Results from reciprocal sister group comparisons. Results from the two reciprocal methods for sister group selection. The bars to the left show to what extent contrasts in host diversity is positively correlated with species richness, the bars to the right show to what extent contrasts in species richness is positively correlated with host diversity. When selecting sister groups on the basis of differences in host plant diversity the correlation was more pronounced than when using species richness as the basis for sister group selection. The different outcome of the two methods of sister pair selection suggests that while increases in species richness is not necessarily followed by higher host diversity, increased host diversity is predictably followed by increased species richness.