Cytogenetic and molecular approaches reveal cryptic diversity in Alpine scorpions in the genus Euscorpius

Phenotypic conservatism is typical for many scorpion taxa.In layman's term, this mean that many scorpion species look morphologically similar making it almost impossible to separate them by traditional taxonomical methods. The European genus Euscorpius Thorell, 1876 (Euscorpiidae) is an excellent example of this. Originally this genus contained less than then species, while today it contains no less than 64 species.

And it seems that there is still more to come. By using a new combination of cytogenetic and molecular methods, Jana Štundlováa and co-workers have recently published a study of the three Alpine species of the subgenus Euscorpius (Alpiscorpius): E. (A.) alpha, E. (A.) germanus, and E. (A.) gamma.

Their study reveals a cryptic diversity in the populations of the Alpine species, with several "races" (highly distinct karyotypic races) within each species. These races had discrete geographical distributions. Even though these results clearly shows several independent taxa, a thorough taxonomical revision with morphological studies of the subgenus is necessary before any taxonomical decisions can be made.

Some of the methods used in this study are new and open new possibilities for our understanding of the species diversity of scorpions.

Abstract:
Over time, mountain biota has undergone complex evolutionary histories that have left imprints on its genomic arrangement, geographical distribution and diversity of contemporary lineages. Knowledge on these biogeographical aspects still lags behind for invertebrates inhabiting the Alpine region. In the present study, we examined three scorpion species of the subgenus Euscorpius (Alpiscorpius) from the European Alps using cytogenetic and molecular phylogenetic approaches to determine the variation and population structure of extant lineages at both chromosome and genetic level, and to provide an insight into the species diversification histories. We detected considerable intraspecific variability in chromosome complements and localization of the 18S rDNA loci in all studied species. Such chromosome differences were noticeable as the existence of three [in E. (A.) alpha and E. (A.) germanus] or four [in E. (A.) gamma] range-restricted karyotypic races. These races differed from one another either by 2n [in E. (A.) alpha 2n=54, 60, 90; in E. (A.) gamma 2n=58, 60, 88, 86–92], or by the karyotypic formula [in E. (A.) germanus 2n=34m+12sm; 36m+10sm; 42m+4sm]. Using mitochondrial (16S rRNA, COI) and nuclear (28S rDNA) genetic markers, we examined genetic variation and reconstructed phylogenetic relationships among the karyotypic races. Both approaches provided evidence for the existence of ten deeply divergent lineages exhibiting the features of local endemics and indicating the presence of cryptic species. Molecular dating analyses suggest that these lineages diversified during the Plio-Pleistocene and this process was presumably accompanied by dynamic structural changes in the genome organization.

Reference:
Stundlova J, Smid J, Nguyen P, Stahlavsky F. Cryptic diversity and dynamic chromosome evolution in Alpine scorpions (Euscorpiidae: Euscorpius). Mol Phylogenet Evol. 2019;134:152-63. [Subscription required for full text]

Thanks to Victor Fet and Frantisek Kovarik for sending me this interesting article!