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In ecology, the occupancy–abundance (O–A) relationship is the relationship between the abundance of species and the size of their ranges within a region. This relationship is perhaps one of the most well-documented relationships in macroecology, and applies both intra- and interspecifically (within and among species). In most cases, the O–A relationship is a positive relationship.〔Gaston, K.J. 1996. The multiple forms of the interspecific abundance-distribution relationship. Oikos 75:211 – 220.〕 Although an O–A relationship would be expected, given that a species colonizing a region must pass through the origin (zero abundance, zero occupancy) and could reach some theoretical maximum abundance and distribution (that is, occupancy and abundance can be expected to co-vary), the relationship described here is somewhat more substantial, in that observed changes in range are associated with greater-than-proportional changes in abundance. Although this relationship appears to be pervasive (e.g. Gaston 1996〔 and references therein), and has important implications for the conservation of endangered species, the mechanism(s) underlying it remain poorly understood〔Gaston, K.J., T.M. Blackburn, J.J.D. Greenwood R.D. Gregory, R.M. Quinn, and J.H. Lawton. 2000. Abundance-occupancy relationships. Journal of Applied Ecology 37(suppl. 1): 39–59.〕 == Important terms == Range – means the total area occupied by the species of interest in the region under study (see below ‘Measures of species geographic range’) Abundance – means the average density of the species of interest across all occupied patches (i.e. average abundance does not include the area of unoccupied patches) Intraspecific occupancy–abundance relationship – means the relationship between abundance and range size within a single species generated using time series data Interspecific occupancy–abundance relationship – means the relationship between relative abundance and range size of an assemblage of closely related species at a specific point in time (or averaged across a short time period). The interspecific O-A relationship may arise from the combination of the intraspecific O–A relationships within the region〔Webb T.J., Noble D. & Freckleton R.P. (2007). Abundance-occupancy dynamics in a human dominated environment: linking interspecific and intraspecific trends in British farmland and woodland birds. Journal of Animal Ecology, 76, 123–134.〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Occupancy–abundance relationship」の詳細全文を読む スポンサード リンク
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