Date of Defense

Spring 4-23-2004


Biological Sciences

First Advisor

Steven Kohler, Biology/Environmental Studies

Second Advisor

Stephen Malcom, Biology


Acquiring resistance to a pathogen, while protecting an organism from the adverse effects of the pathogen, can result in energetic trade-offs that compromise and organism's ability to compete for resources, even in the absence of the pathogen. Such energetic trade-offs appear to affect aquatic invertebrates that are key components in the structure of the respective food webs, such as the prominent caddisfly Glossosoma nigrior, potentially impacting the evolutionary development of entire communities or ecosystems by allowing other species to replace the niches once filled by G. nigrior and other affected species. However, the extent that disease resistance affects the fitness of a resistant population of a species is difficult to glean solely by making comparative observations in the field because of the myriad variables that are present in natural aquatic communities. G. nigrior from two populations - one population which has been exposed to the Cougourdella pathogen, and one which has not; which we hypothesize are resistant and susceptible populations, respectively - were collected and cultivated in controlled laboratory environments to examine the effect that disease resistance has on inter- and intra-specific competitive ability. Interspecific competition was simulated by rearing G. nigrior along with the caddisfly Neophylax concinnus. Our results showed that intraspecific competitive ability is significantly compromised in the infected-recovered population relative to the unexposed population. The extent to which interspecific interactions were compromised in the infected-recovered population was not found to be significant; however, this may have been due to ineffective ratios of the two species in our experimental design or disparities in the sizes of the insects of the two species used in our experiment.

Access Setting

Honors Thesis-Campus Only