Understanding how ecological diversification translates into morphological differentiation is central to explaining the evolution of organismal form and function. True dung beetles (Coleoptera: Scarabaeidae: Scarabaeinae) exhibit diverse resource-use strategies, mainly including tunneling and rolling behaviors, which impose different functional demands on locomotion, excavation, and dispersal. However, it is unclear whether these ecological differences are consistently associated with differentiation in functional traits, particularly across different body-size classes. Here, we compared five dung beetle species representing large and small tunnelers, large and small rollers, and a mixed-strategy species using external structural traits, functional trait analyses, principal component analysis, and allometric modeling. Allometric analyses indicated that most functional traits exhibited similar scaling relationships among species after false-discovery-rate correction, suggesting that structural differentiation was not primarily driven by body-size differences. Functional morphological analyses revealed clear differentiation among species with contrasting resource-use strategies, with variation mainly associated with foreleg proportions, hindleg elongation, and wing morphology. Size-matched comparisons further showed that rollers consistently possessed relatively longer hindlegs and more elongated hind-tibiae than tunnelers across body-size classes, whereas foreleg proportions and protibial structures displayed more variable patterns. The mixed-strategy species exhibited a mosaic combination of traits rather than strictly structural dependencies. These findings demonstrate that dung-relocation strategies are associated with different coordinated functional trait differentiation, highlighting a potential trade-off between excavation-related and locomotion/dispersal-related specialization.

Evolutionary biology faces the important challenge of determining how to interpret the relationship between selection pressures and evolutionary radiation of species. The different biodiversity indicators highlight the disparate nature of biodiversity investigations. However, the influence of ecological factors and the specificity of taxonomic phylogeny have led to controversy over the correlation between these indicators. By combining quantitative morphology and statistical methods, here we analyze the biodiversity under the influences of phylogenetic relation factors represented by higher categories. A total of 8508 species of beetles from 1247 genera, 34 subfamilies, and 10 families of the Scarabaeoidea were selected as a test group; 70% of the family-level samples and 60% of the subfamily-level samples were selected at a proportion of 10–30% of the global described species. The taxonomic categories of family and subfamily were selected for phylogenetic representation, and the analysis of geometric morphometrics on the pronotum and elytron, which represent the major aspect of the morphology in dorsal view, was conducted. Through principal component analysis and Spearman correlation coefficient analysis, it was found that: the morphological diversity of the pronotum is higher in most groups of family/subfamily category than in the elytron; the correlation between the morphological diversity and species richness of the pronotum in the superfamily Scarabaeoidea is higher than that of the elytron; correlations between morphological diversity of the pronotum and taxa richness among sub-/families were always found to be consistent, and it was higher than it in the elytron test. This study compares the correlation between the diversity of different characters and the richness of taxa to interpret the phylogenetic impacts of biodiversity and sheds light on a fresh perspective for detailed studies of the selection pressures and formation mechanisms regulating the rise and fall of species.