Myrtus communis (Myrtaceae) as an alien species in South Africa: Status and prognosis

• Published in: South African journal of botany 2024-03, Vol.166, p.550-560
• Main Authors: Gwynne-Evans, David, Richardson, David M., McKenzie, Robert
• Format: Article
• Language: English
• Subjects: Fire; Management options; Mapping; Plant invasions; Urban-wildland interface
• ISSN: 0254-6299; 1727-9321
• DOI: 10.1016/j.sajb.2023.12.023

•Myrtus communis is an invasive plant, particularly in South Africa.•Seed are killed by fire but plants persist through resprouting.•Fire interval, elevated atmospheric CO2, and successful genetic adaptation likely explain its success.•We consider M. communis to be a Category-E invasive under increased CO2 levels.•We recommend early detection and a swift response to outbreaks and the exploration of effective control treatments. A survey of recovering fynbos vegetation on the Cape Peninsula, Western Cape, South Africa, after a wildfire in April 2021, led to the discovery of a large naturalised population of the shrub Myrtus communis. This species, native to the Mediterranean Basin and Western Asia, is commonly used as an ornamental plant in many parts of the world, including Australia, Europe, New Zealand, South Africa and the United States. It is not recognized in major world invasive databases as being a problematic invasive species. We documented the recovery of this naturalised population and evaluated other records of naturalised occurrences in the Cape Town metropolitan area. We assessed the known characteristics of the species in terms of its fire tolerance, water relations, shade preference, seed set, dispersal and germination. We propose that fire constitutes a useful tool to expose this species for eradication through herbicide application. We argue that there is a limited window-period for eradication of this species locally before it spreads further and potentially exerts impacts on ecosystems.