High diversity and low host-specificity of Termitomyces symbionts cultivated by Microtermes spp. indicate frequent symbiont exchange

Fungus-growing termites (subfamily Macrotermitinae) live in an obligate mutualistic symbiosis with species of the fungal genus Termitomyces (Basidiomycota). Although the species that build large mounds are the most conspicuous, termites of the genus Microtermes construct large underground networks of tunnels connecting many fungus gardens. They are also the only entire genus within the Macrotermitinae in which vertical transmission of the fungal symbiont has evolved. To study patterns of genetic diversity in species of the genus Microtermes and their Termitomyces symbionts, we sampled at three different locations in South Africa and sequenced COI for the termites and ITS for the fungi. We discovered high genetic diversity in both termites and fungal symbionts but very low interaction specificity. This implies that frequent horizontal exchange of fungal symbionts occurs between species, despite vertical transmission across generations. We also estimated colony size based on termite haplotype and fungal genotype combinations and found indications that colonies may extend over large areas. (C) 2020 The Authors. Published by Elsevier Ltd.