Spatial patterns of relatedness within nesting aggregations of the primitively eusocial sweat bee Lasioglossum malachurum

Abstract

Limited natal dispersal can lead to marked spatial genetic structure, which potentially provides benefits to individuals through kin cooperation but also costs through kin competition. We often lack information on the spatial genetic structure of natural populations at a fine enough spatial scale to understand whether relatives nest close enough to interact. The primitively eusocial halictid bee Lasioglossum malachurum forms conspicuous nesting aggregations comprising up to thousands of nests. We test for spatial genetic structure in this species by genotyping one worker per nest from four discrete nesting aggregations around Tübingen, Germany, at 14 microsatellite loci. Genotypes were spatially autocorrelated at a very fine scale (<60 cm) within an aggregation for three of four aggregations, though genetic differentiation was non-existent or limited at coarser spatial scales between local or distant aggregations, respectively. Our results suggest that L. malachurum gynes often exhibit extremely limited natal dispersal, possibly because of the benefits of philopatry and kin cooperation or the avoidance of dispersal costs.