A Comparative Morphotypic Analysis of the First Lower Molars of the Reed Vole Alexandromys fortis (Büchner, 1889) from Insular and Fossil Populations in the South of the Russian Far East (Primorskii Krai).

Abstract—The morphotypic variability of the anteroconid shape of the first lower molar of fossil and modern (continental and insular) populations of the reed vole (Alexandromys fortis) from the territory of Primorye (the south of the Russian Far East) has been analyzed. The morphotypic variability is considered based on the study of variations in the structure of the labial and lingual sides of the anterior unpaired loop and structural features of the lingual reentrant angle 4. Thirty-six morphotypes of the structure of the unpaired anterior loop of anteroconid m1 have been revealed using the developed combinatory matrix. The most widespread morphotype on the continent is IIICa, which prevailed in the Late Pleistocene. The features of the morphotypic composition of m1 in the differentiated populations of the reed vole on the Durnovo, De-Livron, and Vera islands (Peter the Great Bay) are determined both by the phenotypic and genotypic characteristics of the founders of the insular populations. The original new habitat conditions must have initiated a high rate of evolution, released hidden diversity, and increased the number of rare morphotypes. [ABSTRACT FROM AUTHOR]