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A new weed in Australia: Wissadula contracta (Malvaceae)

Given the nature of working as a field ecologist – getting to travel to remote areas and exploring environments rarely accessed by the public – an outcome of many surveys is improving our understanding of species distributions. Field surveys often result in new observations of native and exotic species which when submitted to the relevant authorities (Queensland Herbarium or Australian Museum) can become invaluable knowledge when developing conservation plans and mitigation strategies.

During a recent routine weed survey near Redlynch, north of Cairns, an unfamiliar shrub was observed in an old stockpile area. Notes were collected on the species habit and habitat and a specimen was collected, which we later identified as Wissadula contracta (Link) R.E.Fr., a species of the Malvaceae (Hibiscus) family, which includes familiar genera such as Abelmoschus, Abutilon, Hibiscus, Malva, Sida, and Urena. The species originates from South America, where it is found in Argentina, Guatemala, Mexico, Venezuela, Peru and Brazil. In its native habitat, W. contracta is a species of open roadside areas.

This recent observation represents the first record of the species in Australia. While the population here appears to be self-sustaining, little is known of its invasive potential. The specimen has been submitted in the Queensland Herbarium (BRI), Mt Coot-Tha; Brisbane

We speculate that the species may be a relic of the late Kamerunga State Nursery established in 1889 later operating as the Kamerunga Research Station which was located approximately 600m north-east of the collection location. W. contracta may have been introduced and spread from its original location by humans and/or wildlife. Nevertheless, it is surprising that this species could be undetected for so long given its close proximity to an urban area. Although W. contracta is unlikely to represent a significant threat to the integrity of the local or regional environment, its discovery has provided a glimpse into the history of the region.

Biotropica has recorded new species of weeds in both Australia and Papua New Guinea, and we have extensive knowledge of invasive species identification and management from across Queensland and Papua New Guinea. Our field crew are highly experienced in weed identification and control are fully equipped for control works in all environments.

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A, Leaves towards the base. B, close up of the underside of the leaf lamina showing the presence of star-like (stellate) hairs. C, the inflorescence is a dense panicle with flowers borne on individual pedicels and the bracts subtending each pedicel. D, the fruits are schizocarps with five mericarps.

 

From: Tng DYP, Horner G, Bovini MG. (2021) A South American in Australia: Wissadula contracta (Malvaceae), a distinctive adventive shrub. North Queensland Naturalist 51: 62-66.