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PŘIDAL, A., VESELÝ, P.: Changes in the composition of the bee populations of the Mohelno Serpentine Steppe a er 70 years (Hymenoptera: Apiformes). Acta univ. agric. et silvic. Mendel. Brun., 2011, LIX, No. 6, pp. 291–312 Mohelno serpentine steppe (Mohelenská hadcová step) is a unique natural habitat of European importance. Since its last apidologic proper survey passed about 70 years. The objective of this work was to summarize the results of the apidological survey performed in the national nature reserve Mohelno Serpentine Steppe in a period of 2010–2011, characterize current changes in the composition of bee populations and propose recommendations for the management of this nature reserve. The survey was performed within 20 days and includes a total of 91 hours of observations in the fi eld with exact records of survey localization and weather. A total of 2705 bee individuals were caught using an insect net and examined. 71 to 276 bee individuals were identifi ed on individual days of monitoring. The bee density varied in a range of 18.4–87.1 bees per hour of the pure time of sampling. A total of 176 bee species were identifi ed. 115 bee species from the original list of 232 bee species were confi rmed by this survey (50 %). Species that were not confi rmed could disappear as a result of changes which have occurred in the Steppe biotope over the past 40 years or their disappearance is generally associated with changes in the population of a particular species in Moravia. The disappearance of 17 % of unconfi rmed species (20 species) from the Steppe is very likely to occur but it is not associated with general changes in the population of these species in southern Moravia. 61 out of 176 bee species were recorded in the Steppe for the fi rst time. Pyrobombus lapidarius was eudominant. The highest dominance was observed for Halictus simplex as a representative of the solitary species and for Nomada succincta as a representative of cleptoparasites. However, the major part of cleptoparasites (66 %) was not confi rmed. The Shannon’s index (H’ = 3.97), Equitability (e = 0.77) and the Simpson’s index (c = 0.04) were determined for bee populations. The following species occurred on the Steppe: a) ubiquitous species with an abnormally small population (49 species) and b) steppe specialists (xerothermophile) with abnormally abundant populations and strongly competitive to ubiquitous species (9 species). The survey revealed a signifi cant decrease in the diversity of apidofauna on the Steppe, showing that the degradation change took place only partially and that some rare xerothermophile species on the Steppe were preserved. The composition of apidofauna still maintains its predominant xerothermophile character. The results of the survey were used to propose recommendations for managing the maintenance of the national nature reserve Mohelno Serpentine Steppe. secondary succession, Mohelno serpentine steppe, xerotermophile bee species, Apoidea, Apiformes, apidofauna 292 A. Přidal, P. Veselý The Mohelno Serpentine Steppe (Mohelenská hadcová step, thereina er referred to as “Steppe”) is a unique national nature reserve of European signifi cance. First known records of its botanical signifi cance date back to 1855 (Roemer, 1855). Systematic investigations of this site started in the early 1900s (Veselý, 2010). The fi rst written report about apidological research conducted on the Steppe was submitted in 1944 (Šnofl ák, 1944) and included a total of 227 species according to current taxonomic classifi cation (Přidal & Veselý, 2010a). Other species later found on the Steppe (Tkalců, 1964; Straka et al., 2007) originated from occasional and non-systematic sampling. Literature sources describe a total of 232 bee species found on the territory of the Mohelno Serpentine Steppe (“Steppe”). Some names reported by Šnofl ák (1944) are likely to represent one or two species according to the current taxonomy (Přidal & Veselý, 2010a). In principle, the spectrum of bee species was gradually completed using the results of the apidological survey performed in 2010 (Přidal & Veselý, 2010b). This survey provided interesting records such as the fi ndings of additional 50 bee species that had not been found on the investigated site before. However, many more species remained unconfi rmed on the Steppe by this survey. Such diff erences could be caused by major changes in biotopes of the Steppe that have occurred over the past decades, being particularly manifested by a sharp increase in the degree of steppe’s coverage with woody species and by related microclimatic changes (Veselý, 2002, 2010). This problem has not been addressed for many years. A er 1988, the plant stand in the nature reserve consisting of pine (Pinus) and locus trees (Robinia pseudacacia) was reduced and one part of the plateau was mown irregularly. It was not until May 1997 that sheep grazing was re-introduced on the Steppe. This kind of management is still applied in this nature reserve, according to the Plan of Management for this national nature reserve (Veselý, 2010). Přidal and Veselý (2010c) analysed the description of the site’s condition before 1944 reported by Šnofl ák (1944), comparing it with the current state and emphasizing specifi c features in the Steppe associated with the forage sources for bees and interconnections between individual biotopes. The main objective of this work is to summarize the results of the apidological survey performed in a period from 20 April 2010 to 10 May 2011, analyze the diff erences between the current state and the fi ndings made in previous surveys (Šnofl ák, 1944; Tkalců, 1964; Straka et al., 2007), and focus on xerothermophile bee species with narrow ecological valence (steppe species). The analysis of the results obtained in the apidological survey will be used to propose recommendations for managing the Mohelno Serpentine Steppe in order to preserve and create favourable conditions for valuable xerothermophile communities. MATERIAL AND METHODS Description of the site The specifi c character of biotopes in the Mohelno Serpentine Steppe is due to specifi c subsoil consisting of Serpentine (basic rock with a high content of magnesium) and a typical relief formed by erosion on the subsoil in the distinct meander of the river Jihlava (Fig. 1). The basin of the river Jihlava is cut deeply into the terrain so that the altitude diff erence between the plateau and the river’s water surface may reach 150 m (Fig. 2). Soils formed on the subsoil are shallow with a low content of nutrients, and contain a high portion of fragments from mother rock, which increases the content of air in soil, contributing to soil desiccation (Veselý, 2010). Such soil properties and specifi c microclimatic conditions derived from these properties enable xerothermophile communities to occur on this site. They o en include very rare species that have their northern boundary of occurrence in the Steppe in spite of the fact that the Steppe is located at the foothills of the Bohemian-Moravian Highlands (Českomoravská vysočina). Veselý (2002, 2010) worked up a detailed description of the site, including the description of changes that have occurred on the Steppe over the past 70 years. Methodology of the survey The apidological survey was based on the catching of bees using an insect net with a frame sized 40 cm in diameter and a 70 cm rod. Bees were caught at the sites of their typical occurrence such as fl owers of the bee forage, bare sites on the surface of soil including roads and rock ledges, margins and the surface of low and sporadic growth of grass, in the vicinity of dead wood, on stones exposed to sun, in the close vicinity of lower margins of the top of pine trees or bush plants where males performed hilltopping. The bee caught was immediately identifi cated and its gender was recorded. It was then released (particularly bumble bees, Bombini, and easily identifi able species) and/or placed in an exhaustor containing wood shavings, and subsequently identifi ed a er preparation in a laboratory using a binocular magnifi er at 10–50 fold magnifi cation. The prepared species are currently deposited in the collection of the fi rst author whereas duplicate specimens are deposited in collections of the Entomological Department of the Moravian Museum (Moravské zemské muzeum) in Brno. Honey bee (Apis mellifera Linnaeus, 1758) as a common species was excluded from monitoring and measurement; a total of 200 honey bee colonies are reared in Mohelno. This species was an eudominant species on the Steppe for the whole period of monitoring. Samplings were performed at recorded time intervals whose total length (the interval of observation) and the length of the pure time of Changes in the composition of the bee populations of the Mohelno Serpentine Steppe a er 70 years 293 1: Mohehelno Serpentine Steppe – view of the plateau, a part of the amphiteatre with downy surface and at the bottom valley the river Jihlava (Date: 20. 8. 2006, P. Veselý) 2: Mohehelno Serpentine Steppe – view of the plateau and the south and southwest parts of amphiteatre above the river Jihlava (Date: 20. 8. 2006, P. Veselý) 294 A. Přidal, P. Veselý sampling (i.e. time for searching for bees and collecting bees excluding breaks or transfers between individual sites) were defi ned (Tab. I). Furthermore, weather including maximum, minimum and average temperatures in the interval of observation was recorded together with map squares according to Veselý (2010) where sampling was performed (Tab. II). Transects o en applied in practice were not used in this survey since bee mapping in the heterogenous site of the Steppe was not suitable. Transects can be used in monocultures without major problems (for example, in foddercrop monocultures Háslbachová & Veselý, 1981; Kubišová et al., 1984). Transect sweeping does not provide complete solution (Banaszak, 1980). The method applied in this apidological sur

Changes in the composition of the bee populations of the Mohelno Serpentine Steppe after 70 years (Hymenoptera: Apiformes)