Changes in taxonomic and phylogenetic diversity in the Anthropocene

To better understand how ecosystems are changing, a multifaceted approach
to measuring biodiversity that considers species richness and evolutionary
history across spatial scales is needed. Here we compiled 162 datasets for
fish, bird, and plant assemblages across the globe and measured how
taxonomic and phylogenetic diversity changed at different spatial scales
(within site α diversity and between sites spatial β diversity).
Biodiversity change is measured from these datasets in three ways: across
land use gradients, from species lists, and through sampling of the same
locations across two time periods. We found that local species richness
and phylogenetic α diversity (Faith’s PD) increased for all taxonomic
groups. However, when measured with a metric that is independent of
species richness (phylogenetic species variation, PSV), phylogenetic α
diversity declined for all taxonomic groups. Land use datasets showed
declines in species richness, Faith’s PD, and PSV. For all taxonomic
groups and data types, spatial taxonomic and phylogenetic β diversity
decreased when measured with Sorensen dissimilarity and phylogenetic
Sorensen dissimilarity, respectively, providing strong evidence of global
biotic homogenization. The decoupling of α and β diversity, as well as
taxonomic and phylogenetic diversity, highlights the need for a broader
perspective on contemporary biodiversity changes. Conservation and
environmental policy decisions thus need to consider biodiversity beyond
local species richness to protect biodiversity and ecosystem services.