Local adaptation and species distribution limits along climatic gradients
Temperature increases associated with climate change have shown numerous negative effects on biodiversity and ecosystem functioning. In Australia, hot extremes are expected to be more frequent and intense, with less rainfall in southern Australia, putting pressure on species that are sensitive to warming and drying conditions. Heatwave events on top of constant warming pressure are expected to have the greatest impacts by pushing species beyond their limits leading to population collapses, local extinctions and shifts to novel ecosystems.
Acacia species are widespread and abundant across the Australian landscape, with contrasting distributions traversing mesic to arid biomes from southern temperate and northern tropic bioregions, making them ideal for studying species response to climate change. Close to 1000 of the approximate 1350 species of Acacia throughout the world are found in Australia, including 77 species listed as threatened on the Environment Protection and Biodiversity Conservation Act 1999. Acacia contribute greatly to ecosystem functioning through their role in nitrogen cycling in early to mid-successional vegetation. They provide habitat, floral resources for pollinator species and insects, and have economic benefits through their use in crop production and horticulture. Surprisingly little is currently known about how vulnerable Acacia species are to climate change although such research is critical for their long-term conservation.
My PhD aims to determine the adaptive capacity of widespread and restricted Acacia species to climate change through a combination of approaches: (1) Species Distribution Models to determine species climatic suitability of current ranges relating to their potential niche under current and future conditions; (2) glasshouse manipulation experiments to determine species’ temperature response curve (thermal niche) relating to their fundamental niche; (3) glasshouse temperature manipulation of populations within species to determine genetic adaptation and phenotypic plasticity; and (4) field reciprocal transplants to overcome dispersal limitations and explore factors influencing range limits and local adaptation.
Populations with greater physiological tolerance may be better able to persist through exposure to warmer and more extreme temperatures. Those that exhibit phenotypic plasticity may be better able to adjust to novel conditions by changing traits with climate. Populations may also change traits through genetic adaptation by sorting the standing genetic variation within populations or acquiring genetic variants from other (pre-adapted) populations. It is essential that we understand how species will respond to predicted climate scenarios, in order to adequately inform natural management practices and provide the best opportunity for conservation, particularly for threatened species that may already be close to extinction.
Dr Paul Rymer, Professor Mark Tjoelker, Dr Linda Beaumont