Habitat width along a latitudinal gradient

Abstract

We use the Chowdhury ecosystem model, one of the most complex agent-based ecological models, to test the latitude-niche breadth hypothesis, with regard to habitat width, i.e., whether tropical species generally have narrower habitats than high latitude ones. In two previous studies using the Chowdhury Model, we have shown that simulations result in faster speciation in the tropics and in latitudinal diversity gradients, that the complexity of foodwebs increases with time and at higher rates in the tropics (Rohde & Stauffer 2005), and that latitudinal ranges of species are greater in the tropics, contradicting Rapoport's rule (Stauffer & Rohde 2006). In this paper we show that the Chowdhury Model does not support the latitude-niche breadth hypothesis for the niche dimension habitat width: habitats, measured by comparing species numbers in small and large areas at a particular locality, are generally wider and not narrower in the tropics. This hypothesis cannot, therefore, give a causal explanation of latitudinal gradients in species diversity.