Data from: Disentangling endogenous versus exogenous pattern formation in spatial ecology: a case study of the ant Azteca sericeasur in southern Mexico

Spatial patterns in ecology can be described as reflective of
environmental heterogeneity (exogenous), or emergent from dynamic
relationships between interacting species (endogenous), but few empirical
studies focus on the combination. The spatial distribution of the nests of
Azteca sericeasur, a keystone tropical arboreal ant, is thought to form
endogenous spatial patterns among the shade trees of a coffee plantation
through self-regulating interactions with controlling agents (i.e. natural
enemies). Using inhomogeneous point process models, we found evidence for
both types of processes in the spatial distribution of A. sericeasur. Each
year's nest distribution was determined mainly by a density-dependent
relationship with the previous year's lagged nest density; but using
a novel application of a Thomas cluster process to account for the effects
of nest clustering, we found that nest distribution also correlated
significantly with tree density in the later years of the study. This
coincided with the initiation of agricultural intensification and tree
felling on the coffee farm. The emergence of this significant exogenous
effect, along with the changing character of the density-dependent effect
of lagged nest density, provides clues to the mechanism behind a unique
phenomenon observed in the plot, that of an increase in nest population
despite resource limitation in nest sites. Our results have implications
in coffee agroecological management, as this system provides important
biocontrol ecosystem services. Further research is needed, however, to
understand the effective scales at which these relationships occur.