Tibor Kisbenedek

Orthopteran assemblages as indicators of grassland naturalness in Hungary

Grasslands are among the most threatened habitats on Earth, as large areas have been transformed into agricultural lands. Therefore, the registration of the state of grassland remnants is of crucial importance for conservation. An easy way to survey or monitor a habitat is to choose adequate indicator taxa. North American studies showed that grasshopper communities are good indicators of disturbance. We tested this observation for Hungarian steppes. The orthopteran assemblages of three steppe patches in the Buda Hills (Hungary) were sampled. One site was newly abandoned arable land, the second was a secondary meadow with large mammal grazing pressure, the third was a strictly protected seminatural steppe meadow. Our study in Hungarian steppe remnants supports earlier findings that orthopterans are good indicators for disturbance and naturalness. We found that density was highest on the most disturbed site, while species richness and diversity indices were greatest on the seminatural site. We argue that the use of simple statistical tests (χ2 and rank correlation analysis) may be favoured in inventories or monitoring programs instead of complicated multivariate analysis (e.g., detrended correspondence analysis). The rank correlation analysis on the species abundance/site matrices proved to be the most effective tool in finding differences and similarities between orthopteran communities.

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

Abstract 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. First, we compared the observed species-area curves with the expected curves. 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.