A comparison of two methods for estimating measurement repeatability in morphometric studies

Abstract

O_LIMeasurement repeatability is often reported in morphometric studies as an index of the contribution of measurement error to trait measurements. However, the common method of remeasuring a mounted specimen fails to capture some components of measurement error, and could therefore yield inflated repeatability estimates. Remounting specimens between successive measurements is likely to provide more realistic estimates of repeatability, particularly for small structures that are difficult to measure. C_LIO_LIUsing measurements of 22 somatic and genitalic traits of the neriid fly Telostylinus angusticollis, we compared repeatability estimates obtained via remeasuring (where a mounted specimen is measured twice) versus remounting (where a specimen is remounted between measurements). We also asked whether the difference in repeatability estimates obtained via the two methods depends on trait size. C_LIO_LIRepeatability estimates obtained via remounting were lower than estimates obtained via remeasuring for each of the 22 traits, and the difference between estimates obtained via the two methods was generally greater for small structures (genitalic traits) than for large structures (legs, wings). C_LIO_LIRemounting specimens between successive measurements can provide more accurate estimates of measurement repeatability than remeasuring from a single mount, especially for small structures that are difficult to measure. C_LI