Morphospace dynamics and intraspecies variety of Sorex araneus and S. tundrensis according to recent and fossil data

Several patterns were revealed in a temporal study on morphological variety of Sorex araneus and S. tundrensis (Soricidae, Mammalia). We examined samples from 18 modern and three fossil Early-Late Holocene Uralian localities. We analyzed shape variation of the first lower molar and hemimandible using two-dimensional geometrical landmarks; size differences were estimated by means of three linear measures. A separate purpose was estimation of the measurement error that arose during the data acquisition. We found that the modern samples of both species share underestimated similarity in both size and shape of morphological structures. Regression analysis revealed different phenotypic traits of the mandibular proportion in the large and small shrews regardless of species attribution. A size decrease of S. araneus and conversely a size increase of S. tundrensis both drive the mandibular shape toward phenotypic convergence. This pattern, however, is violated in the fossil samples, where the largest S. tundrensis from a Late Holocene Sim III locality (South Ural) showed a well -distinguishable mandibular shape located in a separate part of the morphospace. In this work, we found that the m1 shape has only weak resolving power as compared to the mandibular or especially skull shape. Nonetheless, even the moderate resolving power of the mandibular shape allowed us to uncover phenotypic changes during the Holocene that have not been noticed by previous researchers at Uralian late Quaternary localities.