Zhehao Tian, Jianxiong Su, Sheng Li, Yijie Tong, Xinpu Wang, Ming Bai
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.