Abstract
Decticus verrucivorus (Linnaeus, 1758) is a wide-ranging, morphologically variable and highly polytypic species. There are two recognized subspecies in mainland France : D. v. verrucivorus L. 1758 and D. v. monspeliensis Rambur in Audinet- Serville, 1839. The latter has a range restricted to Gard and Hérault. This taxon exhibits an early phenology and occupies low altitude xerophytic habitat. Other lowland populations with early phenology are known from many localities, which raises questions about their taxonomic status. In this article, we analyzed the morphology of 258 specimens covering the entire known range in France. Analyzes of linear morphometric measurements indicate that the species shows a great morphological variability which is partly explained by a dichotomy between Mediterranean (Gard, Hérault but also Var and Vaucluse) and non-Mediterranean individuals. The morphological distance between individuals is not correlated with geographical distance. Part of the morphological variation is explained by altitude, with high altitude individuals on average smaller than low altitude ones. However, the difference between Mediterranean and non-Mediterranean populations is not explained by the effect of altitude. The Mediterranean populations east and west of the Rhône river show little differentiation but we do not have enough individuals to properly test this differentiation further. A set of operational criteria is proposed for field identification. We also demonstrated that, for an Orthoptera of the size of the wart-biter, caliper measurements were as accurate as those made with a binocular magnifying glass. This paves the way for non-invasive biometric studies carried out directly in the field. In conclusion, the Mediterranean populations east and west of the Rhône river share a morphological proximity that allows them to be grouped in the same subspecies D. v. monspeliensis, until further investigation clarify if a real difference exists among those populations. In contrast, the xerophilous populations of Quercy, Haute-Garonne and Gers belong to D. v. verrucivorus subspecies.