Abstract
The central role of species competition in shaping community structure in ecosystems is well appreciated amongst ecologists. However species competition is a consistently missing variable in Species Distribution Modelling (SDM). This study presents results of our attempt to incorporate species competition in SDMs. We used a suit of predictor variables including Soil Adjusted Vegetation Index (SAVI), as well as distance from roads, settlements and water, fire frequency and distance from the nearest herbivore sighting (of selected herbivores) to model individual habitat preferences of five grazer species (buffalo, warthog, waterbuck, wildebeest and zebra) with the Ensemble SDM algorithm for Gonarezhou National Park, Zimbabwe. Our results showed that distance from the nearest animal sighting (a proxy for competition among grazers) was the best predictor of the potential distribution of buffalo, wildebeest and zebra but the second best predictor for warthog and waterbuck. Our findings provide evidence to that competition is an important predictor of grazer species’ potential distribution. These findings suggest that species distribution modelling that neglects species competition may be inadequate in explaining the potential distribution of species. Therefore our findings encourage the inclusion of competition in SDM as well as potentially igniting discussions that may lead to improving the predictive power of future SDM efforts.
Highlights
Ecologists appreciate the central role of competition among species in shaping community structure within ecosystems [1, 2]
The predictor variables i.e., Soil Adjusted Vegetation Index (SAVI) as well as distance from roads, settlements and water, distance from the nearest sighting and fire frequency adequately explained the potential distribution of buffalo, waterbuck, wildebeest and zebra in the study area (AUC>0.90)
The AUC became better for warthog and waterbuck when the distance from the nearest sighting was not included as a predictor variable
Summary
Ecologists appreciate the central role of competition among species in shaping community structure within ecosystems [1, 2]. Some species adapt through niche differentiation [11] by avoiding patches where their access to resources is compromised with competition from. It is noteworthy that for some species, the effect of competition on community structure remains largely negligible [13]. These mechanisms put together, help to explain why species select or avoid particular patches. It is for this reason that explaining the geographic distribution of species without using competition as a predictor may not be adequate. The inclusion of species competition in SDMs remains a grey area [6]
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