Population Ecology of Two Endemic, Fire-sensitive, Blue Mountains <i> Banksia</i> Taxa (Proteaceae) in Response to Fire
AbstractBanksia penicillata (northern Blue Mountains) and Banksia paludosa subsp. astrolux (Southern Highlands) occur in small, isolated populations and occasionally as isolated individuals. We undertook a ﬁeld study of both species to better understand their population ecology in relation to ﬁre. Both are large, serotinous, ﬁre-sensitive shrubs with plant-stored seedbank and a relatively short lifespan (<50 years); both were impacted by the severe December 2019 ﬁres. Recruitment is generally ﬁre-related, but some recruitment also occurs in the absence of ﬁre. At a landscape-scale, populations of Banksia penicillata occupy dry sandstone ridgetops, providing variable protection from major ﬁres, with occasional intergenerational long-distance seed dispersal establishing populations of variable duration in sites which do not usually act as ﬁre refugia. Banksia paludosa subsp. astrolux has similar responses, but generally smaller populations and more restricted range. Although some plants have been reported as surviving the 2019 ﬁre in nearby rocky ridgetop refugia, all plants were killed in our study populations and seedling recruitment has not replaced all pre-ﬁre occurrences, despite 18 years since the previous ﬁre. Using a precautionary approach, and in the context of a rapidly changing climate, we recommend that both species would beneﬁt by having populations of varying ﬁre histories and ages >15 years old across the landscape, including some sites with ﬁre intervals >30 years, to provide increased opportunities for distance-dispersal and establishment of new fruiting populations. Applying IUCN threatened species criteria, there is a strong case for listing Banksia paludosa subsp. astrolux as Endangered and Banksia penicillata as Vulnerable.