Delineating wing sexual dimorphism in Culicoides (Diptera: Ceratopogonidae) using novel Bayesian and classical...

Sexual dimorphism remains insufficiently studied in disease vectors, particularly in medically and veterinary important Culicoides species. This study employed both classical and Bayesian wing geometric morphometrics to analyze sexual dimorphism in Culicoides oxystoma, Culicoides peregrinus, Culicoides innoxius, Culicoides huffi, and Culicoides clavipalpis. Classical wing geometric morphometric analysis (CWGM) revealed significant (p < 0.05) female-biased sexual size dimorphism across the investigated species, with females exhibiting larger centroid sizes. Allometric analysis showed that wing shape was significantly (p < 0.001) related to size, yet sexual shape dimorphism persisted after size correction, and males and females exhibited parallel allometric trajectories. Bayesian wing geometric morphometric analysis (BWGM) further quantified sex-specific wing shape variability through posterior estimation of Procrustes variance. In most Culicoides species examined, females exhibited greater within-sex variation than males, except for C. huffi. Sex-specific MCMC convergence of posterior estimates across species further supported the reliability of BWGM. Hellinger distances indicated strong to near-complete divergence between male and female posterior distributions. Moreover, the concordance between CWGM and BWGM results reinforces confidence in the biological relevance of the observed dimorphic patterns. Notably, this is the first time a Bayesian geometric morphometric framework has been used to explore sexual dimorphism, providing robust inferences by explicitly accommodating parameter uncertainty and accounting for sample-size effects when assessing sex-specific wing shape variation.