Accuracy and Precision in Anuran Morphometrics: Artifacts of Preservation

Abstract

Accuracy and precision in anuran morphometrics: artifacts of preservation. Syst. Zool., 31: 266–281.—Univariate comparisons of twenty morphometric characters of sixty adult Bufo marinus recorded before preservation and six and 14 months after preservation reveal a statistically significant heterogeneity among group means of fourteen characters. After six months in preservative, the means of six of these 14 characters are significantly larger, and eight are significantly smaller, than for the same individuals prior to preservation. After eight additional months in preservative, the means of five of these 14 characters differ significantly in the opposite direction of that initially detected. Linear regressions and analyses of covariance suggest that over the range of sizes considered here, preservation effects the elevations but not the slopes of the regressions between pairs of morphometric characters. Sexual size dimorphism in six characters is documented for the fresh material; certain of these intersexual differences are reduced or are undetectable in the preserved material, and in one instance a new, marginally significant, difference is apparent after 14 months in preservative. Not all characters are measurable with equal precision, and there is a highly significant rank correlation between precision and inter-individual character variance. Principal component analyses confirm and extend the univariate findings, and discriminant function analysis reveals differences between fresh and preserved specimens of roughly the same magnitude as those commonly used to justify taxonomic decisions. The assumption that preservation induces tolerably little morphological distortion in frogs appears to be substantially violated, but an unknown proportion of among-group character variation may be attributable to measurer bias. © 1982 Society of Systematic Zoology.