Communities of Digger Wasps (Hymenoptera: Spheciformes) along a Tree Cover Gradient in the Cultural Landscape of River Valleys in Poland.

This study of digger wasps (Hymenoptera: Spheciformes) was carried out in the cultural landscape of the Drweca, Lower Vistula, and Warta river valleys in northern Poland during 2011-2013. The study was undertaken on sites representing a succession gradient from dry grasslands to high levels of tree cover which we hypothesised would influence the structure of digger wasp communities. During our research additional information on flower use, insect prey, and phenology was also recorded and is reported here, revealing dependencies between woodland cover and both the prey and nesting types of digger wasps. A total of 136 species were recorded, i.e., nearly 56% of all Spheciformes species recorded from Poland. Among the species collected, 30 were on the Red List of Threatened Animals in Poland. Most endangered species were recorded in psammophilous grasslands, which are open habitats, and the least in mesic sites. These results significantly update the known distribution of the digger wasp in northern Poland. Knowledge on the biology of digger wasps in Poland is also supplemented by information on the feeding of larvae of 14 species and information on food plants visited by imago digger wasps. The results of our research confirm the correlations between the increase in forest cover and the number of digger wasp species.

Complementary Use of Various Types of Anthropogenic Habitats by Scolia hirta (Hymenoptera: Scoliidae) and Scolia sexmaculata.

Scolia hirta (Schrank) and Scolia sexmaculata (O.F. Müller) are Palearctic, parasitic Aculeata inhabiting forests and forest steppes. At present, the abundance and dispersal of these species are increasing considerably in Poland and other European countries, allowing observation of their possible habitat preferences. The analysis of the preferences of S. hirta and S. sexmaculata was conducted in Northern and North-Eastern Poland based on the evaluation of their occurrence in six types of habitats: (A) psammophilous and xerothermic grasslands, (B) old fields, (C) city outskirts, (D) sites in housing/industrial zones, (E) sand quarries, (F) post-industrial wastelands, and in a total of three types of landscape: 1) semi-natural, 2) urban, and 3) industrial. We demonstrated that the habitat most frequently colonized by S. hirta is post-industrial wastelands, while S. sexmaculata were most often sampled in old fields, with the frequency of 100% and 94.11%, respectively. At the same time, the abundance of the species in these habitats was also the highest, with a mean of 8.00 and 10.88 individuals, respectively. Moreover, S. hirta was relatively frequently found in the urban landscape (67% in city outskirts and 88.23% in the housing/industrial zones), while S. sexmaculata colonized these areas to a considerably low degree (25% in city outskirts and 29.41% in the housing/industrial zones). We also established that the occurrence of the species was affected by the forest cover in the closest vicinity of the study sites, which significantly modified the habitat preference of the species analyzed.

Can soda ash dumping grounds provide replacement habitats for digger wasps (Hymenoptera, Apoidea, Spheciformes)?

BACKGROUND: Published sources document a loss of biodiversity at an extreme rate, mainly because natural and semi-natural ecosystems are becoming fragmented and isolated, thus losing their biological functions. These changes significantly influence biological diversity, which is a complex phenomenon that changes over time. Contemporary ecologists must therefore draw attention to anthropogenic replacement habitats and increase their conservation status. In our studies we show the positive role of soda ash dumping grounds as an alternative habitat for digger wasps, especially the thermophilic species. METHODOLOGY/PRINCIPAL FINDINGS: In the years 2007-2010 we carried out investigations in postindustrial soda ash dumping grounds located in Central Poland. We demonstrated that these areas serve as replacement habitats for thermophilic species of Spheciformes and, indirectly, for their potential prey. The studies were conducted in three microhabitat types, varying in soil moisture, salinity and alkalinity, that were changing in the course of ecological succession. We trapped 2571 specimens belonging to 64 species of digger wasps. Species typical of open sunny spaces comprised 73% of the whole inventory. The obtained results suggest that the stage of succession determines the richness, abundance and diversity of Spheciformes. The most favorable conditions for digger wasps were observed in habitats at late successional stages. CONCLUSIONS/SIGNIFICANCE: Our results clearly showed that these habitats were replacement habitats for thermophilous Spheciformes, including rare taxa that require genetic, species and ecosystem protection, according to the Biodiversity Convention. We showed that some types of industry might play a positive role in the preservation of taxa in the landscape, and that even degraded industrial wasteland can replace habitats under anthropopressure, serving as refugia of biological diversity, especially for disturbance-dependent species.