Climate plays a key role in shaping population trends and determining the geographic distribution of species because of limits in species' thermal tolerance. An evaluation of species tolerance to temperature change can therefore help predict their potential spatial shifts and population trends triggered by ongoing global warming. We assessed inter-and intraspecific variations in heat resistance in relation to body mass, local mean temperatures, and evolutionary relationships in 39 bumblebee species, a major group of pollinators in temperate and cold ecosystems, across 3 continents, 6 biomes, and 20 regions (2386 male specimens). Based on experimental bioassays, we measured the time before heat stupor of bumblebee males at a heatwave temperature of 40°C. Interspecific variability was significant, in contrast to interpopulational variability, which was consistent with heat resistance being a species-specific trait. Moreover, cold-adapted species are much more sensitive to heat stress than temperate and Mediterranean species. Relative to their sensitivity to extreme temperatures, our results help explain recent population declines and range shifts in bumblebees following climate change.

Phenotypic polymorphism can constitute an inherent challenge for species delimitation. This issue is exemplified in bumble bees (Bombus), where species can exhibit high colour variation across their range, but otherwise exhibit little morphological variation to distinguish them from close relatives. We examine the species status of one of the most abundant North American bumble bees, Bombus bifarius Cresson, which historically comprised two major taxa, bifarius s.s. and nearcticus. These lineages are recognized primarily by red and black variation in their mid-abdominal coloration; however, a continuum from black (nearcticus) to red (bifarius s.s.) variation has led to their historic synonymization. Integrating mitochondrial and nuclear data and whole-genome sequencing, we reveal a high level of both mitochondrial and nuclear divergence delimiting two morphologically cryptic species -the red bifarius s.s. and the colour-variable (black to red) nearcticus. Population genomic analysis supports an absence of recent genomic admixture and a strong population structure between the two clades, even in sympatry. Species distribution models predict partially differentiated niches between the genetically inferred clades with annual precipitation being a leading differentiating variable. The bifarius s.s. lineage also occupies significantly higher elevations, with regions of sympatry being among the highest elevations in nearcticus. Our data also support a subspecies-level divergence between the broadly distributed nearcticus and the island population vancouverensis. In this paper, we formally recognize the two species, Bombus bifarius Cresson and Bombus vancouverensis Cresson, the latter including the subspecies B. vancouverensis vancouverensis comb.n. and B. vancouverensis nearcticus comb.n., with vancouverensis the name bearer due to year priority.

1. Bumble bees (Bombus) are a group of eusocial bees with a strongly generalised feeding pattern, collecting pollen from many different botanical families. Though predominantly generalists, some bumble bee species seem to have restricted dietary choices. It is unclear whether restricted diets in bumble bees are inherent or a function of local conditions due to a lack of data for many species across different regions.2. The objective of this study was to determine whether bumble bee species displayed specific patterns of pollen collection, and whether patterns were influenced by phylogenetic relatedness or tongue length, a trait known to be associated with structuring floral visitation.3. Bumble bee pollen collection patterns were quantified from 4,132 pollen loads taken from 58 bumble bee species, representing 24% of the pollen-collecting diversity of this genus. 4. Phylogenetic trait mapping showed a conserved pattern of dietary dissimilarity across species, but not for dietary breadth. Dietary dissimilarity was driven by collection of Fabaceae, with the most similar species collecting around 50%-60% of their diet from this botanical family. The proportion of the diet collected from Fabaceae also showed a conserved phylogenetic signal. Greater collection of Fabaceae was associated with longer tongue lengths, with shorter tongued species focusing on alternative botanical families. However, this result was largely driven by phylogenetic relatedness, not tongue length per se.5. These results demonstrate that, though generalists, bumble bees are still subject to dietary restrictions that constrain their foraging choices. These dietary constraints have implications for their persistence should their core resources decline in abundance.

Global changes are severely affecting pollinator insect communities worldwide, resulting in repeated patterns of species extirpations and extinctions. Whilst negative population trends within this functional group have understandably received much attention in recent decades, another facet of global changes has been overshadowed: species undergoing expansion. Here, we review the factors and traits that have allowed a fraction of the pollinating entomofauna to take advantage of global environmental change. Sufficient mobility, high resistance to acute heat stress, and inherent adaptation to warmer climates appear to be key traits that allow pollinators to persist and even expand in the face of climate change. An overall flexibility in dietary and nesting requirements is common in expanding species, although niche specialization can also drive expansion under specific contexts. The numerous consequences of wild and domesticated pollinator expansions, including competition for resources, pathogen spread, and hybridization with native wildlife, are also discussed. Overall, we show that the traits and factors involved in the success stories of expanding pollinators are mostly species specific and context dependent, rendering generalizations of ‘winning traits’ complicated. This work illustrates the increasing need to consider expansion and its numerous consequences as significant facets of global changes and encourages efforts to monitor the impacts of expanding insect pollinators, particularly exotic species, on natural ecosystems.

Bumble bees (Bombus spp.) are a widespread corbiculate lineage (Apinae: Corbiculata: Bombini), mostly found among temperate and alpine ecosystems. Approximately 260 species have been recognized and grouped recently into a simplified system of 15 subgenera. Most of the species are nest-building and primitively eusocial. Species of Bombus have been more intensely studied than any other lineages of bees with the exception of the honey bees. However, most bumble bee fossils are poorly described and documented, making their placement relative to other Bombus uncertain. A large portion of the known and presumed bumble bee fossils were re-examined in an attempt to better understand their affinities with extant Bombini. The taxonomic affinities of fossil specimens were re-assessed based on morphological features and previous descriptions, and for 13 specimens based on geometric morphometrics of forewing shape. None of the specimens coming from Eocene and Oligocene deposits were assigned within the contemporary shape space of any subgenus of Bombus. It is shown that Calyptapis florissantensis Cockerell, 1906 (Eocene-Oligocene boundary, Florissant shale, Colorado, USA) and Oligobombus cuspidatus Antropov, 2014 (Late Eocene, Bembridge Marls) likely belong to stem-group Bombini. Bombus anacolus Zhang, 1994, B. dilectus Zhang, 1994, B. luianus Zhang, 1990 (Middle Miocene, Shanwang Formation), as well as B. vetustus Rasnitsyn & Michener, 1991 (Miocene, Botchi Formation) are considered as species inquirenda. In the Miocene, affinities of fossils with derived subgenera of Bombus s. l. increased, and some are included in the shape space of contemporary subgenera: Cullumanobombus (i.e., B. pristinus Unger, 1867, B. randeckensis Wappler & Engel, 2012, and B. trophonius Prokop, Dehon, Michez & Engel, 2017), Melanobombus (i.e., B. cerdanyensis Dehon, De Meulemeester & Engel, 2014), and Mendacibombus (i.e., B. beskonakensis (Nel & Petrulevičius, 2003), new combination), agreeing with previous estimates of diversification.

Iberia has one of the richest bee faunas in the world, and the genus Andrena is no exception with around 200 species known from the Peninsula. The fauna of Andrena was largely revised in the 1970s, but since then, it has received little attention. Molecular investigation of the taxonomically challenging subgenus Taeniandrena has revealed that the situation is more complicated than previously thought with several cryptic and overlooked species. From the species allied to Andrena (T. ) gelriae van der Vecht, 1927, Andrena (T. ) gredana Warncke, 1975 stat. nov. from Spain and Portugal is raised to species status, and Andrena (T. ) levante Wood & Praz sp. nov. from southeastern Spain is newly described. Furthermore, Andrena (T. ) benoisti Wood & Praz sp. nov. is described, having previously been referred to as Andrena (T. ) wilkella beaumonti Benoist, 1961. Andrena (T. ) beaumonti stat. rev. is itself distinct and restricted to the High Atlas Mountains of Morocco. Outside of the subgenus Taeniandrena, Andrena (Euandrena) fortipunctata Wood sp. nov. and Andrena (Charitandrena) hattorfiana nigricauda Wood subsp. nov. are described from Spain, and Andrena (Notandrena) juliana Wood sp. nov. is described from Spain and Portugal. The male of Andrena (Lepidandrena) baetica Wood, 2020 is also described. Andrena (Euandrena) impressa Warncke, 1967 stat. nov. is raised to species status, displaying a West Mediterranean distribution. Finally, a further two species of Andrena are newly recorded for Spain, Andrena laurivora Warncke, 1974 and Andrena confinis Stoeckhert, 1930. Altogether, these findings reinforce the fact that our understanding of the taxonomy and distribution of Andrena in southern Europe remains incomplete.

Aim Among the numerous anthropogenic pressures threatening biodiversity, habitat destruction and climate change are pointed to as dominant. In response, a number of mitigation strategies are elaborated to save endangered living organisms. However, the taxonomic level and geographical extent at which conservation strategies should be designed and implemented remain generally unclear. Here, we aim to assess and discuss the importance to apply conservation strategies at an appropriate taxonomic scale. For this purpose, we focus our analyses on bumblebees (genus Bombus), a group of critically important and endangered pollinators. Location West‐Palaearctic. Methods We use a species distribution modelling approach to investigate and compare climatic and habitat‐related variables associated with the distribution of West‐Palaearctic bumblebees. Our analyses are based on a data set gathering more than 125,000 unique observation points for 68 species. Results We highlight species‐specific associations with climatic and land cover variables, depicting the strong relevance of taxon‐specific mitigation strategies for the conservation of those key pollinators. We also identify that the occurrence probability of localized and widespread species is mostly predicted by specific land cover characteristics and climatic conditions, respectively. Finally, we report the general absence of phylogenetic signal associated with the relative importance of each environmental variable in species distribution models, underlining the difficulty to predict species‐specific environmental requirements based on evolutionary relationships. Main conclusions In the light of these results, we conclude that climate change and landscape destruction are not expected to drive the fate of all bumblebee species in a same direction, even for phylogenetically close lineages. We argue in favour of geographically and taxonomically adapted conservation strategies and discuss the limitations of untargeted action plans for species with different climatic/habitat requirements.

While many bee species are experiencing population declines, some host plant generalist bees remain common in Europe, partly because they seem able to shift to new resources. However, foraging on a new alternative plant, such as an invasive species, can modify diet quality and have a potentially detrimental effect on bee health. Herein, we investigated whether the spread of the invasive plant Impatiens glandulifera affects Bombus pascuorum population regarding parasite prevalence, genetic structure, and nest density in Belgium. While no difference in bumble bee genetic structure was detected between invaded and uninvaded sites, we show that I. glandulifera occurrence was significantly correlated with a decrease in the prevalence of Apicystis bombi but not the prevalence of three other parasite species (i.e., Crithidia bombi, Nosema bombi, Nosema ceranae, and Nosema sp.). Regarding our investigations, this effect was likely not due to variation in local bumble bee population fitness before I. glandulifera flowering, nor to the relative abundance of other pollinators such as Apis mellifera, but the unique chemical composition (i.e., polyphenol rich) of the pollen of I. glandulifera remained as an interesting hypothesis. Whereas B. pascuorum queens probably colonize all the potential nesting sites in an area, invaded by I. glandulifera or not, the abundance of polyphenol ampelopsin in pollen from I. glandulifera pollen might reduce local parasite prevalence. Our field study confirms that bumble bee parasite prevalence is potentially related to the particular chemical composition of collected pollen. Plant traits such as secondary metabolite occurrence could play a key role in the health and conservation of bumble bees.