A Heritable Tooth Trait Varying in Two Subspecies of Microtus californicus (Rodentia: Cricetidae)

Teeth with unusually long roots were observed in individuals trapped live from two populations of the California vole, Microtus californicus, and in their laboratory-born progeny. Populations of two nominal subspecies, M. c. californicus and stephensi, were sampled; the incidence of affected individuals differs in the subspecies. Affected individuals are those in which the root of any of the molars, upper or lower, is abnormally long, with distortion in the dentine at the base of the root. The trait is semi-continuous, and there is a threshold for its expression that is lower for males than females. There is also a difference in incidence between the sexes and an age effect in the severity of the anomaly. The trait has a genetic component but the mode of inheritance is not clear.