Context-dependent interactions between an aquatic snail (Lymnaea elodes) and the sterilizing parasite, Echinostoma revolutum
Abstract
Organisms are continually faced with the dilemma of allocating resources to competing functional demands such as growth, reproduction, and survival. The degree to which energy is distributed to each of these traits depends on numerous factors from the genetics of the organism to the prevailing biotic and abiotic conditions. Parasites have been recognized as biotic factors that can have significant effects on host allocation patterns either by competing for host resources directly or by impacting the expression of host resistance. However, little is known about the interactive role that parasitism and other environmental variables play in shaping host life-history patterns. Using a combination of field, experimental, and molecular approaches, I have explored the interactive role that trematode parasitism and environmental factors play in shaping the life-history patterns of the aquatic snail, Lymnaea elodes. Results demonstrate that desiccation and resource limitation in combination with parasite exposure can have significant impacts on host growth, reproduction and survival. In addition, this work has revealed that host genotype can play a critical role in the direction and magnitude of trait expression under varying environmental conditions. Furthermore, host resistance to infection comes at a cost in terms of reduced fitness traits, but this pattern only occurs under particular environmental conditions. Subsequent investigations into the nature of, and the factors underlying, resistance in this system suggest that resistant individuals do not maintain additional constitutive defenses, but instead may express inducible responses upon parasite infection. This research provides important insights into the factors responsible for modulating interactions between hosts and parasites and reinforces the important role that parasites play in host life-history evolution.
Degree
Ph.D.
Advisors
Minchella, Purdue University.
Subject Area
Ecology|Zoology
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