Woody species in resource-rich microrefugia of granite outcrops display unique functional signatures

Refugia are key environments in biogeography and conservation. Because of their unique eco-evolutionary formation and functioning, they should display distinct functional trait signatures. However, comparative trait-based studies of plants in refugia and non-refugia are lacking. Here, we provide a comparison between resource-rich (putative microrefugia for species preferring mesic habitats under increasing aridity) and resource-impoverished woodlands (non-refugia) around two granite outcrops in south-western Australia. We measured and compared six functional traits (bark thickness, foliar delta C-13, foliar C:N, leaf dry matter content, plant height, specific leaf area) in four woody species. We performed multiple-trait, multiple-species and single-trait, within-species analyses to test whether plants in resource-rich habitats were functionally distinct and more diverse than those in the surrounding resource-impoverished woodlands. We found that species in resource-rich woodlands occupied larger and distinct multiple-trait functional spaces and showed distinct single-trait values (for specific leaf area and bark thickness). This suggests that plants in resource-rich woodlands can deploy unique and more diverse ecological strategies, potentially making these putative microrefugia more resilient to environmental changes. These findings suggest that species in microrefugia may be characterised by unique functional signatures, illustrating the utility of comparative trait-based approaches to improve understanding of the functioning of refugia.