Abstract
Morphometric research is being applied to a growing number and variety
of organisms. Discoveries achieved via morphometric approaches are often
considered highly transferable, in contrast to the tacit and
idiosyncratic interpretation of discrete character states. The
reliability of morphometric workflows in insect systematics has never
been a subject of focused research, but such studies are sorely needed.
In this paper, we assess the reproducibility of morphometric studies of
ants where the mode of data collection is a shared routine. We compared
datasets generated by eleven independent gaugers, i.e. collaborators,
who measured 21 continuous morphometric traits on the same pool of
individuals according to the same protocol. The gaugers possessed a wide
range of morphometric skills, had varying expertise among insect groups,
and differed in their facility with measuring equipment. We used
Intraclass correlation coefficients (ICC) to calculate repeatability and
reproducibility values (i.e., intra-, and inter-gauger agreements), and
we performed a multivariate Permutational Multivariate Analysis of
Variance (PERMANOVA) using the Morosita index of dissimilarity with 9999
iterations. The calculated average measure of intraclass correlation
coefficients of different gaugers ranged from R = 0.784 to R = 0.9897
and a significant correlation was found between the repeatability and
the morphometric skills of gaugers (p = 0.016). There was no significant
association with the magnification of the equipment in the case of these
rather small ants. The inter-gauger agreement, i.e. the reproducibility,
varied between R=0.872 and R=0.471 (mean R=0.690), but all gaugers
arrived at the same two-species conclusion. A PERMANOVA test revealed no
significant gauger effect on species identity (R2 =0.69, p=0.58). Our
findings show that morphometric studies are reproducible when observers
follow the standard protocol; hence, morphometric findings are widely
transferable, and will remain a valuable data source for alpha taxonomy.