In situ evolutionary adaptation of Australian plants to climate change

Background/Question/Methods

In Southwestern Australia, a biodiversity hotspot, decreased annual rainfall is causing great concern for the persistence of native flora.  In situ evolutionary adaptation can help species to counter environmental stresses arising from climate change. We propose that species may have significant potential to respond evolutionarily to a changing climate, and ecosystems might be more resilient than we currently believe, with genetic adaptation leading to ‘effect dampening’ within a relatively short time frame. Many Australian species maintain a canopy seed-bank, seeds are stored on the plant for up to 15 years during which time extreme climatic changes may have occurred, e.g. recent extreme droughts in 2006-2010 with less than half of the average rainfall received. Plants with genotypes tolerant to drought are more likely to survive such climatic changes and produce offspring bearing stress-tolerant genes. Thus parental environments can facilitate the evolution of life history, and genetic variation to resist water stress could be accumulated rapidly in seed banks in water-stressed environments. Stresses from climate change might have been an agent of selection for biological adaptation. We aimed to establish the pattern and speed of accumulation of water stress-tolerant genotypes through experimental investigations on growth behavior of seedlings in water stress conditions, using seed-banks with seeds stored across years when selection imposed through declined rainfall is evident.  

Results/Conclusions

We have found that a larger proportion of seedlings descended from plants recruited post-fire in winters with severe drought exhibited higher tolerance to drought treatment than those descended from plants recruited in winters with average, or above rainfall. Seedlings descended from plants that have survived severe drought produced longer root systems, larger leaves, more biomass, and developed thicker leaves, better able to prevent water loss when compared to seedlings descended from plants that have not experienced drought. Our current research is focusing on establishing an association between a shift of gene expression pattern with higher drought tolerance. We concluded that seed-banks have great potential importance in conferring flexibility to species in their response to changing environmental conditions, and may be able to mitigate deleterious impacts from climate change through rapid in situ adaptation and selection. The speed of any adaptive evolutionary change will be critical to an organism’s response to rapid climate change. Further research remains as to what extent the genetic variation in the seed bank may provide the opportunity for rapid adaptation to change in growing conditions.