Local adaptation to climate in Sydney sandstone plant species

Determining the extent and effect of local adaptation on survival is central to understanding plant responses to the abiotic environment. Understanding species capacity to respond to rapid, human-driven changes to climate is essential for conservation planning and ecological restoration. For instance, the presence of local adaptation also influences decisions about the sourcing of seed for revegetation programs. Here, I examine whether germination and establishment of two plant species (Acacia suaveolens and Banksia serrata) show evidence of local adaptation to temperature using germination trials and common garden experiments. Experimental populations were sourced from cold and warm margins of a temperature gradient between the Blue Mountains and Central Coast, New South Wales. We hypothesise higher fitness for individuals grown in ‘home’ conditions relative to ‘foreign’ (e.g higher seedling growth and survival). We found contrasting evidence of local adaptation to local temperature across the range of traits measured in each species. Growth-chamber trials showed B. serrata radicle growth and time till germination were higher at temperatures closer to those experienced by populations in the field, whereas common garden trials at both ends of the temperature gradient showed little to no evidence of local adaptation in the early establishment phase of either species. We discuss the implications of these results for climate change adaptation and ecological restoration projects.