Infrared thermography coupled with finite-element heat-transfer modelling of basking thermoregulation in desert agamid lizards

Abstract

A persistent challenge in lacertid lizard taxonomy is the reliable differentiation of closely related species that share broadly overlapping morphological characteristics, necessitating quantitative morphometric approaches to detect subtle but diagnostically important differences. This research presents a comparative morphometric analysis of body proportions in a newly described lizard species from Eastern Anatolia with four related congener species found across the broader Anatolian and Caucasian region. Morphometric data were collected from a total of 187 preserved specimens representing the new species (n=42), Lacerta agilis (n=45), Lacerta strigata (n=38), Lacerta viridis (n=32), and Lacerta trilineata (n=30). Sixteen linear measurements capturing body, head, and limb dimensions were recorded using digital calipers. Principal component analysis on log-transformed, size-corrected data explained 92.2 percent of total morphometric variation across the first five principal components. The first principal component, accounting for 42.3 percent of variance, was most heavily loaded by head dimensions, while the second component (21.7 percent) reflected limb proportions. Discriminant function analysis achieved an overall classification accuracy of 89.7 percent, with the new species being correctly classified in 92.9 percent of cases. Sexual dimorphism was significant across all five species, with males consistently larger than females in body size and head dimensions, though the degree of dimorphism varied among species. The new species was most clearly differentiated from congeners by its relatively larger head width to head length ratio, shorter forelimb to hindlimb ratio, and higher tail length to snout-vent length ratio. These morphometric findings demonstrate that the new species occupies a distinct position in multivariate morphospace and can be reliably separated from its closest relatives using a combination of body proportion characters, supporting its recognition as a taxonomically distinct entity.