Alien Plants In South Africa Research Articles

Will climate affect the establishment and efficacy of Agnippe sp. #1 (Lepidoptera: Gelechiidae), a promising biological control agent of Mesquite in South Africa?

Several spiny leguminous tree species within the genus Neltuma Raf. (formerly Prosopis L.) (Fabaceae) occur as widespread invasive alien plants in South Africa, exerting severe negative socio-economic and ecological impacts. Given these impacts, South Africa recently released the leaf-tying moth Agnippe sp. #1 (syn. Evippe sp. #1) (Lepidoptera: Gelechiidae) as a biological control agent against invasive Neltuma species in 2021. The widespread invasion of Neltuma spp. across a vast and climatically diverse range of South Africa has led to concerns regarding the establishment and impact of the agent. Therefore, this study aimed to assess the constraints posed by climate to the potential establishment and efficacy of Agnippe sp. #1 using both climatic matching (CLIMEX) and thermal-physiology assessments. Climatic analyses revealed relatively high (71%) and moderate (66%) matches of South Africa to the native (Argentina) and introduced (Australia) ranges of Agnippe sp. #1 respectively. Thermal assessments of Agnippe sp. #1, particularly the 4th instar larvae, determined a CTmin = 0.9 ± 0.3 °C and LLT50 = −11.1 ± 0.4 °C, which suggest the moth is suited mainly to warmer regions of South Africa. Overall, these assessments propose that the establishment and performance of Agnippe sp. #1 is likely to be constrained by climate in parts of South Africa, particularly within the cold semi-arid and temperate provinces of the country. Promisingly, these climatic comparisons suggest that Agnippe sp. #1 may become more widely established in the hottest parts of the Northern Cape province, which remains a major biological control target region for Mesquite in South Africa.

Topsoil and Vegetation Dynamics 14 Years after Eucalyptus grandis Removal in Eastern Cape Province of South Africa.

A great deal of effort has been made to clear invasive alien plants in South Africa, yet it remains unclear if the clearing efforts are yielding positive soil and vegetation recovery trajectories. A few short-term studies have been conducted to monitor soil and vegetation recovery after alien plant removal in South Africa, but convincing, long-term monitoring studies are scarce yet needed. We investigated topsoil and vegetation recovery following Eucalyptus grandis removal 14 years ago by Working for Water in Makhanda, Eastern Cape province of South Africa. The detailed topsoil and vegetation surveys were conducted on forty 10 m × 10 m plots that were in paired cleared and natural sites. The results show no significant differences for the measured soil pH, total N, total C, K, Ca, and Na between the cleared and natural sites, an indication that the two sites are becoming similar. Similarly, the gravimetric soil moisture content shows no significant differences between the two sites, although monthly variations are observed. The topsoils in the cleared sites are hydrophobic as compared to those in the natural sites, which are wettable. We observed no significant vegetation diversity differences between the two sites, with native woody species, such as Crassula pellucida and Helichrysum petiolare, frequently occurring in the cleared sites. We recorded low reinvasion by E. grandis and other secondary invaders like Acacia mearnsii and Rubus cuneifolius in the cleared sites. Based on these results, we conclude that 14 years after E. grandis clearing, both topsoil and vegetation recovery are following a positive trajectory towards the natural sites. However, both reinvasion and secondary invasion have the potential to slow down soil and native vegetation recovery. Recommendations such as timeous follow-up clearing and incorporating restoration monitoring in the WfW clearing programme are discussed.

An Introduction to the Fourth Decadal Review of Biological Control of Invasive Alien Plants in South Africa (2011–2020)

This special issue is the fourth decadal review of biological control of invasive alien plants (biocontrol of weeds) in South Africa, following those published in 1991, 1999 and 2011. Including this introduction, there are 24 papers covering the weed biocontrol programmes, or important developments in the science and practice, from the period 2011-2020. Seventy-two target weed species are covered, including 25 species on which projects were initiated during the past decade. Developments in regulations, mass-rearing and implementation, and community engagement are also reviewed. An updated catalogue of agents released, rejected and under consideration is presented and reflects the most recent methods of quantifying success in weed biocontrol. Key events over the last decade include the hosting of the XIV International Symposium on Biological Control of Weeds to celebrate 100 years of weed biocontrol in South Africa, as well as the establishment of the Centre for Biological Control at Rhodes University. The science and practice of weed biocontrol has expanded significantly in the past decade, with growth in the number of researchers and practitioners, increased funding, and an increased number of scholarly outputs. Unlike many other countries in the world, South Africa has largely avoided constraints due to restrictive and risk averse legislation and bureaucracy, and has continued to release new biocontrol agents at a similar rate to that in previous years. Much of the success of weed biocontrol in South Africa is due to the sustained and increasing support of the Natural Resource Management Programme of the Department of Forestry, Fisheries and the Environment (Working for Water Programme). However, gaps in funding, where no funds are available for months at a time, are a major concern as the weed biocontrol community loses human capital in these periods, and research programmes suffer significant set-backs. Weed biocontrol is an essential component of South Africa's strategy to reduce the negative impacts of invasive alien plants and has contributed significantly towards the protection of the country's ecosystems, indigenous biodiversity, water security, agricultural productivity, and society in general. If the trend of increasing support for weed biocontrol in South Africa continues, we can expect that the benefits for the country at large will increase substantially in the future.

A Catalogue of Natural Enemies of Invasive Alien Plants in South Africa: Classical Biological Control Agents Considered, Released and Established, Exotic Natural Enemies Present in the Field, and Bioherbicides

A catalogue of natural enemies considered and released as biological control (biocontrol) agents against invasive alien plants in South Africa has been maintained for many years, and is updated here to include the period 2011-2020. The current catalogue reorders and separates data for exotic natural enemies that have been approved as classical biocontrol agents, from those on exotic natural enemies that have been considered but not released, exotic natural enemies that have been inadvertently introduced into South Africa with host plants that include target weed species, and locally sourced natural enemies that have been considered as bioherbicides. Ninety weed species have been targeted for biocontrol, with 310 exotic natural enemies considered, 136 classified as de jure or de facto classical biocontrol agents, and 92 established in the field on 66 target weeds. Ten of these species were found to have established independently of being released while research on them was in progress. An additional six exotic species have been found established on target weeds, and 11 locally sourced natural enemies have been considered for inundative or augmentative biocontrol, of which two have been developed commercially. Of the exotic natural enemies deliberately established, 35% inflict extensive damage to their host plants. Insects make up the majority of biocontrol agents (90%), with the balance of 8% being fungi and 2%, mites. Both establishment rates and damage levels vary between taxa. Five biocontrol agents previously considered established, have not been found in the field for several years and their persistence is in doubt. Outcomes of biocontrol at a plant population level are indicated for 54 target weeds on which agents have been established for over a decade. The increase in numbers of target weeds considered, as well as biocontrol agents released, over the past decade, has been enabled by continued generous funding and an efficient release-approval process.

Plant Pathogens and Biological Control of Invasive Alien Plants in South Africa: A Review of Projects and Progress (2011–2020)

The use of plant pathogens for biological control (biocontrol) of invasive alien plants in South Africa was reviewed in 1991, 1999 and 2011. In this review, subsequent progress and projects undertaken in the years 2011 to 2020, on both classical agents using exotic pathogens and inundative agents using indigenous pathogens, are detailed. We report on the impact of several previously introduced exotic fungi, monitored during this period. A significant highlight is the completion of 30 years of annual monitoring, from 1991 until 2020, of the impact of Uromycladium morrisii Doungsa-ard, McTaggart, Geering & RG Shivas (Raveneliaceae) on the density of Acacia saligna (Labill.) Wendel (Fabaceae), with declines of up to 98% recorded at monitored sites. Post-release monitoring also suggested that Entyloma ageratinae R.W. Barreto & H.C. Evans (Entylomataceae), introduced when Ageratina riparia (Regel) R.M.King & H.Rob (Asteraceae) still had a very limited invaded range in South Africa, has prevented the weed from realizing its potential as an invader. Uromycladium woodii Doungsa-ard, McTaggart, Geering & R.G. Shivas (Raveneliaceae) has been established on Paraserianthes lophantha (Willd.) I.C.Nielsen (Fabaceae), as has Puccinia xanthii Schwein (Pucciniaceae) on Parthenium hysterophorus L. (Asteraceae). Prospodium transformans (Ellis & Everh.) Cummins (Raveneliaceae) failed to establish on Tecoma stans (L.) Juss ex Kunth var. stans (Bignoniaceae), while efforts to release Puccinia lantanae Farl. (Pucciniaceae) on Lantana camara L. (Verbenaceae) are underway. Of the established exotic pathogens that are classical biocontrol agents, two are considered to cause extensive damage, two considerable damage, and two moderate damage, to their target weeds. Puccinia arechavaletae Speg. (Pucciniaceae), an adventive fungus that is established on Cardiospermum grandiflorum Sw. (Sapindaceae) following an unknown path of introduction, is proving to be a damaging agent and the implications of its presence in the country are discussed. Early season augmentation of Puccinia eupatorii Dietel (Pucciniaceae) on Campuloclinium macrocephalum (Less.) DC. (Asteraceae) was tested to determine whether damage could be increased, but no difference in the rust's incidence and severity was evident between augmented and naturally infected plants at the end of the growth season. The identity of the indigenous fungus registered as Stumpout®, for the control of coppice growth after felling of Acacia mearnsii De Wild. (Fabaceae), was confirmed as Cylindrobasidium torrendii (Bres.) Hjortstam (Physalacriaceae) rather than C. laeve (Pers.: Fr.) Chamuris, as previously thought. The application of another indigenous fungus, Colletotrichum acutatum J.H. Simmonds (Glomerellaceae), by means of helicopter flights has facilitated its establishment on Hakea sericea Schrad. & J.C. Wendl (Proteaceae), in inaccessible mountainous terrain. For registration purposes, toxicity testing (oral rat LD50) of these indigenous fungi are required. Lethal doses of Cylindrobasidium torrendii, C. acutatum and Pseudolagarobasidium acaciicola Ginns (Phanerochaetaceae), the latter for use against Acacia cyclops G. Don. (Fabaceae), exceeded 2000 mg kg–1 body weight and all three fungi are thus considered safe for application.

Advances in the Regulation of Weed Biological Control in South Africa

Regulation of biological control (biocontrol) is essential to ensure its continued safety and to enhance its acceptability as a key contributor to the management of damaging invasive alien plants in South Africa. Local researchers were concerned that regulators may become risk averse and over-cautious, thus preventing introductions of safe biocontrol agents, as bureaucratic impediments have contributed to the decline in the number of biocontrol releases in several other countries. In South Africa, the introduction of a transparent and inclusive review process has averted these concerns. Legislation in South Africa enables departments concerned with protecting environmental and agricultural resources, to work together to regulate potential risks. An interdepartmental committee, advised by independent specialists, facilitate the review of research into the safety of potential biocontrol agents. Regulators have reviewed and timeously assessed 26 potential biocontrol agents between 2013 and 2020. This has ensured that the considerable benefits from safe biocontrol agents are available for management of some of South Africa's worst invasive alien plants. We review the system in South Africa and suggest possible improvements to the regulatory framework.

Biological Control of Cactaceae in South Africa

Cactaceae are among the most problematic invasive alien plants in South Africa, posing serious negative consequences to agriculture and natural ecosystems. Fortunately, South Africa has a long and successful history of controlling cactus weeds using biological control (biocontrol). This paper reviews all the biocontrol programmes against invasive alien Cactaceae in South Africa, focusing on the decade since the last review published in 2011, up to, and including 2020. Biocontrol programmes against 16 target weeds are summarised, all of which rely on either the galling mealybug, Hypogeococcus sp. (Pseudococcidae), or various species or intraspecific lineages of cochineal insects (Dactylopius spp., Dactylopiidae) as agents. New agents are being considered for the three target weed species, Opuntia elata Salm-Dyck, Opuntia megapotamica Arechav. and Trichocereus spachianus (Lem.) Riccob., while permission to release a new agent against Cylindropuntia pallida (Rose) F.M. Knuth has recently been granted. The biocontrol agent, Dactylopius opuntiae (Cockrell) ‘stricta’, which has been utilised for the successful control of Opuntia stricta Haw., has shown some promise as an agent against one of the worst cactus weeds in the country, the North Cape/Free State variety of Opuntia engelmannii Salm-Dyck. Post-release monitoring and recent observations of the status of control for the 11 other cactus weeds, all of which have well-established agents, are provided. Taxonomic uncertainties and misidentifications of both target weeds and agents has been a constraint to biocontrol efforts, but this has been partially overcome through the use of genetic techniques. Biocontrol is particularly successful in controlling cactus weeds compared to most other taxonomic groups, and it is likely that past successes can be repeated with new target weeds. Mass-rearing and redistribution of agents are essential to gain the maximum possible benefit from cactus biocontrol agents, and recent increases in mass-rearing outputs have been beneficial.

Motivations and contributions of volunteer groups in the management of invasive alien plants in South Africa’s Western Cape province

Background: Research and management of biological invasions traditionally focuses on state operated large scale control initiatives, with little emphasis on volunteers. Volunteering can, however, contribute to detection, eradication and containment of invasive alien plant species (IAPS). Understanding the extent of involvement of volunteers in invasive alien species management is important. Similarly, understanding volunteers’ motivations to volunteering is important to improve the success of invasive alien species management. Objective: In this study we aimed to: 1) identify volunteer groups controlling IAPS in the Western Cape province of South Africa, 2) understand their practices and contributions towards detecting and controlling IAPS, 3) examine volunteer’s motivations for controlling IAPS, and, 4) identify the challenges individual volunteers and groups face. Methods: The data were collected using online questionnaires. Results: In total, we identified 52 volunteer groups. We broadly estimate that these groups clear nearly 8000 ha of land with estimated labour costs of ZAR 6.5 million annually (equivalent to USD 0.38 million) when aligned with formal state management cost estimates. Most volunteer groups raise their own funds to facilitate their work, however, many suggest support from government entities, landowners and Non-Government Organisations would help. Most volunteers (82%) detect and report invasive species to their team leaders, citizen science platforms and relevant authorities. Volunteers themselves gain physical and psychological fulfilment and build their social capital by meeting new people. Conclusion: Our findings point to the valuable contribution of these groups, but also the need for better co-ordination and engagement between volunteer groups and mandated authorities on science, policy and management.

The effect of accessibility and value addition on the costs of controlling invasive alien plants in South Africa: A three-species system dynamics model in the fynbos and grassland biomes

We developed a two-biome (grasslands and fynbos) system dynamics model simulating invasions of three invasive alien plant species – black wattle (Acacia mearnsii) and two pine species (Pinus patula and Pinus pinaster) – and some of the consequences. The model considers three components: invasion dynamics; revenue from the sale of woody products derived from clearing invasive alien plants; and a coefficient that models the effect of increased accessibility to invaded areas. The model shows that increasing the returns on value added products (VAPs) from invasive alien plants (IAPs) by between 70% and 130% results in positive nett present values (NPVs) of R2.7 million for P. patula, R151.7 million for P. pinaster and R115.9 million for A. mearnsii (1996 base year). At the same time, the invasion of these species is reduced dramatically by 2025. The results show that there is much scope, and indeed a clear requirement, for improved returns on investment from harvesting these species through increasing the returns from VAPs. However, accessibility to invaded areas would need to be increased for positive nett gains in water yields and other returns to be maximised.

Historicising perceptions and the national management framework for invasive alien plants in South Africa

This article offers a historical framework for understanding changes to human perceptions and efforts to manage invasive alien plants and weeds in South Africa from the mid-nineteenth century until the present. The article argues that South African legislation and policy for managing invasive alien plants and weeds has historically been limited because people have held contradictory values about plants, many private land owners have lacked resources and have not been compelled to follow government legislation and because policy has reflected the interests of a small group of farmers or scientific experts who have had limited influence on most private land owners and traditional land users. Successful control efforts often relied on technical expertise that was applied controversially or could be implemented on government land without extensive public consultation or social conflict. The creation of a national framework for invasive alien plants through the Working for Water Programme in 1995 and National Environmental Management of Biodiversity Act (no. 10) of 2004 (NEMBA) has increased public awareness, but the Programme and NEMBA remain limited by many of the same institutional and social constraints that experts and institutions faced in the past. In conclusion, the article draws on history to provide insights to contemporary challenges.

Noxious to ecosystems, but relevant to pharmacology: Four South African alien invasive plants with pharmacological potential

Alien invasive plants pose a huge threat to natural and semi-natural ecosystems in their introduced ranges thereby compromising ecosystem integrity. However, anecdotal and empirical evidence suggests that some invasive alien plants are used in traditional medicine due to their pharmacological activities. Here, we evaluated the antimicrobial activity of 70% ethanol, dichloromethane, acetone and hot water extracts of four invasive alien plants in South Africa viz. Dolichandra unguis-cati, Cardiospermum grandiflorum, Chromolaena odorata and Gomphrena celosioides against pathogenic and non-pathogenic microbes. The test organisms included Staphylococcus aureus, Salmonella enterica serovar Typhimurium (S. Typhimurium), Salmonella Dublin, Klebsiella pneumoniae, Enterococcus faecalis, Escherichia coli, Pseudomonas aeruginosa, Mycobacterium aurum, M. fortuitum, M. smegmatis, Candida albicans, Aspergillus fumigatus and Cryptococcus neoformans. Phytochemicals that may be responsible for antimicrobial activity were determined using standard phytochemical methods. A further objective was to investigate the safety of these plants by conducting cytotoxicity and genotoxicity tests. All solvent extracts of plants investigated exhibited a broad spectrum of antibacterial activity with minimum inhibitory concentration (MIC) values ranging from 0.039 to 2.5 mg/ml, with the acetone and dichloromethane extracts showing better activity against E. coli, K. pneumoniae and E. faecalis (MIC between 0.039 and 0.078 mg/ml). Of all extracts tested, only the ethanol extracts of C. grandiflorum showed good antimycobacterial activity with MIC of 0.078 mg/ml against M. smegmatis. In contrast, C. grandiflorum only showed moderate antifungal activity, while dichloromethane and acetone extracts of the other three plants were very effective against C. neoformans and A. fumigatus with MIC values ranging from 0.019 to 0.078 mg/ml. All four plants moderately inhibited C. albicans at MIC of 0.156 mg/ml. The plant species were rich in phenolics, flavonoids and tannins in varying amounts and had relatively low levels of cytotoxicity and none was mutagenic. Promising selectivity index values (between 10 and 50) highlight the potential of these plant species as sources of antimicrobial remedies. Despite the ecological noxiousness of these alien invasive plants, our findings suggest that they possess some antimicrobial properties that are too pharmacologically relevant to ignore.

The Management of Invasive Alien Plants in South Africa: Strategy, Progress and Challenges

The Management of Invasive Alien Plants in South Africa: Strategy, Progress and Challenges

Comparative Early Life Stage Toxicity of the African Clawed Frog, Xenopus laevis Following Exposure to Selected Herbicide Formulations Applied to Eradicate Alien Plants in South Africa.

The rise in pesticides application has increased the need for better understanding of their ecological impacts. The global amphibian declines, for example, have been positively correlated with pesticides use. The differential susceptibility in the developmental stages of amphibians to chemical substances are still largely unknown. We examined the 96-h differential toxicity responses of embryos, premetamorphic and transitional larval stage of Xenopus laevis, to six formulated aquatic herbicide products containing the active ingredients of diquat dibromide (Midstream), glufosinate ammonium (Basta), imazapyr (Arsenal), and three glyphosate formulations (Roundup, Kilo Max, and Environ Glyphosate). The results showed the premetamorphic stage as the most sensitive to the herbicides toxicity. This study confirmed that the developmental stage at which amphibian are exposed to contaminants is critical to their survival and that the chemical contamination hypothesis of the global decline of amphibians should continue to be considered. This establishment of the premetamorphic larval as sensitive toxicity representative for all developmental stages of X. laevis means that this stage could be used more extensively in pesticides toxicity assessments.

Characteristics of selected non-woody invasive alien plants in South Africa and an evaluation of their potential for electricity generation

Alien invasive plants (AIPs) pose a threat to the existence of plant and animal biodiversity in the ecosystems they invade. They need to be cleared, monitored and eventually eradicated from the landscape. The potential and the economic viability to supply non-woody AIP biomass for electricity generation were assessed in this study, which was conducted on samples from 13 common non-woody AIPs in South Africa, namely: Arundo donax (giant reed), Lantana camara (lantana), Pontederia cordata (pickerel weed), Ricinus communis (castor-oil plant), Opuntia ficus-indica (sweet prickly pear), Solanum mauritianum (bugweed), Atriplex nummularia (saltbush), Cestrum laevigatum (inkberry), Senna didymobotrya (peanut butter cassia), Chromoleana odorata (chromoleana), Eichhornia crassipes (water hyacinth), Cerus jamacaru (queen of the night) and Agave sisilana (sisal plant). Proximate and ultimate analysis was made in order to assess the suitability of the biomass for different thermo-chemical conversion techniques for electricity generation. A financial evaluation of the costs to supply biomass to the plant gate was performed by combining the harvesting, chipping and transport costs. The results showed that the biomass of giant reed, lantana, bugweed, saltbush, inkberry, cassia and Chromoleana may be used to generate electricity through combustion, although the total average cost was approximately 50% higher than that of woody biomass feedstock, requiring a ‘fuel cost subsidy’ to justify their utilisation for energy production.

Assessing the status of biological control as a management tool for suppression of invasive alien plants in South Africa

Background: Biological control of invasive alien plants (IAPs) using introduced natural enemies contributes significantly to sustained, cost-effective management of natural resources in South Africa. The status of, and prospects for, biological control is therefore integral to National Status Reports (NSRs) on Biological Invasions, the first of which is due in 2017. Objectives: Our aim was to evaluate the status of, and prospects for, biological control of IAPs in South Africa. We discuss expansion of biological control and suggest indicators to be used in the upcoming NSR to assess sufficient growth. Method: We used published literature, unpublished work and personal communication to assess the status of biological control of IAPs. We propose indicators based on the targets for biological control that were proposed in the 2014 ‘National Strategy for dealing with biological invasions in South Africa’. To prioritise targets for future efforts, we used published lists of damaging IAPs and assessed the prospects for their biological control. Recommendations for using biological control as a management tool were made after discussion among the authors and with colleagues. Results: Significant control of several Cactaceae, Australian Acacia species and floating aquatic plants, and many other IAPs has been achieved in South Africa since 1913. Recently, biological control has benefited from improved international collaboration, a streamlined application process for the release of new biological control agents (resulting in the approval of 19 agents against 13 IAP species since 2013), and increased funding and capacity. There is still a need to improve implementation and to better integrate biological control with other control methods. In order to maximise benefits from biological control, increased investment is required, particularly in implementation and post-release evaluation, and in targeting new IAPs. Proposed targets for growth between 2017 and 2020 include an increase in financial investment in research by 29%, implementation by 28% and mass-rearing by 68%. Research capacity should increase by 29%, implementation capacity by 63% and mass-rearing capacity by 61%. New research projects should be initiated on 12 new IAP targets, while post-release monitoring efforts should be expanded to another 31 IAPs. Conclusion: Biological control of IAPs has contributed substantially to their management in South Africa, and continues to do so. Further investment in targeted aspects of IAP biological control will increase this contribution.

Changes in the composition and distribution of alien plants in South Africa: An update from the Southern African Plant Invaders Atlas

Background: Data on alien species status and occurrence are essential variables for the monitoring and reporting of biological invasions. The Southern African Plant Invaders Atlas (SAPIA) Project has, over the past 23 years, atlassed alien plants growing outside of cultivation. Objectives: To document changes in the alien plant taxa recorded in SAPIA, assess trends in invasive distributions and explore effects of management and regulations.Method: The numbers of alien plant taxa recorded were compared between May 2006 and May 2016, and changes in the extent of invasions at a quarter-degree squares (qds) scale were compared between 2000 and 2016. The effectiveness of regulations and interventions was assessed in terms of the relative change in the extent of invasions. Results: As of May 2016, SAPIA had records for 773 alien plant taxa, an increase of 172 since 2006. Between 2000 and 2016, the number of qds occupied by alien plants increased by ~50%, due both to ongoing sampling and to spread. Successful classical biological control programmes have reduced the rate of spread of some taxa and in a few cases have led to range contractions. However, other interventions had no detectable effect at a qds scale. Conclusions: South Africa has a growing number of invasive alien plant species across an increasing area. More taxa should be listed under national regulations, but ultimately more needs to be done to ensure that management is strategic and effective. SAPIA is a valuable tool for monitoring alien plant status and should be developed further so that invasions can be accurately tracked over time.

Grasses as invasive plants in South Africa revisited: Patterns, pathways and management

Background: In many countries around the world, the most damaging invasive plant species are grasses. However, the status of grass invasions in South Africa has not been documented recently. Objectives: To update Sue Milton’s 2004 review of grasses as invasive alien plants in South Africa, provide the first detailed species level inventory of alien grasses in South Africa and assess the invasion dynamics and management of the group. Method: We compiled the most comprehensive inventory of alien grasses in South Africa to date using recorded occurrences of alien grasses in the country from various literature and database sources. Using historical literature, we reviewed past efforts to introduce alien grasses into South Africa. We sourced information on the origins, uses, distributions and minimum residence times to investigate pathways and patterns of spatial extent. We identified alien grasses in South Africa that are having environmental and economic impacts and determined whether management options have been identified, and legislation created, for these species. Results: There are at least 256 alien grass species in the country, 37 of which have become invasive. Alien grass species richness increased most dramatically from the late 1800s to about 1940. Alien grass species that are not naturalised or invasive have much shorter residence times than those that have naturalised or become invasive. Most grasses were probably introduced for forage purposes, and a large number of alien grass species were trialled at pasture research stations. A large number of alien grass species in South Africa are of Eurasian origin, although more recent introductions include species from elsewhere in Africa and from Australasia. Alien grasses are most prevalent in the south-west of the country, and the Fynbos Biome has the most alien grasses and the most widespread species. We identified 11 species that have recorded environmental and economic impacts in the country. Few alien grasses have prescribed or researched management techniques. Moreover, current legislation neither adequately covers invasive species nor reflects the impacts and geographical extent of these species. Conclusion: South Africa has few invasive grass species, but there is much uncertainty regarding the identity, numbers of species, distributions, abundances and impacts of alien grasses. Although introductions of alien grasses have declined in recent decades, South Africa has a potentially large invasion debt. This highlights the need for continued monitoring and much greater investment in alien grass management, research and legislation.

Digestive efficiency of indigenous and invasive avian species fed fruit of invasive alien plants in South Africa

Many highly invasive plant species produce fleshy fruit that are consumed and dispersed by frugivorous birds. However, little is known about assimilation efficiency of invasive fruit by indigenous and invasive avian species. We investigated whether indigenous Knysna (Tauraco corythaix) and Purple-crested (Gallirex porphyreolophus) Turacos and invasive alien Rose-ringed Parakeets (Psittacula krameri) met their energy demands when fed fruits of four fleshy- fruited invasive alien plant species: Solanum mauritianum, Cinnamomum camphora, Psidium guajava and Morus alba. Birds were fed single-fruit diets for two consecutive days and energetic parameters were calculated for all fruit diets. Our results showed that generally both invasive and indigenous avian species managed to gain their daily energy requirements from fruits of the four respective invasive plants, suggesting that they can meet their energetic demands by feeding on them only. The exception was P. krameri, which did not feed on S. mauritianum fruit. These findings may explain why fruits of invasive alien plants are attractive to most avian frugivores and highlight the role of avian frugivores in their dispersal.

The noncoding trnH-psbA spacer, as an effective DNA barcode for aquatic freshwater plants, reveals prohibited invasive species in aquarium trade in South Africa

The negative effects of invasive alien aquatic plants raise concern globally. These effects are predicted to increase in the future due to a rapid development in transport modes (air, terrestrial, and water) that facilitate connection between continents, difficulties inherent to identification of potentially problematic species, and for aquatic systems, insufficiently regulated aquarium and ornamental pond industries. In this study, we aimed to assist traditional species identification methods with genetic methods and provide ways of verifying the status of alien plants (invasive or non-invasive) sold in aquarium market in South Africa. To this end, the best DNA barcode for South Africa's freshwater plants was identified; a DNA barcode library was assembled and aquarium plants sold in Johannesburg (South Africa) were screened using this DNA barcode. We found that trnH-psbA was a reliable single DNA barcode for freshwater plant species in South Africa. We therefore assembled a trnH-psbA library on BOLD (Barcode Of Life Database) to assist in future identification of unknown or taxonomically doubtful freshwater alien plants in South Africa. Using this region to screen aquarium species, we found surprisingly that some prohibited aquatic invaders are already in circulation in the local aquarium trade, including Hydrilla verticillata (L.f.) Royle, Egeria densa Planch., Myriophyllum spicatum L., and Echinodorus cordifolius (L.) Griseb. This raises concern and calls for a strict regulation of species traded in aquarium industries to be implemented, as well as a need for public environmental education on the threat posed by invasive and potentially invasive plants for South Africa's natural aquatic ecosystems.

Ingestion by an invasive parakeet species reduces germination success of invasive alien plants relative to ingestion by indigenous turaco species in South Africa

Avian frugivores play a key role in seed dispersal of many plant species, including invasive alien plants. We assessed the effect of gut passage on the germination of selected invasive alien plant species in South Africa. Fruits of four fleshly-fruited invasive alien plant species: Solanum mauritianum, Cinnamomum camphora, Psidium guajava, and Morus alba, were fed to two species of indigenous turacos, Knysna (Tauraco corythaix) and purple-crested (Gallirex porphyreolophus) turacos, and to invasive rose-ringed parakeets (Psittacula krameri). Seed retention time was determined as this can influence both seed dispersal and germination success. Germination success of ingested seeds was compared with that of manually de-pulped seeds, as well as to seeds in whole fruit. The germination success of seeds of all the invasive plant species increased significantly after ingestion by both turaco species compared with seeds from whole fruits. Germination success of manually de-pulped seeds did not differ significantly from that of turaco ingested seeds. In contrast, seed passage through the digestive tract of rose-ringed parakeets significantly reduced germination success and viability of ingested invasive plant species. Our results suggest that Knysna and purple-crested turacos are legitimate seed dispersers of fleshy-fruited invasive plants, while rose-ringed parakeets are mainly seed predators. Although seed predation by rose-ringed parakeets negatively affects the reproductive success of these plants, it is unlikely that this will suppress the spread of these invasive alien plants in South Africa as they are already well established. Furthermore, they can facilitate dispersal by seed regurgitation and dropping uneaten fruits away from the parent plant. Similar trends could be expected for indigenous seeds that rose-ringed parakeets feed on and therefore these birds remain a negative influence within invaded ecosystems.