Comparing the preferences of three herbivore species with resistance traits of 15 perennial dicots: the effects of phylogenetic constraints

Differences in palatability between 15 perennial dicotyledonous herbaceous plant species were investigated in a multiple choice test, involving three generalist herbivores. Palatability was compared with two categories of plant traits: defence characteristics and growth properties. On theoretical grounds, we expected a positive relationship between growth rate and palatability, and a negative relationship between palatability and defence traits. The possible effect of phylogeny on the outcome of the comparisons was investigated by analysing the data using phylogenetically independent contrasts. The three herbivores showed remarkably similar preferences, which indicates that the results of the choice experiment are a good representation of leaf palatability. The significant negative correlations found in a direct comparison between herbivore preference and relative growth rate, and between herbivore preference and lignin and dry matter content, did not hold after phylogenetic correction. On the other hand, one relationship emerged only when comparing phylogenetically independent contrasts: contrary to expectation, a negative relation was noted between juvenile growth rate and plant palatability. A possible explanation for the contradictory nature of this result is the uniformly ready availability of resources in our experiment.