## 3 Results  
The results of the odontometrical analysis are summarized in Figure 5.  
Figure 5: (**A**) Distribution of the row scores of the first two components of PCA. The \(p\) value of Bonferroni tests reveals whether significant differences are present between the geographical populations. Colours are consistent with those used in Figure 2. (**B**) Individual PC scores and odontometric variables. The ellipses contain 95% of the data. The examination of the morphospace obtained through a PCA analysis and testing the differences among the populations with a MANOVA analysis revealed significant differences among the three geographical districts (Pillai's Trace = 0.082; \(p\) < 0.001). The first two PCs were statistically significant and accounted for 59% of the variance (Figure 5A). The following correlation analyses showed that the first axis (34% of explained variance) had a positive correlation with AP, PR and TL, but a negative correlation with AL (\(p\) < 0.01). The second axis (25% of explained variance) was positively influenced by AL and PR (\(p\) < 0.01) (Figure 5B). In the palatilar length analysis, we considered that the Montefalco sample consisted of 11 specimens with anterior loops \(\leq\) 20%, 11 specimens with anterior loops \(\geq\) 30% and 19 specimens with anterior loops within the 20-30% interval. The main results are shown in Figure 6.  
No significant differences in palatilar lengths were found between individuals with more-or-less-opened anterior loops (ANOVA F = 1.194; \(p\) = 0.059) nor were statistically significant correlations between palatilar lengths and anterior loop percentages found (R = \(-\)0.3, \(p\) = 0.061). Regarding the genetic analyses, 32 sequences of the _Microtus cytb_ gene of specimens belonging to Montefalco sampling site were obtained. Ten sequences were performed overlapping the three fragments and covered the entire _cytb_ (1143 bp). The others were obtained using only fragments 2 and 3 (629 bp in total) and ranged from 588 to 629 bp in length due to a poor electropherogram quality of three samples. All sequences were deposited in GenBank under the Accession Numbers ON815278-ON815292. Every polymorphism was inspected to check that the theorical protein translation was possible and all alternative codons were _sensu_. A total of 17 haplotypes were found and desegregated, as reported in Figure 7.  
Figure 6: Regression and correlation analysis of palatilar lengths (mm) and the anterior loop percentages among the m\({}_{1}\) groups. The largest points (+) depict the centroids of each group with the standard errors for both variables. The black line represents the common regression line while the coloured ones, those of each individual group. No specimen belonging to the Montefalco sample was attributed to the _M. brachycercus_ haplogroup (orange in Figure 7). New haplotypes found in Montefalco described two main ramifications: one including only two haplotypes (hapM12 and hapM13) and the other grouping eight haplotypes (hapM1-hapM8). The other four haplotypes were dispersed across the _M. savii_ network (hapM9-hapM13) or represented as an independent haplogroup, as was the case with hapM15. The high number of haplotypes was caused by an abundance of rare mutations whose presence was noticed in just one or few individuals at a time. This scenario was confirmed by the Tajima Neutrality test. Montefalco's sample pool showed a negative Tajima's D, suggesting an excess of low-frequency polymorphisms, i.e., fewer haplotypes that influenced an observed value lower than the expected one (\(\Theta\)-Pi \(<\Theta\)-k). This can be due to an abundance of rare alleles presumably caused by a recent population evolving after expansion. The evolutionary history was inferred using the Maximum Likelihood (ML) method and Jukes-Cantor model [43] on 60 nucleotide sequences; the tree with the highest log likelihood (\(-2024.87\)) is shown. The percentage of trees in which the associated taxa clustered together is shown next to the branches.