The geographic scaling of biotic interactions
Miguel B. Araújo Alejandro Rozenfeld
Miguel B. Araújo Alejandro Rozenfeld
A central tenet of ecology and biogeography is that the
broad outlines of species ranges are determined by climate, whereas the
effects of biotic interactions are manifested at local scales. While the
first proposition is supported by ample evidence, the second is still a
matter of controversy. To address this question, we develop a
mathematical model that predicts the spatial overlap, i.e.
co‐occurrence, between pairs of species subject to all possible types of
interactions. We then identify the scale of resolution in which
predicted range overlaps are lost. We found that co‐occurrence arising
from positive interactions, such as mutualism (+/+) and commensalism
(+/0), are manifested across scales. Negative interactions, such as
competition (−/−) and amensalism (−/0), generate checkerboard patterns
of co‐occurrence that are discernible at finer resolutions but that are
lost and increasing scales of resolution. Scale dependence in
consumer–resource interactions (+/−) depends on the strength of positive
dependencies between species. If the net positive effect is greater
than the net negative effect, then interactions scale up similarly to
positive interactions. Our results challenge the widely held view that
climate alone is sufficient to characterize species distributions at
broad scales, but also demonstrate that the spatial signature of
competition is unlikely to be discernible beyond local and regional
scales.
Expected co‐occurrence across biotic‐interaction space. Colours on the
top graph indicate the intensity of the predicted co‐occurrence between
species A (y axis) and B (x axis), where increasing gradients of red
indicate increased co‐occurrence and increasing gradients of blue
indicate decreased co‐occurrence. The light gray line indicates the
portion of biotic‐interaction space where co‐occurrence between two
species is no different than expected with the null model. The numbers
on the y and x axes represent interactions (I) of varying signal (+, −,
0) and strength (≥ 0 ≤ 1). The lower scatter diagrams provide examples
of simulated distributions of species A (black) and B (gray), with their
respective co‐occurrence (red), for interactions of varying sign and
strength. Both species have prevalence ρ= 0.3.
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