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International audience; The species international trade leads to multiple non-native invasions. Besides species invasions, commercial exchanges may also contribute to translocation between closely related taxa or allopatric populations. Consequently, preserving endemic taxa and specificity of local populations require to regulate commercial translocations of species or populations. To be efficient such regulation needs a resolved taxonomy and a thorough analysis of the population structure of native taxa/populations. To provide guidelines for an efficient regulation of the trade of Bombus terrestris within its natural range, we analyzed its taxonomy and its population structure using an integrative taxonomic approach. Our results show that B. terrestris translocations involve two species, three subspecies, and several populations with weak differentiation. These different levels of differentiation imply specific and appropriate regulations of translocations with different levels of prioritization. We ultimately assess the relevance of current policies and propose potentially efficient regulations for policy-makers. Such integrative taxonomic approach should be used in other traded polytypic species.

Males of Bombus terrestris (L.) adopt a patrolling behaviour during their nuptial parade using cephalic labial gland (CLG) secretions containing sexual pheromones to attract conspecific virgin queens. The changes in chemical composition of their CLG secretions with age are quite well known. In this study, we investigate the evolution of CLG secretions with age in greater detail and compare behavioural reactions of conspecific virgin queens to the secretions. We show that compounds of CLG secretions follow two profiles. Most of the compounds increase from the first day after emergence until the bees are 15-days-old and then decrease. Others are less abundant in 1 to 15-day-old males and then increase (e.g. tricosane, tricosene, henicosane, tetradecanoic acid, pentacosene, pentacosane, heptacosene, heptacosane, nonacosene and geranylcitronellyl tetradecanoate). Differences in secretion composition lead to preferences of virgin queens for males according to the male’s age. Virgin queens prefer the pheromonal gland secretions of bees of the following ages in decreasing order; 1 day = 3 days < 7 days = 30 days < 15 days < 10 days. The virgin queens are strongly attracted by secretions containing high amounts of 2,3-dihydrofarnesol, 2,3-dihydrofarnesal, ethyl dodecanoate and hexadecanol. On the contrary, geranylcitronellol is more abundant in 30-day-old males.

Studies of bumble bee male sex pheromones are often based on hexane extraction of cephalic labial gland secretions. Here, we propose an alternative extraction procedure based on whole head extractions. To test this method, we compared cephalic parts of the labial glands (CLG) to whole head extractions using high-sensitivity gas chromatography coupled to mass spectrometry (GC–MS) analysis. Two species were analyzed: Bombus terrestris dalmatinus and Bombus ignitus ignitus. We used correlation coefficients, cluster analysis and the two-group k-means method to test the similarity between the two extractions of the two species. We also used the indicator value (IndVal) method to characterize the indicator compounds of each procedure. Statistical analyses reveal a similar compound extraction using both methods. This simplified sample preparation gives reliable results and is more suitable for broad-scale sampling both by specialists and by amateur collectors. Using this method, we provide the first description of the male pheromonal secretions of B. ignitus ignitus and demonstrate that these secretions are very similar to the pheromonal blend of B. terrestris dalmatinus where 44/51 compounds are shared.

Bombus terrestris is one of the most abundant bumblebee species in the West-Palaearctic. Its widespread domestication results in the movement of many colonies. The aim of this paper is to describe the 9 subspecies currently recognised and to list some of their most obvious characteristics. Bombus terrestris is not declining anywhere, on the contrary, its synanthropic spread through domestication may be expected. However, its autumn and winter populations rely on a restricted choice of flowers so they may be threatened locally by scrub clearance and the destruction of their favourite autumnal flowers.

International audience; AbstractMany 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 pre-mating isolation among subspecies.

Among the large number of exocrine glands described in bees, the tarsal glands were thought to be the source of footprint scent marks. However, recent studies showed that the compounds used for marking by stingless bees are secreted by leg tendon instead of tarsal glands. Here, we report on the structure of leg tendon glands in males of Bombus terrestris, together with a description of the chemical composition of their secretions and respective changes of both during the males' lives. The ultrastructure of leg tendon glands shows that the secretory cells are located in three independent regions, separated from each other by unmodified epidermal cells: in the femur, tibia, and basitarsus. Due to the common site of secretion release, the organ is considered a single secretory gland. The secretion of the leg tendon glands of B. terrestris males differs in its composition from those of workers and queens, in particular by (1) having larger proportions of compounds with longer chain lengths, which we identified as wax esters; and (2) by the lack of certain hydrocarbons (especially long chain dienes). Other differences consist in the distribution of double bond positions in the unsaturated hydrocarbons that are predominantly located at position 9 in males but distributed at seven to nine different positions in the female castes. Double bond positions may change chemical and physical properties of a molecule, which can be recognized by the insects and, thus, may serve to convey specific information. The function of male-specific compounds identified from their tendon glands remains elusive, but several possibilities are discussed.

Age-related changes of antennal-active components of male labial gland extracts were studied in two closely related bumblebee species, Bombus terrestris and B. lucorum. In B. terrestris, compounds eliciting electroantennogram (EAG) responses of virgin queens were ethyl dodecanoate, 2,3-dihydrofarnesal, 2,3-dihydrofarnesol, hexadecan-1-ol, octadeca-9,12,15-trien-1-ol, and geranylcitronellol. Compounds that elicited EAG responses from queens of B. lucorum were ethyl dodecanoate, ethyl tetradec-7-enoate, ethyl tetradec-9-enoate, ethyl hexadec-9-enoate, hexadecan-1-ol, hexadec-7-enal, octadeca-9,12-dien-1-ol, octadeca-9,12,15-trien-1-ol, and octadecan-1-ol. Quantities of these compounds in the labial glands changed significantly over the lifetime of the respective males of the two species. In both species, concentrations of the respective compounds reached their maximum within seven days after eclosion. Subsequently, a rapid decrease in the amount of EAG-active compounds occurred in B. terrestris, whereas in B. lucorum the amount of active compounds stayed approximately constant or decreased at a slow rate. Microscopy showed that in B. terrestris secretory cells of the labial glands undergo apoptosis from the fifth to the tenth day of life, whilst in B. lucorum labial gland cells remain unchanged throughout the life of the males.

b Variations of secretions of the cephalic part of the labial glands from four different subspecies of Bombus terrestris, B. t. terrestris, B. t. lusitanicus, B. t. sassaricus, and B. t. dalmatinus, were investigated. 95 compounds were detected in the whole data set: 54 in B. t. terrestris ,5 4 inB. t. lusitanicus, 48 in B. t. sassaricus, and 44 in B. t. dalmatinus. The (E)-2,3-dihydrofarnesol is the main compound in B. t. dalmatinus and B. t. sassaricus, while it is dihydrofarnesyl dodecanoate in B. t. terrestris and B. t. lusitanicus. A principal component analysis produced a pattern showing three well distinct groups corresponding to dalmatinus, sassaricus, and terrestris þ lusitanicus.