Molecular and chemical characters to evaluate species status of two cuckoo bumblebees: Bombus barbutellus and Bombus maxillosus (Hymenoptera, Apidae, Bombini)

Systematic Entomology (Impact Factor: 2.55). 07/2011; DOI: 10.1111/j.1365-3113.2011.00576.x

ABSTRACT Many methods, based on morphological, molecular or chemical characters, have been used to address the question of species taxonomic status. Integrative taxonomy aims to define stronger supported taxonomic hypotheses by considering complementary datasets from different characters. By following an integrative approach, the present study includes molecular, chemical and morphological criteria to establish the taxonomic status of two rare and doubtful cuckoo bumblebee taxa: Bombus (Psithyrus) barbutellus and Bombus (Psithyrus) maxillosus. These two sympatric taxa are discriminated by few morphological criteria (mainly wing darkness and hair length). We used these morphological character diagnoses to establish an a priori status of our samples (23 specimens). We developed a combined molecular dataset from one nuclear gene, elongation factor 1α (EF-1α), and one mitochondrial gene, cytochrome c oxidase subunit I (COI ), spanning 1623 bp, and a chemical dataset of sexual marking pheromones (73 compounds). The molecular data were subjected to maximum-likelihood and Bayesian phylogenetic inference under partitioned model and maximum parsimony. The chemical data were analysed by clustering and the two-group k-means method to test divergences between the two species. The resulting phylogenetic trees show no consistent divergence between the two taxa. Moreover, we found no divergence in the sexual marking pheromones in the clustering and two-group k-means analyses. These converging results support the conspecificity of both taxa. Nonetheless, our determinations using the traditional morphological criteria separated our samples into two taxa. We conclude that the morphological criteria seem to relate to intraspecific variations: B. maxillosus is regarded as a syn.n. of B. barbutellus.


Available from: Patrick Lhomme, Jun 14, 2015
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    ABSTRACT: Thanks to the EU FP7 project STEP (Potts et al. 2011), over one million bumblebee records from all over Europe have been collated. Based on data from 1970 to 2000 we modelled the current climatic niche for almost all European species (56 out of 69) and projected future climatically suitable conditions based on three climate change scenarios (SEDG, BAMBU and GRAS) for the years 2050 and 2100. Due to limited knowledge of actual bumblebee dispersal, we made two extreme assumptions: (i) the species has full dispersal abilities (meaning that the species is able to spread all over its suitable area) or (ii) the species is unable to disperse at all (i.e. that changes in climatic conditions can only lead to projected range retractions). However, to aid the assessment as to which of these two extreme assumptions are more likely to meet reality, we also provide a rough indication of the species’ potential dispersal ability based on the ecology of the different bumblebees. The book includes up-to-date pin-pointed maps and photographs of all West-Palaearctic bumblebee species, including Russian and Near-Orient ones. Since bumblebees are mainly adapted to colder conditions, they appear as highly vulnerable to climate change. In 2100, depending on the scenario of climate change, up to 36% of the European bumblebees are projected to be at an high climatic risk (i.e. losing more than 80% of their current range), 41% will be at risk (loss between 50% and 80%). Non-modelled species are all very rare and localised and their ranges are most likely to be shrinking considerably under all of the scenarios. Only a few species are projected to benefit from climate change and can potentially enlarge their current distributions in Europe, such as B. argillaceus and B. haematurus. As expected, the three scenarios considerably differed in their projections for 2100. While under the moderate change scenario (SEDG) only five species are projected to be at the verge of extinction by 2100, twenty species are at particularly high risk under the intermediate change scenario (BAMBU). Under the most severe change scenario (GRAS) as many as 34 species are projected to lose almost all of their climatically suitable area. Also the ability to keep track with climate change has a considerable impact of the projected changes. For instance, under the most severe climate change scenario (GRAS) nine species are at an extremely high climatic risk when full dispersal is assumed for all of them. However, under the assumption of no dispersal within the next 100 years 34 species would fall into this category. When potential dispersal abilities, inferred from species traits and their auto-ecologies, are considered to decide for which species no or full dispersal assumptions are more realistic, it seems that up to 3 species might expand their ranges by 2100, no species is likely to remain at the status quo, and 25 species would be at an extremely high climatic risk. We also found that for many species (about 30%), especially the cold-adapted ones in Alpine and Arctic regions (e.g. B. alpinus, B. balteatus, B. hyperboreus and B. polaris) their dispersal abilities are actually irrelevant for the assessment of their future fate because climate change will only lead to reductions of areas with suitable climatic conditions while no extra suitable regions will emerge. 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Finally, the idea of assisted migration, i.e. purposeful anthropogenic translocations, seems appealing at first sight for species whose original distributional areas are projected to shrink tremendously and cannot move to suitable areas because of natural or anthropogenic barriers. However, the feasibility of such actions is still questionable. To conclude, climatic risks for bumblebees can be extremely high, depending on the future development of human society, and the corresponding effects on the climate, strong mitigation strategies are needed to preserve this important species group and to ensure the sustainable provision of pollination services, to which they considerably contribute.
    02/2015: pages 1-246; Pensoft Publishers, Sofia., ISBN: 978-954-642-769-4 (e-book), 978-954-642-768-7 (hardback)
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    ABSTRACT: Many species display local variations in pre-mating signals and in mating preferences. This may lead to discrimination against potential foreign mates that may ultimately lead to reproductive isolation. However, the extent to which population differentiation in mating cues affects the species recognition has received little empirical support. Here we investigate the consequence of geographic differentiation in male reproductive traits on female preferences to these traits in Bombus terrestris. We characterise (1) the geographic differentiation in male cephalic labial gland secretions (CLGS), a key trait for mate attraction and (2) the preference of virgin females to the CLGS of different subspecies. Our results show geographic CLGS differences parallel with divergences in female preferences for these secretions. This geographic CLGS differentiation in males, along with female preference for sympatric males could lead to or reflect a premating isolation among subspecies.
    Apidologie 02/2015; early view. DOI:10.1007/s13592-015-0349-y · 1.54 Impact Factor
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    ABSTRACT: The evolution of signals and reproductive traits involved in the pre-mating recognition has been in focus of abundant research in several model species group such as bumblebees (genus Bombus). However, the most studied bumblebee reproductive trait, the male cephalic labial gland secretions (CLGS), remains unknown among bumblebee species from South America. In this study we investigated the CLGS of five South American bumblebees of the subgenera Thoracobombus (Bombus excellens, B. atratus) and Cullumanobombus (B. rubicundus, B. hortulanus and B. melaleucus) comparing their secretions to those of European closely related species. Our results show an obvious interspecific differentiation in all subgenera. The interspecific differentiation in Thoracobombus involves different compounds with a large abundance (main compounds) while all Cullumanobombus share the same main components. This suggests that in Cullumanobombus subgenus differentiation in minor components could lead to species discrimination.
    Chemistry & Biodiversity 01/2015; accepted. · 1.80 Impact Factor