title: Rapid Diversity Loss of Competing Animal Species in Well-Connected Landscapes.
abstract: Population viability of a single species, when evaluated with metapopulation based landscape evaluation tools, always increases when the connectivity of the landscape increases. However, when interactions between species are taken into account, results can differ. We explore this issue using a stochastic spatially explicit meta-community model with 21 competing species in five different competitive settings: (1) weak, coexisting competition, (2) neutral competition, (3) strong, excluding competition, (4) hierarchical competition and (5) random species competition. The species compete in randomly generated landscapes with various fragmentation levels. With this model we study species loss over time. Simulation results show that overall diversity, the species richness in the entire landscape, decreases slowly in fragmented landscapes whereas in well-connected landscapes rapid species losses occur. These results are robust with respect to changing competitive settings, species parameters and spatial configurations. They indicate that optimal landscape configuration for species conservation differs between metapopulation approaches, modelling species separately and meta-community approaches allowing species interactions. The mechanism behind this is that species in well-connected landscapes rapidly outcompete each other. Species that become abundant, by chance or by their completive strength, send out large amounts of dispersers that colonize and take over other patches that are occupied by species that are less abundant. This mechanism causes rapid species loss. In fragmented landscapes the colonization rate is lower, and it is difficult for a new species to establish in an already occupied patch. So, here dominant species cannot easily take over patches occupied by other species and higher diversity is maintained for a longer time. These results suggest that fragmented landscapes have benefits for species conservation previously unrecognized by the landscape ecology and policy community. When species interactions are important, landscapes with a low fragmentation level can be better for species conservation than well-connected landscapes. Moreover, our results indicate that metapopulation based landscape evaluation tools may overestimate the value of connectivity and should be replaced by more realistic meta-community based tools.
authors.affiliation: Dep. Alterra-Biodiversity and Policy, Wageningen University and Research Centre, PO Box 47, NL-6700AA, Wageningen, The Netherlands; Dep. Forest ecology and forest management, Wageningen University, PO Box 47, NL-6700AA, Wageningen, The Netherlands.
authors.forename: Peter
authors.initials: P
authors.lastname: Schippers
authors.affiliation: Biometris, Department of Mathemical and Statistical methods, Wageningen University, PO Box 16, NL-6700AA, Wageningen, The Netherlands.
authors.forename: Lia
authors.initials: L
authors.lastname: Hemerik
authors.affiliation: Dep. Alterra-Environmental risk assessment, Wageningen University and Research Centre, PO Box 47, NL-6700AA, Wageningen, The Netherlands.
authors.forename: Johannes M
authors.initials: JM
authors.lastname: Baveco
authors.affiliation: Dep. Alterra-Biodiversity and Policy, Wageningen University and Research Centre, PO Box 47, NL-6700AA, Wageningen, The Netherlands.
authors.forename: Jana
authors.initials: J
authors.lastname: Verboom
mesh_terms: D044822:Biodiversity; D008954:Models, Biological