Search

Multisource approaches in taxonomy gather different lines of evidence in order to draw strongly supported taxonomic conclusions and constitute the basis of integrative taxonomy. In the case of overlooked taxa with disjunct distributions for which sampling is more challenging, integrative approaches help to propose stable hypotheses at the species and subspecies levels. Here, based on genetic and semio-chemical traits, we performed an integrative taxonomic analysis to evaluate species delimitation hypotheses within a monophyletic group of bumblebees (Hymenoptera, Apidae, Bombus) including the formerly recognised subgenera Eversmannibombus, Laesobombus and Mucidobombus which are now included in the subgenus Thoracobombus. Our results demonstrate the conspecificity of several polytypic taxa, and we formally recognise the subspecies Bombus laesus aliceae comb. nov. Cockerell, 1931, endemic to North Africa, based on its allopatry, unique mitochondrial haplotype and divergent cephalic labial gland secretions. This highlights the need to maintain studying polytypic complexes of bumblebee taxa for which phylogenetic relationships could be still entangled and eventually implement conservation strategies for taxonomically differentiated lineages.

Social parasitic Hymenopterans have evolved morphological, chemical, and behavioral adaptations to overcome the sophisticated recognition and defense systems of their social host to invade host nests and exploit their worker force. In bumblebees, social parasitism appeared in at least 3 subgenera independently: in the subgenus Psithyrus consisting entirely of parasitic species, in the subgenus Alpinobombus with Bombus hyperboreus, and in the subgenus Thoracobombus with B. inexspectatus. Cuckoo bumblebee males utilize species-specific cephalic labial gland secretions for mating purposes that can impact their inquiline strategy. We performed cephalic labial gland secretions in B. hyperboreus, B. inexspectatus and their hosts. Males of both parasitic species exhibited high species specific levels of cephalic gland secretions, including different main compounds. Our results showed no chemical mimicry in the cephalic gland secretions between inquilines and their host and we did not identify the repellent compounds already known in other cuckoo bumblebees.

Cold-adapted species are expected to have reached their largest distribution range during a part of the Ice Ages whereas postglacial warming has led to their range contracting toward high-latitude and high-altitude areas. This has resulted in an extant allopatric distribution of populations and possibly to trait differentiations (selected or not) or even speciation. Assessing inter-refugium differentiation or speciation remains challenging for such organisms because of sampling difficulties (several allopatric populations) and disagreements on species concept. In the present study, we assessed postglacial inter-refugia differentiation and potential speciation among populations of one of the most common arcto-alpine bumblebee species in European mountains, Bombus monticola Smith, 1849. Based on mitochondrial DNA/nuclear DNA markers and eco-chemical traits, we performed integrative taxonomic analysis to evaluate alternative species delimitation hypotheses and to assess geographical differentiation between interglacial refugia and speciation in arcto-alpine species. Our results show that trait differentiations occurred between most Southern European mountains (i.e. Alps, Balkan, Pyrenees, and Apennines) and Arctic regions. We suggest that the monticola complex actually includes three species: B. konradini stat.n. status distributed in Italy (Central Apennine mountains), B. monticola with five subspecies, including B. monticola mathildis ssp.n. distributed in the North Apennine mountains; and B. lapponicus. Our results support the hypothesis that post-Ice Age periods can lead to speciation in cold-adapted species through distribution range contraction. We underline the importance of an integrative taxonomic approach for rigorous species delimitation, and for evolutionary study and conservation of taxonomically challenging taxa.

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-11-en-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.