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INTRASPECIFIC COMPETITION AND THE EVOLUTION OF VIRULENCE IN A PARASITIC TREMATODE
Author(s) -
Gower Charlotte M.,
Webster Joanne P.
Publication year - 2005
Publication title -
evolution
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.84
H-Index - 199
eISSN - 1558-5646
pISSN - 0014-3820
DOI - 10.1111/j.0014-3820.2005.tb01014.x
Subject(s) - biology , intraspecific competition , virulence , parasite hosting , schistosoma mansoni , competition (biology) , biomphalaria glabrata , genotype , host (biology) , experimental evolution , zoology , evolutionary biology , ecology , genetics , helminths , gene , schistosomiasis , world wide web , computer science
Intrahost competition between parasite genotypes has been predicted to be an important force shaping parasite ecology and evolution and has been extensively cited as a mechanism for the evolution of increased parasite virulence. However, empirical evidence demonstrating the existence and nature of intraspecific competition is lacking for many parasites. Here, we compared within‐host competitiveness between genetic strains of Schistosoma mansoni with high (HIGH‐V) or low (LOW‐V) virulence to their intermediate snail host, Biomphalaria glabrata . Groups of snails were exposed to either one or the other of two parasite strains, or a mixed infection of both strains, and the resulting progeny were identified using a molecular marker. In two separate experiments investigating simultaneous and sequential infections, we demonstrated that the lifetime reproductive success of parasite strain HIGH‐V was reduced in the presence of a faster replicating parasite genotype, LOW‐V, regardless of whether it was in a majority or minority in the initial inoculum of the simultaneous exposure or of its relative position in the sequential exposure experiment. Thus, we demonstrate competition between parasite genotypes and asymmetry in competitive success between parasite strains. Moreover, since the less virulent strain investigated here had a competitive advantage, we suggest that a high frequency of multiple infections could favor the evolution of less, rather than more, virulent parasites in this system.