Disentangling dispersal from phylogeny in the colonization capacity of forest understorey plants

Summary: Habitat patches that have been completely cleared of their original vegetation historically and subsequently recolonized naturally provide a useful study system to explore the importance of the processes involved in community assembly. Forests where the understorey vegetation is recovering from past agricultural land use form an iconic example of such a system. The colonization capacity of forest plant species into post-agricultural forests has been related to dispersal traits in previous comparative analyses, demonstrating the significance of dispersal limitation. Yet, none of them has evaluated evidence for a phylogenetic signal in colonization capacity and, thus, explored the possibility that the dispersal traits are correlated with unmeasured establishment-related traits that are also shared through common ancestry. Here, we analysed the colonization capacity of 330 species into post-agricultural forests across seven different landscapes in Europe and North America. With phylogenetic meta-analysis models, we quantified the phylogenetic signal in colonization capacity and tested whether the colonization - dispersal trait relationships are confounded by phylogenetic non-independence. Closely related forest understorey species were more similar to one another in terms of their capacity to colonize post-agricultural forests than were more distantly related species. The correlations between dispersal traits and colonization were not independent from phylogeny. While we found some evidence of phylogenetic clustering of species' frequencies in post-agricultural communities, this was apparently not a result of strong filtering on dispersal traits. Synthesis. Given the phylogenetic signal in plant colonization capacity, a multitude of conserved species characteristics may explain community assembly in forests. Earlier trait-based syntheses strongly emphasised dispersal, but the factors limiting establishment and persistence of forest herbs in post-agricultural forests may be more nuanced than generally appreciated. Given the phylogenetic signal in plant colonization capacity, a multitude of conserved species characteristics may explain community assembly in forests. Earlier trait-based syntheses strongly emphasised dispersal, but the factors limiting establishment and persistence of forest herbs in post-agricultural forests may be more nuanced than generally appreciated. © 2014 British Ecological Society.