Ligustrum L. (Oleaceae) in South Africa: Introduction history and invasion ecology
Why this work is in the frame
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Bibliographic record
Abstract
• Several species of the genus Ligustrum (Oleaceae; privets) are very popular ornamental plants around the world and some species are major invaders. • Privets were introduced to South Africa at least as early as 1887 and naturalisation was first reported in 1975. Two species ( L. lucidum and L. sinense ) are invasive over large areas in the country, but little is known of the history and invasion ecology of these species and about privets in general in South Africa. • This study reviewed the introduction history of Ligustrum species in South Africa, assessed the number of species currently present and their distribution in cultivation and as naturalised/invasive populations. It also explored the potential range of the two most widespread species in South Africa ( L. lucidum and L. sinense ), and conducted formal risk analyses of the five most common Ligustrum species. • Ligustrum lucidum and L. sinense are already widespread, with hotspots of cultivated and naturalisation in the Western Cape, KwaZulu-Natal, and Gauteng. Both species have the potential to spread further, especially in the north-eastern parts and south-western parts of the country. • A fine-scale study of the distribution of cultivated and wild-growing L. lucidum and L. sinense in Stellenbosch (the urban area with the most comprehensive data) revealed the importance of riparian habitats for the establishment of potentially invasive populations. • Information presented in the study provides the foundation for a revision of the legal status of Ligustrum species in South Africa and for the development of management plans. Ligustrum is a genus of woody plants comprising 46 accepted species that have been widely moved around the world, with species showing varying levels of progression along the introduction-naturalisation-invasion continuum. Ligustrum species (privets) have been widely cultivated in South Africa as ornamental plants and have become naturalised and invasive in many areas. Little information is available on the introduction status, distribution, invasion ecology and impacts of privets in the country. We: 1) conducted a literature search to construct a timeline of Ligustrum introductions to South Africa; 2) assessed which species are currently present in the country; 3) evaluated the current distribution using multiple data sources and the potential distribution of L. lucidum and L. sinense using species distribution modelling; 4) provided insights on the invasion ecology of L. lucidum and L. sinense in the Stellenbosch urban area and along the Eerste River; and 5) conducted formal risk analyses for the five Ligustrum species listed in South Africa’s alien and invasive species legislation ( L. japonicum, L. lucidum, L. ovalifolium, L. sinense and L. vulgare ). Fourteen Ligustrum taxa are known to have been introduced to South Africa, the earliest record being for L. japonicum in 1887. Ligustrum species were found in 151 quarter-degree cells (QDCs) across South Africa. The most widespread species are L. lucidum (138 QDCs), L. sinense (47 QDCs) and L. ovalifolium (21 QDCs). Ligustrum lucidum and L. sinensis are both widespread invaders (category E in the Blackburn framework for biological invasions), L. ovalifolium is widely naturalised (category D1) and the other taxa are all in category B2. The highest number of taxa in a single QDC was seven (in Pretoria, Gauteng) and the highest number of observations in a QDC was 485 (in Stellenbosch, Western Cape). Sixteen hotspots of naturalisation and invasion were identified around the country. A fine-scale study was conducted for the two Ligustrum species with the most comprehensive data ( L. lucidum and L. sinense ) around Stellenbosch. Climatic niches for L. lucidum and L. sinense in South Africa differed from those based on records elsewhere in the world. Predicted suitable areas for both L. lucidum and L. sinense spanned the eastern and southwestern parts of the country, although L. sinense had a smaller potential range in the east. In the local-scale study (Stellenbosch), Generalised Additive Models highlighted the importance of riparian habitats for the establishment of potentially invasive populations. Formal risk analyses for all five reviewed species ( L. japonicum, L. lucidum, L. ovalifolium, L. sinense , and L. vulgare ) yielded high-risk scores, highlighting the current and potential impacts of these species. Urgent attention is needed to manage the genus in South Africa, starting with a re-assessment of the legislative status of all taxa in the genus.
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Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from it