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 283 a Landscape Protection Area has been legally protected since 1976. The Kis-Balaton Landscape Protection Area today is a flood prevention system consisting of two main parts. Kis-Balaton Water Protection System stage 1 (KBWPS-I) (1985) is characterized by open water surfaces with relatively narrow reedbedts along the dikes, while KBWPSII (1992) contains vast reedbeds and sedgy marshes, and less open water. The building of infrastructure necessary for the filtering system accompanying the increased water level after the 1992 reconstruction has fragmented considerably the original marshland area and isolated the refuge habitats. Marshlands are important habitats for small mammals (

MARTIN et al. 1991, KRITSOFIK 2001, BIAS & MORRISON 2006, SCOTT et al. 2008, MICHELAT & GIRAUDOUX 2006) and thus small mammals are typical objects of biodiversity monitoring of the relict KisBalaton marshlands. Small mammals are often used as an indicator species group (CAREY & JHONSON 1995, PEARCE & VENIER 2005); they have an important role in ecosystem and foodwebs, because they are primary consumers (HAYWARD & PHILLIPSON 1979, HUNTLY 1991), they are also prey for many carnivore mammals and birds of prey (KORPIMÄKI & KREBS 1996, KLEMOLA et al. 2003, TOME 2003). Small mammals respond rapidly to disturbance and other anthropogenic effects (Fox 1996, BUTET et al. 2006, PANZACCHI et al. 2010). Changes in the structure of their communities indicate the possible degradation of their environment (habitat degradation, fragmentation, antropogenic distrubance etc.). Because of the relict characteristic of these marshlands, the water-reserve system maintaining human interventions affect appreciably the biodiversity, thus the hypothesis-testing control of these effects are highlighted projects in the Hungarian Biodiversity Monitoring System (HBMS). In the view-point of composition of the small mammal communities existing in the refuge marshland habitats of KisBalaton there is a habitat specialist character species which has great importance and appears on the Habitat Directive list; this species is the root vole, Microtus oeconomits (Pallas 1776), whose conservation and maintenance is one of the greatest problems of local environment protection. With special regard to the isolated occurrence of this species in the Kis-Balaton region there were several projects applied for examining the composition of small mammal assemblages of the area. These researches have examined whether (1) human interventions and disturbances related with the marshlands have measurable effect on the diversity and temporal composition of small mammal assemblages (

LELKES & HORVÁTH 2000, HORVÁTH 2001, 2004) and if (2) they fulfilled the examination of small mammal assemblages of different-sized and isolated islands (FARKAS et al. 1998, FARKAS & CZABÁN 2007). We have been examining the composition of small mammal fauna of Kis-Balaton Landscape Protected Area since 1999 within the framework of HBMS program where our main aim is the spatial-and temporal monitoring of subpopulation patterns of the relict root vole. In the sampling approach of the 11-year long period we have applied two successive strategies. When we could catch root vole individuals in habitat patches which are adequate for the species, we applied population-level monitoring that concentrates on smaller areas. However, when the state of the habitat had deteriorated and the number of the individuals of the given species had decreased dramatically or the species disappeared from the area because of human interventions or weather conditions, we switched from population-level monitoring to faunistical monitoring approach that needs greater trapping expenditure and associates with more habitats. In the present study we have evaluated the presence-absence data derived from a 3-year long period of the faunistical mapping of several micro-habitats after the local extinction of the endangered root vole. Based on the nestedness analysis and the counted character- or indicator values derived from the hierarchical classification of habitat