L. Forró szerk.: Miscellanea Zoologica Hungarica 12. 1998 (Budapest, 1998)

Farkas, S.: The terrestrial isopod fauna of the Rinya region II. Péterhida

70 b c d e f g h i j traps Fig. 3: Spatial distribution of T. rathkii and T. ratzeburgi (traps "a"-"e":oak forest; "f'-"g": ecotone zone; "i"-"h": ruderal vegetation) was equal along the transect; (2) T. rathkii prefers the ruderal vegetation and avoids the inside of the oak forest, and T. ratzeburgi shows an opposite preference. The difference is particularly conspicuous in the case of gravid females. The first conclusion is in harmony with the results of earlier studies, according to which A. vulgare and P. collicola have wide tolerance of habitat. This ubiquituos character is indicated by the fact that the change of vegetation does not affect their spatial distribution. A. vulgare lives in wet deciduous forests (Beyer 1964), on moving dunes (Davis & Sutton 1977) and on grasslands (Hassal & Dangerfield 1989). In Hungary this species is abundant in the relic oak forests (Szlávecz 1991), but occurs in open, dry meadow habitats as well (Szlávecz 1995). Hornung (1992) found it in humid depressions of the sandy areas of the Great Hungarian Plain. P. collicola may occur in very different habitats, too. Loksa (1966) collected it on the south-facing, dry slopes of the Hungarian Mountain Range. Szlávecz (1991) found this species in the open, saline places and oak forests of the Hortobágy National Park, in oak-elm-ash gallery forests and in sandy pedunculate oak-silver-lime forests of Bátorliget Natural Reserves. The species is evenly distributed among the habitats (Szlávecz 1995). The species occurred in all studied vegetation types in the Pilis Biosphere Reserve, as well (Szlávecz 1988). The interpretation of the second conclusion is difficult, because there is scarce information about the habitat preference of T. ratzeburgi. This species likes dry woodlands (Gruner 1966). According to our hypothesis the preferred habitat perfectly covers its niche, so its competi-