SAMPLE SHAPE, SPATIAL SCALE AND SPECIES COUNTS - IMPLICATIONS FOR RESERVE DESIGN

The optimal design of nature reserves has been a hotly debated topic f or some years. One contentious issue has concerned the ideal shape of reserves, with several researchers suggesting that reserves should be as nearly circular as possible to minimize edge-related degredation an d potential 'peninsularity' effects. This paper demonstrates an advant age to non-circular reserves: given the spatial autocorrelation of env ironmental conditions and species ranges, elongated samples should ten d to capture a greater diversity of conditions and, consequently, a gr eater number of species. To test this idea, samples of 16 cells, arran ged as 4x4 squares, 2x8 rectangles and 1x16 lines were considered in m apped plant distributions at spatial scales ranging from cells of I m( 2) to 2500 km(2). Overall, elongated samples tended to capture signifi cantly larger numbers of species than did their square counterparts, a s predicted. The degree of elongated sample advantage was very similar at all but the smallest of the scales considered, suggesting that the pattern of species turnover (beta-diversity) is nearly scale-independ ent or fractal in nature. As the advantages of elongation are largely scale-independent and the only documented disadvantages (edge effects) are very scale-dependent, the optimal shape of a reserve for species sampling should shift as a function of reserve size, with large reserv es becoming increasingly elongated. (C) 1997 Published by Elsevier Sci ence Ltd.