Orthopterans in small steppe patches: an investigation for the best-fit model of the species-area curve and evidences for their non-random distribution in the patches

摘要

Distribution of orthopterans were studied in 27 steppe patches in the Buda Hills, Hungary. The smallest patches were about 300 m(2), the largest 'continents' were over 100 000 m(2). We collected 692 imagoes of 32 species and 1 201 imagoes of 28 species in July 1992 and July 1993, respectively. We found that the best-fit models for the species-area curves were both the power function and exponential models. The multivariate regression model incorporated area and distance from large patches as significant factors in determining the number of species. The correlation analysis revealed that the elevation and the height of grass vegetation also influenced the distribution of species. We applied three methods for testing whether the distribution of orthopterans was random or not. Fir st, we compared the observed species-area curves with the expected con es, Second, we compared the small-to-large and large-to-small cumulative curves. Finally, we compared the observed species-area curves with the rarefaction curves. All three methods for both years showed that the occurrence of orthopterans in the steppe patches was not random. A collection of small islands harboured more orthopteran species than one or two large patches of the same area. (C) Elsevier, Paris. [References: 40]