Hot Topic

Invader from the dark side

Tuesday, 10 November 2015  | 

Key Points

  • Weeds are often associated with high light and disturbed habitats but shade-tolerant weeds are gaining attention as serious invaders of rainforests worldwide
  • The shade-tolerant Cherry Guava (Psidium cattleianum) is emerging as a serious invader of rainforest understoreys in the Wet Tropics of North Queensland, and is well-known to have the potential to displace native vegetation.
  • The prognosis for control is good but incisive action is needed.

Authors: DYP Tng (James Cook University), MW Goosem (James Cook University), CP Paz (James Cook University), and SGW Laurance (James Cook University)

Environmental weeds typically invade open, disturbed areas or vegetation edges, and can have devastating ecological and economic consequences. The National Weeds List in Australia informs the public and land managers on weeds prioritized for management, but shade-tolerant weeds that can invade forest ecosystems are inadequately listed. Such weeds are now globally recognized for their ability to impact native vegetation. The Cherry Guava (Psidium cattleianum) from Brazil, a shrub of the Myrtle family (Myrtaceae), is an exceptional example.

1. Cherry Guava was probably introduced to Australia for its edible fruits. The earliest record (1940s) was in Koah, Far North Queensland. Currently, Cherry Guava infestations are found in three World Heritage Areas in Australia: the Wet Tropics in Queensland; Gondwanan Rainforests of Queensland/New South Wales, and Lord Howe Island. It is listed as a noxious weed only in NSW. There are no Australian regulations restricting import or sale.

2. The Global Invasive Species Database lists Cherry Guava among the World’s 100 Worst Weeds – it tolerates shade; grows and matures rapidly; produces a heavy fruit set and seedling bank; is spread by native and feral animals; coppices extensively; and forms multi-stemmed thickets. It can displace native vegetation. Infestations in Australia appear free of natural enemies and resistant to Myrtle Rust which affects co-occurring native members of the Myrtaceae. In Hawaii, Seychelles and Mascarene Islands, natural forested ecosystems are severely impacted after introductions in the early- to mid-1800s.

3. Cherry Guava spread is ongoing, but given the recent Australian history and localized infestations, eradication may be possible with incisive intervention. Government listings and restricting import and sale are first steps. Options to eliminate infestations could combine ecotourism, volunteers and biological control agents.

More on this Hot Topic:

– Link to peer-reviewed article via Austral Ecology –

If you have recently published an update on this topic, please contact the HT author for your research to be considered for addition to the evidence review.

 

Supporting Research

Title
Aims
Atlas of Living Australia.2014. URL: http://bie.ala.org.au/ (Accessed: 11 Dec 2014).
User generated search on Psidium cattleianum (Myrtaceae) in Australia to generate distribution records.
Auld T.D., & Hutton I. (2004). Conservation issues for the vascular flora of Lord Howe Island. Cunninghamia 8, 490-500.
To describe the nature of the major threats to the flora of Lord Howe island and to suggest an area-based scheme for the relative conservation significance of remaining vegetation
Cooper W, Cooper WT. (2004) Fruits of the Australian Tropical Rainforest. Nokomis Editions, Victoria, Australia.
To provide botanical drawings and keys detailing the diversity of fruits in Australian tropical rainforests.
Fleischmann K. (1997) Invasion of alien woody plants on the islands of Mahé and Silhouette, Seychelles. J. Veg. Sci. 8, 5-12.
To present a quick and easily method of repeatable evaluation of the state of invasion of alien woody plants and the ecological status on the Seychelles Islands.
Global Invasive Species Database. 2014. Psidium cattleianum. http://www.issg.org/database/species/ecology.asp?si=59&fr=1&sts=sss&lang=EN [Accessed 9th December 2014]
Provides dedicated species portraits and literature compilations on invasive species
Huenneke L. F., Vitousek P. M. (1990) Seedling and clonal recruitment of the invasive tree Psidium cattleianum: Implications for management of native Hawaiian forests. Biol. Conserv. 53, 199-211.
To investigate the reproductive ecology and seed germination physiology of Psidium cattleianum
keys.lucidcentral.org, (2015) Psidium cattleianum (Strawberry Guava). [online]. Available from: http://keys.lucidcentral.org/keys/v3/eafrinet/weeds/key/weeds/Media/Html/Psidium_cattleianum_%28Strawberry_Guava%29.htm [Accessed March 10, 2015].
To describe the biological attributes of Psidium cattleianum and control measures available
Lorence D. H., Sussman R. W. (1986) Exotic species invasion into Mauritius wet forest remnants. J. Trop. Ecol. 2, 147-162.
Vegetation sampling in mature evergreen wet forest in Mauritius (Mascarene Islands) to assess the extent of invasion by weedy exotics
Martin P. H., Canham C. D., Marks P. L. (2009) Why forests appear resistant to exotic plant invasions: intentional introductions stand dynamics and the role of shade tolerance. Front. Ecol. Environ. 7, 142-149.
A synthetic review on the role of shade tolerant plants as significant invaders of forested ecosystems globally
Morin L, Aveyard R, Lidbetter J. (2011) Myrtle rust: host testing uunder controlled conditions. NSW Department of Primary Industries, West Pennant Hills, NSW, Australia.
To test the susceptibility to Myrtle rust in representative taxa of the Myrtaceae
Shiels AB., Ennis MK, Shiels L. (2014) Trait-based plant mortality and preference for native versus non-native seedlings by invasive slug and snail herbivores in Hawaii. Biol Invasions 16, 1929-1940
Tested how traits drive gastropod herbivory on native and non-native plants (including Psidium cattleianum) in Hawaii
Wikler, C., Pedrosa-Macedo J. H., Vitorino M. D., Caxambú M. G., Smith C. W. (2000) Strawberry guava (Psidium cattleianum) – Prospects for biological control. pp. 659-665. In: N R. Spencer (eds.) Proceedings of the X International Symposium on Biological Control of Weeds 4-14 July 1999, Montana State University, Bozeman, Montana, USA.
Study and review potential biocontrol agents for P. cattleianum.