Roger M. Denome
Research Interests
I'm interested in how changes in the size of a population alter the genetics of that population. Populations that are going through drastic changes in size fall into two general groups:
1. Invading populations. These organisms are usually recent immigrants, often introduced through human intervention. This group includes many of the common “weed” species introduced accidentally. It also includes organisms that are spreading rapidly because humans have altered the normal mechanisms that keep the species in check.
2. Collapsing populations. This includes all of the endangered species and those that go through population bottlenecks as part of their normal population cycles.
There is a large body of theory on this subject, but until recently tools did not exist to test this theoretical work on real populations. Molecular genetics has changed this. My graduate work on the molecular biology of gene expression was an excellent education in the techniques that have been co-opted by population geneticist to study population dynamics. Game management groups have been extremely interested in these data and have supplied financial support and samples (e.g. tissue from mule deer, whitetail deer, several elk species, moose, three subspecies of bighorn sheep). Recently, I've expanded my work to carnivores ( wolves, coyotes and striped skunks).
Work with coyotes and skunks is the focus of my lab at present. Collaborations with the Maine Department of Inland Fish and Game and Dr. Gwilym Jones at Northeastern University have produced baseline data on the genetic variation associated with relatively long-standing populations of coyotes in Maine and southeastern Canada. Recent work in collaboration with the Watershed Institute of Massachusetts and Bill Petri at Boston College has begun to look at coyote populations that have expanded onto Cape Cod in the last 20 years. This work addresses the following questions:
1. Compared to established populations, how much genetic variation exists in new populations of an invading species?
2. In a “linear environment” like Cape Cod, is there a gradient of genetic variation that results from the limited ability of the population to migrate along the peninsula?
3. How effective is the Cape Cod Canal as a barrier to migration?
The answers to each of these questions has implications for managing the increasing number of encounters between humans and coyotes. If the aim of game management is to minimize the effects of coyotes on humans, then a full understanding of the rate at which coyotes invade territory and the genetic “robustness” of the resulting population is essential. If the aim of game management is to minimize the effects of humans on coyotes, then defining migration strategies and minimum sustainable population sizes is essential.
My lab is also working on the genetics of striped skunks on Thompson Island in Boston Harbor. Several hundred striped skunks (Mephitis mephitis) live on the island. Because skunks are the major reservoir for rabies in Massachusetts, there are continuing efforts to keep skunk populations under control, especially in urban areas. Although there have been several attempts to rid Thompson Island of skunks, the population remains relatively robust. The reason for this resilience is unknown. Either there is a steady flow of new immigrants from the mainland, or the skunks of Thompson Island are extremely good at evading capture.
The question that we are trying to answer has to do with the origin and maintenance of the Thompson Island skunk population. Using molecular genetic methods, we are assaying the genetic differences between the population on the mainland and the population on the island. The results of these tests will allow us to distinguish between two alternate hypotheses about this population:
1. The island is relatively isolated from the mainland and skunk migration onto the island from the mainland is rare. If this is the case, the island population should have low levels of genetic variation compared to mainland populations.
2. The island is not isolated from the mainland; skunk migration on and off the island is common. If this is the case, island and mainland populations should be virtually genetically identical.
If the former hypothesis is correct, control of the island population should be relatively easy. Once skunks are removed from the island, they should be slow to reestablish themselves. If the latter hypothesis is correct, there is little hope of containing the island population. It is effectively an extension of the mainland population.