The different facets of native bird diversity (taxonomic, functional and phylogenetic) as predictors of alien birds increasing richness and expanding range in Great Britain

Abstract

Native-alien species relationship is one of the potential mechanisms to explain alien species' success. Most approaches have so far focused on species richness, but species-centric approaches alone are of limited explanatory ability. We utilized the breeding bird atlases of Great Britain at three time points, to examine the temporal patterns of alien bird species assemblages' richness and composition and analyze the spatio-temporal relationship between them and native species functional and phylogenetic diversity. Alien birds were successful in increasing their average local richness and range from the 1970s to the 2010s, without high values of the replacement component of β-diversity in most assemblages and with increasing richness in the majority of atlas cells. Communities with higher native diversity were positively associated with higher alien species richness and overall, our results showed that native biodiversity metrics can act as reliable predictors of alien species richness patterns. Native phylogenetic diversity emerged as an important predictor of alien species richness, whereas functional diversity was not as successful. Phylogenetic diversity may have captured native species' functional differences more effectively and/or the added layer of phylogenetic information increased phylogenetic diversity's ability to predict alien species richness patterns and may be indicative of evolutionary processes reflecting the mechanisms shaping native-alien species' relationship. If we were to predict where these alien birds may spread within the next 20 years, our results point to phylogenetically rich communities. This is likely a reflection of habitat heterogeneity and/or resource availability in these communities. In any case, a multifaceted approach is preferable, as different measures highlight different mechanisms driving communities' invasibility.