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

Systematic Entomology (Impact Factor: 2.78). 07/2011; DOI: 10.1111/j.1365-3113.2011.00576.x


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.

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Available from: Patrick Lhomme, Oct 08, 2015
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    • "Sex pheromones are used widely by animals, especially by insects, for mate finding (Wyatt 2014). While pheromones often are studied for pest control (Howse et al. 1998; Witzgall et al. 2010) or for intrinsic interest in their (bio)synthesis (Jurenka 2004; Mori 2004), fewer studies have used sex pheromones as phylogenetic characters of relatedness , or for the verification of species status, even though the idea of using sex pheromones for this purpose has been around for at least half a century (e.g., Calam 1969; Lecocq et al. 2011; Horak et al. 1988; Renou et al. 1988; Sanders 1971; Svensson et al. 2013). Click beetles (Elateridae) are among the most species-rich insect families, consisting of approximately 10,000 described species (Costa et al. 2010). "
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    ABSTRACT: Despite sex pheromones being highly species specific, their use as phylogenetic characters and a tool for the verification of species status are still relatively few compared to use of morphological and molecular characters. Earlier studies revealed that within the click beetle species Idolus picipennis, two types can be separated based on pheromone composition. Gas chromatography/mass spectrometry analysis of pheromone from a third type of Idolus revealed the presence of geranyl hexanoate and geranyl octanoate in a ratio of ca. 1:9. Neryl esters and farnesyl esters, present in the glands of the other two species, are absent in this type. In field experiments, males of all three types were attracted specifically to synthetic mixtures of pheromone resembling their own females. This suggests that cross attraction among different types is unlikely and indicates that they are likely distinct species. Using the large numbers of male beetles caught in pheromone traps, morphological differences between the species were studied and an identification key derived. This study highlights the role of sex pheromones as a powerful tool in integrative taxonomy and systematics to study the phylogenetic position and evolution of taxa and to determine the taxonomic status of cryptic species.
    Journal of Chemical Ecology 08/2015; 41(8). DOI:10.1007/s10886-015-0606-6 · 2.75 Impact Factor
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    • "Therefore, the present more feasible bioassays should be extended to all taxa included in B. terrestris and coupled with other eviden ce (i.e. integrative taxonomy; Lecocq et al. 2011; 2014) and possibly other reproductive traits to conclude to pre-mating isolation. "
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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.
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    • "CGLSs are species-specific secretions synthesized de novo by cephalic labial glands (Žáček et al., 2013). CLGSs consist of a complex mixture of (mainly aliphatic) compounds, with several main components (Coppée et al., 2008; Lecocq et al., 2011). By main compounds, we mean compounds that have the highest relative proportion among all compounds of CLGSs at least in one individual of the taxa. "
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    ABSTRACT: The recent development of integrative taxonomic approach in bumblebees has led to unexpected merging or splitting of several taxa. Here we investigate the taxonomic statuses of one of the most abundant, widespread, and polytypic Palearctic bumblebee: Bombus pascuorum. The latest review of this species includes 24 subspecies. We use (i) an integrative approach based on genetic markers and male chemical reproductive traits and (ii) compared our result with the former classifications. Our result show that all B. pascuorum taxa are conspecific and share the same male chemical reproductive traits. The genetic structure observed in one mitochondrial and two nuclear markers poorly reflect the current subspecific classification. Indeed, the concordance of population genetic differentiation, population geographic distribution, and population colour pattern similarity suggest a different meaningful prospective classification with four taxon complexes: (i) the B. pascuorum dusmeti group including all taxa from Iberian Peninsula and South West France, (ii) B. pascuorum rehbinderi, (iii) B. pascuorum siciliensis, and (iv) B. pascuorum floralis groups (including all other here studied taxa).
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