There are a plethora of potential mechanisms affecting the assembly of biological communities, but most, in some way, include a role for either species similarities or differences. An important question is whether assembly rules differ for native versus exotic plants. Here I will discuss how, using phylogenetic relationships, native and exotic plant communities in northern/central California differ in whether they are comprised by more or less closely related species, and if this changes with richness patterns. Further, I will examine phylogenetic diversity patterns and turnover among sites across larger spatial scales (i.e., phylobetadiversity). Generally, exotics tend to be much more locally phylogenetically clustered than natives. Also, exotics show low phylogenetic turnover compared to natives, indicating larger range sizes of clades. From these results we can infer differing mechanisms of community assembly, where in situ evolution among natives promotes species differences and local competitive sorting, while the phylogenetically-clustered exotics likely share key traits that make them successful over large spatial scales.