Dale H. Clayton, Principal Investigator

Why are there so many species on earth? Although speciation is understood better now than it was in Darwin's day, we are still a long way from having a clear understanding of the processes responsible for diversification. In the Clayton Lab we are interested in these processes, particularly in the context of host-parasite interactions. Our research focuses on “permanent” parasites, such as lice, which complete their entire life cycle on the body of the host. Indeed, this lab may be the world headquarters for research on the evolutionary ecology of lice (Insecta: Phthiraptera). It's a big fish - small pond thing. Some pretty strange things go on around here, like moving host-specific lice from one species of bird to another. We are probably the only people on earth who actually worry about running out of lice. Conversations in local restaurants draw stares of disbelief from other patrons (not to mention copious scratching). We don't get invited to parties much . . .

So why lice? Because they provide real advantages for tackling questions in evolutionary biology. Since lice seldom leave the body of the host, their niche parameters are far easier to measure than those of most organisms, both in ecological and evolutionary time. The phylogeny of many genera is congruent with that of the host, making it possible to reconstruct not only the parasite's evolutionary history, but also the environmental context in which the parasite evolved. Congruence is seldom perfect, however, because parasites occasionally switch to new host lineages over evolutionary time. This is when things get interesting.

We ask questions such as the following:  What governs switching ability and the host specificity of parasites? Do novel parasites out-compete resident parasites? Do switching parasite lineages undergo more or less adaptive radiation? Are these lineages more virulent or more benign to their hosts than lineages with a longer history of association? What is the role of phoresis (hitchiking) of host specific parasites on more mobile, less specific parasites, such as hipposboscid flies? How do birds and mammals defend themselves against ectoparasite communities? What is the relative importance of grooming, dusting, sunning, anting and other behaviors? Do ectoparasites use cryptic coloration to avoid the main host defense (preening)?

We use a variety of empirical tools.  These tools include molecular systematics, comparative morphological studies, and experimental work in both the laboratory and field. Much of the lab work involves captive birds and their parasites. We also do a good deal of fieldwork collecting specimens of birds and parasites in exotic localities such as Australia, Borneo, China, Mexico, New Guinea, and the Philippines. In short, we stay pretty busy!