Habitat Destruction Alters the Mechanisms of Species Coexistence by Modifying Competitive Structure

Habitat destruction is a major driver of biodiversity decline, yet how it reshapes multispecies coexistence by altering interaction structure remains unclear. We adopt a spatially explicit metacommunity model framework under a homogeneity assumption and introduce a tunable parameter controlling intransitive competition. Within this framework, we represent the system using a generalized Lotka–Volterra model to examine how coexistence mechanisms respond to habitat destruction. Our findings demonstrate that (1) coexistence is not driven by a single mechanism: under transitive competition, it highly relies on niche differentiation, whereas in intransitive structures, coexistence can be maintained even with low niche differentiation. (2) Habitat destruction compresses the feasible coexistence space, but regions dominated by different mechanisms respond asymmetrically, with niche-difference-driven coexistence shrinking and intransitive-dominated coexistence expanding under certain conditions. (3) The difference stems from habitat destruction, altering the relative proportions of intraspecific and interspecific competition, driving the community beyond the coexistence threshold. This reduces the probability of coexistence and reshapes the relative importance of several coexistence mechanisms. This finding provides a new theoretical perspective for biodiversity in fragmented landscapes.