R.J. Chinnock and C.J. Brodie
State Herbarium of South Australia, Plant Biodiversity Centre, PO Box 2732, Kent Town, South Australia 5071, Australia.
National Herbarium of Victoria, Royal Botanic Gardens Melbourne, Birdwood Avenue, South Yarra, Victoria 3141, Australia.
Cite this article as:
Chinnock, R., Stajsic, V. and Brodie, C. (2012). Mesembryanthemum guerichianum Pax (Aizoaceae): A weedy alien species new to Australia. Plant Protection Quarterly 27(2), 83-8.
A newly discovered alien species of Mesembryanthemum, M. guerichianum Pax, is reported for Australia for the first time. It occurs in South Australia, New South Wales and Victoria. It has been overlooked in the past presumably having been mistaken for the widespread M. crystallinum L. which it is closely related to.
A detailed account of the species based on Australian populations is given including a description, distribution, ecology, and a brief discussion is provided on current views on the generic limits of Mesembryanthemum. A key to the species of Mesembryanthemum in Australia is provided, and the species is compared with M. crystallinum.
On a collecting trip in late November and early December 2011 to the Mildura area in the far north-west of Victoria, one of us (VS) observed extensive populations of a species of Mesembryanthemum along the Sturt Highway west of Mildura. The species was spectacularly in flower and superficially similar to M. crystallinum L. in having vegetative and floral parts covered with obvious bladder cells but it differed in having an erect central stem, commonly 0.3–0.6 m tall, larger leaves with very distinctive undulate margins, longer pedicels and flowers at least twice the size. Subsequently and independently, on a trip in mid-January 2012 to the Renmark area of South Australia one of us (RJC) made similar observations. The characters of the plants were found to be consistent with the account of Mesembryanthemum guerichianum Pax given in Gerbaulet (2001), and we herewith provide an account of this species in Australia. Mesembryanthemum guerichianum is indigenous to Namibia and South Africa, and probably south-west Angola (Gerbaulet 2001).
Mesembryanthemum guerichianum (Figures 1-6) has obviously been present in Australia for a considerable time but it appears to have been completely overlooked, presumably having been mistaken for M. crystallinum (Figures 7-8). An examination of the M. crystallinum collections held at the State Herbarium of South Australia found no specimens of M. guerichianum filed under this name but a single collection made by P.C. Jobson et al. in New South Wales east of Mildura was discovered filed under this species in the National Herbarium of Victoria. This collection, made in November 2000, is the first known record of M. guerichianum for Australia.
In 2001, Gerbaulet presented an overview of Mesembryanthemum, in which 16 species were treated. Klak et al. (2007) published a phylogeny of subfamily Mesembryanthemoideae and pointed out that Mesembryanthemum sensu Gerbaulet (2001) was non-monophyletic, and proposed a broader circumscription of the genus submerging 11 genera into Mesembryanthemum, including Aptenia and Psilocaulon, both of which are also naturalised in Australia. The expanded concept of Mesembryanthemum increased the genus to 101 species (Liede-Schumann and Hartmann 2009).
Liede-Schumann and Hartmann (2009) acknowledged that maintaining the previous circumscription of Mesembryanthemoideae consisting of 12 genera most likely rendered Mesembryanthemum polyphyletic, and was subsequently in dire need of further study, but suggested that the previous classification recognising the 12 genera be retained until further and better resolving data was available. For the purposes of this paper, we support the cautious view taken by Liede-Schumann and Hartmann in considering that the taxonomic conclusions presented by Klak et al. (2007) are premature and further molecular studies are required before adopting the proposed classification. We note too that the ‘Plants of southern Africa: an online checklist, version 3’ produced by the South African National Biodiversity Institute (PosA 2009), the online website GRIN (2012) and the online Australian Plant Census (APC 2012) have also not adopted the classification proposed by Klak et al. (2007) at this stage.
Until now, three alien species of Mesembryanthemum, originating from southern Africa, have been widely recorded from southern Australia, extending from Western Australia to South Australia, New South Wales, Victoria and Tasmania, e.g. Venning (1984), Jessop (1986), Hnatiuk (1990), Jacobs and Highet (1990), and Walsh (1996).
Of the three species previously recorded from Australia, the Common Ice-plant, Mesembryanthemum crystallinum (Figures 7 and 8) is perhaps the best known. It is widespread in coastal sandy or saline areas but it also occurs in inland places especially in open disturbed areas, on a variety of soil types, often on saline sites. It is a low growing plant rarely exceeding 10–20 cm high but it can form mats to over 1.5 metres in diameter. The species is characterised by the very obvious glistening water storage bladder epidermal cells on the stems, leaves, pedicels and sepals. The whitish or slightly pinkish flowers range from 10–30 mm diameter. This weedy species has naturalised in many parts of the world including countries surrounding the Mediterranean, Macranesia, North America, South America, Australia and New Zealand. Kapitany (2007) provides a series of excellent photographs of M. crystallinum and M. nodiflorum L.
Mesembryanthemum nodiflorum, like M. crystallinum, is also very widespread across southern Australia often favouring saline habitats, and it is common in inland and coastal areas especially in samphire (Tecticornia spp.) ecosystems. Like M. crystallinum, this species has naturalised in various parts of the world including Italy, Spain, Portugal, Greece and the south west of the United States of America.
Mesembryanthemum aitonis Jacq. appears to have only naturalised on sandy soils in Australia, particularly in coastal areas. It is quite common in South Australia, but it is local and known only from a few scattered locations in Western Australia and New South Wales. In Victoria, it was presumed extinct not having been collected since 1912 (Walsh 1996), but was rediscovered in February 2010, near one of the sites where it was originally collected.
Mesembryanthemum guerichianum Pax, Bot. Jahr. Syst. 19, 1: 133 (1894).
Annual or biennial flattened to rounded shrub up to 1 m tall and 2.4 m across with stem, leaves, floral branches, flowers and fruits clothed in prominent succulent epidermal bladder cells; bladder cells oblong (drying scaly) to ± mammiform; mammiform ones often with an elongated narrow extension at apex (drying hair-like). Central stem erect with a leafy apex, 30–60(–100) cm tall, from which arise lateral floral branches in leaf axils; basal part of central stem becoming somewhat woody up to 25 mm diameter, vegetative stems and floral branches at least basally distinctly angled-ribbed. Leaves opposite, decussate, petiolate, succulent, mid green, paler on lower surface or reddish (exposed drier sites), dull on both surfaces, with a slightly unpleasant scent; petiole 18–55 mm long, sulcate above, base dilated, amplexicaul; lamina folded, with margins ± parallel and prominently undulate, although flattened in small seedling leaves, ovate-spathulate to lanceolate, apex attenuate, mucronate, (55–)60–110(–155) mm long, (18–)35–45(–55) mm wide, 2–3 mm thick. Floral branches arising in leaf axils of successive pairs, at first ascending but with length spreading and bending downwards towards substrate. Floral leaves linear to narrowly spathulate or ovate, obtuse to acute, (13–)20–25(–38) mm long, 5–10(–15) mm wide, decreasing in size along floral branch towards apex. Flowers (15–)40–60(–70) mm diameter, petiolate, opening mid-afternoon to dusk, slightly sweet, musty-scented. Sepals 5, unequal, outer 2–3 larger, triangular to oblong-ovate, ± triquetrous distally, lacking membranous margins, adaxial surface smooth, 9–12 mm long, 5–7 mm wide; inner 2–3 smaller, similar in shape but with well-defined whitish membranous margins, 6–8 mm long, ca. 5 mm wide. Petaloid staminodes fused in lower part forming a tube, white, numerous ca. 180–220. Stamens in 6–7 rows, filaments very pale green, anthers pale yellow. Stigmas 5, erect tapering distally, cream. Fruit (submature): 5-ribbed, 15–20 mm diameter, succulent, red, prominently clothed with epidermal bladder cells, glossy, (mature): dehiscent, hygrochastic, 10–15 mm diameter, dry, 5-valved, straw-coloured; valves blackish-brown on margins, glossy, incurved at apex, beaked. Seed pale brown, ± triangular, tuberculate, 0.7–0.8 mm long and broad (description based entirely on Australian plants), (Figures 1-6).
SOUTH AUSTRALIA: 10.1 km W of South Australia/Victoria Border near turnoff to Talda, Sturt Highway, 19.i. 2012, R.J. Chinnock 10353 & C. Brodie (AD, MEL), R.J. Chinnock 10354 & C.J. Brodie (AD, MEL, NBG, NSW); 9.6 km E of Paringa Post Office near turnoff to Loxton, Sturt Highway, 18.i.2012, C.J. Brodie 4071 & R.J. Chinnock (AD, MEL, PERTH); 9.6 km E of Paringa Post Office near turnoff to Loxton, Sturt Highway, 19.i.2012, R.J Chinnock 10352 & C.J. Brodie (AD, BRI, PRE). NEW SOUTH WALES: N side of Sturt Highway, 10.xi.2000, 10.1 km E of Mildura, P.C. Jobson 6739, A.E. Orme, & G.M. Towler (CANB, MEL, NSW); Gol Gol, Sturt Highway, 01.ii.2012, V. Stajsic 6031 & R.J. Chinnock (AD, MEL, NSW). VICTORIA: Merrinee North, Sturt Highway, 01.xii.2011, V. Stajsic 5999 & D.E. Albrecht (AD, MEL); Between Merbein South and Wargan, Sturt Highway, 31.i.2012, V. Stajsic 6027 & R.J. Chinnock (AD, MEL); Between Merbein South and Wargan, Meridian Road (100 metres N of Sturt Highway), 31.i.2012, V. Stajsic 6028 & R.J. Chinnock (AD, MEL); Near Red Cliffs Lawn Cemetery, Red Cliffs-Meringur Road, 01.ii.2012, V. Stajsic 6032 & R.J. Chinnock (AD, MEL); Thurla, Sturt Highway, 100 metres E of Magnum Avenue, 01.ii.2012, V. Stajsic 6036 & R.J. Chinnock (MEL); Banks of Murray River by river bridge on New South Wales/Victoria border, Wentworth road, 31.i.2012, R.J. Chinnock 10356 (AD, MEL).
As far as is known, M. guerichianum is currently rare in South Australia, and known only from two relatively close sites on the Sturt Highway east of Renmark. On a trip at the end of January 2012 we (VS and RJC) discovered that M. guerichianum is very common and widespread in the Mildura region of Victoria. It is common between Merrinee North and Merbein South (west of Mildura) along the Sturt Highway and side roads, extending south to Red Cliffs and Thurla. The greatest distance between the currently known populations in Victoria is about 20 km.
During the same trip we also discovered the species at one site in New South Wales near Gol Gol, opposite the city of Mildura. It is very likely that the species is more widespread, perhaps especially in northwest Victoria.
In southern Africa, M. guerichianum occurs in the drier regions, on sandy plains and along roadsides (Klak 2000). In Victoria, populations at many sites extended for kilometres along roadsides forming dense impenetrable stands from the road edge to the fence-line of adjacent farmland or private land (Figure 5).
The species was observed invading degraded roadsides with relatively little remnant native vegetation, as well as behaving as an environmental weed and frequently invading remnant vegetation of varying quality along the roads and adjacent private land (Figure 6). In contrast to M. crystallinum and M. nodiflorum which favour usually saline habitats in inland and coastal areas especially in samphire (Tecticornia spp.) ecosystems, M. guerichianum appears to favour red brown sandy loam soils, appearing to avoid (at least for now) heavier soils and communities on heavier soil types such as Eucalyptus largiflorens F.Muell. ex Miq., dominated woodland, Chenopodium nitrariaceum (F.Muell.) F.Muell. ex. Benth. and Muehlenbeckia florulenta Meisn. shrublands, and seasonally wet depressions. At Merrinee North in Victoria, M. guerichianum has been found growing in Casuarina pauper F.Muell. ex L.A.S.Johnson open woodland with a chenopod dominated understorey, with associated species including *Asphodelus fistulosus L., Austrostipa nitida, (Summerh. & C.E.Hubb.) .W.L.Jacobs & J.Everett, Enchylaena tomentosa R.Br., Maireana brevifolia (R.Br.) Paul.G.Wilson and *Salvia verbenaca L. More commonly it has been found in mallee communities, including Eucalyptus dumosa A.Cunn. ex J.Oxley and Eucalyptus leptophylla F.Muell. Along the Meridian road, between Wargan and Benetook (south of Sturt Highway) in Victoria, it is the dominant understorey species along several kilometres of the remnant roadside mallee vegetation.
At Gol Gol in New South Wales M. guerichianum grows in Eucalyptus dumosa and Eucalyptus leptophylla mallee community, with a mostly chenopod dominated understorey, with associated species including *Asphodelus fistulosus, *Conyza sp., Enchylaena tomentosa, Exocarpos aphyllus R.Br., *Heliotropium europaeum L. ,*Lycium ferocissimum Miers, Maireana brevifolia, *Psilocaulon granulicaule (Haw.) Schwantes, *Reichardia tingitana (L.) Roth, Salsola australis R.Br., *Salvia verbenaca, Sclerolaena diacantha (Nees) Benth., and Sida intricata F.Muell. This incursion extends onto partially cleared private land.
In South Australia, M. guerichianum is known from two sites only a few kilometres apart along the Sturt Highway east of Renmark growing along the road adjacent to cultivated land. One population consisted of just two plants, one on either side of the road about 50 metres apart where they had managed to establish among chenopod dominated low shrubland largely of Maireana brevifolia, M. pentatropis (Tate) Paul.G.Wilson, Enchylaena tomentosa, and *Psilocaulon granulicaule.
The second site near the turnoff to Talda consisted of many hundreds of plants ranging from seedlings to a large patch 11 metres across. This population occurred on clay loam soil with a sandy surface in Acacia ligulata A.Cunn. ex Benth and Dodonaea viscosa Jacq. shrubland. Many of the seedlings occurred under the Dodonaea shrubs and in open areas among them, and in this latter area the leaves were often quite reddish. Associated shrubby species included Maireana brevifolia, Enchylaena tomentosa, Sclerolaena diacantha, Solanum esuriale Lindl., Sida fibulifera Lindl. and Sida ammophila F.Muell ex J.H.Willis.
We have not observed M. guerichianum invading crops or in recently harvested wheat paddocks, but we have observed it growing in disturbed or degraded paddocks. The abundance of M. guerichianum may be dependent on annual rainfall, as is the case with M. crystallinum and M. nodiflorum (CSIRO 2012).
Carr et al. (1992) included Mesembryanthemum crystallinum in their list of environmental weeds (i.e. plants that invade native vegetation, usually adversely affecting regeneration and survival of the indigenous flora and fauna) of Victoria, and they rated it as posing a very serious threat to mallee shrublands, lowland and grassy woodland, and saline and sub-saline wetlands. Based on our observations we consider M. guerichianum as being a very serious environmental weed, currently primarily invading mallee shrublands, particularly roadsides, often including remnant native vegetation. These roadside remnants are often the last remaining examples of native vegetation in what is otherwise a sea of cleared cultivated land.
The Victorian incursions appear to be beyond extirpation, with the total area invaded exceeding several hundred hectares, and the incursions spread over an area of about 20 km. It will be important to prevent M. guerichianum invading mallee areas of significant conservation value. The New South Wales and South Australian incursions appear relatively localised, and eradication is possible. However, not all seed will germinate immediately following dispersal so follow-up checks of the sites will be vital for a number of years after eradication of the population to eliminate any new seedling recruitment that may have occurred.
The first few pairs of seedling leaves in Mesembryanthemum guerichianum have an ovate ± flattened lamina that lies on, or close to, the substrate. Successive leaf pairs on the developing elongating stem gradually become lanceolate with the two halves of the lamina angled to almost parallel with each other and the leaf margins prominently undulate (Figure 1). Floral branches can arise in the leaf axils at a very early stage when the plant is only 4–5 cm tall. At this stage the floral branches are short, usually having no more than 1–4 flowers. Under good growth conditions with ample soil moisture plants grow rapidly with the floral branches developing secondary, tertiary and higher levels of branching and growing considerable lengths of up to 1.2 m. Initially the floral branches are spreading to ascending but as they elongate they gradually start bending downwards, due to the weight, towards the substrate. Older floral branches eventually dry-off remaining firm and providing support for succeeding branches above them.
When the plants were observed in late November (VS) they were in full bloom, with flowering almost complete by February (VS and RJC). Klak (2000) gives the flowering period as being between September and December, which is probably consistent with Australian observations. The flowers open mid-afternoon and close around dusk (VS and RJC).
Although flowers are commonly 40–60 mm diameter (Figure 3), it was noted at one population (V. Stajsic 6032 and R.J. Chinnock) that some plants had occasional very small flowers comparable in size with M. crystallinum on the extremities of aging branches that had largely dried off. Unlike Mesembryanthemum crystallinum the floral bracts (leaves) dry off rapidly and eventually shed so that the floral branches are leafless
Both Klak (2000) and Gerbaulet (2001) comment that the bladder cells in M. crystallinum are much larger than in M. guerichianum, which however, we do not find to be a useful character in distinguishing the two species. A comparison of some vegetative and floral features of M. guerichianum and M. crystallinum is given in Table 1 and a revised key to the species of Mesembryanthemum in Australia is provided below.
Key to species of Mesembryanthemum naturalized in Australia
1a. Leaves linear, subterete
1b. Leaves ovate to lanceolate
2a. Leaves ovate to spathulate, flattened, entire, papillae (bladder cells) on vegetative and floral parts usually < 1 mm broad; flowers milky white; petaloid staminodes about as long as sepals
2b. Leaves ovate to lanceolate, flattened to strongly folded, margins irregular to strongly undulate; papillae on vegetative and floral parts 1–2 mm broad; flowers white to pinkish, semi-translucent; petaloid staminodes much longer than sepals
3a. Plant annual; plant prostrate, to 20 cm high, spreading; stem terete; pedicel 0–5(–12) mm; flowers 10–20(–30) mm diameter;
3b. Annual or biennial shrub (possibly annual under adverse conditions); plant with an erect central stem 30–60(–100) cm high; stem angled-ribbed (see Figure 2); pedicel 20–30 mm long; flowers (15–)40–60(–70) mm diameter
One of us (VS) is grateful to the National Herbarium of Victoria for financing the January/February 2012 collecting trip to Mildura, and the staff at the State Herbarium of South Australia for the processing of material and the forwarding of specimens to the National Herbarium of Victoria. We are grateful to Dr Cornelia Klak, (Bolus Herbarium, University of Cape Town), Priscilla Burgoyne (National Herbarium, South African National Biodiversity Institute, Pretoria) and Dr Maike Gerbaulet (Hitzacker, Germany) for comments and/or confirmation of the identification of Mesembryanthemum guerichianum.
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