Calotriton asper

García-Salmerón, Alejandro, Muñoz-Muñoz, Francesc, Soler-Membrives, Anna & Valbuena-Ureña, Emilio, 2025, Head form variation in mountain newts of the genus Calotriton (Amphibia, Salamandridae) in a phylogeographic context, Zoologica Scripta 54 (4), pp. 473-486 : 479

3.3 | Head form variation in C. asper

In the Pyrenean brook newt, the size of the head was significantly associated to body size (R 2 =.84, F 1,161 = 1981.8, p <.01) and differed significantly between sexes (R 2 =.08, F 1,161 = 177.4, p <.01) and populations (R 2 =.01, F 1,161 = 3.1, p <.01). Significant differences in head size were detected in several pairs of populations, especially involving Oto and Vilanova de Meià (Table 3). In all populations the males had bigger heads than females when controlling for body size (Figure S2). The shape of the head was significantly associated with head size (R 2 =.07, F 1,161 = 14.2, p <.01) and differed between sexes (R 2 =.03, F 1,161 = 5.5, p <.01) and populations (R 2 =.14, F 1,161 = 4.1, p <.01). Twenty-one out of 28 pairs of populations showed significant differences in head shape (Table 4). In the PCA of the C. asper sample, the first two PCs (PC1 and PC2) explained respectively 27.6% and 18.2% of total shape variation. While shape changes explained by PC1 mainly involved intrapopulation variation, those explained by PC2 seemed to show a geographic pattern, with eastern populations (such as VID and SSE) at one extreme, western populations (OTO and SAR) at the other, and central populations in the middle (Figure 5). These differences mainly involved a general widening of the head, especially at the epibranchial prominence, a shortening of the snout, an anterior projection of the mouth commissure and a shortening and medial displacement of the eyes from western to eastern populations (Figure 5).