Sex-dependent trait variation and environmental associations in a subtropical dung beetle: integrating single-trait analyses and network topology

Abstract

Intraspecific trait variation is increasingly recognised as a key component of ecological responses to environmental change in both tropical and subtropical ecosystems, yet sex-specific differences in phenotypic integration remain largely understudied. We investigated sexual dimorphism in the dung beetle Onthophagus atripennis across seven subtropical forest plots in southwestern China, by integrating single-trait analyses with trait network approaches. We measured 18 morphological traits in 299 individuals (150 females and 149 males). At the single-trait level, six morphological traits differed significantly between sexes, with males consistently larger than females; these differences were concentrated in body size and structures associated with digging. Trait–environment associations also diverged between sexes, with females showing more specific responses to herb-layer diversity and litter cover, whereas males exhibited more diffuse responses across altitude, litter thickness, and shrub structure. At the trait network level, although network parameters did not differ significantly between sexes, environmental drivers affected network integration in a sex-specific manner. Females showed increased network integration in response to steeper slopes and thicker litter, whereas males displayed decreased integration at higher elevations. These results indicate that sex differences were primarily reflected in trait values, in trait–environment associations, and in network–environment associations, rather than in intrinsic differences in static network topology. Owing to limited plot-level replication ( n = 7 plots available for network analyses), these results should be interpreted as exploratory and hypothesis-generating. Our findings suggest that sex-specific perspectives could improve assessments of functional responses in soil fauna. This is particularly relevant for tropical and subtropical forest restoration efforts.