Adding attractive semio-chemical trait refines the taxonomy of Alpinobombus (Hymenoptera: Apidae)

Abstract

Species taxonomy of bumblebees (Bombus Latreille, 1802) is well known to be problematic due to a potentially high intra-specific variability of morphological traits while different species can converge locally to the same color pattern (cryptic species). Assessing species delimitation remains challenging because it requires to arbitrarily select variable traits whose accuracy continues to be debated. Integrative taxonomic approach seems to be very useful for this group as different independent traits are assessed to propose a rational taxonomic hypothesis. Among operational criteria to assess specific status, the reproductive traits involved in the pre-mating recognition (i.e., the male cephalic labial gland secretions, CLGS) have been premium information. Since these secretions are supposed to be species-specific, these chemical traits can bring essential information where species delimitation is debated. Here, we describe and compare the CLGS of 161 male specimens of nine Alpinobombus taxa: alpinus , balteatus , helleri , hyperboreus , kirbiellus, natvigi , neoboreus , polaris , and pyrrhopygus. We aim also to test the congruence between this new information (reproductive traits) and published genetic dataset. Our results emphasized six distinct groups with diagnostic major compounds: (a) alpinus + helleri with hexadec-9-en-1-ol; (b) polaris + pyrrhopygus with two major compounds hexadec-9-en-1-ol and hexadec-9-enal; (c) balteatus with tetradecyl acetate; (d) kirbiellus with geranyl geranyl acetate; (e) hyperboreus + natvigi with octadec-11en-1-ol; (f) neoboreus with octadec-9-en-1-ol. Based on this new information, we can confirm the species status of B. alpinus , B. balteatus , B. hyperboreus , B. kirbiellus , B. neoboreus , and B. polaris . We also confirm the synonymy of helleri (Alps) with alpinus (Sweden). However, the specific status of natvigi (Alaska) and pyrrhopygus (Sweden) is questionable and these taxa do not have specific CLGS composition.bumblebees / species / cephalic labial gland secretions / arcto-alpine distribution / chemical trait

The utility of wing morphometrics for assigning type specimens to cryptic bumblebee species

“…In the global analysis and even more particularly among queens, HRs of these two species were close to 50%, which is particularly low compared with the other species of the subgenus. Two interpretations of these taxa have been argued: either that this is a case of conspecific taxa as species in status nascendi (Martinet et al, 2018) or that these are two separate species in the sense of evolutionarily independent lineages that have not yet been in sympatry, so that substantially divergent mate-recognition systems have not yet evolved (Williams et al, 2019). We confirm that the two species of the other controversial pair (i.e.…”

“…In addition to morphology and genetics, these taxa have also been assessed in terms of cephalic labial gland secretions (CLGS), a pre-mating recognition system in bumblebees (Ayasse & Jarau, 2014). Using this method, B. polaris could not be significantly separated from B. pyrrhopygus, and B. hyperboreus could not be separated from B. natvigi (Martinet et al, 2018). Our results corroborate the similarity of one pair of taxa: B. polaris and B. pyrrhopygus.…”

“…COI barcode) and/or chemical (i.e. male cephalic gland secretion) data published by Williams et al (2015Williams et al ( , 2019 and Martinet et al (2018) (see Table S1 for detailed information). When possible, we sampled 60 specimens for each taxon from five different populations (i.e.…”

“…Based on genetic (Cameron et al, 2007) and morphological features (Richards, 1968;Ito, 1985), this subgenus is supported as a monophyletic taxon but the number of species is still debated mainly because authors follow different species concepts and/or methodologies (e.g. Williams et al, 2016Williams et al, , 2019Martinet et al, 2018;). Recent revisions on skeletal morphology, pheromones (i.e.…”

“…Recent revisions on skeletal morphology, pheromones (i.e. chemical traits) and genetic markers have concluded that there are from four to nine species, including cryptic species, in the last hypothesis (Martinet et al, 2018;Williams et al, 2019; Fig. 1).…”