Darwin’s preadaptation hypothesis and the phylogenetic structure of native and alien regional plant assemblages across North America

Abstract

AbstractAimStudies focusing on relatively small spatial scales have shown that alien plants are more likely to invade phylogenetically clustered communities, and that the introduction of alien plants further increases phylogenetic clustering in the recipient communities. However, whether these patterns hold at a continental scale remains untested. Here, we investigate the phylogenetic structure of native and alien regional assemblages of angiosperms across North America.LocationNorth America north of Mexico.Time periodCurrent.Major taxon studiedAngiosperms (flowering plants).MethodsWe divided North America into 65 regions across two longitudinal zones, and collated native and naturalized alien species lists of angiosperms for each region. Two phylogenetic metrics, which represent different evolutionary depths, were used to quantify phylogenetic structure of angiosperms as a whole and each major clade in each region, and were related to temperature and precipitation using correlation analyses.ResultsWe found that alien angiosperm richness is highest in regions with diverse and phylogenetically dispersed native floras. The introduction of alien species nearly uniformly increases phylogenetic clustering.Main conclusionsAlien species are generally from the same major clades as native species, consistent with Darwin’s preadaptation hypothesis. The results of this study are consistent across a wide range of phylogenetic extents, but not always with analyses conducted at smaller spatial extents.