No abstract

Sweat bees in the subgenus Lasioglossum (Dialictus) are one of the most diverse and abundant bee taxa, and a critically important component of bee biodiversity. Yet, the most basic taxonomic knowledge of these bees is lacking in many regions. As a step towards a better understanding of the L. (Dialictus) of the western Nearctic region, a revision of the ‘red-tailed’ L. (Dialictus) species was completed. Thirty-six species were revised, 20 of which are described as new, and two names are treated as junior subjective synonyms. Descriptions, figures, distribution maps, floral hosts, and keys to species for females and males are provided. The following 20 species are described as new: Lasioglossum (Dialictus) arenisaltans sp. nov., L. (D.) argammon sp. nov., L. (D.) austerum sp. nov., L. (D.) cactorum sp. nov., L. (D.) cembrilacus sp. nov., L. (D.) clastipedion sp. nov., L. (D.) clavicorne sp. nov., L. (D.) decorum sp. nov., L. (D.) festinum sp. nov., L. (D.) imbriumbrae sp. nov., L. (D.) julipile sp. nov., L. (D.) lilianae sp. nov., L. (D.) meteorum sp. nov., L. (D.) miltolepoides sp. nov., L. (D.) minckleyi sp. nov., L. (D.) perditum sp. nov., L. (D.) rufornatum sp. nov., L. (D. ) spivakae sp. nov., L. (D.) tessellatosum sp. nov., and L. (D.) torrens sp. nov. Previously unknown males of L. (D.) clematisellum (Cockerell, 1904), L. (D.) droegei Gibbs, 2009, L. (D.) kunzei (Cockerell, 1898), and L. (D.) pallidellum (Ellis, 1914) are described and figured for the first time. Lasioglossum (Dialictus) clarissimum (Ellis, 1914) (= Halictus clarissimus Ellis, 1914) and L. (D.) perexiguum (Sandhouse, 1924) (= Halictus (Chloralictus) perexiguus Sandhouse, 1924) are new subjective junior synonyms of L. mesillense (Cockerell, 1898) (= Halictus nymphalis var. mesillensis Cockerell, 1898). A lectotype specimen is newly designated for L. mesillense, for which the location of the type material has not previously been known. The following five new records for Mexico are reported: L. clematisellum, L. droegei, L. eophilus (Ellis, 1914), L. kunzei, and L. pallidellum.

Biodiversity promotes ecosystem function (EF) in experiments, but it remains uncertain how biodiversity loss affects function in larger-scale natural ecosystems. In these natural ecosystems, rare and declining species are more likely to be lost, and function needs to be maintained across space and time.Here, we explore the importance of rare and declining bee species to the pollination of three wildflowers and three crops using large-scale (72 sites across 5000 km 2 ), multi-year datasets. Half of the sampled bee species (82/164) were rare or declining, but these species provided only $15% of overall pollination. To determine the number of species important to EF, we used two methods of "scaling up," both of which have previously been used for biodiversity-function analysis. First, we summed bee species' contributions to pollination across space and time and then found the minimum set of species needed to provide a threshold level of function across all sites; according to this method, effectively no rare and declining bee species were important to pollination. Second, we account for the "insurance value" of biodiversity by finding the minimum set of bee species needed to simultaneously provide a threshold level of function at each site in each year. The second method leads to the conclusion that 25 rare and eight declining bee species (36% and 53% of all rare and declining bee species, respectively) are included in the minimum set. Our findings provide some of the strongest evidence yet that rare and declining species are key to meeting threshold levels of EF, thereby providing a more direct link between real-world biodiversity loss and EF.

A revised key to the 94 species of Lasioglossum (Dialictus) currently known to occur in Canada is presented, incorporating new species and taxonomic updates since the publication of the first key in 2010. Two new species, Lasioglossum (Dialictus) immigrans and Lasioglossum (Dialictus) onuferkoi, are described from Canada. Lasioglossum (D.) ascheri, L. (D.) stictaspis, and L. (D.) tegulariforme are reported or confirmed from Canada for the first time. Lasioglossum (D.) gaudiale (Sandhouse, 1924) and L. (D.) helianthi (Cockerell, 1916) are resurrected from synonymy with L. (D.) tegulariforme (Crawford, 1907). The following five new synonymies are established: L. (D.) stictaspis (Sandhouse, 1923) (= L. (D.) albuquerquense (Michener, 1937)); L. (D.) ascheri Gibbs, 2011 (= L. (D.) curculum Gibbs, 2011); L. (D.) helianthi (Cockerell, 1916) (= L. (D.) imbrex Gibbs, 2010); L. (D.) megastictum (Cockerell, 1937) (= L. (D.) punctiferellum (Cockerell, 1937)); and L. (D.) obnubilum (Sandhouse, 1924) (= L. (D.) lilliputense Gibbs, 2010). Previously undescribed males of L. (D.) helianthi, L. (D.) reasbeckae, L. (D.) tegulariforme, and L. (D.) weemsi are diagnosed and figured.

The University of Minnesota Insect Collection holds a rich collection of bees from Itasca State Park, MN, from 1937 and 1938. This collection formed the historical baseline data for comparison with a new survey conducted from 2011 to 2013, to measure changes in bee species over the last 75 yr. Bees were collected with timed net surveys and trap nests at eight different sites within the park. Megachilidae were the focal family for the current study, due to their importance as commercial pollinators and their unique nesting habits. Species richness and diversity of Megachilidae in the new survey were both significantly lower than that of the historical collection but were not significantly different when species accumulation curves were extrapolated to estimate the true species richness. Eleven species in the historical collection were not rediscovered, while three species not previously collected in Itasca State Park were found in 2011-2013.