Research from Curtin University has found the future survival of iconic banksias in southwestern Australia may depend on the length of time in between local bushfire cycles.
More than 150 species of Banksia are present in the region, forming an important part of the Australian shrublands. Banksia attenuata is the most widely distributed of all western banksias, spanning a wide climate and environmental range in Western Australia from Kalbarri National Park in the north to Cape Leeuwin in the south.
The research team, led by Dr Tianhua He of Curtin’s Department of Agriculture and Environment, investigated the impact of recent changes in rainfall, temperature and fire regimes on the amount of adaptive genetic variation in Banksia attenuata, analysing the ability of the plant to withstand future changes in rainfall, high temperatures and increased fire susceptibility.
“Our previous research suggests that Banksia attenuata has been around for about 19 million years, which implies it has a long evolutionary history of being able to withstand changes in climate and environment,” Dr He said.
“However, by analysing genes that are directly responsible for the plant’s evolutionary adaptation, it was revealed that shortened fire cycles, predominantly a consequence of recent human activities, imposed the strongest pressure on the Banksia attenuata populations in southwestern Australia.”
Dr He explained that recurrent fire has been a major evolutionary force for Australian plants for at least 80 million years, however, plants are not adaptive to a fire itself; they adapt to specific fire regimes, such as the frequency and intensity of the fire.
“In the regions of southwestern Australia with shortened fire cycles, frequent fire has depleted much of adaptive gene diversity in the populations of Banksia attenuate,” Dr He said.
“This is because there was no sufficient fire-free time for accumulation of viable seeds, leading to the failure of establishment of seedlings between fire cycles.
“With more frequent fire cycles, the long-term population size of the species would be affected.”
The research team also evaluated the impact of changes in climate over the past 40 years on the evolutionary potential of the Banskia attenuata. They estimated the ability of the species to withstand variations to rainfall and increased temperatures, as well as other environmental characteristics that may be associated with climate change.
“Most of the revealed adaptive genes associated with rainfall and high temperature were shown to have multiple alleles, which suggests that recent changes in rainfall and temperature have had little impact so far on the Banksia’s ability to adapt to these environmental changes,” Dr He said.
“It’s also important to note that over the past 40 years, there is no record of a Banskia species becoming locally extinct during a continuous decline in the water table, such as what is happening in the Gnangara Mound, north of Perth, Western Australia.
“While the plant may be able to withstand the projected decline in rainfall associated with climate change, the continuing rise of summer temperatures may increase the frequency of bushfires, which our research suggests may hinder the future survival of Banksia attenuata, and other plant species with similar life history,” Dr He said.
Published in the journal Scientific Reports, the full paper entitled Evolutionary potential and adaptation of Banksia attenuate (Proteaceae) to climate and fire regime in southwestern Australia, a global diversity hotspot, can be found on the Nature website.
This research was supported by the Australian Research Council. Curtin PhD student Haylee D’Agui contributed significantly to the work.