Morphological characterization of some poorly known populations of the genus Spalerosophis Jan, 1865 (Reptilia: Colubridae): is the geometric morphometrics useful to identify them as taxonomic units?

Despite the use of traditional morphology as a standard method for species identification, additional methods like image-based analysis can be desirable to differentiate species and populations. In this study, we used traditional morphology and geometric morphometrics (GM) to describe three distinct populations of the genus Spalerosophis and test the hypothesis that all populations are morphologically distinct. A total of 132 specimens were analysed and based on morphological traits (morphometric, meristic, and colour pattern) subcaudal scales was the only distinguishable trait between Spalerosophis diadema cliffordii and Spalerosophis diadema schirasianus. In addition, Spalerosophis atriceps showed significant differences in most studied characters compared to the other two populations. In the geometric morphometric analysis, we placed 2D Landmarks on the dorsal view images of the head of 93 specimens. Canonical variate analysis (CVA) showed significant differences among the head shape of all three populations. There was an increase in the head width, snout length, and curvature in the posterior part of parietals from west Africa in S. d. cliffordii to the north of India in S. atriceps. This may be the result of variations in their environmental factors, diet and the amount of time that has passed since their separation.