Gut microbial compositions mirror caste-specific diets in a major lineage of eusocial insects

Abstract

25Eusocial insects owe their ecological success to the division of labour and processes within colonies 26 often rely on the presence of specific microbial symbionts, but associations between microbial 27 community compositions and castes with different tasks and diets within colonies remain largely 28 unexplored. Fungus-growing termites evolved to use fungi to externally degrade plant material, 29complemented by specific and complex gut microbiotas. Here we explore to which extent division 30 of labour and dietary differences within fungus-growing termite castes are linked to gut bacterial 31 community structure. Using amplicon sequencing, we characterise community compositions in 32 sterile (worker and soldier) and reproductive (queen and king) termites and combine this with gut 33 enzyme, microscopy, and in situ analyses to further elucidate sterile caste-specific microbiota 34 compositions. Gut bacterial communities are structured primarily according to termite caste and 35 genus. In contrast to the observed rich and diverse sterile caste microbiotas, royal pair microbiotas 36 are extremely skewed and dominated by few bacterial taxa, reflecting the specialised dietary intake 37 and unique, reproduction-centred lifestyle of the queen and king. 38 39