Exotic trees modify the thermal landscape and food resources for lizard communities

Increasing numbers of invasive plant species are establishing around the globe, and these species frequently form dense stands that alter habitat structure in critical ways. Nevertheless, little is known about the mechanisms underlying the impacts of invasive alien plant species on native fauna. We first ask whether alien pine trees impact lizard species richness in the Cape Floristic Region of South Africa, a world-renowned biodiversity hotspot, by examining differences in lizard species richness, abundance, and diversity between native mountain fynbos and exotic pine tree-dominated habitats. We then examine two mutually non-exclusive processes: (i) changes in the thermal quality of the habitat and (ii) changes in the availability of food resources, to explain differences in lizard assemblages among habitat types. Lizard richness, abundance, and diversity were greater in fynbos habitat than in fynbos heavily invaded by pine and in pine plantations. The thermal quality of the environment and food resources was consistently higher in native fynbos than in pine forests, but these responses were more varied when comparisons were made along an invasion gradient and among seasons. Our results suggest that management strategies must consider spatially and temporally detailed measurements of thermal regimes and resources to assess the impacts of invasive vegetation on reptile diversity.