What determines "suitable habitat" for metapopulation studies? An analysis of environmental gradients and species assemblages in xeric forest openings.

PREMISE OF THE STUDY: For metapopulation and metacommunity studies, "suitable habitat" is an area within an otherwise inhospitable matrix in which a species can potentially or does occur. When examining aquatic habitats, for example, this habitat is much easier to define than in terrestrial regions. We tested the assumption that suitable habitat can be delimited in terrestrial ecosystems. METHODS: We surveyed vascular plant species found in 38 forest openings (open suitable habitats) within a matrix of dry forest (an inhospitable habitat) at three sites in southern Illinois over two growing seasons. We compared species composition and environmental variables between these two habitats at three sites using non-metric multidimensional scaling (NMDS) and analysis of similarity (ANOSIM). KEY RESULTS: Distinctions such as high canopy openness and high soil temperature were common to all forest openings compared with the forest matrix. Differences in canopy openness and soil temperature were correlated with significantly different vegetation between forest openings and forest matrix at each of the three sites. Among the three sites, 9.3-18.9% were forest opening specialists, consisting of 44 taxa, of which the majority were herbaceous forbs. CONCLUSIONS: The distinction between suitable and unsuitable habitat for some plant species may depend on a few variables, which may not be consistent between sites. This distinction means that there are potentially more situations than previously thought that metapopulation and metacommunity theory may be capable of explaining, meaning that more systems can be studied using a metapopulation context than previously thought.