Abstract
As the key pollinators of most flowering plants, bees are essential for maintaining healthy ecosystems and many of our agricultural crops. Bees are estimated to contribute $14 billion a year to the US economy. An important step in the conservation of bees is an understanding of their phylogeny. A classification based on their evolutionary history forms the basis for all other scientific endeavors pertaining to bees.
Apidae is one of the most diverse families of bees. Of the 3166 described species, approximately 25% are thought to be cleptoparasitic. Cleptoparasitic bees do not build their own nests or forage for their offspring. Instead, they enter the nest of a host bee, lay an egg in a cell, and then usually leave. Once the parasite larva emerges, it feeds on the food that had been provided for the host larva. Repeated evolution of cleptoparasitic behavior is thought to distort phylogenies for the Apidae, because cleptoparasitic adaptations (e.g. loss of pollen collecting and nest construction structures) promote monophyly of the parasites when in reality they are believed to be polyphyletic.
For my thesis, I am exploring the phylogenetic relationships of the Apidae to determine from what nonparasitic groups the cleptoparasitic lineages arose. To investigate this problem, the sting apparatus of members of all 33 apid tribes, 20 of which are cleptoparasitic or contain cleptoparasites, and suitable outgroups are being studied in addition to characters previously used. It is highly probable that some independent origins of cleptoparasitism have led to different adaptations of the sting apparatus (for oviposition in host brood cells and defence of the parasite against the host) in different apid clades. This suggests the potential of the sting apparatus in helping resolve apid phylogenetic relationships, as new characters from the sting will not suffer from convergence in cleptoparasites as other morphological characters often do.
In addition to sting apparatus and other morphological data, successful resolution of this problem requires molecular data. Therefore, I am sequencing 5 genes, which now seem like promising candidates for higher-level bee phylogeny, for each taxon. An attempt is also being made to find primers for new genes that would help resolve these relationships.
Resolving the phylogeny for the Apidae would be of great importance. It would answer the highly debated question of how many origins of cleptoparasitism there has been within the Apidae. The classification of Apidae is currently based on the results of Roig-Alsina and Michener (1993). If parts of their phylogeny are not supported by this analysis of their data in combination with molecular and other morphological characters, a reanalysis of the classification of Apidae would be possible and perhaps needed.
Also, questions could be investigated such as whether or not parasites tend to evolve from their host, is social parasitism a precursor to cleptoparasitism, has the morphological divergence among different cleptoparasites been driven by increasingly specialized adaptations to the demands of parasitizing different hosts, have distantly related genera converged on the same hosts and if so how have their modes of parasitism converged.
