Question

.  Can you draw a conclusion between specific patch types and abundance of wild bees?

Answer 1

Forests are important natural and semi-natural terrestrial ecosystems, and natural disturbances and forest management operations within these ecosystems can create suitable habitats for wild bees. Both natural and human disturbances often drive the regeneration of forests, which leads to a succession in plant communities, affecting animals (Horn, 1974). Studies have demonstrated that different species prefer specific successional stages and the diversity of various taxa peaks at different times as succession proceeds (Spies & Turner, 1999). The early successional stages of forests can be dominated by grasses and herbaceous plant species because tree canopies often do not dominate the forests. These provide open ground and rich understory plant communities as resources which attract and sustain the diversity of pollinator taxa (Hanula, Ulyshen, & Horn, 2016; Swanson et al., 2011). This tendency has been reported for numerous species of wild bees, implying that the creation of open areas after harvest or natural disturbance in forests or in forests with very low basal areas can contribute to the conservation and restoration of habitats for wild bee species(Hanula, Horn, & O’Brien, 2015; Taki, Okochi et al., 2013).

The idea that the number of species increases with area, namely, the species richness–area relationship (SAR), is one of the few broadly accepted laws in ecology (Lawton, 1999). Although still debated, various mechanisms have been proposed to explain this general pattern. Because larger habitats typically have larger population sizes compared with smaller areas, larger areas tend to have higher species richness (number of species with at least one individual). This is a concise explanation of SARs determined by random placement models (Coleman, Mares, Willig, & Hsieh, 1982; Williams, 1995), and holds unless population densities of individual species greatly decrease with area (Yamaura, Connor, Royle, Itoh, Sato, Taki, et al., 2016). Deviations from constant densities, such as positive density–area relationships (Bender, Contreras, & Fahrig, 1998; Connor, Courtney, & Yoder, 2000) can affect the form of SARs and have important implications from an application perspective.

Therefore, this study examined the relationships between population densities of individual species comprising communities of bees (Hymenoptera: Apoidea: Anthophila) and the area of early-successional plantation patches. The overall objective of this study was to model SAR and species abundance–area relationship (AAR) based on density–area relationships. Because we could not survey the total area of the patches, we used the framework of a hierarchical community model (HCM) to account for spatial incompleteness in the field sampling (Yamaura, Connor, et al., 2016Yamaura, Connor, Royle, Itoh, Sato, Taki, et al., 2016). HCM treats communities as ensembles of individual species and constructs models of rare species by borrowing information from common species (Ovaskainen & Soininen, 2011). This is a great benefit in accounting for species richness in communities where rare species can play important roles (Dorazio, Royle, Soderstrom, & Glimskar, 2006), and provides the underlying species-level mechanisms of community-level SAR and AAR. These outcomes should help to identify effective management operations for forests and plantations to conserve and restore bee diversity in early successional plantation forest.

In total, 3469 wild bee individuals of 189 species belonging to 25 genera were collected on the 23 calcareous grasslands, representing 55% of the wild bee species occurring in Upper Franconia the number of individuals and of species are given for all tested groups of wild bees. A total of 35 species were endangered according to the Red List of Bavariaand most of those were habitat specialists.