Ábrahám Levente (szerk.): Válogatott tanulmányok VI. - Natura Somogyiensis 19. (Kaposvár, 2010)
HORVÁTH GY., HERCZEG R., TAMÁSI K. & SALI N.: Nestedness of small mammal assemblages and role of indicator species in isolated marshland habitats
282 NATURA SOMOGYIENSIS chastic - i.e. random - or other differring patterns describing studies in the review of BÁLDI (2003) which discusses the nestedness of communities. This study ( BÁLDI 2003) has a great importance in the comparing surveys of island communities in the description of metapopulation- and community patterns, therefore the nestedness was interpret firsly by the analysis of species compositon. Nestedness is a pattern where the species composition of one island can be found in the species composition of an other, larger island at the same time, and fiithermore it contains the species composition of differring smaller islands too (PATTERSON & ATMAR 1986, CUTLER 1994). Nestedness is among the most frequently cited patterns (WRIGHT et al. 1998, BLOCH et al. 2007, ULRICH et al. 2009). Nestedness pattern most often is used to explore the structure of communities, such as islands within an archipelago (PATTERSON & ATMAR 1986, KRISTUFEK & KLETECKI 2007), habitat fragments within a landscape (ATMAR & PATTERSON 1993, PATTERSON & ATMAR 2000, GANZHORN & EISENBEISS 2001), isolated peaks along a mountain range (PATTERSON 1990, MCDONALD & BROWN 1992, COOK 1995), temporal changes on disturbed ( BLOCH et al. 2007) and revolutionary relationships in non-isolated areas. The nestedness also is useful to describe spatial distribution of species in less discrete habitats (PATTERSON & BROWN 1991, BAKER & PATTERSON 2011). Significant nestedness was extensively manifested in case of different taxons and ecosystems. However, the most important questions by the examination of nestedness patterns are that (1) which species and in what kind of measure are responsible for the unexpected incidences and (2) which islands, isolated fragments or habitat patches are those where we are able to detect more or less presences than the expected (SIMBERLOFF & MARTIN 1991, BÁLDI 2003). We can show these unexpected occurrences with the study of nestedness and these objects will be called idiosyncratic species or areas (ATMAR & PATTERSON 1993). Thus the important aim of nestedness analysis was always identifying such 'deviating' species and to infer the causes of idiosyncracy. With the knowledge of these we can value which species have an indication characteristic, which cause-effect factors are indicated by these species and which species are responsible for the pushing away of ordered nestedness pattens. The identification of idiosyncratic sites are practical applications in conservation ecology, wich have been discussed with regard to the single-large-or-several-small (S.l.o.s.s) debate ( ULRICH et al. 2009). This has a great importance in the planning of environmental management of endangered species in fragmented habitats. The fragmentation of habitats by human land use and disturbences is one of the most important impact modifying the composition of natural species assemblages (e.g. WILCOX & MURPHY 1985, GAINES et al. 1992, Noss & CSUTI 1997, BROKAW 1998; LOMOLINO & PERAULT 2000). The effects of these activities accompany the substitution and local extinction of some species, which is the one of the key problems of nature conservation ( BÁLDI 2003). The analysis of nestedness patterns of assemblages can be a useful method for nature conservation management (PATTERSON 1987), because nestedness subsets can also be generated through extinction (PATTERSON & ATMAR 1986, GANZHORN & EISENBEISS 2001). The negative effects of natural and human disturbances are even more obvious in the marshlands. Wetlands and marshlands all around the world have been lost in the past century and the remaining marshlands have been degraded to different degrees because of the adverse influences of human activities (EPPINK et al. 2004, FRASER & KEDDy 2005, ZHIJUN et al. 2010, TOUSIGNANT et al. 2010). Kis-Balaton is worth considering as one of these endangered areas of Hungary, being the biggest near-natural wetland habitat in our country (14745 ha). The marshland area was drained in the 1920s and the Kis-Balaton as
