Historic and current distribution of an endangered stonefly Perla grandis (Plecoptera: Perlidae) in the Czech Republic

Abstrakt: The rare stonefly Perla grandis Rambur, 1842 was recorded in several montane streams in the Hercynian mountain system and in the Carpathians in the 20th century. Now it is classified as endangered in the Red List of invertebrates of the Czech Republic due to the scarcity of recent records. The aim of this study is to examine its status at the localities where it was recorded in the first half of the 20th century and summarize all available data on its distribution in the Czech Republic. We found a considerable decline of the species in the Labe River basin as it was not re-collected at the localities of historic occurrence in the Krkonoše Mts., Orlické hory Mts. and Šumava Mts. and was not recorded at any new locality. This disappearance was probably a result of acidification of freshwater habitats in these regions in the second half of the 20th century. At present, Perla grandis is only frequent and locally abundant in montane streams in the Beskydy and Jeseníky Mts. which were not so severely affected by acidification. It inhabits mostly epirhitral sections of streams, but it can occur even in sections on the boundary between epirhitral and hypocrenal. It was found at elevations from 520 to 820 m a.s.l. It prefers fast flowing streams with a stable circum-neutral pH and substratum dominated by stones and boulders (lithal).

Klíčová slova: Perla maxima, Perlidae, Plecoptera, faunistics, long-term changes, habitat requirements, acidification, area restriction, Central Europe