MATING STRUCTURE AND NESTMATE RELATEDNESS IN A COMMUNAL BEE, ANDRENA-JACOBI (HYMENOPTERA, ANDRENIDAE), USING MICROSATELLITES

Complex eusocial insect societies are generally matrifilial, suggestin g kin selection has been of importance in their development. For simpl er social systems, factors favouring their existence, in particular ki n selection, have rarely been studied. Communal nesting is one of thes e simple social organizations, and is found in a diversity of insect s pecies. To examine whether kin selection may play a role in the evolut ion and maintenance of communality, we estimated genetic relatedness o f nestmate females of the facultatively communal bee, Andrena jacobi. Microsatellite loci were developed for this species and used to analys e individuals from two populations. Loci were variable, they were in h eterozygote deficit and showed positive inbreeding coefficients. This may arise from nonrandom mating: previous observations (Paxton & Tengo 1996) indicate that a large proportion of females mate intranidally w ith nestmate males in their natal nests before first emerging. Nestmat e relatedness was low, no different from zero for all loci in one popu lation and for three of four loci in the other population. The large n umber of nestmates sharing a common nest (up to 594) may explain the l ow relatedness estimates, although relatedness was also independent of the number of females sharing a nest. Lack of inclusive fitness payof fs could constrain social evolution in this communal species.