Invasive potential of Melaleuca parvistaminea in South Africa and the need to assess invasive potential of dry-seeded Myrtaceae
Llewellyn Jacobs1,2,3, Dave Richardson2, John Wilson2,3
1 Scientific Services, CapeNature, Private Bag X5014, Stellenbosch, 7599
2Centre of Excellence for Invasion Biology, Department of Botany and Zoology, University of Stellenbosch, Private Bag X1, Matieland, 7602
3Invasive Species Programme, South African National Biodiversity Institute, Private Bag X7, Claremont, 7735
Melaleuca parvistaminea Byrnes (Rough-barked Honey myrtle) was first brought to SANBI's ISP attention in 2009. Here we describe the survey and management of the population (the first record of an invasion for this species in the world). As yet not all areas have been searched exhaustively. We have found over 13 000 plants spread over 372 ha (condensed canopy area of ~0.73 ha) at 3 sites between Tulbagh and Wolseley, in the Western Cape. Population structure indicates considerable spread by seed with at least 63% of plants being seedling or juvenile. Clearing and fire trigger seed release causing prolific recruitment (up to ~18 000 seedlings/m2) after winter rain. No evidence for a soil stored seed bank was found. Risk assessment shows significant invasive potential, while bioclimatic niche modelling indicates high suitability in the southern Cape region. Plants however only reproduce at 5 years or older, allowing for sustained clearing efforts before juveniles can set seed.
Initially, this serotinous reseeder was identified as Melaleuca ericifolia Sm. (Swamp paperbark), a sister taxon, but examination of morphology and reproductive characters led to revised identification, highlighting the need for taxonomic work on new detections.
Given the potential for the species to dominate wetland habitats, we propose that this species should be listed as a target for compulsory control (i.e. eradication). We estimate eradication would currently cost ~R1.6 million.
There are several other invasive melaleucas in South Africa, and we briefly discuss current management and research efforts on each. Building on this work, we propose an MSc- project looking at a detailed assessment of dry-seeded Myrtaceae—assessing the factors that determine success at each stage of invasion at a global scale; evaluating which species are present in South Africa and which pathways these are associated with; and exploring the mechanisms underlying invasiveness in the ornamental genera Melaleuca and Callistemon.
The Southern African Weed Science Society is a voluntary association, founded in 1978, for scientists and managers in weed science and related disciplines. The Society's mission is to further weed science in Southern Africa through: improving control of the many weeds that drastically reduce our crop production and the alien invader plants that impact on our natural resources; supporting the use of the most efficient and environmentally acceptable control methods to benefit soil, water and atmosphere as well as plant and animal life. The Society promotes weed science in the sub-continent by: holding regular conferences & workshops; supporting the publication of the South African Journal of Plant & Soil; distributing a regular newsletter; encouraging contact with international weed science organisations and local, allied agricultural, industrial, biological and conservation organisations; providing functions and awards to stimulate and recognise excellence and service.
Communicating invasives in a digital era
Nurseries and Pet Trade Partnership, Environmental Programmes
Invasive alien species (IAS) are considered by the International Union for Conservation of Nature (IUCN) to be the second greatest threat to biodiversity on Earth, after climate change. Scientists have battled invasives for a century, governments have employed a range of strategies to control invasives for two decades and conservationists have been flagging the issue as environmentally critical for years. It is now time to take the issue of invasives to the people.
Environmental Programmes is a pioneering leader in the field of communicating the issue of invasives in South Africa. This presentation surveys the communication strategies used internationally over the past decade, explores the range of communication channels open to scientists and professionals working with invasives in South Africa and proposes an exciting new campaign for promoting the issue of invasive species to the public this summer. If you would like people across the world to better understand your work in the field of invasive species in South Africa, this presentation will give you a step-by-step guide on what to do…
Kay Montgomery has a Masters in Geography and Environmental Sciences from the University of the Witwatersrand and has spent two decades working in the South African media. She has worked on various communication and stakeholder projects for Working for Water, Working on Fire and Working for Wetlands - now Environmental Programmes – since 1999.
The unofficial Working for Water website was created in 2009 to overcome maintenance delays and content restrictions associated with the corporate website. During its four year existence, the site has been visited by 1,534 unique visitors, 80% from South Africa. The site’s focus is on labour- intensive, established, terrestrial invasive alien plant operational support and planning and is divided into assessment, strategy, implementation and monitoring & evaluation pages. The site hosts the only sources of the national assessments; prioritisation strategies; treatment tables, density, workload and herbicide estimation tools; and mechanical, chemical & biological control spatial data.
The power of molecular ecology in uncovering the truth behind Tamarix invasion in South Africa
1School of Animal, Plant and Environmental Sciences, University of the Witwatersrand, Private Bag X3, WITS 2050, South Africa
Tamarix (Tamaricaceae) is from the Old World, but has become naturalized and invaded other parts of the world including South Africa. Tamarix usneoides is the only species native to southern Africa, but the exotic species T. aphylla, T. chinensis, T. parviflora and T. ramosissima have been reported to be present in South Africa and these Tamarix species are hypothesized to be hybridizing among themselves and with the indigenous T. usneoides. Among the exotic species, T. chinensis, T. ramosissima and their putative hybrids have become invasive. Tamarix usneoides is used in southern African mines for phytoremediation as it has the ability to hyper-accumulate sulphate and heavy metals from Acid Mine Drainage from Tailing Storage Facilities and excretes gypsum (CaSO4). Tamarix species are morphologically and ecologically similar, making them difficult to distinguish and hybridization adds to the taxonomic confusion. Identification of Tamarix species in South Africa is of great importance because of the invasive potential of T. chinensis, T. ramosissima and their putative hybrids, and also because of the potential usefulness of T. usneoides. This investigation aimed to identify populations of pure T. usneoides that can be cloned for cultivation for phytoremediation on the mines, and to reveal the geographic origin of the invasive species to facilitate a biological control programme. Nuclear (ITS) and plastid (trnS-trnG) DNA sequence data and the multilocus Amplified Fragment Length Polymorphisms (AFLPs) markers were used in this study to characterize southern African Tamarix species and their putative hybrids. Phylogenetic analyses and population genetic structure confirm the presence of three Tamarix species in South Africa (T. chinensis, T. ramosissima and T. usneoides) with admixed individuals. The indigenous T. usneoides is clearly genetically distant from the alien species T. chinensis and T. ramosissima. Although the exotic species remain largely unresolved in the phylogenies, they are distinctly separated through AFLP markers. The Tamarix infestation in South Africa is dominated by hybrids between T. chinensis and T. ramosissima, and the parent species match their counterparts from their places of origin in Asia, which can provide the source of potential biological control agents. Some remote populations, e.g. in north western South Africa at the border with Namibia, of pure breeding T. usneoides have been identified and these should be used as a source of genetic material that can be propagated for planting on the mines for phytoremediation programmes.