Disparity of Structural Variants of the m1 Anterokonid in the Vole Genera Stenocranius and Alexandromys (Arvicolini, Rodentia): Qualitative and Quantitative Approaches

Variation of anteroconid morphotypes was studied using traditional and GM methods in five vole species: Stenocranius gregalis , Alexandromys middendorffii , A . mongolicus , A . mujanensis , and A . oeconomus . The morphotypical space is three-dimensional within the framework of the traditional approach, with the axes being formed by (1) the complexity of the curve of the lingual and (2) labial sides of the AUL, and (3) the overall number of closed triangles. The total number of morphotypes for four species of Alexandromys is 56, with 30 of them being actualized (the degree of completeness of the morphospace is 53.6%). The thin-plate spline and Procrustes distance analyses were used in the quantitative approach. The distribution of morphotypes in the space of the first two relative warps (RWs), both for individual species and for their combination, displays an arcuate configuration. The first RW is associated mainly with the complication/simplification of the buccal side of the anteroconid, while the second RW with the bilateral complication/simplification and simultaneous extension/compression of the anteroconid. The part of the potential morphospace that corresponds to a moderately complicated and maximally elongated anteroconid remains unfilled. The distribution of morphotypes for all species in the space of the first two axes of multidimensional scaling forms a single and roughly homogeneous cloud that almost evenly fills the total morphospace. The correlation coefficients between the matrices of morphogenetic and Procrustes distances between morphotypes calculated for each of the species vary from 0.56 to 0.73.