Evolutionary Ecology

, Volume 9, Issue 1, pp 82–92

Trade-offs and the evolution of host specialization

  • Amitabh Joshi
  • John N. Thompson


Trade-offs in performance on different hosts are thought to promote the evolution of host specificity by blocking host shifts. Yet, in contrast, most experiments using phytophagous insects have shown performance on alternative hosts to be uncorrelated or positively correlated. Recent quantitative genetic models based on mutation—selection balance indicate that underlying constraints on the simultaneous maximization of different components of fitness may not always generate negative genetic correlations. We suggest an alternative or additional explanation for the lack of observed negative genetic correlations. If performance is polygenically controlled and some performance loci possess only antagonistically pleiotropic alleles, then the expression of trade-offs in performance will vary over time in populations. Consequently, a trade-off will be seen only in populations that have adapted to two hosts and are at or close to genetic equilibrium. Therefore, studies testing performance on a novel as compared with a normal host will generally yield non-negative genetic correlations between performance on the two hosts. The results of published studies are consistent with the predictions of this hypothesis.


trade-offs performance normal versus novel hosts host specificity host range host specialization 


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Copyright information

© Chapman & Hall 1995

Authors and Affiliations

  • Amitabh Joshi
    • 1
  • John N. Thompson
    • 2
  1. 1.Department of Genetics and Cell BiologyWashington State UniversityPullmanUSA
  2. 2.Departments of Botany and ZoologyWashington State UniversityPullmanUSA
  3. 3.Department of Ecology and Evolutionary BiologyUniversity of CaliforniaIrvineUSA

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