Isolated habitats harbor more species, new math shows—with practical implications
Researchers have cracked a 30-year-old ecological puzzle: why species thrive in fragmented landscapes. The finding—that limited movement between habitat patches actually increases local biodiversity—matters for conservation planning, habitat restoration, and predicting how ecosystems respond to development, land use change, and climate disruption.
Originaltitel: Weak dispersal and landscape size inevitably promote local biodiversity in heterogeneous metacommunities of competing species
Abstract We provide a general theoretical explanation for a longstanding result in spatial ecology: weak dispersal among habitat patches promotes local biodiversity. Using analytical approximations of spatial Lotka–Volterra competition models, we show that species persistence in heterogeneous landscapes can be expressed as a function of regional abundance and local invasion growth rates. We further demonstrate that local multispecies coexistence is governed by the feasibility domain, linking spatial coexistence to a structural property of nonspatial competitive systems. Together, these results explain why weak dispersal increases local species richness and why this effect strengthens with landscape size. We test these predictions using numerical simulations and find that the theory breaks down only when both dispersal and competitive interactions are very strong, in which case dispersal has a unimodal effect on coexistence. In contrast, landscape size retains a positive effect on coexistence whenever an effect is detectable. We then apply the theory to long-term data from a natural Daphnia metacommunity. We detect strong preemptive competition among species and find no detectable effect of dispersal rate on local coexistence, whereas species co-occurrence increases with local landscape size, as predicted by theory. Together, our results identify how dispersal, interaction strength, and landscape size jointly regulate biodiversity in competitive systems.