RELATEDNESS AND POPULATION STRUCTURE OF THE PRIMITIVELY EUSOCIAL BEE LASIOGLOSSUM ZEPHYRUM (HYMENOPTERA: HALICTIDAE)...

Lasioglossum zephyrum is a primitively eusocial bee, which nests in small colonies of up to 20 individuals. The nests occur in patchily distributed aggregations of from a few to over 1,000 nests along periodically disturbed stream and river banks in eastern North America. We used five polymorphic allozyme loci to test for geographic structure and estimate relatedness in eight patches of nests from five aggregations in Douglas Co., Kansas. Autocorrelation analysis of gene frequencies, plus a multilocus G test, revealed a low but significant tendency for differentiation among nests within patches, among patches within aggregations, and among aggregations. Small numbers of nests restricted estimation of relatedness to three patches, of which only one had a sample size large enough to yield confidence limits narrow enough to be informative. The limits from this patch of 20 nests are 0.64 < 0.8245 < 1.01. While these limits are consistent with the true value being 0.75 (that expected under male-haploidy if each nest results from the reproduction of a single, once-mated female), the occurrence of some nests with three or more genotypes shows that nest makeup is more complex than this, so that a lower value, say 0.7, is more plausible. This value is sufficiently high to indicate that kin selection is probably important in these populations.