Exotic trees modify the thermal landscape and food resources for lizard communities
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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.
KeywordsEctotherm Thermoregulation Operative temperatures Preferred body temperature Pinus radiata
Funding for this project was provided by the DST-NRF Centre of Excellence for Invasion Biology (C.I.B), Stellenbosch University, South Africa, and E.S. was supported by a C.I.B bursary. All applicable institutional guidelines for the care and use of animals were followed (# SU-ACUM12:00023) and Cape Nature granted collection permits (# 0056-AAA041-00006). The authors thank M. Logan, A.E. Magurran and an anonymous referee for useful comments on the manuscript, and the Speirs family and G. Williams for access to field sites.
Author contribution statement
SCT formulated the idea, ES conducted the fieldwork, and ES and SCT developed methodology, performed statistical analyses, and wrote the manuscript.
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