Abstract:

Aims: By conducting a quantitative morphological assessment of continuous characters—specifically the pronotum and elytron—of three fungivorous beetle taxa belonging to the genera Dorcatoma, Mycetophagus, and Aspidiphorus distributed across different altitudinal zones in the Chebaling National Nature Reserve, Guangdong Province, this study investigates the adaptive morphological changes of beetles along an altitudinal gradient and elucidates the relationship between morphological variation and environmental factors. 

Methods: Based on geometric morphometrics, the left outline of the pronotum and elytron of three beetle taxa was quantified. Principal component analysis and canonical variate analysis were employed to investigate morphological differences among beetle populations from different altitudinal regions, while traditional body size measurements were used to assess patterns of body size variation. 

Results: Morphological traits of beetle assemblages differed significantly across altitudinal gradients, with variation in elytron shape being more pronounced than that of the pronotum. The deformation patterns of the pronotum and elytron differed among the three beetle taxa. In Dorcatoma spp., both pronotum and elytron shapes were significantly influenced by altitude, and the elytron became narrower and more elongated at Altitudinal Gradient III. In Mycetophagus spp., pronotum shape showed no significant altitudinal effect, whereas elytron shape varied significantly across altitudinal gradients. In contrast, neither pronotum nor elytron shape in Aspidiphorus spp. showed significant responses to altitude. Traditional morphometric analyses further revealed that only the body length of Aspidiphorus spp. differed significantly among altitudinal gradients, whereas body size remained relatively stable in Dorcatoma spp. and Mycetophagus spp. 

Conclusion: Altitudinal gradient is a significant ecological factor influencing the morphological changes of the pronotum and elytron in beetles. However, its effect varies among species. This study provides new empirical evidence from a morphological perspective, highlighting the impact of ecological gradients on insect morphological variation and potential adaptive evolution, thus offering fresh insights into the ecological drivers of animal morphology evolution.

Key words: Ecological factors, morphological evolution, elevation gradients, beetles, geometric morphometrics