Morphometric variation in the skull of Brown Bear in Alborz and Zagros mountains

Measurements and delineation of organism’s morphologic characterization is an useful tool for identification and taxonomy of them and also, from the perspective of evolutionary ecology, for describing the adaptation of different populations of a species to local conditions is important. Brown Bear is the largest carnivore of Iran and is widely distributed in mountainous areas of North and West of the country. In this study, a total of 21 skulls (including 11 of the Alborz Mountains and 10 skulls of the Zagros Mountains) were collected and 26 variables for each of the skulls were measured. We log-transformed the measured variables to provide normality and using geometric mean the effect of size and age was removed. Significant Differences in measured variables was examined using t-test and then we performed principle component analysis (PCA) to extract orthogonal multivariate axes describing size and shape of the specimens. The results of t test revealed that between Alborz and Zagros specimens eight variables had significant difference. We found that based on the size, Alborz specimens were larger than the Zagros samples. Also, PCA performed on the eight significant variables, indicated a noteworthy difference in the size, but no in the shape, of the skull of the respected population of two regions, which was led to comprise two quite distinct groups.