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Low migration decreases interference competition among parasites and increases virulence
Author(s) -
VIGNEUX F.,
BASHEY F.,
SICARD M.,
LIVELY C. M.
Publication year - 2008
Publication title -
journal of evolutionary biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.289
H-Index - 128
eISSN - 1420-9101
pISSN - 1010-061X
DOI - 10.1111/j.1420-9101.2008.01576.x
Subject(s) - biology , virulence , host (biology) , competition (biology) , bacteriocin , symbiotic bacteria , bacteria , nematode , microbiology and biotechnology , population , ecology , symbiosis , genetics , gene , demography , sociology
Abstract Competition among different parasite genotypes within a host is predicted to affect virulence. The direction of this effect, however, depends critically on the mechanisms that parasites use to compete or to cooperate with each other. One mechanism that bacteria use to compete with each other is via the production of bacteria‐killing toxins, called bacteriocins. This warfare among parasites within a host is predicted to reduce the rate of host exploitation, resulting in lower virulence. By contrast, if parasites within a host are highly related, there could be a reduction in within‐host conflict, increasing virulence. We examined this idea by allowing an insect‐parasitic nematode ( Steinernema carpocapsae ) and its symbiotic bacteria ( Xenorhabdus nematophila ) to evolve for 20 passages under two different migration treatments (low and high). We found that host mortality rates were higher in the low‐migration treatment when compared with the high‐migration treatment. In addition, bacteria isolated from the same insect host inhibited each other’s growth, but only in the high‐migration treatment. These results show that population structure and interactions among parasites within hosts can be critical to understanding virulence.