Functional differentiation of ground-dwelling beetle communities as an adaptation to fragile alluvial fan habitats in arid regions.

Abstract

Alluvial fans are typically fragile and unstable landforms in arid regions, and their bioenvironmental coupling mechanisms remain unclear. The aims of this study were to test the hypothesis that elevation gradients drive beetle functional group differentiation through environmental filtering, reveal the core strategies of functional group adaptation to fragile habitats, and provide a theoretical basis for arid ecological restoration. Five transects were established along the alluvial fan elevation gradient, and ground-dwelling beetles were collected using pitfall trapping. Species and functional diversity analyses were conducted, and functional groups were classified using hierarchical clustering. The associations between functional traits and environmental factors were analyzed using RLQ and fourth-corner analysis. A total of 8251 ground-dwelling beetles were collected, and community diversity varied significantly with elevation. The first two axes of the RLQ explained 91.28% of total co-inertia. Feeding habits, activity rhythms, hind legs, antennae, and head width were significantly correlated with environmental variables. The five functional groups showed a gradient distribution from the fan apex to the fan margin: "broad-headed nocturnal saprophagous group → nocturnal carnivorous group → nocturnal phytophagous group → diurnal phytophagous group → long-legged and long-antennae diurnal phytophagous group." Combined with partial least squares structural equation modeling (PLS-SEM), this study confirmed the rule that alluvial fan instability regulates habitat heterogeneity through elevation gradients, which in turn drives beetle functional group differentiation. Functional groups can serve as indicators of habitat stability. This study deepens understanding of insect community assembly mechanisms in fragile landforms and provides scientific support for arid ecosystem protection and restoration.