![]() Another dimension of this rethinking of ecotones is their description as representing a spatial hierarchy (Gosz, 1991, 1993). This includes biological productivity, genetic diversification, evolutionary adaptation, interspecific interactions, and the aggregation and movement of organisms, nutrients, and other materials (Risser, 1995), although a single ecotone may not exhibit all these characteristics (Walker et al., 2003). The principle conclusion of this body of research is that ecotones can now be described as areas where biophysical factors, biological activity, and ecological evolutionary processes are concentrated and intensified. ![]() This new synthetic view has been substantiated by theoretical and empirical studies (Smith et al., 1997 Fagan et al., 1999). In the new synthesis (Holland et al., 1991 Hansen and Di Castri, 1992 Risser, 1995), ecotones are described as dynamic and more complex constituents of ecological systems that influence biodiversity and ecosystem function disproportionately to their geographic extent, and all spatial scales. They were viewed as relatively static zones and landscape boundaries favored as habitat by some species and crossed by other species encroaching “alien” habitat or ecosystems. In this article, we briefly summarize this expanded view of ecotones and consider the evidence based on a review of the literature and EID reports for the role of ecotones in infectious disease emergence on this basis.Įcotones were originally described as specialized wildlife habitat represented by readily identifiable edges or transitions zones between major vegetation cover types (Clements, 1905 Leopold, 1933 Odum, 1971). Yet the role of ecotones as a factor contributing to the global EID phenomenon has not been critically examined taking into account the synthesis based on a re-examination of ecotones based by landscape ecologists (Holland et al., 1991 Hansen and Di Castri, 1992 Risser, 1995). However, his focus was on an analogous concept he coined “chronotones,” and their potential for contributing to understanding disease outbreaks and control measures targeting environmental factors. ![]() Bradley ( 2004) briefly summarized the history of ecotones in epidemiology with regard to their significance in providing specialized habitat for hosts or vectors, as the interface between human settlements and natural ecosystems, and where humans come in contact with a “new” ecosystem. The pathogen’s themselves may concentrate in their host populations at ecotones as is apparent for some arboviruses (Yuill, 1986). Ecotones have been identified as potentially important for some eukaryotic parasites in terms of host seeking (Burg, 2001) and host switching (Hoberg et al., 2002). Mosquitoes responsible for the transmission of encephalitis virus have been found to congregate at ecotones (Lothrop et al., 2002), and populations of competent rodent reservoirs (white-footed mouse) for Lyme disease preferentially inhabit ecotones (LoGiudice et al., 2003). Studies in Europe and North America have shown tick vectors of a number of significant zoonotic infectious diseases are most abundant in these ecotones (Goddard, 1997 Lindstrom and Jaenson, 2003 Pietzsch et al., 2005). Some recent field studies have suggested ecotones as habitats where rates of infectious parasitic diseases in wildlife are high and may increase due to climate-driven shifts in ecotones (Svobodova et al., 2004). They are used to describe field study or sampling locations (Bennett et al., 1999 Townsend et al., 2003 Eisen et al., 2004) and features of possible surveillance value using remote sensing (Wilson, 2002b). However, the similar disease ecologies of these with about half of the approximately 130 zoonotic EIDs suggests ecotones, particularly their anthropogenic origination or modification, may be generally associated with ecotones and the global trend of increasing EIDs.Įcotones, the edges or transition zones between two adjacent ecological systems are frequently mentioned in the zoonotic and vector-borne disease literature. Yet these are the only diseases for which specific landscape ecological information exists in the literature or disease reports. A review of the literature suggests that ecotones play a role in a number of the most important EIDs. Parallel research on emerging infectious diseases (EIDs) and the causes of increased rates of pathogen transmission, spread, and adaptation suggests a correspondence between ecotonal processes and the ecological and evolutionary processes responsible for zoonotic and vector-borne emerging infections. More recent research in landscape ecology has produced an expanded view of ecotones and elaboration of their characteristics and functions in ecosystems. Recognition of the significance of the boundary between ecological systems, often referred to as the ecotone, has a long history in the ecological sciences and in zoonotic disease research.
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