Research in the Rich lab focuses on the evolutionary dynamics of pathogen and host populations. We are particularly interested in the processes that have altered the genes and genomes of these organisms in a way that has facilitated their continued interaction. Some parasite-host associations date far back in the geologic record, indicating a finely tuned balance in the antagonism of their shared evolution. The genetic novelties that permit rapid, somatic generation of a near-infinite ensemble of immunoglobulin diversity, are testament to such a history. Coincident with these events are the innovations in genomes of parasites, which have provided these organisms with adaptive mechanisms for avoiding the hypervariable immune response of their hosts. My research aims are to discern the importance of various factors—such as natural selection, horizontal exchange of genetic material, population structure, development of novel gene functions and differential expression—in shaping past and present host-parasite interactions. By determining the extent of genetic variation among populations of these organisms, it becomes possible to make strong inferences about the mechanisms that, (a) generate variation, and (b) serve to maintain high level of variation and its concomitant, adaptive-potentiality.

The rapid, recent influx of modern molecular biology techniques coupled with our ever-increasing theoretical knowledge of molecular evolution, make it now possible to determine the short-and long-term evolutionary histories of human parasites and associated diseases. My research incorporates these various tools in research programs encompassing two distinct human pathogen systems: (1) Plasmodium falciparum, the mosquito-borne, protozoan agent of malignant malaria, and (2) Borrelia spp., the tickborne spirochetes of Lyme disease and relapsing fever. Both systems are fascinating models for studying complex interactions of pathogen-vector-host coevolution and for determining the means by which their genomes are shaped by these interactions.