Immigrations of species into indigenous communities are a major thread to biodiversity but it remains unclear why some types of communities are heavily affected and others hardly. We hypothesize this may reflect differences in the evolutionary history of different types of communities. Some types of plant communities are dominated by a single evolutionary radiation into a given environment with most species coming from the same lineage, other types of communities were open to the immigration from many evolutionary lineages, each contributing only few species. Here we test whether openness to many lineages (i.e. phylogenetic overdispersion) throughout evolution increases or decreases openness to aliens today. We analyze plant associations across The Netherlands. We quantify the average proportion of alien species in local plots and correlate it against the phylogenetic dispersion of the incumbent species in local plots not yet colonized by alien species.
Results/Conclusions
We find that the phylogenetically overdispersed associations have significantly lower percentages of aliens than phylogenetically clustered associations. The effect of phylogenetic dispersion remains highly significant even after accounting for the number of incumbent species, the representation of the dominant lineage, or means and variances of multiple abiotic factors and disturbance. We conclude that immigration of potentially complementary lineages in the evolutionary past may render communities resistant to aliens today, whereas community types that were isolated from immigration in the past may be “naïve” and suffer from negative interspecific interactions and may thus be easily invasible today. Until now, such mechanisms had been invoked only at the scale of oceanic islands.
