Morphological Variability in Two Populations of Millipede Glomeris hexasticha Brandt, 1833 (Diplopoda: Glomerida: Glomeridae): Traditional and Geometric Morphometric Approaches

Abstract

Environmental factors and human activities can affect the variation (at both inter- and intrapopulation levels) in the shape and size of various morphological traits, which play a role in behaviour, dispersal and reproductive strategies. Although inter- and intrapopulation morphological variation has been investigated in certain millipede species utilising both traditional and geometric morphometric methods, such research has not yet been conducted on glomerids. Therefore, this study aims to investigate morphological variation in specific traits at both mentioned levels in Glomeris hexasticha Brandt, 1833. Analysed individuals were collected from two populations in Belgrade, Serbia. Both traditional and geometric morphometric techniques were employed to assess morphological variability. Landmarks and semilandmarks were placed on the antennae, gnathochilariums, legs, collums, anal shields and telopods. Morphological variability was analysed using ImageJ, CoordGen, MorphoJ, and R program package. No significant interpopulation size differences in the analysed morphological traits were observed; however, significant sexual size differences were noted in both populations, with females being the larger sex. Shape variation was identified in some morphological traits at inter- and intrapopulation levels. The shape of the analysed morphological traits demonstrates greater phenotypic plasticity compared to the size of the same traits in G. hexasticha exposed to varying environmental pressures.