Abstract: Ecologists frequently use a supertree method to generate phylogenies in ecological studies. However, the robustness of research results based on phylogenies generated with a supertree method has not been well evaluated. Here, we use the angiosperm tree flora of North America as a model system to test the robustness of phylogenies generated with a supertree method for studies on the relationship between phylogenetic properties and environment, by comparing the relationship between phylogenetic metrics and environmental variables derived from a phylogeny reconstructed with a supertree method to that derived from a phylogeny resolved at species level. North America was divided into equal area quadrats of 12 100 km². Nine indices of phylogenetic structure were calculated for angiosperm tree assemblages in each quadrat using two phylogenies resolved at different levels (one resolved at the family level and the other resolved at the species level). Scores of phylogenetic indices were related to two major climatic variables (temperature and precipitation) using correlation and regression analyses. Scores of phylogenetic indices resulting from the two phylogenies are perfectly or nearly perfectly correlated. On average, there is no difference in the variation explained by the two climatic variables between scores of phylogenetic indices derived from the two phylogenies. Our study suggests that a phylogeny derived from a well resolved family-level supertree as backbone with genera and species attached to the backbone as polytomies is robust for studies investigating the relationship between phylogenetic structure and environment in biological assemblages at a broad spatial scale.

Key words: phylogenetic diversity, phylogenetic niche conservatism, phylogenetic resolution, phylogenetic structure, phylomatic, polytomy, supertree