Reference genome for the Mojave poppy bee (Perdita meconis), a specialist pollinator of conservation concern.

The Mojave poppy bee, Perdita meconis Griswold (Hymenoptera: Anthophila: Andrenidae), is a species of conservation concern that is restricted to the eastern Mojave Desert of North America. It is a specialist pollinator of two poppy genera, Arctomecon and Argemone (Papaveraceae), and is being considered for listing under the US Endangered Species Act along with one of its pollinator hosts, the Las Vegas bearpoppy (Arctomecon californica). Here, we present a near chromosome-level genome of the Mojave poppy bee to provide a genomic resource that will aid conservation efforts and future research. We isolated DNA from a single, small (<7 mm), male specimen collected using non-ideal preservation methods then performed whole-genome sequencing using PacBio HiFi technology. After quality and contaminant filtering, the final draft genome assembly is 327 Mb, with an N50 length of 17.5 Mb. Annotated repetitive elements compose 37.3% of the genome, although a large proportion (24.87%) of those are unclassified repeats. Additionally, we annotated 18,245 protein-coding genes and 19,433 transcripts. This genome represents one of only a few genomes from the large bee family Andrenidae and one of only a few genomes for pollinator specialists. We highlight both the potential of this genome as a resource for future research, and how high-quality genomes generated from small, non-ideal (in terms of preservation) specimens could facilitate biodiversity genomics.

Bees without Flowers: Before Peak Bloom, Diverse Native Bees Find Insect-Produced Honeydew Sugars.

Bee foragers respond to complex visual, olfactory, and extrasensory cues to optimize searches for floral rewards. Their abilities to detect and distinguish floral colors, shapes, volatiles, and ultraviolet signals and even gauge nectar availability from changes in floral humidity or electric fields are well studied. Bee foraging behaviors in the absence of floral cues, however, are rarely considered. We observed 42 species of wild bees visiting inconspicuous, nonflowering shrubs during early spring in a protected Mediterranean habitat. We determined experimentally that these bees were accessing sugary honeydew secretions from scale insects without the aid of standard cues. While honeydew use is known among some social Hymenoptera, its use across a diverse community of solitary bees is a novel observation. The widespread ability of native bees to locate and use unadvertised, nonfloral sugars suggests unappreciated sensory mechanisms and/or the existence of an interspecific foraging network among solitary bees that may influence how native bees cope with scarcity of floral resources and increasing environmental change.

Patterns of widespread decline in North American bumble bees.

Bumble bees (Bombus) are vitally important pollinators of wild plants and agricultural crops worldwide. Fragmentary observations, however, have suggested population declines in several North American species. Despite rising concern over these observations in the United States, highlighted in a recent National Academy of Sciences report, a national assessment of the geographic scope and possible causal factors of bumble bee decline is lacking. Here, we report results of a 3-y interdisciplinary study of changing distributions, population genetic structure, and levels of pathogen infection in bumble bee populations across the United States. We compare current and historical distributions of eight species, compiling a database of >73,000 museum records for comparison with data from intensive nationwide surveys of >16,000 specimens. We show that the relative abundances of four species have declined by up to 96% and that their surveyed geographic ranges have contracted by 23-87%, some within the last 20 y. We also show that declining populations have significantly higher infection levels of the microsporidian pathogen Nosema bombi and lower genetic diversity compared with co-occurring populations of the stable (nondeclining) species. Higher pathogen prevalence and reduced genetic diversity are, thus, realistic predictors of these alarming patterns of decline in North America, although cause and effect remain uncertain.

Pollination Biology and Life History Traits of the Rare Las Vegas Bear Poppy (Arctomecon californica).

Arctomecon californica, the Las Vegas bear poppy, is a rare plant found only in the eastern Mojave Desert of North America. Because of recent declines in the populations of this endemic plant, conservationists are currently seeking protection for A. californica under the US Endangered Species Act. In this study, we investigated the natural history of A. californica and documented insect visitors potentially pollinating A. californica in Clark County, Nevada. We find that the populations of A. californica fluctuate from year to year, with many populations declining by over 90% from 2021 to 2022. The pollinator communities of A. californica also vary from year to year. In some years, specialist bees in the genus Perdita make up the majority of pollinators, while in other years, generalist bees like Apis mellifera and Hylaeus dominate. Furthermore, we confirm what previous work has suggested, that A. californica requires pollinators to set seed, yet not all insect visitors are good pollinators. This work provides useful natural history information about the Las Vegas bear poppy, which will be informative to conservationists designing strategies to protect this imperiled species.

Interspecific geographic distribution and variation of the pathogens Nosema bombi and Crithidia species in United States bumble bee populations.

Several bumble bee (Bombus) species in North America have undergone range reductions and rapid declines in relative abundance. Pathogens have been suggested as causal factors, however, baseline data on pathogen distributions in a large number of bumble bee species have not been available to test this hypothesis. In a nationwide survey of the US, nearly 10,000 specimens of 36 bumble bee species collected at 284 sites were evaluated for the presence and prevalence of two known Bombus pathogens, the microsporidium Nosema bombi and trypanosomes in the genus Crithidia. Prevalence of Crithidia was ≤10% for all host species examined but was recorded from 21% of surveyed sites. Crithidia was isolated from 15 of the 36 Bombus species screened, and were most commonly recovered from Bombus bifarius, Bombus bimaculatus, Bombus impatiens and Bombus mixtus. Nosema bombi was isolated from 22 of the 36 US Bombus species collected. Only one species with more than 50 sampled bees, Bombus appositus, was free of the pathogen; whereas, prevalence was highest in Bombus occidentalis and Bombus pensylvanicus, two species that are reportedly undergoing population declines in North America. A variant of a tetranucleotide repeat in the internal transcribed spacer (ITS) of the N. bombi rRNA gene, thus far not reported from European isolates, was isolated from ten US Bombus hosts, appearing in varying ratios in different host species. Given the genetic similarity of the rRNA gene of N. bombi sampled in Europe and North America to date, the presence of a unique isolate in US bumble could reveal one or more native North American strains and indicate that N. bombi is enzootic across the Holarctic Region, exhibiting some genetic isolation.

Predicting changes in bee assemblages following state transitions at North American dryland ecotones.

Drylands worldwide are experiencing ecosystem state transitions: the expansion of some ecosystem types at the expense of others. Bees in drylands are particularly abundant and diverse, with potential for large compositional differences and seasonal turnover across ecotones. To better understand how future ecosystem state transitions may influence bees, we compared bee assemblages and their seasonality among sites at the Sevilleta National Wildlife Refuge (NM, USA) that represent three dryland ecosystem types (and two ecotones) of the southwestern U.S. (Plains grassland, Chihuahuan Desert grassland, and Chihuahuan Desert shrubland). Using passive traps, we caught bees during two-week intervals from March-October, 2002-2014. The resulting dataset included 302 bee species and 56 genera. Bee abundance, composition, and diversity differed among ecosystems, indicating that future state transitions could alter bee assemblage composition in our system. We found strong seasonal bee species turnover, suggesting that bee phenological shifts may accompany state transitions. Common species drove the observed trends, and both specialist and generalist bee species were indicators of ecosystem types or months; these species could be sentinels of community-wide responses to future shifts. Our work suggests that predicting the consequences of global change for bee assemblages requires accounting for both within-year and among-ecosystem variation.

Bee species checklist of the San Francisco Peaks, Arizona.

BACKGROUND: Here we present a checklist of the bee species found on the C. Hart Merriam elevation gradient along the San Francisco Peaks in northern Arizona. Elevational gradients can serve as natural proxies for climate change, replacing time with space as they span multiple vegetation zones over a short geographic distance. Describing the distribution of bee species along this elevation gradient will help predict how bee communities might respond to changing climate. To address this, we initiated an inventory associated with ecological studies on pollinators that documented bees on the San Francisco Peaks. Sample sites spanned six life zones (vegetation zones) on the San Francisco Peaks from 2009 to 2019. We also include occurrence data from other studies, gathered by querying the Symbiota Collection of Arthropods Network (SCAN) portal covering the San Francisco Peaks region (hereafter referred to as "the Peaks"). NEW INFORMATION: Our checklist reports 359 bee species and morphospecies spanning five families and 46 genera that have been collected in the Peaks region. Prior to our concerted sampling effort there were records for 155 bee species, yet there has not been a complete list of bee species inhabiting the Peaks published to date. Over a 10-year period, we documented an additional 204 bee species inhabiting the Peaks. Our study documents range expansions to northern Arizona for 15 species. The majority of these are range expansions from either southern Arizona, southern Utah, or the Rocky Mountain region of Colorado. Nine species are new records for Arizona, four of which are the southernmost record for that species. An additional 15 species are likely undescribed.

Decades of native bee biodiversity surveys at Pinnacles National Park highlight the importance of monitoring natural areas over time.

Thousands of species of bees are in global decline, yet research addressing the ecology and status of these wild pollinators lags far behind work being done to address similar impacts on the managed honey bee. This knowledge gap is especially glaring in natural areas, despite knowledge that protected habitats harbor and export diverse bee communities into nearby croplands where their pollination services have been valued at over $3 billion per year. Surrounded by ranches and farmlands, Pinnacles National Park in the Inner South Coast Range of California contains intact Mediterranean chaparral shrubland. This habitat type is among the most valuable for bee biodiversity worldwide, as well as one of the most vulnerable to agricultural conversion, urbanization and climate change. Pinnacles National Park is also one of a very few locations where extensive native bee inventory efforts have been repeated over time. This park thus presents a valuable and rare opportunity to monitor long-term trends and baseline variability of native bees in natural habitats. Fifteen years after a species inventory marked Pinnacles as a biodiversity hotspot for native bees, we resurveyed these native bee communities over two flowering seasons using a systematic, plot-based design. Combining results, we report a total of 450 bee species within this 109km2 natural area of California, including 48 new species records as of 2012 and 95 species not seen since 1999. As far as we are aware, this species richness marks Pinnacles National Park as one of the most densely diverse places known for native bees. We explore patterns of bee diversity across this protected landscape, compare results to other surveyed natural areas, and highlight the need for additional repeated inventories in protected areas over time amid widespread concerns of bee declines.

Phylogeny and biogeography of bees of the tribe Osmiini (Hymenoptera: Megachilidae).

The Osmiini (Megachilidae) constitute a taxonomically and biologically diverse tribe of bees. To resolve their generic and suprageneric relationships, we inferred a phylogeny based on three nuclear genes (Elongation factor 1-alpha, LW-rhodopsin and CAD) applying both parsimony and Bayesian methods. Our phylogeny, which includes 95 osmiine species representing 18 of the 19 currently recognized genera, is well resolved with high support for most basal nodes. The core osmiine genera were found to form a well-supported monophyletic group, but four small genera, Noteriades, Afroheriades,Pseudoheriades and possibly Ochreriades, formerly included in the Osmiini, do not appear to belong within this tribe. Our phylogeny results in the following taxonomic changes: Stenosmia and Hoplosmia are reduced to subgeneric rank in Hoplitis and Osmia, respectively, Micreriades is recognized as a subgenus in Hoplitis and the subgenus Nasutosmia is transferred from Hoplitis to Osmia. We inferred a biogeographic scenario for the Osmiini applying maximum likelihood inference and models of character evolution. We provide evidence that the Osmiini originated in the Palearctic, and that extensive exchanges occurred between the Palearctic and the Nearctic. The latter finding may relate to the fact that many osmiine species nest in wood or in stems, facilitating dispersal by overseas transport of the nests.

Checklist of bees (Hymenoptera: Apoidea) from managed emergent wetlands in the lower Mississippi Alluvial Valley of Arkansas.

BACKGROUND: Here we present the results from a two-year bee survey conducted on 18 managed emergent wetlands in the lower Mississippi Alluvial Valley of Arkansas, USA. Sample methods included pan traps, sweep netting and blue-vane traps. We document 83 bee species and morphospecies in 5 families and 31 genera, of which 37 species represent first published state records for Arkansas. The majority of species were opportunistic wetland species; only a small number were wetland-dependent species or species largely restricted to alluvial plains. NEW INFORMATION: We present new distributional records for bee species not previously recorded in managed emergent wetlands and report specimens of thirty-seven species for which no published Arkansas records exist, expanding the known ranges of Ceratina cockerelli, Diadasia enavata, Lasioglossum creberrimum, Svastra cressonii and Dieunomia triangulifera. We also distinguish opportunistic wetland bee species from wetland-dependent and alluvial plain-restricted species.

Effects of the insecticide phosmet on solitary bee foraging and nesting in orchards of Capitol Reef National Park, Utah.

Capitol Reef National Park, in southcentral Utah, contains 22 small orchards planted with antique fruit varieties by Mormon pioneers beginning over a century ago. The orchards continue to be managed in a pick-and-pay program, which includes spraying with phosmet to suppress codling moth (Cydia pomonella L.). The park is also home to a rich diversity of flowering plants, many of which are rare, bee-pollinated, and have populations within 1 km of the orchards. Over 3 yr, we studied the short-term effects of phosmet spraying on bee populations: (1) foraging on plants within the orchard understory and adjacent to it; and (2) nesting in, and at several distances from, the orchards. We recorded a rich bee fauna (47 taxa) in the orchards and on plants nearby. In 2 yr (2002 and 2004), we found no difference in the number of native bee visits to several species of plants flowering in and near to orchards immediately before and 1 d after spraying. Conversely, our nesting studies using the semidomesticated alfalfa leafcutting bee, Megachile rotundata (F.), showed strong significant declines in the number of adult males, nesting females, and progeny production subsequent to spraying at distances up to 160 m from sprayed orchards where the bees were presumably foraging. We showed that M. rotundata is negatively affected by phosmet spraying and suggest that caution should be exercised in its use in areas where bees are apt to forage.

A review of the cleptoparasitic bee genus Townsendiella (Apidae, Nomadinae, Townsendiellini), with the description of a new species from Pinnacles National Park.

The cleptoparasitic bee genus Townsendiella Crawford (Nomadinae, Townsendiellini) is a rare group restricted to the southwestern United States and adjacent Mexico, whose taxonomy and biology remain poorly known. This paper describes Townsendiella ensifera sp. n., the first known record of this genus from Pinnacles National Park. A key to the species of the genus is provided. Several potential areas of future research are also discussed.

Taxonomic utility of niche models in validating species concepts: A case study in Anthophora (Heliophila) (Hymenoptera: Apidae).

Taxonomy has far-reaching effects throughout biology, and incorrect taxonomy can be detrimental in many ways. Polymorphic species complexes, many of which exist in the bee genus Anthophora Latreille, lend themselves to such difficulties. This study employs environmental niche mapping (ENM) and traditional morphological analyses to investigate the validity of the subjective synonymy of Anthophora (Heliophila) curta Provancher with the senior synonym A. squammulosa Dours. Eleven of fifty morphological characters consistently differentiate the two putative species, with an additional five characters sometimes separating them. Additionally, based on over 1000 georeferenced museum specimens, the geographic ranges of the two taxa do not overlap. The two entities also react differently to the bioclimatic variables based on correlation analysis. We further tested the two-species hypothesis by constructing ENMs with informative bioclimatic variables associated with locality records. Their modelled distributions overlapped less than 1%, suggesting discrete environmental boundaries. The variables which contributed most to each species' model also differed. These differences are explored in relation to their habitats. The combined morphological and biogeographic analysis indicates that A. curta and A. squammulosa are distinct species. Based on the accumulated evidence the synonymy is formally rejected and A. curta is recognized as a valid species. Five additional taxa (A. bispinosa Cockerell, A. franciscana Cockerell, A. usticauda Cockerell, A. u. cinerior Cockerell, A. zamoranella Cockerell) are newly synonymized with A. squammulosa and Anthophora curta var. melanops Cockerell is newly synonymized with A. curta. Implications outside of taxonomy are discussed. 

Origins, evolution, and diversification of cleptoparasitic lineages in long-tongued bees.

The evolution of parasitic behavior may catalyze the exploitation of new ecological niches yet also binds the fate of a parasite to that of its host. It is thus not clear whether evolutionary transitions from free-living organism to parasite lead to increased or decreased rates of diversification. We explore the evolution of brood parasitism in long-tongued bees and find decreased rates of diversification in eight of 10 brood parasitic clades. We propose a pathway for the evolution of brood parasitic strategy and find that a strategy in which a closed host nest cell is parasitized and the host offspring is killed by the adult parasite represents an obligate first step in the appearance of a brood parasitic lineage; this ultimately evolves into a strategy in which an open host cell is parasitized and the host offspring is killed by a specialized larval instar. The transition to parasitizing open nest cells expanded the range of potential hosts for brood parasitic bees and played a fundamental role in the patterns of diversification seen in brood parasitic clades. We address the prevalence of brood parasitic lineages in certain families of bees and examine the evolution of brood parasitism in other groups of organisms.

Taxonomic notes on the small resin bees Hypanthidioides subgenus Michanthidium (Hymenoptera, Megachilidae).

As part of ongoing investigations on anthidiine bees, the type of Anthidium albitarse Friese was found to be conspecific with one of the two species of the small resin bees Hypanthidioides subgenus Michanthidium. The new combination, Hypanthidioides (Michanthidium) albitarsis, is the oldest name, resulting in Gnathanthidium sakagamii Urban as a new junior synonym. The previously unknown male of the second species, Hypanthidioides ferrugineus, is described and figured, including the genitalic structure and associated sterna. Males and females of Hypanthidioides ferrugineus have been collected from flowers of Cuphea sp. (Lythraceae).

Two new species of Paratrigona and the male of Paratrigona ornaticeps (Hymenoptera, Apidae).

Two distinctive new species of the Neotropical stingless bee genus Paratrigona Schwarz from Ecuador and Paraguay are described and figured. The Ecuadorian species, Paratrigona scapisetosasp. n.,belongs to the haeckeli-lineatifrons group and is easily distinguished from its congeners by the unique shape and pubescence of the antennal scape, which is distinctly convex on its outer margin and bears thick, long, simple hairs along its inner margin. The Paraguayan species, Paratrigona wasbauerisp. n.,belongs to the lineata group and is easily distinguished by the pattern of body pubescence in both sexes and male genitalic characters. The male of the Mesoamerican species Paratrigona ornaticeps (Schwarz) is described and figured. New geographical records for Paratrigona impunctata and Paratrigona opaca, and an updated key to the haeckeli-lineatifrons and lineata species groups are provided.