Ant parasitoids in the Orasema coloradensis species group and the problem of host relationships

Monday, November 11, 2013
Exhibit Hall 4 (Austin Convention Center)
Austin Baker , Entomology, University of California, Riverside, CA
The Orasema coloradensis species group is a monophyletic group (2 described species, 15 estimated) of ant-parasitizing wasps in the Nearctic. Like all wasps in the family Eucharitidae, Orasema lay their eggs away from their hosts in plant tissue. The eggs hatch into mobile first instar larvae, called planidia, that likely attach themselves to ant foragers or ant prey items, and are then carried into the nest. There is one host record of O. coloradensis on Formica (Formicinae) based on planidia found on their mouthparts and excavation of ant nests. This is the only species of Orasema with a non-Myrmecinae host record. Furthermore, three genetically similar but phenotypically distinct varieties of another Orasema species have been discovered to use different ant hosts. Similar morphological patterns have been observed in museum specimens in the O. coloradensis group, but they lack molecular and host association data. If this pattern of intraspecific host-dependent phenotypic variation is confirmed in other groups of Orasema, then the number of species in this genus -- and perhaps many other groups of parasitoid wasps -- may be less than has been previously estimated. This may have implications in the utility of these wasps as biological control agents, and might make this group ideal for studying speciation at the population level once more data have been obtained. I will present preliminary observational data and outline my research goals to: build a molecular phylogeny, establish accurate host records, and determine if there is host-specific variation within species of Orasema.
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