Matskási István (szerk.): A Magyar Természettudományi Múzeum évkönyve 83. (Budapest 1991)
Kisbenedek, T.: Habitat preference and seasonality of spider (Araneae) communities in dolomitic grasslands
The number of arthropods caught by traps depends on their activity so data represent values of the socalled activity density, rather than that of the absolute ones. Catching efficiency depends on the environment and the studied groups (NENTWIG 1988, RHUSTON et al. 1989). Results Fourteen samplings were carried out between April and October in 1988, and altogether 5669 individuals were caught. 101 species belonging to 22 families were identified in the collected material (Table 2). On the basis of the mode of preying, 5 large guilds could be separated: wanderers, orb-weavers, random-web weavings, tubular-web weavings, aerial-web weavings. 95.45% of the spiders collected belonged to the nonweavers (Table 1). The species abundance curve of the whole community has a lognormal shape distorted to some extent. For 19 species, the peak of the curve is in the third octave, so these data give a good representation of the species inhabiting the area (Fig. 3). Total number of individuals culminates in summer and activity has its maximum in June with the abundance of 892 individuals/sample) at the beginning, and 834 individuals/sample) at the end of the month. This is almost a three times more value than arised from the first sample in spring (231 individuals/sample) and the last one in autumn (239 individuals/sample). The whole community shows the minimum size at the beginning of autumn (141 and 153 individuals/sample) (Fig. 1). Segregation of sexes shows that the maxmium in summer is produced by the activity of males, especially in June (644 indiviuals/sample). From the end of July until the beginning of September the activity of immatures and females is characterestic (Fig. 2). The mean diversity of the whole community for the 7 month period is 2.599. Diversity shows the minimum in June and the maximum in April (Fig. 4). Number of species is the highest at the beginning of July (51 species) and in May (49 species), and the minimum value of the species trapped is reached at the beginning of October (25 species) (Table 3). The values of the Berger-Parker index are the highest in midsummer (52.2 %) (Fig. 5). Diversity showed inversed relationship with dominance, so the minimum value of diversity occurs when it has its maximum (Fig. 6). The 12 most frequently caught species were selected from the community. They constribute more than 74 % of the total abundance, therefore they can be considered essential components in the structure of the community. Both sexes of these species except Coelotes longispina - belong to the guild of wandering hunters. The male of this species begins its wandering only after maturation. The proportion of diurnal and nocturnal species is about 50-50 %. In the 3 patches of the habitat, according to the dominance values, the ratio of diurnal and nocturnal species in patch A is 75.69% / 24.03%, B 64.73% / 35.26% in patch B, and 45.08% /54.91% in patch C (Fig. 9 and 10.). The Zodarium sp. shows the highest dominance value of the species (42.68 %), which is almost double of the 2nd highest one (Harpactes rubicundus: 20.35 %). In dominance values high fluctuation can be found among the diurnal species, while it is much more steady in nocturnal ones (Table 4). April is the only month when the average dominance of nocturnal species in seasonal distribution is higher than that of the diurnal ones. The proportions of diurnal predators in June and July are 79.66 % and 72.92 %, respectively. In the rest of the months it is about 50 %. The number of dominant species is between 2-3 species per month and they represent an even ratio between diurnal and nocturnal species in all of
