Effects of Dimensionality of Space on the Presence/Absence of Multiple Species

A key problem in ecology is to predict the presence/absence of species across a geographical region. Addressing this problem in a multi-species community with priority effects (i.e., initial abundances determine the presence/absence of species) is a challenging task because species presence/absence depends on many factors such as abiotic environments, biotic interactions (i.e., interactions among species) and dispersal process. While various ecological factors have been considered, less attention has been given to the problem of understanding how dimensionality of space, in interaction with other factors, shape community assembly in the presence of priority effects. In this paper, we employ partial differential equations models (in one- and two-dimensional space) to examine the consequences of different dimensionality of space on the occurrence of priority effects and species coexistence in multi-species communities. We discover that as well as a pronounced increase in system complexity, adding a second space dimension essentially modifies the strength of priority effect. It is also observed that more outcomes with multi-species coexistence emerge as dimensionality of space is increased. As such, incorporating dimensionality in an ecological system with heterogeneous environments could engender additional insights on species coexistence mechanisms (as compared to just adding an extra dimension in the case of purely homogeneous space). These effects will strongly depend on how each interacting species responds to the environmental gradients. Overall, this study is among the first to explicitly show that combinations of distinct abiotic factors can shape the distributions of multiple competing species that are different from those in single abiotic factor case, and some dispersing species may respond to complex sets of abiotic and biotic conditions in variable ways.