Geo-morphometric approaches to the study of sexual size dimorphism in murid rodents
2015
Afshan, K. (Pir Mehr Ali Shah Arid Agriculture Univ., Rawalpindi (Pakistan). Dept. of Zoology) | Rizvi, S.S.R. (Pakistan Science Foundation, Islamabad (Pakistan). Pakistan Museum of Natural History) | Muhammad, A. (Pir Mehr Ali Shah Arid Agriculture Univ., Rawalpindi (Pakistan). Dept. of Zoology) | Qayyum, M.
Sexual size dimorphism (SSD) based on the presence of external genitalia has extensively been documented in mammals, which however, poses impediments in the identification of the sex of specimens based on morphometric traits. Recent advances in geometric morphometric (GM) and multivariate analyses can assist to differentiate sexual dimorphism in animals. The present study was based on morphometric measurements taken from adult Norway rats. The results showed that the magnitude of SSD with regards to the shape and size differs among the sexes. Males were consistently larger in all morphometric measurements than females but considerable overlap between the sexes resulted in no single measurement being a useful discriminator of sex. A principal components analysis on a correlation matrix of nine morphometric measurements indicated that the first principal component was a good `body size' indicator explaining 49% of the variance in the original matrix. The new characters ratios tail length/body length (BL), BL/body weight (BW), length of front foot/width of front foot and length of hind foot/width of hind foot were introduced, which increases the discrimination tendency up to 60%. The results of the study accentuate the need to incorporate GM methods in rodent taxonomy and in the identification of specific features rendering sexual dimorphism in murid rodents.
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