Uherkovich Ákos: A Villányi-hegység botanikai és zoológiai alapfelmérése (Dunántúli Dolgozatok Természettudományi Sorozat 10., 2000)

Sólymos Péter: Comparative malacological survey of the Szársomlyó and the Fekete Hill (Villány Hills, S Hungary). - Összehasonlító malakológiai vizsgálatok a Szársomlyón és a Fekete-hegyen (Villányi-hegység)

SÓLYMOS, P.: COMPARATIVE MALACOLOGICAL SURVEYS IN THE VILLÁNY HILLS The field surveys were carried out in 1996-1999. Four equally 1 litre volume soil samples were taken from each sampling sites (Fig. 1, Table 1). The soil samples were washed on 0.8 mm mesh because of the easier selection (KROLOPP 1995). The selected malacological material contained both living and dead individuals and those were identified according to KERNEY et al. (1983) and Soós (1943). The number of apexes was counted in order to estimate the number of individuals per sample. In the case of the genus Truncatellina the broken or juvenile shells were distributed among the three Truncatellina species according to their relative abundances in the given samples. Data analyses Similarity of the species composition was calculated by the Bray-Curtis quantitative dissimilarity index, and the similarity structure was analysed by hierarchical cluster analysis with using of the Ward-Orlóci fusion method (MISSQ) and by Nonmetric Multidimensional Scaling (NMDS). The NuCoSA package (TÓTHMÉRÉSZ 1993a) was used for these computations. The traditional Shannon diversity index was used (with natural logarithm). The diversity statistics were calculated by the DivOrd package (TÓTHMÉRÉSZ 1993b). To find character species of the cluster hierarchy the IndVal method (DUFRÊNE & LEGENDRE 1997) was used. This method combines the mean number of species individuals with its relative frequency of occurrence in the various groups of sites in the cluster hierarchy. The index is maximum when all individuals of a species are found in a single group of sites and when the species occurs in all sites of that group, it is a symmetrical indicator (its presence contributes to the habitat specificity and its presence can be predicted in all sites of the group, indicator value >55%). Other species must be considered as accidental ones, these are asymmetrical indicators (their presence cannot be predicted in all samples of one habitat, but contributes to the habitat specificity, indicator value <55%). The index for a given species is independent of the other species relative abundances (DUFRÊNE & LEGENDRE 1997, MCGEOCH & CHOWN 1998). The statistical significance of the species indicator values is evaluated using a randomization procedure by 1,000 random permutations. The IndVal 2 package (DUFRÊNE & LEGENDRE 1997) was used for the computations. Results and discussion During the four-year survey (1996-1999) of the Szársomlyó and the Fekete Hill 16.776 individuals of 28 mollusc species were collected from 18 sampling sites (72 soil samples) (Table 2). The ordination of the soil samples shows the separation of the open (group 1.1. and 1.2.) and closed (group 2.1. and 2.2.) areas (Fig. 2). The separation between the open groups is less expressed than between the closed groups. By the ordination of the sampling sites the separation between the closed areas is more detectable and the open groups are similar to each other as well (Fig. 3). The classification of the sampling sites shows the same result as the ordination. The first disjunction level divides the cluster into two main groups, the groups of the closed (group 1.1. and 1.2.) and open (group 2.1. and 2.2.) areas. Within these main groups we can differentiate sub-groups on lower cluster levels. These sub-groups can be named as extreme (moderately diverse, group 1.2. and 2.1.) and moderate (diverse, group 1.1. and 2.2.) cluster groups (Fig. 4).