Intensive grazing alters the diversity, composition and structure of plant-pollinator interaction networks in Central European grasslands.

Complex socio-economic, political and demographic factors have driven the increased conversion of Europe's semi-natural grasslands to intensive pastures. This trend is particularly strong in some of the most biodiverse regions of the continent, such as Central and Eastern Europe. Intensive grazing is known to decrease species diversity and alter the composition of plant and insect communities. Comparatively little is known, however, about how intensive grazing influences plant functional traits related to pollination and the structure of plant-pollinator interactions. In traditional hay meadows and intensive pastures in Central Europe, we contrasted the taxonomic and functional group diversity and composition, the structure of plant-pollinator interactions and the roles of individual species in networks. We found mostly lower taxonomic and functional diversity of plants and insects in intensive pastures, as well as strong compositional differences among the two grassland management types. Intensive pastures were dominated by a single plant with a specialized flower structure that is only accessible to a few pollinator groups. As a result, intensive pastures have lower diversity and specificity of interactions, higher amount of resource overlap, more uniform interaction strength and lower network modularity. These findings stand in contrast to studies in which plants with more generalized flower traits dominated pastures. Our results thus highlight the importance of the functional traits of dominant species in mediating the consequences of intensive pasture management on plant-pollinator networks. These findings could further contribute to strategies aimed at mitigating the impact of intensive grazing on plant and pollinator communities.

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.