Unstable population structure of the herbivore is the most likely cause of the lack of regional adaptation. We found that population structure is not stable over time: we found population differentiation at the regional scale in the first year of sampling, but not in the second year. Finally, with a microsatellite study we investigated population structure of U. ornatrix is subjected to divergent selection even at the regional scale.

These results, combined with our previous evidence for plant population differentiation based on larval performance on fresh fruits, suggest that U. With a series of common-garden experiments we show that some plant traits that may affect herbivory (pyrrolizidine alkaloids and extrafloral nectaries) vary at the regional scale, while other traits (trichomes and nitrogen content) just vary at the continental scale. We performed field observations that show that specialist and non-specialist polyphagous herbivore incidence varies among populations at both scales. In the present study, we sampled the same sites to investigate factors that may contribute to the lack of differentiation at the regional scale. In a previous study, we showed adaptive differentiation in the arctiid moth Utetheisa ornatrix to its host plant, the pyrrolizidine alkaloid-bearing legume Crotalaria pallida, at the continental scale, but found no differentiation at the regional scale. However, empirical studies looking for parasite local adaptation show great variation in outcomes, and the reasons for such variation are largely unknown. Local adaptation of parasites to their hosts due to coevolution is a central prediction of many theories in evolutionary biology. Varying Herbivore Population Structure Correlates with Lack of Local Adaptation in a Geographic Variable Plant-Herbivore InteractionĬogni, Rodrigo Trigo, JosÃ© R.

Tonic ornatrix