The taxonomic status of the Eurasian water vole Arvicola amphibius, has been highly questioned and undergone many nomenclature changes since 1549, the year of its first description by Georg Agricola. This is due to the two different ways of life of these animals, which present terrestrial and aquatic populations. The purpose of our study is to investigate the cranial shape variation of Eurasian water vole in Italy using two-dimensional geometric morphometrics in order to give a contribute to the taxonomic assessment of this taxon. The study examined 84 samples of the vole skull and jaw from three Italian Museums of Natural History (Florence, Verona and Bozen), from ISPRA of Ozzano dell'Emilia (National Institute for Protection and Environmental Research) and from two private collections. Each sample was photographed and analyzed in three different skull projections (dorsal, ventral and lateral). Furthermore, picture of the jaw were collected in order to analyze teeth shape. We used a standardize protocol to take pictures of the samples to avoid to introduce a bias in the analysis. Anatomical landmarks were collected on each photo through the software tpsDig2. The four raw landmark configurations (one for each skull projection and the teeth), were subsequently centered, scaled and rotated through a Generalized Procrustes Analysis (GPA) by using the software MorphoJ. The obtained aligned configurations (shape+size) were successively used to perform statistical analyses, using the software R. The differences in size were visualized using box-plots, grouping specimens on the basis of latitude, OTU (Italian administrative regions) and sex, and successively tested by using ANOVA test and HSD Tukey test. Shape differences were investigated by Principal Component Analysis (PCA) and Canonical Variate Analysis (CVA) vole sample and on the sample averaged by latitude and by OTU. The obtained results have shown that there is any size sexual dimorphism. By contrast there is a significant size difference between the Italian voles and those from Germany, Switzerland and north-eastern Italy (Bozen), which are smaller than the Italian ones. PCA and CVA performed on skull and jaw configurations suggested the presence of a latitudinal trend of shape change in all the skull projections and in the teeth. The results show that on the basis of the shape the European and Italian voles can be separated in two well distinct groups, with the first, according to deformation grids, showing a shorter and wider skull respect to the latter. The large differences observed between the Italian and the European water voles suggest that the first can represent a distinct taxonomic entity with deserve further investigations.
Geometric Morphometrics and taxonomy of Arvicola amphibius in Italy
P Colangelo
2016
Abstract
The taxonomic status of the Eurasian water vole Arvicola amphibius, has been highly questioned and undergone many nomenclature changes since 1549, the year of its first description by Georg Agricola. This is due to the two different ways of life of these animals, which present terrestrial and aquatic populations. The purpose of our study is to investigate the cranial shape variation of Eurasian water vole in Italy using two-dimensional geometric morphometrics in order to give a contribute to the taxonomic assessment of this taxon. The study examined 84 samples of the vole skull and jaw from three Italian Museums of Natural History (Florence, Verona and Bozen), from ISPRA of Ozzano dell'Emilia (National Institute for Protection and Environmental Research) and from two private collections. Each sample was photographed and analyzed in three different skull projections (dorsal, ventral and lateral). Furthermore, picture of the jaw were collected in order to analyze teeth shape. We used a standardize protocol to take pictures of the samples to avoid to introduce a bias in the analysis. Anatomical landmarks were collected on each photo through the software tpsDig2. The four raw landmark configurations (one for each skull projection and the teeth), were subsequently centered, scaled and rotated through a Generalized Procrustes Analysis (GPA) by using the software MorphoJ. The obtained aligned configurations (shape+size) were successively used to perform statistical analyses, using the software R. The differences in size were visualized using box-plots, grouping specimens on the basis of latitude, OTU (Italian administrative regions) and sex, and successively tested by using ANOVA test and HSD Tukey test. Shape differences were investigated by Principal Component Analysis (PCA) and Canonical Variate Analysis (CVA) vole sample and on the sample averaged by latitude and by OTU. The obtained results have shown that there is any size sexual dimorphism. By contrast there is a significant size difference between the Italian voles and those from Germany, Switzerland and north-eastern Italy (Bozen), which are smaller than the Italian ones. PCA and CVA performed on skull and jaw configurations suggested the presence of a latitudinal trend of shape change in all the skull projections and in the teeth. The results show that on the basis of the shape the European and Italian voles can be separated in two well distinct groups, with the first, according to deformation grids, showing a shorter and wider skull respect to the latter. The large differences observed between the Italian and the European water voles suggest that the first can represent a distinct taxonomic entity with deserve further investigations.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
