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.