Somogyi Múzeumok Közleményei 17/B. - Természettudományi tanulmányok (2006)

Farkas, Sándor: The terrestrial Isopod Fauna of South Transdanubia (Hungary) - Dél-Dunántúl szárazföldi ászkarák (Isopoda: Oniscidea) faunája

THE TERRESTRIAL ISOPOD FAUNA OF SOUTH TRANSDANUBIA 165 Discussion Species list and distribution in Hungary The 31 species which were collected during this study from South Transdanubia constitute 60% of the Hungarian terrestrial isopod fauna. Three of them (P. franzi, P. vulcanius and A. nasatum) were new to the country (FARKAS 2003, FARKAS 2004C, FARKAS and VADKERTI 2002). The macroclimate and the vegetation of the Central European countries do not differ significantly. Under the moderated wet continental conditions similar isopod faunas have evolved. The majority of the species and their number correspond to each other in the fauna of Germany (ALLSPACH 1992, GRÜNER 1966), Poland (DOMINIAK 1970) and the Czech Republic (FRANKENBERGER 1959). A. vulgare, P. collicola, H. riparius and T. rathkii are the most common species as they frequently occur in all kinds of habitats. While there are many information on the extraordinary wide tolerance of A. vulgare (SCHMALFUSS 2003), the ecology of P. collicola is less known. The latter was collected mainly in wet habitats (alder woodlands, riverine forests) in the Czech Republic (FLASAROVÁ 1995, TAJOVSKY 1998). In an earlier research, it proved to be one of the dominant species of the dry, thermophilous white oak scrub woodlands in Hungary (Loksa 1966). According to my study, it occurred in the highest amount in two habitats extremely differed: in the wet marshes and dry black locust plantations. These facts suggest that P. collicola has a good ability to tolerate the different moisture conditions of habitats. Zoogeography The high amount of introduced and synanthropic species shows the significant effect of human activity on the isopod fauna. The species distributed from Central Europe to the Balkan Peninsula compose the biggest homogeneous group. Two of the most common (H. riparius, P. collicola) and four characteristic species (A. zenckeri, L minutus, P. politus and T. nodulosus) belong to this class. The relation of the different Alpine and lllyrean species is low (5 species; 15 %). Probably these facts could be explained by both climatic and historical reasons. After the last glacial period, significant amount of the present Hungarian fauna came from the Balkans to the Carpathian basin. It was pointed out in case of several taxonomic groups (VARGA 2003). The remaining, heterogeneous part of the species is distributed in different parts of Europe (H. danicus, T. rathkii, etc.) or cosmopolite {A. vulgare). Characteristic species of first order habitats The association of A. zenckeri with the definitely damp, open habitats was revealed by VERHOEFF (1931). In Hungary, the species was mentioned as a common and abundant isopod of „wet fields" (KESSELYÁK 1936), but in contradiction with this statement, there were only two distribution data of A. zenckeri all over the country (FORRÓ and FARKAS 1998). The present research made perfectly clear that this species is not rare and could be find in the majority of marshy habitats like non tussock beds of large sedges (Carex sp.) in South Transdanubia. TAJOVSKY (1998) proved the negative impact of spring flood on terrestrial isopod assemblages in the wet, riverine woodlands. Only T. rathkii was able to survive the inundation while the other species were annihilated. After every flood, „empty" biotopes come into being that will be colonised soon by the most dispersive species, i.e. by the four most frequent woodlice. The frequency of P. collicola, H. riparius and T. rathkii peaked in this habitat, but these species still are not real characteristic species of wetland forests since they are high presented in other habitats, too. Their good colonisation ability and wide ecological tolerance make possible their high frequency and abundance in riverine woodlands. P. politus is considered as a woodlands and shrubberies inhabiting species (GRÜNER 1966). It lives primarily in different oak woodlands in Hungary (LOKSA 1966). In our study, its frequency was higher in the fresh oak woodlands than in the dry forests, the species is characteristic in the latter habitat by the statistical analysis, after all. KESSELYÁK (1936) ranged L. minutus among the common but never abundant isopods of the Hungarian woodlands, but distribution data