Skull Morphology of Four Species of Zokors (Rodentia, Myospalacinae)
Skull Morphology of Four Species of Zokors (Rodentia, Myospalacinae)
Yao Zou, Shien Ren, Miao Xu, Nannan Liang, Xuxin Zhang, Chongxuan Han and Xiaoning Nan
ABSTRACT
Zokors are one of the subterranean rodents in the subfamily Myospalacinae. Extant zokors include two major genera, Eospalax and Myospalax, which can be distinguished by skull shape. However, due to few available studies on skull morphology of zokors, the interspecific differentiation of their skulls is still unclear. To differentiate among species and to describe the sexual dimorphism within each species, we measured morphological variation using one-way analysis of variance and cluster analysis in four species of zokor including Eospalax cansus, Eospalax rothschildi, Eospalax baileyi, and Myospalax aspalax. We also used principal component analysis and dichotomy to explore key measurements which could reflect skull differences to the maximum. In addition, we tested the correlations between environmental factors and skull measurements for each species. The results of variance analysis indicated that three zokors showed male-biased sexual size dimorphism except for E. baileyi. We also found that there were significant differences of linear measurements among four species. The results of cluster analysis showed that the four species of zokors divided into two branches, one including E. cansus and E. rothschildi, the other E. baileyi and M. aspalax. The results of principal component analysis showed that the variables that contribute to the first principal component were related to skull size, and the variables which contribute to the second principal component were different between sexes. Thus, linear measurements that reflect the skull size such as cranial length, basal length and cranial base could be key measurements for cluster and classification. Zygomatic breadth could be considered as quantifiable differences between the two genera Eospalax and Myospalax. We suggest that the clustering patterns could be related to climate and geographical factors. Finally, it was found that most of the skull measurements were positively correlated with latitude but negatively correlated with annual mean temperature and precipitation, which follows Bergmann’s rule. This work provides a significant reference value to scholars who apply themselves to pest control and to the classification and identification of zokors using morphology.
To share on other social networks, click on any share button. What are these?
