Diversification of morphological characteristics among geographically separated populations is particularly important in understanding evolutionary processes and is considered the early stage of allopatric speciation. In the present study, we investigated geographic variation in scorpion populations of Bothriurus bonariensis (Koch 1842). Our principal goal was to compare different populations of this species with regard to its distribution, analyzing somatic and genitalic characters. In Argentina, specimens of B. bonariensis from Entre Rios and Corrientes Provinces are dark brown, while specimens from La Pampa have reddish coloration. Scorpions of this species from Brazil and south of Uruguay are totally black. Also, we observed variability in body size, some morphological characteristics of adult specimens (e.g., prosoma length, hand height, hand width, and telson height), and genitalic traits (e.g., hemispermatophore lamina length, basal and distal lamina width, dorsal fold length). Results indicate the presence of evident geographic variation: populations from Argentina show similar morphological patterns that differ from populations from Uruguay. We discuss these data in the context of the current phylogeographical and evolutionary knowledge of this species.

Differences in sexual signals among species are common, and may influence mate recognition and reproductive isolation. In scorpions, behavioural mechanisms and other sexual signals involved in mate selection and reproductive isolation have been scarcely studied. In this paper, we compare different male sexual signals between two distant populations of the scorpionBothriurus bonariensis, one located in Uruguay and the other in Central Argentina. We compare sexual behaviours from intra-populations and inter-populations matings. In addition, we extent this comparison to the secreted compounds and morphology of the exocrine glands located on the dorsal side of the telson in this species. Males ofB. bonariensisperformed stimulatory behaviours to the female with different frequency of occurrence and duration in the two populations. Chemical analyses of the glandular extracts showed that Uruguayan males present compounds which are absent in males of Argentinian population. In addition, we observed that in inter-population matings, stimulatory behaviours had intermediate patterns to intra-population matings. However, males failed to achieve a successful sperm transfer with females of different population. Mechanisms of sexual isolation between these two distant populations ofB. bonariensisapparently seem to have evolved due to divergence in allopatry. The differences in stimulatory levels during courtship between the two populations studied here give evidence for an early behavioural divergence promoted by sexual selection.