George Eickwort, PhD - US grants

Doctoral student Byron Alexander proposes to study the ancestor-descendant relationships within the bee genus Nomada, using morphological data from the literature, museum visits, and from borrowed collections. His advisor, George Eickwort, is a leading researcher on social insects. Both social and parasitic behavior have evolved from nest-building ancestors in this genus, and it is unclear whether 1) the social species are a separate evolutionary branch within the genus, or 2) social behavior has evolved independently several times. A well-established evolutionary framework for this group would provide the means for assessing these alternatives. The evolution of behavior is an important facet of biology, and behavior of certain insects such as bees can have important economic implications. The proposed research can have subtantial impact beyond the small community of specialists working on this taxon.

Workers in eusocial Hymenoptera colonies (relatedness asymmetry present) are predicted to favor a more female-biased sex-ratio as compared to the sex-ratio favored by workers in parasocial colonies (relatedness asymmetry absent). Experiments on the primitively eusocial sweat bee Augochlorella striata, with random assignment of colonies to a eusocial and parasocial condition confirmed the predicted female-bias in eusocial colonies, but were unable to test the hypothesis that worker reproduction of males is greater in parasocial than in eusocial colonies. The determination of maternity of males by means of a genetic analysis is essential to test this hypothesis. This study will involve genetically fingerprinting reproductives, workers, and male sexuals of the experimental nests in order to compare worker reproduction of males in eusocial and parasocial colonies. Because of parthenogenetic production of males, all bands in a fingerprint of a male must also be present in the fingerprint of his mother. Maternity of males can therefore be determined by matching fingerprints of males to fingerprints of putative mothers (e.g. foundresses and workers). If evidence from genetic fingerprinting refutes the hypothesis of worker reproduction, relatedness asymmetries deriving from haplodiploidy remain as the only explanation of the observed sex-ratio adjustments. This would imply that social behavior in A. striata evolved not only in response to ecological constraints limiting reproductive options, but also in relation to genetic variables (relatedness asymmetries) intrinsic to the haplodiploid system of sex-determination.