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Evolutionary factors influencing the nature of parasite specificity

Published online by Cambridge University Press:  16 March 2011

M. L. Adamson  and
J. N. Caira
M. L. Adamson
Affiliation:
Department of Zoology, University of British Columbia, Vancouver, B.C., V6T 1Z4, Canada
J. N. Caira
Affiliation:
Department of Ecology and Evolutionary Biology, University of Connecticut, Storrs, Connecticut, 06269-3043 U.S.A.
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Summary

This article considers how specificity patterns are shaped during the course of parasite evolution. Parasites are first and foremost specific to site, or microhabitat; host ranges are far more subject to change than is microhabitat. Specificity results from a number of convergent phenomena starting with habits (microhabitat and feeding styles) of free-living progenitors and the way in which the parasitic association arises (e.g., passive oral contamination as opposed to intrusive entry). These bias the types of interaction parasites have with the host, and, through this, the way specificity develops. Host ecology acts as an external factor affecting specificity and predominates in parasites that interact minimally with the hosts physiological and immune systems. Coevolutionary factors are more important in parasites that feed on host tissues or occur in extraintestinal sites. Here, parasites must present the right cues, and respond appropriately to the host defense system. The ability to generalize these cues and responses across host boundaries may act as a constraint on host range. The functional role of the host in the parasite life history also affects the degree of specificity; thus, parasites may act as host generalists in hosts that act as trophic channels to the final host. The role of competition in determining specificity is difficult to assess. However, competition has been reported to influence microhabitat and host distribution through interactive site selection and/or competitive seclusion.

Keywords

Tissue specificitysite specificityhost specificitycoevolutioncompetitionevolution
Type
Research Article
Information
Parasitology , Volume 109 , supplement S1: Parasites and behaviour , 1994 , pp. S85 - S95
Copyright
Copyright © Cambridge University Press 1994

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