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
290 NATURA SOMOGYIENSIS y 0.5 in 2007, which reflects that the level of nestedness of assemblages recorded for this year was lower and the pattern was less ordered. It is important to highlight in the results of year 2007 that the smallest difference can be seen between the weighted-interaction nestedness (WIN) value and the mean value of randomisation process (d rn cj), so the level of significance of z score was the lowest by this analysis. The summarized statistical values of nestedness analysis - based especially on the species composition of 2005 and 2006 - confirmed the nestedness of small mammal assemblages of examined habitat patches (Table 2). Beside the evaluation of the nestedness patterns of data matrices of the three years characterized by different trapping expenditure we were curious what kind of nestedness patterns can be seen by the small mammal assemblages of the 7 variously isolated groves (macro-habitats) on the basis of the summarized data of the three years. The latter three years were characterized by habitat regeneration following the bountiful rainwater and the ceasure of human disturbances. WINE calculates a weighted-interaction distance (d^), which estimates nestedness taking into account the number of events in the links (Fig. 2). Based on the pattern of colour plots we are able to explain the peak values of idiosyncratic species and isolated habitats. In 2005 six idiosyncratic species contributed to the disorder (C. suaveolens, M. oeconomus, M. arvalis, A. terrestris, R. rattus, M. spicilegus). Common vole (M arvalis ) did not increas the disorder with its high value, but with its presence. From the perspective of investigated areas the idiosyncratic habitats were KE_1 and H I. In the Keletiberek habitat (KE_1) we found that the habitat altering effects of previous disturbances were the main community organiser external constraint factor, while in case of the Halász-rét (HI) it was the effect of bountiful rainwater and the water regulations in the neighbourhood of River Zala. Although, in the next year (2006) the nestedness pattern resembled to the maximum nestedness matrix based on the higher value of WINE that is demonstrated by the graphic illustration of the results. We could also identify several idiosyncratic species S. araneus, M. agrestis and A. flavicollis — in this year based on the unexpected appearance and absence (Fig. 2.). Five species (C. suaveolens, M. spicilegus, Neomys fodiens, R. rattus, S. minutus) had higher weighted distance values, which decreased the orderedness of the system. By analysing the habitats we found that three of them (KEI, KE_2 and H I) were idiosyncratic. Regarding the identification of the idiosyncratic habitats we can conclude the same like for the previus year. We received the lowest level of nestedness for 2007 based on the original data matrix, and WINE placed the position of the pattern between the random pattern and maximum nestedness. This year is the most unorganised among the three examined years, which is caused by the following species: N. anomalus, M. spicilegus, S. araneus, M. agrestis, A. agrarius. The presence or absence of several species was unexpected (A. flavicollis, A. terrestris, M. oeconomus, A. sylvaticus). Considering the habitats it can be laid down that KE 2, KE 3 and B 2 habitats were responsible for the disorder (Fig. 2.). Determining the indicator values (IndVal) of species The greater trapping effort that was applied in 2005 aiming at the rediscovery of root vole (M oeocnomus) resulted data from 6 macro-habitats and 7 habitat patches, from which data we could perform the IndVal analyses. In this year 11 species received the significant indicator or character value from the 16 small mammals (Table 3). The most important result of the 2005 sampling period is that we could catch several individuals of the critically endangered root vole in the Halász-rét (H I) area among the sampled habitats. In 8 of the 11 species characterized by maximum indicator value the IndVal values were lower than 55% (Table 3). Through the classification performed on the basis
