Static genetic and phenotypic allometry of dental traits in inbred and hybrid house mice.

Static allometric coefficients were estimated by regression and reduced major axis methods for second and third mandibular molar widths scaled on body weight in 42-day-old inbred and hybrid house mice. Phenotypic slopes were calculated by combining inbred and hybrid strains, and genetic slopes were obtained from differences among the strains. It was hypothesized that the genetic scaling, which reflects the expected evolutionary allometry between populations if they have been produced from directional selection on body weight alone, would exceed the phenotypic scaling. The genetic coefficients were generally higher (average regression estimates in inbreds = 0.65) than the phenotypic ones (comparable average = 0.47), but the differences were non-significant. It was concluded that the higher scaling of tooth dimensions in interspecies versus intraspecies comparisons typically found in previous studies therefore could not necessarily be explained as a secondary response to selection for body size, although more information is needed about trends in the scaling of mammalian teeth at different ages.