Island Biogeography of Fens in South-Central and Southwestern Michigan
Hoffhines, Michael A.
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The theory of island biogeograhy as presented by Mac Arthur and Wilson (1967) states that biotic diversity is directly proportional to area, where diversity is measured in number of species present. The relation is commonly of the form S=c Az, where S equals the number of species present and A the island area. c is a parameter that depends upon the taxon and biogeographic region, as well as the population density determined by those two parameters. z is a parameter that generally falls between 0.20 and 0.35 for ocean islands (Mac Arthur and Wilson, 1967). Attempts have been made to generalize this relation to include mainland habitat islands (Mac Arthur, 1972). In this study, a number of fens in south-central and southwestern Michigan are surveyed to determine to what extent the flora of these fens fits the theory of island biogeography. The relation is significant, with z-values within the range commonly encountered on habitat islands. However, the collected floristic data more accurately fits a linear model. This is probably a result of the range of values of area considered in the study. The linear model, then, may not predict fen diversity over all ranges of area.