Lizards in Dunes and Swales: Habitat Structure and Assemblage Patterns

Habitat structure mediates thermoregulation, foraging opportunities, and access to refugia, shaping how animals use space and encounter risk. Dune–swale mosaics provide sharp structural contrasts over short distances, offering a natural test of structure–assemblage links and spacing relative to shelter. We compared lizard assemblages and the positions of active lizards relative to vegetative cover across interdunal swales and adjacent sand dunes in central South Australia. At replicated sites in Arid Recovery Reserve and Andamooka Pastoral Station, we quantified vegetation and ground-layer structure, sampled assemblages with pitfall traps and active searches, and measured each active lizard's distance to the nearest vegetative refuge. We tested whether the expected structural contrast between dunes and swales was evident at our study sites, whether lizard community composition and assemblage metrics differed between landforms, and whether active lizards in structurally simpler habitat occurred closer to vegetative cover than those in more complex habitat. Dunes were more structurally complex than swales, lizard communities differed significantly between landforms, and abundance was higher on dunes, whereas richness and diversity were broadly comparable. However, active lizards in both landforms occurred at similar distances to vegetative cover. These findings identify habitat structure as a key driver of assemblage differences, while showing that we did not detect a significant habitat-level difference in active lizards' distance to vegetative cover under the present sampling design. We interpret implications for predation risk broadly in a multi-predator context and recommend coupling behavioural metrics with predator-activity indices and repeating sampling across wet and dry years.