Patterns of sexual size dimorphism in cattle breeds support Rensch’s rule

摘要

Rensch’s rule describes the pattern of sexual size dimorphism (SSD) claiming that in taxa where males are the larger sex, larger species generally exhibit higher male to female body size ratios. Agreement with Rensch’s rule is manifested by the slope of the allometric relationship between male and female body size exceeding one. In this paper we have tested the hypothesis that recent rapid evolutionary changes of body size accompanying domestication process and morphological radiation of domestic breeds follow Rensch’s rule. We have analyzed literature data on adult body size of males and females in domestic cows, yaks, buffaloes and other bovines (315, 12, 24 and 2 breeds, respectively) and compared it with SSD in 18 wild species/subspecies of the subfamily Bovinae. Male to female body mass ratio in domestic cows (1.48) was fairly comparable to that found in other species of domestic and wild bovines except domestic buffaloes (1.19). In cows we have demonstrated clear positive allometry of male to female body mass ratio (slope 1.21) predicted by Rensch’s rule, however, no such clear relationship was found when body mass was replaced by shoulder height. These findings are in agreement with those we have previously reported in other livestock species, goats and sheep.