CHANGES IN THE TERRESTRIAL SPIDER FAUNA (ARACHNIDA: ARANEAE) OF A NORTH GERMAN RAISED BOG DISTURBED BY HUMAN INFLUENCE. 1964–1965 AND 1986–1987: A COMPARISON

Abstract

AbstractThe terrestrial spider fauna of a North German bog relict, initially examined in a pitfall trap study in 1964–1965, was the subject of a similar examination 22 years later. Between the investigations the bog, which was still in a quite pristine state, had considerably changed its ecological character due to progressive draining. Sixty-eight spider species were collected. Many of them are characteristic for bogs, but none can be regarded as bog-specific. On a general species level no clear clues about consequences of biotope changes could be ascertained; 81% of the former species were found again.The most informative data are provided by species composition and abundance of the more prevalent spider species. In 1964–1965 the spider fauna was clearly dominated by photophilous species, many of them additionally preferring wet or moist biotopes. Twenty-two years later the proportion of photophilous species had decreased in favour of more skotophilous species.The scale of changes in biotope characters is regarded as the most probable explanation for this phenomenon, especially the increase of "shrubbiness" in vegetation and the nearly total loss of peatmosses. The spider Antistea elegans (Blw.), Hahniidae, is discussed as a possible indicator species for monitoring hydrological changes in bog biotopes.