| Abstract: |
The genetic features of dermatoglyphic ridge counts were investigated using multivariate maximum likelihood estimation and the largest data set with pedigrees to date. The results of this study differ from previous studies primarily because summary statistics such as Total Ridge count (TRC) were avoided, and finger-level variation was accounted for. TRC was empirically shown to inflate heritability estimates because the repeatability of TRC (.57) is much lower than the previously assumed near-total heritability of TRC. Multivariate heritabilities (mean =.31) of dermatoglyphic ridge counts in the fingers are much lower than has been estimated and assumed, and the heritabilities of palm and toe ridge counts are very similar to finger ridge counts. The components of dermatoglyphic variation are best understood developmentally. Ridge count heritabilities are lower due to significant dominance and environmental effects, but also to a high level of genetic integration, as shown by high genetic correlations among variables. A high degree of genetic integration lowers multivariate heritabilities for each covariate. Epidermal Growth Factor, with its widespread action on the developing fetus and the epidermis, may be an especially important regulatory hormone for developmental integration. The level of integration is much lower in the phenotypic variance-covariance matrix than in the additive genetic variance-covariance matrix due to varying and independent dominance and environmental effects. These effects produce relatively larger variances in the phenotypic variance-covariance matrix compared to the additive genetic variance-covariance matrix. As a result, the phenotypic variance-covariance matrix is not proportional to the additive genetic correlation, and phenotypic dermatoglyphic traits cannot be expected to reflect the phylogenetic relationships between populations when used in an analysis of population structure. The lower integration of the phenotypic variance-covariance matrix also produces overestimates of statistical significance for phenotypic distances among populations and inflated measures of overall diversity. A larger proportion of statistically significant distances and greater diversity among populations are ubiquitous using phenotypic, as opposed to genetic, data. The components of variation among dermatoglyphic variables in this analysis may have revealed a quantitative genetic basis for these pervasive patterns.
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