Evol Ecol Res 3: 191–197 (2001)     Full PDF if your library subscribes.

Variation in fecundity among populations of snails is predicted by prevalence of castrating parasites

Amy C. Krist

Department of Biology, Indiana University, Bloomington, IN 47405, USA

Address all correspondence to Amy C. Krist, Department of Biology, University of Wisconsin-Eau Claire, Phillips Hall 330, Eau Claire, WI 54701, USA.
e-mail: kristac@uwec.edu


Life-history theory predicts that high mortality should cause selection for high reproductive effort. Because parasitic castration has an equivalent role to mortality, from a fitness perspective, populations with high prevalence of castrating parasites are predicted to exhibit high reproductive effort relative to populations with low prevalence. I examined this prediction by studying populations of the freshwater snail, Elimia livescens, that vary in prevalence of castrating trematodes. Specifically, I determined whether there was a positive relationship between reproductive output and prevalence of castrating trematodes among populations. Consistent with predictions, females from populations with a high prevalence of castrating trematodes produced more eggs than females from populations with a low prevalence. Either genetic canalization or phenotypic plasticity may have caused the relationship between reproductive output and parasitism. By either mechanism, the results suggest that castrating parasites shape the life histories of their hosts.

Keywords: castrating parasites, fecundity compensation, life-history theory, reproduction, snails, trematodes.

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