EVOLUTION OF PARASITISM
Although parasitism is a ubiquitous lifestyle, little empirical evidence exists for how and why parasitism evolves from free-living lineages. A commonly proposed hypothesis for the evolution of parasitism posits that transient host-associations served as evolutionary stepping-stones towards more obligate parasitism. For this hypothesis to hold, host-association behavior must be heritable. Using artificial selection I experimentally evolved a facultatively parasitic mite (Macrocheles muscaedomesticae) to exhibit increased propensity to attach to a fly host (Drosophila hydei). This branch of research provides some of the first evidence for heritability in parasite host-association behavior, and empirical support for a major assumption regarding how parasitic lifestyles evolve.
As a postdoctoral researcher at the University of Florida, I have been investigating consistent individual differences in behavior within and among mite populations. Working with collaborators, we have revealed significant repeatability in individuals’ attachment behavior, where some individuals consistently attach to hosts when repeatedly exposed while others never attach to a host. We are now assessing the costs and benefits associated with each of these behavioral phenotypes and asking how these consistent individual differences in behavior can influence general processes in parasite ecology like host selection and parasite aggregation.
DO MITES SERVE AS IMPORTANT DISEASE VECTORS AMONG ARTHROPODS?
Emily Stone and Elise Richardson, an undergraduate and Master's student in the Keiser lab (https://www.keiserlab.com/people) have performed experiments that demonstrate mites are capable of vectoring the beautiful (red pigmented growth in image) but deadly arthropod pathogen Serratia marcescens. The image to the right shows the post-mortem cultures of a mite that had previously attached to a fly that was experimentally infected with S. marcescens (top) and an uninfected control fly that the mite at the top attached to after attaching to the infected fly. With help from Dr. Brian Lazzaro (http://www.lazzaro.entomology.cornell.edu/index.html), we hope to soon get back into the lab to determine whether mites are truly ingesting bacteria and transmitting it to other flies when feeding on their hemolymph or if it is sloppy contact-transmission. It could be that mites' legs and/or mouthparts become contaminated after feeding on an infected host and spread it to other hosts they subsequently contact.