COMMUNITY COMPOSITION AND NESTED-SUBSET ANALYSES - BASIC DESCRIPTORS FOR COMMUNITY ECOLOGY

Three primary descriptors of community structure are the number, ident ities (composition), and abundances of species therein. Over the past 35 years, most attention has focused on relationships involving number (species-area and species-energy relation ships) or abundance distrib utions (broken-stick, geometric, log-normal, core-satellite, etc.). Co mposition patterns have bren underemphasized, even though several tool s for addressing particular non-random patterns in species composition are available. One non-random pattern in community composition is nes ted subset structure. A community has a nested subset structure if the species found in depauperate replicates are also found in progressive ly more Species-rich assemblages. In this review, the problems of fail ing to consider composition patterns like nestedness are described, us ing species-area relationships and the SLOSS debate (single large or s everal small reserves) as an example. In addition, nestedness analyses are promoted as: 1) important descriptive tools for determining wheth er a community has this common non-random pattern of species compositi on, and 2) as important investigative tools for suggesting mechanisms potentially structuring a community.