Data from: Individual and interactive effects of chronic anthropogenic disturbance and rainfall on taxonomic, functional and phylogenetic composition and diversity of extrafloral nectary-bearing plants in Brazilian Caatinga

Chronic anthropogenic disturbance (CAD) and climate change represent two
of the major threats to biodiversity globally, but their combined effects
are not well understood. Here we investigate the individual and
interactive effects of increasing CAD and decreasing rainfall on the
composition and taxonomic (TD), functional (FD) and phylogenetic diversity
(PD) of plants possessing extrafloral nectaries (EFNs) in semi-arid
Brazilian Caatinga. EFNs attract ants that protect plants against insect
herbivore attack and are extremely prevalent in the Caatinga flora.
EFN-bearing plants were censused along gradients of disturbance and
rainfall in Catimbau National Park in north-eastern Brazil. We recorded a
total of 2,243 individuals belonging to 21 species. Taxonomic and
functional composition varied along the rainfall gradient, but not along
the disturbance gradient. There was a significant interaction between
increasing disturbance and decreasing rainfall, with CAD leading to
decreased TD, FD and PD in the most arid areas, and to increased TD, FD
and PD in the wettest areas. We found a strong phylogenetic signal in the
EFN traits we analysed, which explains the strong matching between
patterns of FD and PD along the environmental gradients. The interactive
effects of disturbance and rainfall revealed by our study indicate that
the decreased rainfall forecast for Caatinga under climate change will
increase the sensitivity of EFN-bearing plants to anthropogenic
disturbance. This has important implications for the availability of a key
food resource, which would likely have cascading effects on higher trophic
levels.