1. Grassland ecosystems are imperiled by agricultural activity worldwide. Restoring grassland habitat is important to conserving grassland fauna and preserving ecosystem services, but more knowledge is needed on the impact that local and landscape factors have on patterns of diversity. We focused on whether prairie grassland restorations along a gradient of increasing agricultural cover in the surrounding landscape would be inhabited by less diverse and/or more homogenous native bee communities. Native bees are a specific target for many grassland restoration efforts, and supporting their local and β-diversity in reconstructed habitats is of mounting interest. We also investigated if higher floral resource richness within restorations could help ameliorate negative effects of agricultural landscapes. 2. We sampled 16 prairie restorations in Minnesota (USA) that varied along a gradient of increasing agricultural land cover around the site. We characterized floral resource richness at all sites beginning in mid-May and ending in mid-September. We used GLMMs and multivariate analyses to disentangle how floral resource richness and percentage of surrounding land cover in agricultural production are associated with the local and β-diversity of bee communities. 3. Local bee diversity increased with increasing local floral resource richness, independent of the surrounding landscape. Bee β-diversity was not impacted by local floral resource richness or percentage of agricultural cover in the surrounding landscape, indicating local and landscape factors are not substantially impacting the homogeneity of bee communities across restorations. 4. Synthesis and applications. We found that, regardless of agricultural cover in the surrounding landscape, more florally rich plantings attract more diverse bee communities. We recommend that habitat plantings prioritize local scale diversity, and that potential sites where the landscape is dominated by agricultural production should not be overlooked for restoration.
Grasslands are among the planet’s most imperilled ecosystems, largely because habitat conversion has caused extreme biodiversity loss. In response, managers and scientists aim to recreate grassland habitat, yet these reconstructed grasslands are often species‐poor and lose diversity through time. One potential mechanism to promote biodiversity in grasslands is spillover, or the targeted dispersal of species across habitat boundaries from areas of high to low biodiversity. There is potential for native species to disperse via spillover from high‐quality remnant habitat and establish in reconstructions, thus increasing biodiversity. However, plant dispersal and establishment are often context dependent, and the conditions that promote spillover in grasslands are largely unknown. Here we examine the contexts under which spillover can enhance biodiversity in grasslands. Specifically, we investigate whether the species richness of reconstructions and individual plant dispersal traits alter spillover. To do so, we surveyed plant species richness at reconstructed grasslands of varying diversity adjacent to remnant grasslands. We found that spillover from remnants supplies reconstructions with rare species that would otherwise not be present, but only in reconstructions with lower overall richness. Furthermore, spillover was more likely to occur for species with wind dispersed seeds than species with unassisted seed dispersal. Synthesis and applications. Our results show that the context dependency of both dispersal and establishment processes are critical to understanding when and where spillover can promote biodiversity in reconstructed systems. Understanding these contexts will help land managers leverage natural dispersal to mitigate biodiversity loss by anticipating which species are likely to arrive in reconstructions without assistance and when they are likely to establish.
1. Grassland restoration is an important tool for conserving bee biodiversity within agricultural landscapes. Restorations foster increases in local bee abundance and α-diversity; however, these measures are insufficient for understanding whether remnant communities are being conserved. We compared native bee α-diversity, β-diversity and community composition between restored and remnant prairies in Minnesota, USA. We then investigated two potential drivers of bee community dissimilarity between restored and remnant prairies: proportion of agricultural land surrounding a restoration and differences in floral community between restored and remnant prairies.
Augochloropsis and other shiny green Halictinae have had various taxonomic issues and are often misidentified. One prevailing taxonomic issue is that Augochloropsis metallica (Fabricius) has two subspecies, that have long been recognized as morphologically distinct (Augochloropsis metallica metallica and Augochloropsis metallica fulgida (Smith), but the subspecies are inconsistently applied in the literature. Here, we review the Augochloropsis of the Midwest and further address the Augochloropsis species in the broader United States to resolve the outstanding taxonomic issues with the midwestern species. We provide identification keys and diagnoses for the genera and species of the shiny green Halictinae of the midwestern United States, which includes the genera Agapostemon, Augochlora, Augochlorella, and Augochloropsis. This work results in taxonomic changes to Augochloropsis. Augochloropsis sumptuosa (Smith) is split into two species, with the name Augochloropsis sumptuosa retained for the eastern form, and Augochloropsis humeralis (Patton), stat. nov., reinstated for the western form. Augochloropsis metallica is split into five species, with two of those species occurring in the midwestern United States: Augochloropsis metallica and Augochloropsis viridula (Smith), stat. nov. Examination of the holotype of Augochloropsis fulgida (Smith) revealed that it does not agree with the prevailing concept of Augochloropsis metallica fulgida; it is reinstated as Augochloropsis fulgida, stat. nov., but is currently known only from the holotype female from Florida. Augochloropsis cuprea (Smith), long considered to be a synonym of Augochloropsis metallica, is also distinct, and we are reinstating Augochloropsis cuprea, stat. nov., though the range of this species is unclear. We further recognize Augochloropsis fulvofimbriata (Friese), stat. nov., from South and Central America, as distinct. These changes result in a total of three Augochloropsis species in the Midwest and seven named species in the United States. We are aware of additional species from the southern and southwestern United States that are undescribed, and we highlight additional taxonomic work that remains to be done.
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