Geographic Variation of Melanisation Patterns in a Hornet Species: Genetic Differences, Climatic Pressures or Aposematic Constraints?

Abstract

Coloration of stinging insects is often based on contrasted patterns of light and black pigmentations as a warning signal to predators. However, in many social wasp species, geographic variation drastically modifies this signal through melanic polymorphism potentially driven by different selective pressures. To date, surprisingly little is known about the geographic variation of coloration of social wasps in relation to aposematism and melanism and to genetic and developmental constraints. The main objectives of this study are to improve the description of the colour variation within a social wasp species and to determine which factors are driving this variation. Therefore, we explored the evolutionary history of a polymorphic hornet, Vespa velutina Lepeletier, 1836, using mitochondrial and microsatellite markers, and we analysed its melanic variation using a colour space based on a description of body parts coloration. We found two main lineages within the species and confirmed the previous synonymy of V. auraria Smith, 1852, under V. velutina, differing only by the coloration. We also found that the melanic variation of most body parts was positively correlated, with some segments forming potential colour modules. Finally, we showed that the variation of coloration between populations was not related to their molecular, geographic or climatic differences. Our observations suggest that the coloration patterns of hornets and their geographic variations are determined by genes with an influence of developmental constraints. Our results also highlight that Vespa velutina populations have experienced several convergent evolutions of the coloration, more likely influenced by constraints on aposematism and Müllerian mimicry than by abiotic pressures on melanism.

Evolution of wing shape in hornets: why is the wing venation efficient for species identification?

“…Relationships between taxa were determined following the phylogenies of the genera Vespa and Provespa (Saito & Kojima, ; Perrard et al ., ) combined with the genetic analysis of V. velutina populations (Perrard et al ., ; Fig. a).…”

“…Wing shape could thus be selected by mimicry pressures on the flight sound. A second explanation could be that genes influencing the patterning of pigmentation, such as genes Hox (Kopp et al ., ; Perrard et al ., ), may also be involved in the development of similar venation patterns.…”

Not simply red: Colouration of red wood ant Formica rufa (Hymenoptera: Formicidae) is polymorphic, modular and size-dependent

“…Applying the modularity concept has resulted in the precise description of abnormalities such as gynandromorphs in Pheidole (Hymenoptera: Formicidae) ants (Yang & Abouheif, 2011) and might be useful for further revealing other signs of developmental instabilities. Modular colouration is described by Williams (2007) in bumblebees and by Perrard et al (2014) in the yellow-legged hornet Vespa velutina (Lepeletier, 1836). Modular organisms may exhibit differentiated or restricted phenotypic responses, as various modules may have different response thresholds to the same inducing factor (Forsman, 2015).…”

Diversity in warning coloration: selective paradox or the norm?

“…Given this evidence, it is clear that in order to understand how the genetic architecture of warning coloration enables or constrains morphological variation we need more information about the genes and gene networks at play, as well as a broader taxonomic coverage of the genetic architecture. Alongside the work already carried out on snakes, promising taxa include wasps (Perrard et al, ) and ladybird beetles (Lee et al, ). The latter are particularly intriguing as, unlike Heliconius spp., there is scant evidence of hybridisation, and for two highly polymorphic species ( H. axyridis and A. bipunctata ) multiple morphs have been produced in the laboratory that are scarce in the field (Majerus, ; Hodek, van Emden & Honek, ).…”