Microbiomes of host-cleptoparasites and other wild bees

Studies on microbiomes are essential for understanding the various roles microbes play in the health of bees, yet many wild bees including cleptoparasitic species continue to be underexplored. To alleviate this gap, we analyzed bacterial and fungal microbiomes of cleptoparasitic species Nomada articulata, N. illinoensis, Holcopasites calliopsidis, Triepeolus pectoralis, Sphecodes monilicornis and Coelioxys octodentatus with 16S rRNA and ITS1 metabarcoding and compare results to the microbiomes of their hosts and other wild bees with various functional traits. We found that a parasitic lifestyle was associated with a significantly richer bacterial microbiome compared to other social or diet lifestyles, and that ground-nesting bees have a richer bacterial microbiome than stem-nesting bees. Fungal diversity was only found to be greater in solitary bees compared to eusocial species. Hosts and cleptoparasites had similar bacterial and fungal microbiomes, with only two exceptions. N. articulata have a richer bacterial microbiome compared to its host Agapostemon virescens but not to its other host A. sericeus, whereas N. illinoensis showed a significantly different fungal beta diversity compared to its potential hosts Andrena crataegi and An. wilkella. Cleptoparasites were also found to uniquely associate with several understudied bacterial microbes. Finally, the inclusion of previously published wild bee microbiome studies further confirmed phylogenetic conservation of corbiculate core bacteria. Overall, our study is the first to assess the diversity ofmicrobiomes of underexplored wild bees including cleptoparasitic species and reveals important insight into unique and shared microbes in wild bees and host-cleptoparasite pairs.