New records of alien and potentially invasive grass ( Poaceae ) species for southern Africa

Copyright: © 2021. The Authors. Licensee: SANBI. This work is licensed under the Creative Commons Attribution 4.0 International License. Background: The grasses (Poaceae) of the Flora of Southern Africa (FSA) region (i.e. Botswana, Eswatini, Lesotho, Namibia and South Africa) are relatively well documented, for both native and non-native species. Visiting taxonomic expertise nevertheless reveals new FSA and in-country records, particularly of non-native species. Such records provide an opportunity for improving biosecurity relating to potentially invasive but hitherto undetected non-native Poaceae in the FSA region.


Introduction
The grass family Poaceae is relatively well-documented for the Flora of Southern Africa (FSA) region (comprising Botswana, Eswatini, Lesotho, Namibia and South Africa), with old and recent country-level treatments (e.g. Gibbs Russell et al. 1990;Fish et al. 2015) that incorporated efforts of numerous researchers who focused on different individual genera (Fish et al. 2015, see references therein), as well as more recent treatments of individual genera e.g. Anthoxanthum L. (Mashau 2016); Festuca L. (Sylvester et al. 2020a); Poa L. (Soreng et al. 2020).
In many countries, grasses have become the most damaging of invasive plants (D'Antonio & Vitousek 1992;D'Antonio et al. 2011;Gaertner et al. 2014), with knowledge of the distribution and ecology of these non-native grasses New records of alien and potentially invasive grass (Poaceae) species for southern Africa crucial for effective habitat management (e.g. Gaertner et al. 2014;Visser et al. 2017;Monnet et al. 2020). Visser et al. (2017) notes that there is much uncertainty regarding the identity, numbers of species, distributions, abundances and impacts of alien grasses in the FSA region, with only 37 of the known 256 non-native species in the region considered to be invasive. Despite this lag in non-native Poaceae knowledge, South Africa has some of the most progressive invasive species legislation in the world, including for known invasive Poaceae: 18 species are listed in the National Environmental Management: Biodiversity Act's Alien and Invasive Species Lists (2016).
Even less known is the impact of invasive or alien grasses in the high-elevation Drakensberg Mountain Centre of Floristic Diversity and Endemism (DMC) of southern Africa (Carbutt 2019). The DMC, covering some 40 000 km 2 , contains the only true alpine region in Africa south of Mount Kilimanjaro (Carbutt 2019). These high-elevation Afromontane and alpine areas are renowned for their high levels of plant diversity and endemism, with the DMC hosting ± 2 520 angiosperm species (Carbutt & Edwards 2004) of which 227 are endemic (Carbutt & Edwards 2006;Carbutt 2019). This high importance for biodiversity is matched by the socio-ecological importance of these ecosystems, with a significant rangeland-based agrarian community relying on the DMC for their livelihoods (subsistence-based livestock herding being the dominant land-use). Any potential threat to this, such as that posed by potentially invasive alien plants, should be taken very seriously.
During extensive field collecting and ecological research by the authors in the DMC area, new records of alien grass species were discovered that add a further three species to the known flora of the DMC (Carbutt & Edwards 2004Carbutt 2019), and raise concerns over their potential ecological impact.

Materials and Methods
The new records were collected during extensive fieldwork conducted by SPS, RJS, MDPVS and AM in the DMC between 1 Feb. and 9 Mar. 2020, with specimens deposited in the PRE, NU and US [exported, awaiting accession] herbaria (Herbarium acronyms follow Thiers [continuously updated]). Herbarium study was also conducted at PRE between 13 and 20 Mar. 2020.
Distribution: Of Eurasian origin; introduced into many other temperate areas of the World (POWO 2020, and references therein). This is the first report of the species for sub-Saharan Africa and the FSA region; it may also be the first verified specimen from the African continent, as it is noted with '?' for Morocco and Tunisia by Dobignard and Chatelain (2010: 213) (Figure 2).  Nees, which were found in the vicinity, and are just as capable of forming a close sward, should rather be used in seeding projects as opposed to these non-native species.
Similar species: Agrostis gigantea Roth, an alien species now naturalised in the FSA region (Fish et al. 2015), is closely related and similar in terms of: plants always with extensively creeping rhizomes, usually without stolons; leaf blades generally flat (A. capillaris often with basal blades involute and culm blades flat); panicles open or only partially contracted after flowering, generally > 5 cm long (sometimes as short as 3 cm in A. capillaris); primary panicle branches without branchlets at least in the proximal half; floret notably shorter than the glumes, usually 1 ∕ 3 -3 ∕ 4 the length of the glumes, without a rachilla prolongation; paleas reaching ( 2 ∕ 5 -) 2 ∕ 3 -3 ∕ 4 the length of the lemma; lemmas muticous or with an awn of varying length, ranging from a short straight awn, 0.2-1.0 mm long, to a long geniculate and twisted awn to 4 mm long, inserted basally, medially or in the upper half of the lemma, not surpassing or greatly surpassing the glumes. Agrostis capillaris is primarily differentiated from A. gigantea by the ligule of the tiller leaves being distinctly shorter than wide [sheath should be expanded to be able to see this clearly] and ≤ 1 mm long ( Figure 1B) (vs. as long as or distinctly longer than wide, 1-3 mm long in A. gigantea), ligules of culm leaves 0.5-1.5(-2.9) mm long, shorter to sometimes longer than wide (vs. 2-8 mm long, as long as or distinctly longer than wide in A. gigantea). Agrostis capillaris can also usually be readily distinguished from A. gigantea by its shorter size, culms being 10−75(−90) cm tall, and thinner blades of culm leaves (0.6−)1.0−4.0(−5.0) mm wide as opened out which are sometimes inrolled (Figure 1) (vs. culms 40−100(−120) cm tall, blades of culm leaves (2−)3−8 mm wide, always flat in A. gigantea) although there are smaller variants of A. gigantea with thinner leaves which can superficially resemble A. capillaris. In these cases of ambiguity, the ligule will always settle the identity (also see notes and key in Sylvester et al. 2020b).
Agrostis stolonifera L., a species not known from southern Africa, but which is native in temperate Eurasia and northern Africa reaching as far south as Chad, and which is widely introduced elsewhere (POWO 2020, and references therein), also bears similarities to A. capillaris. Agrostis stolonifera is primarily differentiated from A. capillaris by the ligule of tillers 1-3 mm long and culm leaves 2.0-6.5 mm long, always distinctly longer than broad. The habit also differs, with A. stolonifera usually extensively stoloniferous with stolons 5-100(-200) cm long [these often not collected as part of herbarium specimens], rhizomes usually absent (vs. extensively rhizomatous, sometimes also stoloniferous, in A. capillaris). Cope and Gray (2009) (Figures 3, 4).

Many heterotypic synonyms (POWO 2020).
Distribution: Native range is sub-arctic and temperate Northern Hemisphere (Figure 4). The native range of F. rubra s.l. is noted to extend into northern Africa by POWO (2020), although the subspecies or varieties of F. rubra described from high-elevation Morocco and Algeria have been re-assigned to other species of Festuca (Dobignard 2010). Thus, it is unclear whether F. rubra occurs naturally, or has been introduced, in northern Africa: Dobignard and Chatelain (2010: 296) note '?' for Morocco and the Madeira islands. Our collection from South Africa is therefore possibly the first verified specimen from the African continent. It does, however, occur on sub-Antarctic Marion Island (one of South Africa's two islands in the Prince Edward Islands group), where it is recorded as a major invasive species (Greve et al. 2017). Festuca rubra has also been introduced to Australia, New Zealand, and South and Central America (POWO 2020, and references therein) where it has become naturalised, but is not considered invasive.  Notes: Festuca rubra is generally not considered invasive in the areas where it has been introduced and naturalised (except for Marion Island), and is not included in the IUCN Global Invasive Species Database (http:// www.iucngisd.org/gisd/). It was found to be locally common and is likely to have been sown in a seed mixture for maintenance of the Tiffindell ski slopes, which has subsequently spread into nearby alpine grassland (see notes under Agrostis capillaris above).
Traditional circumscription of infraspecific taxa within F. rubra has been brought into question (Saikkonen et al. 2019); although our specimen keys fairly solidly to F. rubra subsp. rubra in the treatments by Hubbard (1984), Cope and Gray (2009), and Darbyshire and Pavlickf (2007), we prefer to present the new record at the species rank here.     Figure 3D) (vs. 10-20 mm long in F. africana); anthers 1.8-4.5 mm long ( Figure 3E) (vs. 0.8-1.8 mm long in F. drakensbergensis, F. exaristata, and rarely F. killickii); ovary apex glabrous ( Figure 3F) in 1963and 1980(Gibbs Russell et al. 1990Fish et al. 2015). Our collection in the Eastern Cape extends the species range c. 950 km eastward. It is also feasible to say that the species has likely established in adjacent Lesotho, which was less than 100 m away on the opposite bank of the Telle River. Jarava plumosa has its native range in austral South America, covering central and eastern Argentina, Chile, Uruguay, to as far north  Figure 6). The species has also been documented as becoming naturalised in Adelaide, Australia (Gardner et al. 1996;Wilson 2009), as well as California, USA (Arriaga 2007), and Palestine (Danin 2004  Notes: Gardner et al. (1996) noted the vigorous nature of Jarava plumosa and how, despite efforts to remove the plant since as far back as 1968, it continued to establish at the Botanic Gardens of Adelaide and was subsequently found in the South Parklands bordering Adelaide. The first record of J. plumosa outside of its natural range comes from South Africa, from collections made in the UCT campus in 1963and 1980(Gibbs Russell et al. 1990). Our discovery of an abundant population of J. plumosa by the side of the Telle River, Eastern Cape, South Africa, points to the likelihood that this species has a wider distribution than previously realised, and has been overlooked. The species exhibits certain traits pointing to its potential to become invasive, such as the apical pappus highly adapted to anemochory, and long awns that easily attach to clothing, fur etc. to aid in zoochory. Closely related species in the genera Nassella (

Similar species:
In southern Africa, J. plumosa could be mistaken for Stipagrostis anomala De Winter, which also has a pappus-like plume of long hairs, 4-8 mm long, emerging from the apex of the lemma and/or lower part of the awn. Jarava plumosa can be differentiated from S. anomala by the pappus-like hairs being found on the apex of the lemma and base of the awn (vs. hairs restricted to just base of awn in S. anomala), callus being obtuse (vs. pungent), and a perennial habit (vs. annual) ( Figure 5B-C).

Conclusions
Three new non-native grass species are added to the flora of the DMC and the FSA: two (Agrostis capillaris and Festuca rubra) in the alpine sub-centre, and one (Jarava plumosa) in the montane sub-centre. Although still apparently highly localised, the unique alpine habitat in southern Africa -with the closest ecological comparison in South Africa and FSA being the Prince Edward Islands -suggests that F. rubra in particular could become a species of concern, and should be monitored with the intention of eradication while still localised. Similarly, the presence of the potentially highly invasive species J .plumosa in the highly degraded and stressed Figure 6. Jarava plumosa global distribution map, with country-or regional-level shading, taken and modified from POWO (2020).
xeric rain-shadow region of Telle Bridge requires further population assessment to determine abundance and distribution. All three of these grasses should be looked out for across the DMC for additional undetected populations.