Indirect relation between species extinction and habitat destruction

To study local destruction of habitat, we present a lattice ecosystem compo sed of prey (X) and predator (Y). This system corresponds to a lattice vers ion of the Lotka-Volterra model, where interaction is allowed between neigh boring lattice points. The lattice is partly destroyed, and destructed site s or barriers are randomly located between adjacent lattice points with the probability p. The barrier interrupts the reproduction of X, but the speci es Y suffers no direct damage by barriers. This system exhibits an extincti on due to an indirect effect: when the density p of barriers increases, the species Y goes extinct. On the other hand, an initial suppression of X may later lead to the increase of X. The predator Y decreases in spite of the increase of X. These results cannot be explained by a mean-field theory suc h as the Lotka-Volterra equation. We discuss that endangered species may be come extinct by a slight perturbation to their habitat. (C) 2001 Elsevier S cience B.V. All rights reserved.