Root-suckering and Clonality in a Blue Mountains Banksia Taxon (Proteaceae)

Abstract

We report novel observations of widespread root-suckering from shallow lateral roots, and clonal morphology in 29 populations of plants ascribed to Banksia paludosa subsp. paludosa in the upper Blue Mountains, NSW, and differing from southern populations (Southern Highlands and Woronora Plateau) which are lignotuberous resprouters.

Following fire, Blue Mountains populations can resprout to form multi-stemmed shrubs appearing to be lignotuberous resprouters, but form root connected populations of sometimes closely spaced ramets in discrete areas. New single- or multiple-shoot root suckers frequently arise following fire from lateral roots at varying distances from the nearest established ramets. No lignotubers (developed on seed-grown plants) were observed, but multi-stemmed ramets which survive multiple fires may develop small, swollen, woody underground structures where they originate from lateral roots, but these are also frequently killed by fire and thus not reliably persistent regenerative organs. Cone development is rare, compared with southern populations, and no seedling recruitment was observed in any population.

Such geographically widespread and ubiquitous root-suckering has not previously been reported in Banksia species in eastern Australia, though it has been reported in southwestern Australian species and in an ecotype of Banksia marginata from western Victoria and South Australia. We suggest that Blue Mountains populations of this species may represent a distinct taxon with a different post-glacial history and recommend genetic and taxonomic studies to better understand the relationships with related species, including the identity and placement of the Blue Mountains root-suckering taxon reported here.