Eusociality as a neglected aspect of wild bee α‐diversity and its potential impact on diversity estimation

Abstract

1. Bees provide important ecosystem services and are subjects of extensive studies on their α-diversity, which is generally calculated with indices that integrate the number of species with their abundances. Variation in social behaviour, though expected to impact genetic diversity, is still largely neglected in such studies.2. We propose a simple method to show how sociality may affect diversity indices, when a surrogate of genetic diversity is taken into account. This method weighs the number of sampled females (N) to obtain new abundance values (N W ), by taking into account relevant biological traits affecting genetic structure of populations, that is, the number of (natal) nests from which the sampled females originated (which depends on brood productivity and sex ratio) and the genetic relatedness among such females.3. Solitary species tend to have greater N W than eusocial ones especially at larger sample sizes. Across studies on 121 bee communities, we found that Taxonomic distinctness, Shannon-Wiener diversity and Gini-Simpson dominance tended to be greater when based on N W rather than on N. Such differences increased in communities with decreasing number of eusocial species and with increasing proportion of individuals from eusocial species.4. The results suggest that taking into account the social organisation of wild bees may have important consequences in estimating α-diversity, thus claiming for future efforts in collecting biological data on as many wild bee species as possible to improve the precision of N W estimations. For example, stressors affecting more solitary bees could impoverish communities dominated by few but abundant eusocial species, more than expected by using unweighted abundances.