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INFECTIVITY, MULTIPLE INFECTIONS, AND THE GENETIC CORRELATION BETWEEN WITHIN‐HOST GROWTH AND PARASITE VIRULENCE: A REPLY TO HOCHBERG
Author(s) -
Ebert Dieter
Publication year - 1998
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.1558-5646.1998.tb02267.x
Subject(s) - infectivity , virulence , biology , parasite hosting , host (biology) , correlation , positive correlation , virology , genetics , gene , virus , medicine , geometry , mathematics , world wide web , computer science
Two experimental studies, Ebert (1994) and Ebert and Mangin (1997), described a genetic correlation between parasite virulence and the number of transmission stages found in the hosts. It was concluded that this correlation is evidence that within‐host growth rate of the parasite is positively correlated with virulence. Hochberg (1998) has criticized this interpretation, arguing that differential infectivity and density‐dependent parasite growth could confound the results. Here I point out that density dependence is unlikely to have confounded the results, but, at least for Ebert (1994), differential infectivity is likely to have been a confounding factor. However, Ebert and Mangin (1997) measured infectivity and showed that strains with higher infectivity had lower virulence, which is contrary to Hochberg's hypothesis. In summary, I conclude that differential infectivity played a role in the assessment of the correlation between parasite reproduction and virulence, but that differential within‐host growth remains the most likely explanation for the correlation observed in Ebert and Mangin (1997).