Conservation of Queen Pheromones Across Two Species of Vespine Wasps

Abstract

Social insects are known for their reproductive division of labor between queens and workers, whereby queens lay the majority of the colony's eggs, and workers engage mostly in non-reproductive tasks. Queens produce pheromones that signal their presence and fertility to workers, which in turn generally remain sterile. Recently, it has been discovered that specific queen-characteristic cuticular hydrocarbons (CHCs) function as queen pheromones across multiple lineages of social insects. In the common wasp, Vespula vulgaris, several long-chain linear alkanes and 3-methylalkanes were shown to act as queen signals. Here, we describe similar bioassays with a related species of highly eusocial vespine wasp, the Saxon wasp, Dolichovespula saxonica. We show that a blend of queen-characteristic hydrocarbons that are structurally related to those of the common wasp inhibit worker reproduction, suggesting conservation of queen pheromones across social wasps. Overall, our results highlight the central importance of CHCs in chemical communication among social insects in general, and as conserved queen pheromones in these social wasps in particular.

Conserved queen pheromones in bumblebees: a reply to Amsalem et al.

“…Secondly, one should start with a common pool of individuals and then randomly allocate them to treatments, rather than allocating different pools (e.g., young and old workers, or big and small workers) to different treatments, producing confounding effects. This can be done by splitting colonies randomly and equally between pheromone treatments (as in e.g., Van Oystaeyen et al, 2014; Holman et al, 2010; Holman, Lanfear & D’Ettorre, 2013; Holman, Hanley & Millar, 2016; De Narbonne et al, 2016; Oi et al, 2016), or randomly assigning whole colonies to different treatments (e.g., Van Oystaeyen et al, 2014; Holman, 2014). It is also important to run the different experimental treatments in parallel, rather than running one treatment and then another, such that environmental factors or cohort effects could confound the results (it is unclear whether this was done in Amsalem, Orlova & Grozinger (2015), but the differences in sample size and worker colony origin imply that it was not).…”

“…This theory originally rested on indirect evidence, including observations that queens and workers apparently always differ in their CHC profiles (reviewed in Van Oystaeyen et al, 2014), that CHC profiles correlate with inter-individual variation in fecundity within a given caste (e.g., D’Ettorre et al, 2004; Holman, Dreier & D’Ettorre, 2010), and that workers can discriminate between the CHCs of fertile and non-fertile individuals (Dietemann et al, 2003; D’Ettorre et al, 2004). Recently, studies using synthetic hydrocarbons have experimentally demonstrated that queen-like CHCs affect worker ovarian development (in seven species; Van Oystaeyen et al, 2014; Holman et al, 2010; Holman, Lanfear & D’Ettorre, 2013; Holman, Hanley & Millar, 2016; Holman, 2014; De Narbonne et al, 2016; Oi et al, 2016), and/or induce behavioural changes in workers that are putatively related to reproduction (in three species; Holman et al, 2010; De Narbonne et al, 2016; Smith, Millar & Suarez, 2015; Smith, Hölldobler & Liebig, 2009). A recent comparative analysis of chemicals thought to be correlated with caste or fertility in 64 species of social Hymenoptera concluded that these chemicals were most commonly saturated CHCs, and that the correlation between saturated CHCs and female fecundity appears to be ancestral in Hymenoptera (Van Oystaeyen et al, 2014).…”

Queen Recognition Signals in Two Primitively Eusocial Halictid Bees: Evolutionary Conservation and Caste-Specific Perception

“…In addition, n-alkenes have been shown to be expressed to a greater extent in workers compared with queens in both species. In other eusocial insect species, n-alkanes and especially n-alkenes have been shown to function as queen signals among almost all investigated species so far [6,[8][9][10][11][12][13][14][15]. Indeed, CHCs are thought to be linked to the ovarian development in insects, and as queen signals may have evolved from byproducts of the ovarian activation, they might function as queen signals possibly across all social insects [6,15,51].…”

“…Simple long-chain cuticular hydrocarbons (CHCs) have been shown to exert an effect on the behavior of workers or an inhibitory effect on their reproductive physiology by inducing sterility or inhibiting the ovarian development of workers. Such Insects 2019, 10, 416 2 of 17 effects have been investigated in several ant species (Lasius niger, L. flavus, L. lasioides, Cataglyphis iberica, Odontomachus brunneus, and Aphaenogaster cockerelli), the common wasp Vespula vulgaris and the Saxon wasp Dolichovespula saxonica, the stingless bee Friesella schrottkyi, and the bumblebee Bombus terrestris [6,[8][9][10][11][12][13][14][15]. Additionally, a comparative study across more than 60 different social insect species has indicated that fertile females exhibit, in general, a higher amount of long-chain CHCs than nonfertile females [15].…”

Preface: Pheromone-Mediation of Female Reproduction and Reproductive Dominance in Social Species

“…However, the ubiquitous occurrence of hydrocarbons, coupled with their easy detection and synthesis through common methodologies, may bias our conclusion regarding their importance in regulating reproductive decisions, compared to the more elaborate chemical signals. Such a bias may further lead to conclusions such as hydrocarbons may act to coercively inhibit worker reproduction or that their role in regulating reproduction in social insects is conserved across taxa (Oi et al 2016; Van Oystaeyen 2014; but see Amsalem et al 2015;Kather and Martin 2015;Nunes et al 2017 for different conclusions). It is not inconceivable that, similar to the highly chemically-diverse alarm or trail pheromones of social insects, pheromone-regulating reproduction are diverse rather than conserved.…”