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Banksia ionthocarpa

Status: Endangered on the EPBC Act list

Banksia ionthocarpa subsp. ionthocarpa Banksia ionthocarpa subsp. ionthocarpa is a tufted shrub with a very short stem and leaves up to 30 cm long. The leaf lobes are broadly triangular, up to 8 mm and cut within 1.5 mm of the midrib. The subspecies is an obligate seeder (fire killed, with seedlings growing from a seed bank after fire). With pale-yellow flowers borne close to the ground within the leaves, B. ionthocarpa subsp. ionthocarpa has characteristic follicles (dry fruit containing seeds) that are not woody, differing from those found in most Banksia species. Each follicle contains one seed, is about 5 mm in size and covered in 7-8 mm long erect hairs. The subspecies is also unusual in that the floral bracts (leaves around the flower) do not elongate as the fruits develop. Banksia ionthocarpa subsp. chrysophoenix Banksia ionthocarpa subsp. chrysophoenix is a shrub to 40 cm high with underground stems. The leaves are rigid, with straight margins. The follicles (not seen when mature) are long and ovate, narrowing at the base, and covered in a felt-like covering of cottony hairs on one edge. They also have the characteristic apical tuft found in the other subspecies (Pieroni 2000; George 2005; Cavanagh & Pieroni 2006). Flowering occurs from July to September. Banksia ionthocarpa subsp. chrysophoenix differs from B. ionthocarpa subsp. ionthocarpa through its fire-tolerant underground stems capable of post-fire resprouting, as well as straighter leaf lobes (George 2005; Cavanagh & Pieroni 2006). Banksia ionthocarpa subsp. chrysophoenix also predominately reproduces clonally, whilst B. ionthocarpa subsp. ionthocarpa reproduces sexually (Millar et al. 2010). This description was adapted from DEC 2007.

Government evidence of impact of climate change:

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  • Australian Government, Conservation Advice, Banksia ionthocarpa

    Threats The known subpopulations of both subspecies of B. ionthocarpa are threatened by inappropriate fire regimes and drought associated with climate change; habitat disturbance and grazing.

    This is likely to continue in the future; with south western WA projected to experience decreased rainfall; increased average temperatures and increased frequency of droughts as a result of climate change (CSIRO Bureau of Meteorology 2015).

    Current seedling survival is poor; primarily as a result of drought stress; and any further adverse change in conditions due to climate change will be severely detrimental to recruitment.

    While occasional fire is required for B. ionthocarpa subsp. ionthocarpa seedling recruitment; inappropriate timing; intensity; and frequency of fire may be detrimental to the subspecies; as plants need to reach reproductive maturity to build up a seed bank A too frequent fire regime ( 15 years) is likely to kill adult B. ionthocarpa subsp. ionthocarpa plants before soil stored seed banks or sufficient seeding can be occur to replace the parent plants (Brown et al. 1998); and a drying climate may also lengthen the minimum fire interval required for self replacement of obligate seed regenerators such as B. ionthocarpa subsp. ionthocarpa (Enright et al. 2014).

    Substantial germination has also been observed after an extreme rainfall event in 2005) indicating that the species has the capacity for non fire related germination from the soil seed bank.

    The species is threatened by several fire related threats; including high frequency fire; fire disease interactions and fire promoted weed invasion.

    In the 2008 2013 recovery plan for B. ionthocarpa subsp. chrysophoenix; fire was not classified as a threat; though it is indirectly impacted by a lack of fire in the region.

    These altered fire regimes can create conditions that are favourable to the establishment and spread of weeds (D’Antonio Vitousek 1992 Grigulis et al. 2005) that can outcompete B. ionthocarpa subsp. ionthocarpa.

    Conduct surveys for both subspecies to detect new subpopulations or individuals; especially after a bushfire has impacted the species habitat.

    Increase understanding of both subspecies fire ecology; and response to low and high frequency and low and high intensity fires.

    Drought may directly impact B. ionthocarpa subsp. ionthocarpa by reducing flowering; seed set and subpopulation recruitment; and by increasing plant mortality (Barrett Cochrane 2004).