Data from: Plant protection services mediated by extrafloral nectaries decline with aridity but are not influenced by chronic anthropogenic disturbance in Brazilian Caatinga

1. Most terrestrial species occur in human-modified landscapes that are
experiencing climate change. In addition to direct impacts on species,
both anthropogenic disturbance and climate change can have important
effects through changes in species interactions, including the disruption
of ecological services provided by them. 2. Here we investigate how
chronic anthropogenic disturbance (CAD) and aridity affect the
effectiveness of plant protection services provided by ants to plants
bearing extrafloral nectaries (EFNs). 3. The study was conducted across 13
01-ha plots distributed along CAD and aridity gradients in Caatinga
vegetation of northeastern Brazil. We focused on Pityrocarpa moniliformis,
the most abundant and widely distributed EFN-bearing tree species
occurring in our study area, and used experimental attack rates on
termites as a measure of effectiveness of ant protection services. We
investigated the relative roles of nectar production (volume and
concentration) and ant species composition in mediating the effects of CAD
and aridity on the effectiveness of protection services. 4. Attack rates
by ants declined with increasing aridity but were not related to CAD. The
volume of extrafloral nectar declined with increasing CAD but was not
affected by aridity, whereas the concentration was not related to either
CAD or aridity. The composition of attendant ant species varied with
aridity but not with CAD. 5. Synthesis: The decline in ant-protection
services with increased aridity was therefore mediated by changes in the
composition of attendant ant species rather than by changes in the
production of extrafloral nectar. Our findings suggest that CAD does not
affect plant-protection services provided by ants but highlights the
vulnerability of EFN-bearing plants to climate change through decreased
predation of herbivores.