Acta Universitatis Agriculturae et Silviculturae Mendelianae Brunensis (Jan 2011)
Changes in the composition of the bee populations of the Mohelno Serpentine Steppe after 70 years (Hymenoptera: Apiformes)
Abstract
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 field 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 identified 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 identified. 115 bee species from the original list of 232 bee species were confirmed by this survey (50 %). Species that were not confirmed 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 unconfirmed 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 first 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 confirmed. 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 significant 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.
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