Matskási István (szerk.): A Magyar Természettudományi Múzeum évkönyve 83. (Budapest 1991)

Báldi, A. ; Ádám, L.: Habitat selection of ground-dwelling beetles during dolomitic succession

There are habitat specialists and habitat generalists among beetle species (WiTOWSKI 1978), and generalists can be found in more types of habitats than specialists (HANSKI 1982a, 1982b). In the present study values of the habitat selection index ranged from 1.87 to 4.00, supporting this statement. At the individual level the habitat preference may be distinct or shared (ROSENZWEIG 1985). The predator species Ocypus olens distinct in the close dolomitic grassland habitat. In the forest three other predator species, namely Carabus convexus, Pterostichus melas and Abax ater shared the habitat, therefore they showed similarly high habitat preference. At the group level the herbivores were the most habitat specialists. According to BUSE (1988) this is the result of the requirements of a beetle species for a specific host plant species. Some of the congeneric species showed different habitat preference. For example Pseudocypus picipennis occurred in the close dolomitic grassland, but Ocypus olens preferred the oak forest. Two Onthophagus species (O. fracticornis and grossepunctatus) preferred the dolomitic steppe meadow, but the third species (O. nutans) preferred the forest. Three Nicrophorus species (N. humator, N. vespillo, N. vespilloides) showed another type of habitat preference, each of them preferred the forest habitat. The mean habitat fidelity values, ranked into successional order, showed high values in the close dolomitic grassland, and lower values both in the dolomitic steppe meadow and in the oak forest. The open dolomitic grassland habitat was not considered here, because it had only one characteristic species, namely Pedinus femoralis. Temporal changes of the habitat selection index did not correlate with the number of individuals. The habitat selection index of Carabus convexus and Pedinus femoralis significantly decreased with time, because humidity decreased and food became less abundant in summer, therefore the individuals dispersed to search better conditions. The habitat selection index of the Sisyphus schaefferi showed a similar pattern to the changes of the previous species in the first half of the study, but the values of the index increased in the second. The difference may be the consequence of different overwintering strategies of the species. Carabus convexus and Pedinus femoralis overwinter as a larva, but Sisyphus schaefferi mostly as an imago. The two Nicrophorus species are generalists (see below), therefore they had not significant claims for a specific habitat. The values of habitat selection index of Geotrupes vernalis showed large oscillations, therefore the temporal changes were not significant, though the habitat selection of the species seemed to be decreased. Among the five feeding types which we separated (Table 1), the herbivores and somewhat the predators may be considered as specialists, because of their claims for specific food. The dung feeders, detritus feeders and scavengers are rather considered as generalists. The values of habitat selection index supported this hypothesis, because the herbivores and predators had higher habitat selection values than the others. The scavengers showed the lowest value of habitat selection index. This may be due to their attraction to the traps from large distances because of the smell of dead beetles. * * * Acknowledgements - We thank G. SZÉL and G. HRASKÓ for field assistance, and C. MOSKAT for his helpful comments on the manuscript. This study was made within the framework of the "Succession Research Project", an OKKFT programme of the Hungarian Natural History Museum supported by the OMFB.