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
HORVÁTH ET AL.: SMALL MAMMALS 299 decreased the nestedness with their unexpected presence regarding the sampled marshlands. Although the field vole (M agrestis) indicated the regeneration of the given habitat, yet - because of its absence in some patches - it is a idiosyncratic species in the nestedness analysis. This result showed that this species is a good indicator of regenerating sedgy habitat patches, but it has not even appeared generally in every marshland where the difference of environmental factors and the fragmentation of macro-habitats play an important role. We received other results by analyzing which species are responsible for the nestedness pattern and how high indicator values do they have in the habitat stmcture according the 2007 data. The assemblage structure seemed to be the less nested and altogether we could highlight 8 small mammal species as idiosyncratic ones. We received maximum indicator values at 5 occasions from the 8, the striped filed mouse (A. agrarius) and the common shrew (S . araneus) were symmetrical indicators, although they had the least importance in the variance of the theoretical maximum nestedness pattern. Miller's water shrew (N. anomalus) as an asymmetrical indicator appeared in a given habitat patch of Keleti-berek, therefore both of its significant value and idiosyncratic nature was caused by its unexpected presence. Finally, we emphasize the values of root vole, because we could record its recolonized groups in the habitat patches of Balatoniberek, where it indicated the regenerated, undisturbed environment. The root vole as a habitat specialist indicator has appeared in the nestedness analysis as an idiosyncratic species. These results proved admittedly that the root vole - as a habitat specialist species - is very sensitive to the habitat fragmentation and the human disturbances, so the pattern of its presence influences considerably the nestedness of small mammal assemblages of the examined marshlands. The nestedness analysis and calculation of indicator values of the species provide useful information for the environment protection about the organisation of small mammal assemblages in an altering environment, about the habitat use and colonization abilities of generalist and specialist species and the species turnover processes, especially about the presence-absence relations changing within the small mammal assemblages through human disturbances and water states. Based on the two parallel community ecological analyses we are able to draw inferences about the relation between small mammals and their occupied habitat patches within isolated refuge macrohabitats, about the relation between habitat quality and the habitat selection of small mammals. These results provide more useful information for nature protection than we can receive with the diversity analysis of those small mammal assemblages which are characterized by low species richness. In the near future it is very important to evaluate long-term monitoring data in terms of exploring the nestedness patterns, where the changes in the structure of assemblages could be examined not only spatially but temporally as well ( BÁLDI 2003a, BLOCH et al. 2007), focusing on recolonisation and species turnover processes. Acknowledgement Monitoring activities were supported by the Balaton Uplands National Park Directorate.
