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<p>The sand-swimming skink, Scincus scincus, exhibits pronounced cranial adaptations for its fossorial lifestyle, yet the interplay between sexual selection and allometry in shaping its skull remains unquantified. This study utilizes a structure-from-motion photogrammetry workflow and three-dimensional geometric morphometrics (3D GMM) to analyze cranial variation in 48 adult skulls (22 males, 26 females) from southeastern Algeria. We investigated sexual dimorphism in skull size (centroid size) and shape, while rigorously quantifying the role of static allometry using the symmetric component of landmark configurations. Results, validated by high-repeatability landmarking (<i>R</i> &gt; 0.95), confirm significant male-biased size dimorphism. A multivariate regression identified a significant pattern of static allometry (<i>P</i> = 0.007), indicating that size-related shape changes are a consistent factor in adult morphology. Crucially, the sexes exhibit divergent allometric trajectories, as demonstrated by a significant size × sex interaction term (<i>P</i> = 0.015). This indicates that males and females follow different shape trajectories as they increase in size. While mean shape differences were not significant after controlling for this divergence (<i>P</i> = 0.096), males exhibited significantly higher morphological disparity than females (<i>P</i> = 0.023), suggesting relaxed stabilizing selection on male cranial geometry compared to the tightly canalized female phenotype. We propose that the intense biomechanical constraints of “sand-swimming” impose a stabilizing pressure that limits extreme morphological divergence between the sexes. This study provides the first 3D morphometric quantification of the S. scincus skull, elucidating how static allometry and ecological constraints interact to produce a functionally conserved morphology in a highly specialized desert reptile.</p>

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Sexual dimorphism and allometry of the skull in the sand-swimming skink, Scincus scincus (LINNAEUS, 1758): a three-dimensional geometric morphometric analysis

  • 期刊论文

  • 发表日期：

    2026年7月23日

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  • Mohamed Amine Fares,
  • Aicha Mouane,
  • Maria Chikha,
  • Khadra Afaf Bendrihem,
  • Hayat Laoufi,
  • Asma Abid,
  • Fahima Neffar,
  • Bahia Bacha,
  • Salima Zereg,
  • Saoucen Alayat Moufida,
  • Souad Aouimeur,
  • Aziza Ferag

摘要

The sand-swimming skink, Scincus scincus, exhibits pronounced cranial adaptations for its fossorial lifestyle, yet the interplay between sexual selection and allometry in shaping its skull remains unquantified. This study utilizes a structure-from-motion photogrammetry workflow and three-dimensional geometric morphometrics (3D GMM) to analyze cranial variation in 48 adult skulls (22 males, 26 females) from southeastern Algeria. We investigated sexual dimorphism in skull size (centroid size) and shape, while rigorously quantifying the role of static allometry using the symmetric component of landmark configurations. Results, validated by high-repeatability landmarking (R > 0.95), confirm significant male-biased size dimorphism. A multivariate regression identified a significant pattern of static allometry (P = 0.007), indicating that size-related shape changes are a consistent factor in adult morphology. Crucially, the sexes exhibit divergent allometric trajectories, as demonstrated by a significant size × sex interaction term (P = 0.015). This indicates that males and females follow different shape trajectories as they increase in size. While mean shape differences were not significant after controlling for this divergence (P = 0.096), males exhibited significantly higher morphological disparity than females (P = 0.023), suggesting relaxed stabilizing selection on male cranial geometry compared to the tightly canalized female phenotype. We propose that the intense biomechanical constraints of “sand-swimming” impose a stabilizing pressure that limits extreme morphological divergence between the sexes. This study provides the first 3D morphometric quantification of the S. scincus skull, elucidating how static allometry and ecological constraints interact to produce a functionally conserved morphology in a highly specialized desert reptile.