Downy Star-bush  |  

Asterolasia phebalioides

Status: Vulnerable on the EPBC Act list

Asterolasia phebalioides (Downy Star-bush) belongs to the family Rutaceae. It is an open to compact shrub growing to one metre high. The leaves are leathery and wedge to heart-shaped with rounded tips, often partly or strongly folded, five to ten millimetres long and two to six millimetres wide, and densely crowded on short branches. The stems and leaves have a dense covering of short, grey to brown, star-shaped, woolly hairs. Flowers are small, terminal and solitary, bright yellow in colour, sessile and closely subtended by five leafy bracts. Each petal is six to ten millimetres long and covered with fine hairs in a star formation on the outer surface, while the sepals are greatly reduced or absent. The stigma is deeply divided into five spreading linear lobes (SA Herbarium 2007; Carter 2010). Asterolasia muricata (Lemon Star-bush) grows with Downy Star-bush on Kangaroo Island in the Ravine de Casoars Wilderness Area. It differs from Downy Star-bush in having oblong leaf lamina and the upper surface of leaves covered with short, hard-pointed protuberances.

Government evidence of impact of climate change:

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  • Australian Government, Conservation Advice, Asterolasia phebalioides

    Threats Downy Star bush is threatened by disease climate change; which drives more frequent fires and altered rainfall lack of soil disturbance vegetative clearing and introduced grasses.

    Climate change is predicted to increase the intensity and frequency of fires.

    This type of event is increasingly likely to reoccur as a result of climate change; and the severity and frequency present a major threat of extinction for the Downy Star bush.

    Climate change Change to precipitation Timing current The CSIRO and Bureau of Meteorology (2015) patterns Confidence projected predict eastern Australia will experience decreased rainfall; increased frequency of Consequence moderate droughts and average temperatures.

    Such changes Trend increasing in climate may cause widespread plant mortality Extent across the entire in forest ecosystems; as many plants are range vulnerable to drought stress and hydraulic failure (Allen et al. 2010 Choat et al. 2012).

    Downy Star bush is threatened by several fire related threats; including high frequency fire; fire disease interactions and fire promoted grass invasion.

    Threat Status and severity a Evidence Fire Increased frequency of Timing current Fire frequency is important; as plants require the bushfires Confidence observed time to mature and set enough viable seed to recruit post fire.

    A high frequency fire regime (less than the range time to set enough viable seed to replace the population) is likely to reduce the population size and vigour of Downy Star bush.

    Analysis by the Wildlife and Threatened Species Bushfire Recovery Panel; based on intersecting the modelled distribution of Downy Star bush with the National Indicative Aggregated Fire Extent Dataset; indicates that approximately 16 percent of the range of Downy Star bush was within the extent of the 2019 2020 bushfires (Gallagher 2020).

    This fire disease interaction is relevant for Downy Star bush which faces the threat of high frequency fires.