Changes in Community Composition and Functional Traits of Bumblebees in an Alpine Ecosystem Relate to Climate Warming.

Climate warming has been observed as the main cause of changes in diversity, community composition, and spatial distribution of different plant and invertebrate species. Due to even stronger warming compared to the global mean, bumblebees in alpine ecosystems are particularly exposed to these changes. To investigate the effects of climate warming, we sampled bumblebees along an elevational gradient, compared the records with data from 1935 and 1936, and related our results to climate models. We found that bumblebee community composition differed significantly between sampling periods and that increasing temperatures in spring were the most plausible factor explaining these range shifts. In addition, species diversity estimates were significantly lower compared to historical records. The number of socio-parasitic species was significantly higher in the historical communities, while recent communities showed increases in climate generalists and forest species at lower elevations. Nevertheless, no significant changes in community-weighted means of a species temperature index (STI) or the number of cold-adapted species were detected, likely due to the historical data resolution. We conclude that the composition and functionality of bumblebee communities in the study area have been significantly affected by climate warming, with changes in land use and vegetation cover likely playing an additional important role.

Response of wild bee diversity, abundance, and functional traits to vineyard inter-row management intensity and landscape diversity across Europe.

Agricultural intensification is a major driver of wild bee decline. Vineyards may be inhabited by plant and animal species, especially when the inter-row space is vegetated with spontaneous vegetation or cover crops. Wild bees depend on floral resources and suitable nesting sites which may be found in vineyard inter-rows or in viticultural landscapes. Inter-row vegetation is managed by mulching, tillage, and/or herbicide application and results in habitat degradation when applied intensively. Here, we hypothesize that lower vegetation management intensities, higher floral resources, and landscape diversity affect wild bee diversity and abundance dependent on their functional traits. We sampled wild bees semi-quantitatively in 63 vineyards representing different vegetation management intensities across Europe in 2016. A proxy for floral resource availability was based on visual flower cover estimations. Management intensity was assessed by vegetation cover (%) twice a year per vineyard. The Shannon Landscape Diversity Index was used as a proxy for landscape diversity within a 750 m radius around each vineyard center point. Wild bee communities were clustered by country. At the country level, between 20 and 64 wild bee species were identified. Increased floral resource availability and extensive vegetation management both affected wild bee diversity and abundance in vineyards strongly positively. Increased landscape diversity had a small positive effect on wild bee diversity but compensated for the negative effect of low floral resource availability by increasing eusocial bee abundance. We conclude that wild bee diversity and abundance in vineyards is efficiently promoted by increasing floral resources and reducing vegetation management frequency. High landscape diversity further compensates for low floral resources in vineyards and increases pollinating insect abundance in viticulture landscapes.

Pyrrolizidine Alkaloid Production of Jacobaea aquatica under Different Cutting Regimes.

Jacobaea aquatica (Asteraceae) growing in wet grasslands with low management intensity is regarded as a noxious weed with pyrrolizidine alkaloids (PAs), which cause health problems to livestock. The influence of different management practices on the production of PAs and on the proportion of J. aquatica in the fodder was studied. Five cutting regimes were applied during 4 years on permanent plots in lower Austria. The toxicity of the fodder was assessed by recording dry weight and alkaloid content of J. aquatica and total aboveground biomass. Different cutting regimes had significant effects on the PA content of J. aquatica and on its proportion in the fodder. The content of J. aquatica was lowest in fodder of June and October cuts and highest in second cuts in July and August. Total alkaloid contents exceeding 100 mg/kg were found in fodder harvested in July and August. After cutting, the toxic plants regenerated quickly and produced new flowering stalks within 4-5 weeks. Six macrocylic PAs were evaluated, with Z-erucifoline as the most abundant compound. The alkaloid levels were highest in plants cut during summer when flowering plants were present. Consequently, this fodder should not be fed to livestock over a long period of time.