Non-native bird species will not compensate for the loss of phylogenetic
and functional diversity after the extinction of threatened species
Abstract
Human activities have altered the composition of species assemblages
through the introduction of non-native species and the extinction of
threatened species. However, it remains unclear whether non-native
species can compensate for the loss of threatened species and thus
maintain ecosystem functioning. Here we tested whether non-natives are
functionally and/or phylogenetically similar (compensation hypothesis)
or distinct (shift hypothesis) from native and threatened species on
bird assemblages in 267 regions worldwide. We show that non-native
species were more functionally distinct from threatened species than
expected by chance but more phylogenetically related. Globally, this
results in an increase in the functional richness of bird assemblages
due to the introduction of new functional traits but a decrease in the
phylogenetic richness due to the potential loss of phylogenetically
unique threatened species. Furthermore, these patterns vary across
continents, revealing the role of human history and footprint across the
world and outlining priority areas where international bird conservation
should focus. In the context of the biodiversity crisis and the
increasing number of non-native species worldwide, the changes in the
functional and phylogenetic structure of the bird communities might
increase the vulnerability of ecosystems.