E-mail: sslowins AT indiana DOT edu
The Effect of Plasmodium Infections on the Production of Volatile Compounds in the Avian Preen Gland: A common strategy that parasites employ to enhance transmission among suitable hosts is the manipulation of host behavior. Recent work has demonstrated that domestic canaries (Serinus canaria) experimentally infected with the malaria parasite Plasmodium relictum were more attractive than uninfected canaries to Culex pipiens mosquitoes (a natural vector of Plasmodium). This infection-induced alteration of host attractiveness to mosquitoes is hypothesized to be an adaptive manipulation of the host by the parasite. The specific mechanisms by which Plasmodium influences the attractiveness of infected birds to mosquitoes are unknown. My research is testing the hypothesis that Plasmodium parasitesenhance the attractiveness of their avian hosts to mosquitoes by altering the production of volatile compounds in the preen gland. The preen gland is a small exocrine gland in birds that produces a waxy secretion that contains volatile compounds. I am currently testing the following predictions of my hypothesis: 1) preen oil volatile compounds should covary with the infection status of wild birds, and 2) experimental clearance of Plasmodium parasites should alter the production of volatile compounds in the preen gland. Future work will test the prediction that mosquitoes are more attracted to preen oil samples collected from infected birds than they are to preen oil samples collected from uninfected birds.
The effect of parasites on the ability of self-fertilization to invade obligately outcrossing host populations: I am also interested in how host-parasite coevolutionary interactions affect the evolution of reproductive systems in host populations. A two-fold cost of biparental reproduction results from the inability of males to directly produce their own offspring. Given this fitness cost, populations that reproduce biparentally should be susceptible to invasion by mutants capable of reproducing uniparentally. However, given that biparental reproduction is so common in natural populations, it seems to be associated with substantial fitness benefits that offset the costs. The Red Queen hypothesis suggests that coevolutionary interactions between hosts and parasites can generate negative frequency-dependent selection that favors rapid changes in host genotype frequencies. Perhaps this fluctuating selective pressure can favor bi-parental reproduction and recombination in spite of the costs. I tested the prediction that coevolutionary interactions with parasites can prevent self-fertilization (uniparental reproduction) from invading obligately outcrossing (biparentally reproducing) host populations. I introduced Caenorhabditis elegans hermaphrodites, carrying a dominant wild-type allele permitting both outcrossing and self-fertilization, into C. elegans populations harboring a recessive mutant allele thatconfers obligate outcrossing. Experimental populations were permitted to evolve under 3 parasite treatment regimes. I found that self-fertilization rapidly spread in host populations evolving in the absence of a coevolving parasite, however, the spread of self-fertilization was constrained in host populations that were exposed to the potentially coevolving bacterial parasite Serratia marcescens. My results support the Red Queen hypothesis, and demonstrate that coevolutionary interactions with a virulent parasite can constrain the spread of self-fertilization into obligately outcrossing host populations.