et al, 2019a; and reference therein) and where they play pivotal roles in ecosystem functioning (e.g., Bignell and Eggleton, 2000; and references therein). Within the ecological food web, they are main macro-detrivores, essential for decomposition of dead plant material, and are prey for a wealth of animals from invertebrates (such as ants) to vertebrates (such as birds and mammals). Fungus-growing termites foster biodiversity and are essential for its maintenance, especially in savannah ecosystems

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