Mahonia oiwakensis Hayata (= Mahonia lomariifolia ) (Berberidaceae): A new species for the alien flora of South Africa

Background:  A first record of a naturalised population of  Mahonia oiwakensis  (= Mahonia lomariifolia ) in South Africa is presented. The species is native to China and is cultivated in South Africa as an ornamental plant. Objectives:  To document a new record of  M. oiwakensis , provide a brief description of its morphology and note its ecology and current distribution outside of cultivation in South Africa. Method:  Plants were studied in the field and herbarium vouchers were collected and compared with images of type specimens. Distribution data were collected by means of global positioning system coordinates for each plant, and vegetation and habitat types were recorded for the sites where  M. oiwakensis  was collected. Results:  Two populations of 16 plants were found in South Africa, Gauteng, Pretoria, in the Faerie Glen Nature Reserve and Moreleta Kloof Nature Reserve, in the natural savannah biome, in thornveld and bushveld vegetation. Conclusions: Mahonia oiwakensis  has naturalised in South Africa. Further research is paramount to determine whether the species poses a substantial threat and whether it should be regulated and prioritised for management. It is recommended that this species should be added to the species under surveillance for potential eradication or containment targeting.


Introduction
Mahonia Nutt. is a member of the Berberidaceae family section Longibracteatae, subsection Siamenses (Ahrendt 1961). The family comprises about 650 species in 17 genera and is widely distributed in northern temperate and subtropical mountainous regions (Chen, Li & Ying 2009). Within the Berberidaceae family, Mahonia is the second largest genus after Berberis (Ahrendt 1961). In his streatment, Ahrendt (1961) recognised 200 species in the genus Mahonia, divided into two groups (Orientales and Occidentales) and these groups were further divided into four sections and 14 subsections. The major groupings were primarily based on geographical distribution, that is, all Asian species and one North American species (Mahonia nervosa (Pursh) Natt.) are in the Orientales group, while all the North American species are in the Occidentales group. Sectional grouping was based on various characters, from vegetative to reproductive characters. Recent studies on the seed morphology (Wu et al. 2010) and phylogeny (Kim et al. 2004), however, do not support the treatment of the genus into two groups such that some authors often recognise the genus as part of Berberis. However, Ying, Boufford and Brach (2011) treated the genus Mahonia as distinct from Berberis, with about 60 species worldwide distributed mainly in the East; South-east Asia; West, South, North and Central America; and China. Out of the 60 species, 31 species occur in China of which 27 are endemic while six are insufficiently known (Ying et al. 2011). According to Randall (2017), a number of Mahonia species are listed as either environmental weeds, invasive, naturalised or casual aliens throughout the world, including M. acanthifolia Background: A first record of a naturalised population of Mahonia oiwakensis (=Mahonia lomariifolia) in South Africa is presented. The species is native to China and is cultivated in South Africa as an ornamental plant.
Objectives: To document a new record of M. oiwakensis, provide a brief description of its morphology and note its ecology and current distribution outside of cultivation in South Africa.
Method: Plants were studied in the field and herbarium vouchers were collected and compared with images of type specimens. Distribution data were collected by means of global positioning system coordinates for each plant, and vegetation and habitat types were recorded for the sites where M. oiwakensis was collected.
Results: Two populations of 16 plants were found in South Africa, Gauteng, Pretoria, in the Faerie Glen Nature Reserve and Moreleta Kloof Nature Reserve, in the natural savannah biome, in thornveld and bushveld vegetation.

Conclusions:
Mahonia oiwakensis has naturalised in South Africa. Further research is paramount to determine whether the species poses a substantial threat and whether it should be regulated and prioritised for management. It is recommended that this species should be added to the species under surveillance for potential eradication or containment targeting.

Mahonia oiwakensis Hayata (=Mahonia lomariifolia) (Berberidaceae): A new species for the alien flora of South Africa
Read online: Scan this QR code with your smart phone or mobile device to read online.  (Glen 2002).
Mahonia oiwakensis is an evergreen shrub or small tree (Figure 1) native to China (therefore, it is in the Orientales group according to Ahrendt [1961]) and is known from Hainan, Guizhou, Sichuan, Yunnan and Xizang Provinces (Pan 1998;Ying et al. 2011). The type specimen is from Taiwan. In its native range, the species occurs in scattered subpopulations in coniferous forests and woodlands (Pan 1998).

Materials and methods
Herbarium specimens collected for this study were deposited in the National Herbarium (PRE)

Results and discussion
Records of M. oiwakensis growing outside of cultivation were not found in any of the South African herbaria and those in the neighbouring countries, indicating that this is the first record of the species as an escapee from cultivation in the southern African region. In Zimbabwe, two species of Mahonia are listed in the manual of cultivated plants, M. bealei and M. oiwakensis (listed as M. lomariifolia) (Hyde et al. 2017).
In South Africa, the species was found to occur in two nature reserves, FGNR and MKNR in the Gauteng Province at elevations up to 1500 m above sea level (Figure 2). In these areas, the species occurs in the savannah biome, in two vegetation types: the Gauteng shale mountain bushveld and Marikana thornveld (Mucina & Rutherford 2006). Observations in the surrounding suburbs indicated that the species is being sold in the local nurseries and is planted in gardens as an ornamental plant, and populations reported here could be a result of escape from garden. It is not clear how long these plants have been in these areas, but the annual growth rings on the stem indicated that mature plants might be more than 10 years old and thus these populations are here classified as naturalised, following the definition by Pysek and Richardson (2008), but not invasive.
Plants found at the FGNR were about 12 m away from the storm water drain, in moist soils under the canopy of indigenous trees, suggesting that they might have originated from bird-dispersed seeds (Pysek & Richardson 2008) and have germinated in the moist conditions. In this locality, one mature plant and 10 juveniles were recorded. Those discovered at the MKNR were observed 10 m from the stream (three mature plants) and also scattered along trails within the woodlands ridge (one mature plant and five juveniles). These habitats are in accordance with the native range habitats where it is reported that species in the Orientales group are commonly adapted to undergrowth in evergreen broad-leaved forests, temperate rain forests and occur along rivers in open disturbed areas along forest edges (Guner & Denk 2012).
The invasion risk of the species needs to be assessed as some members of the genus Mahonia can be aggressive invaders, for example, M. aquifolium, which is an aggressive invader in forest in central Germany (Auge & Brandl 1997). Some species of this genus exhibit both vegetative and sexual reproduction, and therefore the reproductive mechanism of the species needs to be investigated. According to the unified framework for biological invasions (Blackburn, et al. 2011), this species falls under the C3 category (i.e. individuals surviving in the wild in locations where introduced, reproduction occurring and population self-sustaining).
The extent of distribution of this species beyond the Gauteng Province is not yet known, and in an attempt to raise awareness, a short article was published in Southern African Plant Invaders Atlas newsletter (July 2017). We recommend further research on this species to determine the potential threats and whether the species should be regulated under the invasive species regulations.