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.

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R e~u le 7 aoct 1985 BOISSELIER-DUBAYLE, M.-C., et R. BAUDOIN. 1986. Contribution de 1'Ctude du polymorphisme enzymatique i la systkmatique des Pleurotes des Ombelliferes. Can. J. Bot. 64 : 1467-1473. Ce travail prksente une contribution i la systCmatique des Pleurotes des Ombelliferes, lesquels sont classiquement rkpartis en trois entitCs. L'Ctude du polymorphisme enzymatique de diffkrentes activitCs enzymatiques par Clectrophorkse, menCe au niveau de dicaryons reconstituCs d'origine contr6lCe et de leurs composants haploides (homocaryons), a permis de determiner le genotype apparent des dicaryons (( sauvages. et d'effectuer un traitement statistique sur les gCnotypes des homocaryons. Les rksultats mettent en Cvidence une dissociation de Pleurotus nebrodensis par rapport i Pleurotus eryngii et Pleurotus ferulae. 11s permettent Cgalement de suggCrer une dissociation de P. nebrodensis en deux formes au moins aussi distinctes l'une de l'autre que ne le sont les deux autres entitCs de Pleurotes (P. eryngii et P. ferulae). DiffCrentes hypothkses relatives aux notions de dynamique interne des populations et d'ivolution de ce groupe hikrarchique de Basidiomycktes sont discuties. BOISSELIER-DUBAYLE, M.-C., and R. BAUDOIN. 1986. Contribution de 1'Ctude du polymorphisme enzymatique i la systCmatique des Pleurotes des Ombelliferes. Can. J. Bot. 64 : 1467-1473.This study presents a contribution to the systematics of Pleurotus species growing on Umbellifers, which are classically divided into three types. Studies of enzyme polymorphism by electrophoresis performed on synthetized dikaryotic mycelia and their haploid components (homokaryons) allowed a genotypic determination of "wild" dikaryons, and a statistical treatment of homokaryotic genotypes. These results show a distinction between P. nebrodensis on one hand, and P. eryngii and P. ferulae on the other hand, and support the hypothesis of a division of P. nebrodensis into two types at least as distinct from each other as P. eryngii from P. ferulae. Different hypotheses related to internal dynamics and evolution of this group of Basidiomycetes are discussed.