Red List of Arachnids of Czech republic

The first selection of endangered species of spiders of the Czech Republic was provided by Buchar (1992) in a popular-scientific “Red Data Book of Czechoslovak invertebrates”. This work was able to comprise only 30 conspicuous, large species of spiders, which inhabited the most endangered biotopes. In the catalogue of spiders of the Czech Republic (Buchar & Růžička 2002) all the data are accumulated and arranged concerning the distribution and occurrence of spiders in the Czech Republic. At the end of 2000, we registered the occurrence of 830 species of spiders in the Czech Republic. Each species is characterized by a set of data and map of distribution in the Central-European net for mapping organisms (Buchar 1982). The degree of endangerment of species is established in the catalogue in accordance with IUCN criteria (IUCN 1994, 2001, Plesník 1995). The degree of endangerment of species in three categories of generally endangered species is established based on criteria B1 (B2) a + b (iii). These criteria are used to consider the magnitude of the area of distribution or area of occurrence together with the number of known localities at which the species occur and decrement (observed or assumed) in the area of occurrence, area of inhabitation or quality of the habitat. Thus, the abundance of species is always evaluated together with the nature of the habitat. For example, the species Dictyna szaboi is considered as critically endangered, since only one specimen was found at only one locality, which was a locality of drifted sands of area smaller than 100 ha, which is immediately endangered by exploitation of sand, forest re-cultivations and growth of self-sowing wood species. The occurrence of the species Maro lehtineni is also known only from the finding of a unique specimen, but it comes from the alpine zone of the mountain range Krkonoše. There is no immediate endangerment of stony areas of the alpine zone and, in addition, this sub-millimetre species probably inhabits dense growths of mosses and lichens and its most numerous populations can escape from the attention, and thus, it is evaluated only as a species, for which sufficient data are not available. Among spiders of the Czech Republic we can consider eight species, which have not been found any more after 1950. The classification of some of these species as extinct is, however, problematic. In the catalogue presented here, this category has not been used. In the case of hidden and inconspicuous species of invertebrates “there are always reasonable doubts about the death of the last individual”. Thus, we consider as “regionally extinct in CR” only the species Lycosa singoriensis (Laxmann, 1770), which is a conspicuous, large spider, whose existence probably would not escape from the attention. The propagation and repeated recession of this species in our country between 1924 and 1950 was described by Kratochvíl (1951). Total of 53 species of spiders from the Czech Republic are classified as critically endangered (CR), 85 species as endangered (EN) and 71 species as vulnerable (VU). Thus, there are total of 209 spider species considered as generally endangered.

Up-to-date list of Czech spiders including their threat-levels can be downloaded at cerveny_seznam_web.xlsx.