Trade-Offs in Fitness on Different Hosts: Evidence from a Selection Experiment with a Phytophagous Mite

This is the authors' abstract. We don't add key points for this paper.

Trade-offs, or negative genetic correlations, in fitness on different hosts have been hypothesized to restrict evolutionary expansion of host range in phytophagous arthropods. I used a population of the polyphagous mite Tetranychus urticae that had been selected for adaptation to tomato plants to determine whether tradeoffs between fitness on tomato and fitness on lima bean occur in this species. Two lines established from the tomato-adapted population and reared on lima bean showed significant declines in ability to survive on tomato after more than 10 generations on bean. The most likely explanation for this result is that tomato-adapted genotypes were selected against on bean. The tomato-adapted population did not have detectably lower survival or fecundity on bean than a control population kept on bean, however, suggesting that tomato-adapted genotypes were at only a slight disadvantage on bean. This study and a similar previous experiment with T. urticae using cucumber and bean provide the only evidence for trade-offs in herbivore populations found to date. Theoretical considerations suggest that the selection techniques used in the studies of T. urticae may be more likely to detect trade-offs than the breeding designs and comparisons among clones used in studies of other herbivores. Thus, the failure of several studies of other herbivores to detect trade-offs may reflect the techniques used.