Long- and short-term changes in the spider assemblages of Sas-hegy (Budapest, Hungary), with special respect to recent grassland rehabilitation treatments

Abstract

Sas-hegy, a dolomitic hill is a treasure of nature enclosed by the Hungarian capital, Budapest. It’s spider fauna is well studied. János Balogh between 1930 and 1934, latter Csaba Szinetár and Ferenc Samu between 1994 and 1998 collected at the place thoroughly. In year 2010 we sampled in the five grassland patches studied in the 90’s using the exact protocol and sampling effort applied during those studies. Our aims were to uncover long-term changes in comparison with the two preceding studies, and short-term changes by quantifying changes since the 1990’s in the spider assemblages of the five grassland patches. Because of the invasive spread of syringa bush a shrub eradication program has started from 2008. This in part affected three of the studied grassland patches. In each of these patches sampling took place both on the eradicated and on the untreated parts. The present study showed the presence of 105 spider species, 16 new for the fauna of the hill. Over 80 years populations of otherwise abundant species mostly increased, and populations of otherwise rare species mostly decreased on the sampling sites, but other ecological mean characters (such as preference for natural habitats) of the species remained mostly unchanged. Most rare and specialist species were recovered. Comparing assemblage compositions to the 90’s we found quite a drift over time. Compared to this drift, the difference between eradicated and untreated parts of the patches was remarkably little, which is likely to be due to the patchy eradication and quick recolonization from untouched habitats. We think, a very precious fauna with lots of rare species managed to persist on the Sas-hegy. Since shrub eradication seems to have created habitats that are more similar to the original ones, this might favour most rare species.