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Insular Biogeography in Continental Regions. II. Cave Faunas from Tessin, Southern Switzerland
Vol. 22, No. 1 (Mar., 1973), pp. 64-76
Stable URL: http://www.jstor.org/stable/2412380
Page Count: 13
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The suggestion that caves are habitat islands was investigated by analyzing species diversity and endemism in a set of 48 caves from Tessin, southern Switzerland, using stepwise multiple regression. Measures of environmental diversity (development, representing area; water content; and the presence or absence of bats, representing the presence of guano) and of isolation (altitude, geographical coordinates, clustering of caves) were expected to contribute to the regulation of species diversity and of numbers of endemic taxa. From 50% to 58% of the variance in numbers of species and of endemics can be accounted for with five independent variables in the regression equations. The Tessin caves can be considered insular insofar as an area affect is demonstrated for the total number of species and for the number of endemics, and as a measure of isolation (altitude) helps in accounting for endemism. Deviation from the insular biogeography theory stems from the lack of isolation or distance effects for the numbers of species (whether troglobitic or not), and from the lack of area effect for the troglophiles and troglobites. The number of species of troglophiles and troglobites is correlated with the water scale, and since the latter is correlated with development one can argue that water scale represents an improved measure of habitat diversity over area. The water scale may be an indirect measure of (i) the food input, or (ii) the rigor of the caves in terms of flooding, or else (iii) dispersal. The lack of isolation or distance effect may be attributed to the geographical nearness of the Tessin caves, which can be likened to islands equidistant from the mainland or source region.
Systematic Zoology © 1973 Oxford University Press