Predators, prey or temperature? Mechanisms driving niche use of a foundation plant species by specialist lizards.

Foundation species interact strongly with other species to profoundly influence communities, such as by providing food, refuge from predators or beneficial microclimates. We tested relative support for these mechanisms using spinifex grass ( spp.), which is a foundation species of arid Australia that provides habitat for diverse lizard communities. We first compared the attributes of live and dead spinifex, bare ground and a structurally similar plant (), and then tested the relative strength of association of two spinifex specialist lizard species ( and ) with spinifex using a mesocosm experiment. Temperatures were coolest within spinifex compared to bare ground and Invertebrate abundance and the threat of predation were indistinguishable between treatments, suggesting temperature attenuation may be a more important driver. Overall, the dragon preferred live over dead spinifex, while the skink preferred dead spinifex, particularly at warmer air temperatures. However, both species displayed individual variability in their use of available microhabitats, with some individuals rarely using spinifex. Our results provide an example of temperature attenuation by a foundation species driving niche use by ectothermic animals.