Entomologica Romanica Vol. 18 / 2013

2013

were identified mountain species at the plain, like H. transsilvanicus, their presence being considered to be a consequence of the mountains neighborhood without an altitudinal transition, as well as the presence of humid and forested habitats in the Tur river protected area (Ferenti et al. 2013). Thus, in the zone are present numerous species like H. transsilvanicus and P. conspersum, which are tied to humid and afforested zones from mountain areas (e.g. Radu 1985, Kontschán 2003, Vilisics et al. 2008, Tomescu et al. 2012). The resemblance of species composition between the two areas shows clearly the origin of the mountain species in the plain, where in addition to these species are some typical ones for plain swamps (Ferenti et al. 2013). Even if the direct collecting method have permitted the collection of some species like Trichoniscus sp., overall the terrestrial isopod assemblages from the studied region are similar with those described previously in the zone and neighbouring areas using pitfail traps (e.g. Hotea et al. 2003, Hotea and Hotea 2008, 2009, 2010, Ferenti and Covaciu-Marcov 2012, Ferenti et al. 2012a). Also, the terrestrial isopod fauna is alike with that previously identified in Maramureș Depression (Vilisics 2008). Our results prove resemblance between the terrestrial isopod fauna of the mountain zone of north-western Romania and the neighbouring plain areas. Probably in the case of terrestrial isopods the contact between Oas Mountains and plain areas permits the existence of this resemblance as well as in the case of other groups (see in: Covaciu-Marcov et al. 2008a). Probably, in the present, the forests from Oas Mountains are a refuge for terrestrial isopods, but in the past this role had had firstly the plains from the vicinity, where some species of other groups, considered glacial relicts, survive (Covaciu- Marcov et al. 2008b). Sometimes short term environmental changes can influence the composition of the fauna (Purger et al. 2007), the attribution of recent biological trends to climate change becoming complicated (Parmesan and Yohe 2003). In the case on north-western Romania the past’s climate changes marks the entire area, both on the ecosystems’ (see in: Ardelean and Karácsonyi 2005), groups’ (e.g. Ferenti et al. 2012b) or species level (e.g. Covaciu- Marcov et al. 2008a). We investigated mostly natural habitats, both wetlands and forests, but also semi natural and artificial ones. The maximum number of species was registered in non-opened, humid, natural and semi natural habitats (coppices or semi natural canals with shrubbery and tree vegetation) and some of the artificial ones. Thus, the species richness / locality were quite low, fact also registered in other cases (Hornung et al. 2008). There were cases when isopod diversity was not reduced once with habitat disturbance increase (Hassall et al. 2006, Hornung et al. 2007). Thus, the artificial habitats prove to be benefit for the species richness, fact that does not support in this case the ecological general rule which affirms that species richness indicates the ecosystem’s stability (see in: Schwartz et al. 2000, Cleland 2012). In the western slope of Oas Mountains artificial habitats often shelter a high number of species, similar to the forests. These artificial habitats either were affected in the past and now are abandoned and invaded partially with vegetation (e.g. abandoned constructions ordinarily surrounded by forests or natural habitats), or they are influenced in the present by human (e.g. distilleries). However, in the orchard the species' number is extremely low, even if it seems it is not more influenced in the present then distilleries for example. Thus, we cannot conclude that human presence itself is the main responsible factor for the terrestrial isopods dispersion shape. Indeed, there were registered significant changes in diversity and species richness along urbanization gradient for terrestrial isopod assemblages (Hornung et al. 2007, 2008), these studies being rather general, not emphasizing on different human activities' effects. Different human activities produce different spatial, microclimatic or chemical changes in habitats (see in: Nogues-Bravo et al. 2008). Thus, terrestrial isopods are influenced furthermore directly by the negative effect of the microclimatic / microhabitats' changes that are induced by the macro habitat resulted from a certain group of human activities. Summarizing on our case, partially re-naturalized constructions and distilleries with abundant organic matter and humidity, thus artificial habitats, which does not contain potentially harmful chemical or microclimatic conditions for terrestrial isopods, are the same beneficial than natural ones. Distilleries also proved to shelter a high species richness and diversity of isopod species in Tur river natural protected area (Ferenti et al. 2013). Instead, orchard, a habitat with potentially large negative chemical influences (insecticides, pesticides, etc.), represent an unfavourable habitat for isopod assemblages. The negative effect of chemicals resulted from different agricultural activities on terrestrial isopods was previously reported (e.g. Staak et al. 1998). Also, it is possible that in orchards the scarcity of terrestrial isopod species to be caused by habitat’s uniformity and regular disturbance. Shelter types used by terrestrial isopods are not ordinarily closely related to habitat types. Thus, often shelters with anthropogenic origin are situated in natural habitats. In Oas Mountains the highest number of species shelters in the humid soil and vegetation near wetlands but an important amount of species was found under debris situated mostly in natural habitats. This fact proves an opportunistic refuge behaviour of terrestrial isopods, they being influenced only by the conditions offered by the shelter. The available shelters and microhabitats proved to be important elements for sheltering native terrestrial isopod species, even in urban areas (Magúra et al. 2008, Vilisics and Hornung 2009). At the same time, it proves the fact that natural habitats are also, at least partly, affected by human. 8

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