Female (top) and male (bottom) diopsid flies of the species Cyrtodiopsis dalmanni. Click on the picture to see a larger version.

One area of this field that I'm particularly interested in is the relationship between the selective value of a sexual ornament and the allometric relationship between ornament size and body size. I have a PhD student, Joanne Pomfret, who is looking (among other things) at the mating system of a dung beetle, Euoniticellus intermedius. The males of this species have horns, but interestingly the slope of the relationship between horn size and body size is less than one, whereas the normal situation for sexually selected characteristics is that the slope is greater than one (see Petrie, M. 1992. Are all secondary sexual display structures positively allometric and, if so, why? Animal Behavior 43:173-175 and Simmons, L.W. and J.L. Tomkins 1996. Sexual selection and the allometry of earwig forceps. Evolutionary Ecology 10:97-104, for more on this). Joanne is investigating the role that the horn plays in the mating behaviour of the beetle. Other groups working on the strange mating behaviour of dung beetles and its evolutionary consequences are Leigh Simmons' group at the University of Western Australia and Doug Emlen's group at the University of Montana. Here's an article about Leigh's research and here's a really nice article by Doug Emlen about dung beetles.

I'm also investigating some aspects of the eyestalks of diopsid flies ('stalk-eyed flies'). These are extraordinary looking flies in which the males carry their eyes on the end of large stalks growing out of the sides of their heads. The picture on the right shows a female (top) and a male from the species Cyrtodiopsis dalmanii, a Malaysian species.They are easy to keep in the lab., which makes them ideal models for studying a variety of questions about the evolution of secondary sexual ornaments. We are looking at two questions with these insects.

1) The role of eyestalks in female diopsids. As you can see, females also have smaller eyestalks, and we are looking into whether the eyestalks of the female have any function, or whether they're simply the result of genetic correlation from selection on males.

2) How might environmental pollution affect sexually selected species? Sexual ornaments like diopsid eyestalks are particularly sensitive to resource availability during the development of the animal. We are starting a series of experiments to look at how environmental pollution might affect this, and whether there might be long-term effects on the evolution of animals exposed to such pollutants.

Other labs doing research on diopsids are Jerry Wilkinson's group at the University of Maryland and the Stalk-Eyed Fly Research Group at UCL.