Whole-genome duplication affects the preference, but not the performance of specialist and generalist herbivores

Herbivore-plant interactions may be strongly affected by whole-genome duplication (WGD), or polyploidy in plants. WGD causes phenotypic changes which may affect the ability of herbivores to feed on polyploid plants. These changes include altering the size of plant organs and changing chemical defense production which, in turn, may differentially affect the preference and performance of herbivores that vary in diet breadth. We examined the direct effect of WGD on preference and performance of a specialist moth, Plutella xylostella, and a generalist moth, Trichoplusia ni. We used choice and no-choice feeding trials where larvae were fed diploids, early generation tetraploids (neotetraploids), and/or established tetraploids of Arabidopsis thaliana. We found that both specialist and generalist herbivores showed differential preference for diploids and neotetraploids, but preference hierarchy depended on the geographic origin of the plants. We also showed that both herbivore species performed similarly on all ploidy levels. Together, the results show that herbivores can successfully complete development on different ploidy levels of A. thaliana. Because WGD is a common mechanism of speciation in plants, the results suggest that WGD may allow herbivores to incorporate new hosts into their diets. This is important because host use plays a major role in the evolution of insect herbivores.