Re-establishment of Carabus (Cathoplius) aliai Escalera, 1944 as a separate valid species (Coleoptera, Carabidae)

Abstract

Carabus (Cathoplius) aliai was described as a separate species by Escalera in 1944 but since the 1950–60s it has been considered as a subspecies of C. (Cathoplius) stenocephalus Lucas, 1866. This downgrading was adopted after examining only a few specimens, due to their rarity in collections. In recent years, an important population of this taxon was rediscovered in the Tan-Tan area in southern Morocco. By combining field observations with laboratory breeding experiments including hybridization trials, and through the morphological examination of a representative number of individuals, it is confirmed that C. aliai is indeed a valid species. Despite close geographic distribution, the morphological and biological characteristics of C. aliai and C. stenocephalus ifniensis Zarco, 1941, its northern substitutive taxon, are very different. Carabus aliai adults are characterized by a smaller size, a slender silhouette, a more brilliant aspect, a narrower pronotum, a coarser elytral sculpture, longer legs, and a wider and a little more curved apex of the median lobe of the aedeagus. Carabus aliai larvae are also characterized by a much smaller size and the C. aliai pupa has a narrower thoracic area and a different chaetotaxy compared to that of C. stenocephalus ifniensis. Contrary to this, C. aliai has a life cycle belonging to the annual univoltine winter semelparous type. Moreover, the duration of its development cycle is shorter. Carabus aliai is a sabulicolous steppe-wandering species with an intensive running activity, while C. stenocephalus ifniensis is a more sedentary taxon. Crossbreeding experiments showed a marked reproductive isolation between C. aliai and C. stenocephalus ifniensis. When F1 hybrids were crossed with one another, a very high mortality rate during embryonic, larval and pupal development was evident and no vital F2 neo-adults were obtained. Morphological and biological differences, together with the reproductive failure in C. aliai × C. stenocephalus ifniensis hybrids, clearly indicate that C. aliai is a separate Cathoplius species that is distributed in an area south of the Anti-Atlas chain, from Plage Blanche (Guelmim) to Lemsid and Bou Kra (south of Laâyoune). Carabus aliai is therefore both a Saharan desert endemic and an Atlantic resident. Moreover, it is the southernmost Carabus species of the western Palaearctic region.