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

Natura Somogyiensis 19 281-302 Kaposvár, 2011 Nestedness of small mammal assemblages and role of indicator species in isolated marshland habitats GYŐZŐ HORVÁTH, RÓBERT HERCZEG, KITTI TAMÁSI & NIKOLETT SALI University of Pécs, Institute of Biology, Deparment of Animal Ecology H-7624 Pécs, Ifjúság u. 6., Hungary, e-mail: hgypte@gamma.ttk.pte.hu HORVÁTH, GY., HERCZEG, R., TAMÁSI, K. & SALI, N.: Nestedness of small mammal assemblages and role of indicator species in isolated marshland habitats. Abstract: The concept of nestedness has important role in community ecology of fragmented habitats that measures the order in presence-absence matrices of species in different communities, and the vulnerability of species to habitat change can be quantified. We have been examining the composition of small mammal assemblages of Kis-Balaton Landscape Protection Area since 1999 within the framework of Hungarian Biodiversity Monitoring System Programme. Our basic question was how much the species turnover processes and the water-level increase following bountiful precipitation as a natural disturbance predominate in directing the composition of small mammal assemblages and in the nestedness pattern in human disturbed habitat patches. Our investigation was based on nestedness analysis and the IndVal method. The results of nestedness analysis showed that the small mammal assemblages of the isolated Kis-Balaton marshland habitat patches are ordered contrary to the random pattern and showed nested pattern. The endangered habitat-specialist root vole appeared as an asymmetrical indicator species regarding its optimal habitat patch, and we evaluated it as an idiosyncratic species in the nestedness analysis. These results proved admittedly that the root vole - as a habitat specialist species - is very sensitive to habitat fragmentation and human disturbance, so the pattern of its presence influences considerably the nestedness of small mammal assemblages of the examined marshlands. Keywords: small mammals, presence-absence, nestedness, indicator value, marshland, disturbance Introduction One of the most important objects and aims of community ecology is to describe and evaluate the community patterns (GEE & GILLER 1987, SOUTHWOOD 1996, WEIHER & KEDDY 1999) and formulate testable null-hypotheses for these examinations (DIAMOND & GIPLIN 1982, GOTELLI & GRAVES 1996, GOTELLI 2000, MOORE & SWIHART 2007). Null models are pattern-generating methods that intentionally exclude a mechanism of interest to determine whether a specific pattern can be produced randomly (GOTELLI 2000; GOTELLI & GRAVES 1996, ULRICH & GOTELLI 2007a, b). LEIBOLD (2002) listed six hypothetical patterns of species' distribution among sites: nested subsets (I), checkerboards (2), Clementsian gradients (3), Gleasonian gradients (4), evenly spaced gradients (5) and random pattern (6). Patterns represent idealized characteristics hypothesized to result from at least one (and generally more than one) potentially important ecological or biogeographical process (LEIBOLD 2002). We can find a detailed overview about the sto-