Invasive engineers

Many invading species modify their physical environments in significant ways. Some do so in such a way that their reproductive output is increased. Currently there is no modeling framework to describe the growth and habitat effects of such invading "ecosystem engineers." A quantitative description of habitat modification is essential for a full understanding of the dynamics and impacts of alien species. We introduce a flexible model to describe the invasion dynamics of species that modify their environment, which makes the simplification of treating space implicitly. We demonstrate that invasive species that modify their environment may have significantly faster growth rates into sub-optimal habitats than species that do not. Thus, the greatest invasion threats may come from species that combine tolerance of sub-optimal conditions with intermediate rates of habitat modification. (C) 2004 Elsevier B.V. All rights reserved.