Mating structure and nestmate relatedness in a communal bee, Andrena jacobi (Hymenoptera, Andrenidae), using microsatellites


  • This paper is a product of the long term and wide-ranging collaboration between the Ecological Research Station of Uppsala University (J. Tengö), with a specialism in field studies of wild bees, and the Department of Genetics of Uppsala University (P. Pamilo, R. Paxton, P. Thorén), with a specialism in the evolutionary biology of social insects. Recent emphasis in the group's social insect work has been placed on the development of microsatellite markers, and for this study they were developed in collaboration with A. Estoup (INRA, Paris).

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Complex eusocial insect societies are generally matrifilial, suggesting kin selection has been of importance in their development. For simpler social systems, factors favouring their existence, in particular kin selection, have rarely been studied. Communal nesting is one of these simple social organizations, and is found in a diversity of insect species. To examine whether kin selection may play a role in the evolution and maintenance of communality, we estimated genetic relatedness of nestmate females of the facultatively communal bee, Andrena jacobi. Microsatellite loci were developed for this species and used to analyse individuals from two populations. Loci were variable, they were in heterozygote deficit and showed positive inbreeding coefficients. This may arise from nonrandom mating; previous observations (Paxton & Tengö 1996) indicate that a large proportion of females mate intranidally with nestmate males in their natal nests before first emerging. Nestmate relatedness was low, no different from zero for all loci in one population and for three of four loci in the other population. The large number of nestmates sharing a common nest (up to 594) may explain the low relatedness estimates, although relatedness was also independent of the number of females sharing a nest. Lack of inclusive fitness payoffs could constrain social evolution in this communal species.