Traits Associated With Local Extinctions of Native Plants in a Species-Rich Urban Reserve

Aims

Understanding the drivers of local extinctions is important for forecasting potential biodiversity losses at larger scales. Many local extinctions are concentrated in urban areas because of stressors such as habitat loss driven by land clearing and urban expansion, and the spread and increase in abundance of invasive species. We aimed to quantify the number of native plant species that have potentially gone locally extinct in a 20-ha conservation-significant urban reserve, assess which traits were more strongly associated with local extinctions and explore the factors driving these local extinctions.

Location

Wategora Reserve, Western Sydney, New South Wales, Australia.

Methods

We conducted an intensive, comprehensive botanical survey of Wategora Reserve across more than 300 h from 2020 to 2023. We compared our species list with a historical list spanning surveys from 1976 to 1992 and compared which native vascular plant species had persisted and which were not redetected, that is, possible local extinctions. We scored all species for seven plant traits and used Pearson's chi-squared tests to compare traits across persistent and extinct species.

Results

Eighty-six of the 300 (29%) native vascular plant species originally recorded in Wategora Reserve from 1976 to 1992 could not be redetected from 2020 to 2023. Compared with persistent native species, native species that went extinct were shorter on average, more likely to have a graminoid growth habit and more likely to be associated with water.

Conclusions

These patterns were likely driven by synergistic stressors including urban stream syndrome and the proliferation of a few highly invasive non-native grass species, which are drivers common to many urban areas globally.