Ruschia turgida (L.Bolus) Klak, 2020

Klak, Cornelia, Schmiedel, Ute & Bruyns, Peter V., 2020, The taxonomic status of Ruschia stricta var. turgida and R. promontorii and a new name for R. vaginata (Ruschieae, Aizoaceae), Phytotaxa 433 (1), pp. 41-54 : 42-49

Ruschia turgida (L.Bolus) Klak , comb. et stat. nov. ≡ Ruschia stricta var. turgida L.Bolus (1930: 207) .

Type:— SOUTH AFRICA. Western Cape, Vanrhynsdorp (3118): Locality uncertain, Mr Parson’s garden, Vanrhynsdorp , without date, Frames sub BOL19209 (holotype BOL129482 !, holotype can be viewed https://plants.jstor.org/stable/history/10.5555/al.ap. specimen.bol129482) ( Fig. 1; water colour of the type collection, Fig. 2 ) .

Description:— Perennial, succulent, stems woody, erect, 15–40 cm × 3 mm, internodes smooth, light brown to grey, 10–25 mm long. Leaves turgid, opposite, ascending, trigonous, not fused at bases, 10–15 mm long, 10 mm broad and thick, with transparent lines along margins, smooth, shiny, light green or glaucous-green and frequently suffused with red ( Fig. 3 ). Flowers solitary, 17 mm diameter, pedicels to 10 mm long, bracts 11 mm long, bases spurred,; calyx lobes 6, subequal, with membranous edges; petals pink, 2- to 3-seriate, inner ones with a red central stripe, obtuse or emarginate, (acute), 13 × 1 mm; filamentous staminodes absent; filaments collected into a cone, white with reddish tips, to 4 mm long, inner ones conspicuously papillate towards the bases, anthers white; stigmas 6, red, slender, narrowly subulate, 3 mm long, top of ovary almost flat or slightly raised. Fruits 6-locular, with broad valve wings, top almost flat to slightly raised, 8 mm diameter, base globose to shortly obconical, keels light brown, long, opening through 180°, smooth, diverging from the base, covering membranes almost complete, thin and flexible, transparent, with an inconspicuous ridge below, without closing bodies ( Fig. 4 ). Seeds numerous, white to light ochre, smooth, 0.9 × 0.6 mm.

Flowering time:— April to August, with the main flowering from May to July.

Taxonomic notes:— Ruschia stricta var. turgida was placed in synonymy under Amphibolia saginata (L.Bolus 1937: 104) H.E.K. Hartmann (1998b: 48) by Hartmann (1998b), but no reason was provided for this decision. Amphibolia saginata is characterized by 5-locular fruits, with closing ledges below the covering membranes and tiny closing bodies. It is endemic to the Lüderitz district in Namibia ( Hartmann 2017). The type locality of R. stricta var. turgida was not reported in Bolus’ protologue, and the plants originated from a garden in Vanrhynsdorp. The holotype of R. stricta var. turgida (BOL129482!) lacks mature fruits. Our recent collections from the Vanrhynsdorp area match the holotype closely. They have fruits and so for the first time their details are available. The fruits of the newly collected material are 6-locular, with broad valve wings, very thin and flexible covering membranes and they lack closing bodies. The flowers also lack filamentous staminodes, as reported for the type. Since the fruits and flowers are not congruent with the features that characterize Amphibolia , R. stricta var. turgida is clearly misplaced in Amphibolia . On the other hand it is also not conspecific with R. stricta . Ruschia stricta var. stricta displays ternate flowers, whereas var. turgida has mostly solitary flowers. Furthermore, fruits of var. turgida have valve wings and lack closing bodies ( Fig. 4 ), whereas the fruits of var. stricta have no valve wings and possess closing bodies. Consequently, we recognize var. turgida as a separate species.

Distribution and ecology:— Ruschia turgida occurs in a restricted area between the Farm Moedverloren and the N7 bridge across the Sout River on the Farm Quaggaskop (Knersvlakte Quartz Vygieveld, Mucina et al. 2006) ( Fig. 5 ). This is an arid winter rainfall area with a mean annual rainfall of about 150 mm (see description of the Biodiversity Observatory S28 Moedverloren in Haarmeyer et al. 2010). The species characterizes a vegetational community which was described by Schmiedel (2002) as “ Ruschia stricta var. turgida Succulent Shrub Community ” ( Fig. 6 ). This community can be found in broad valleys at an elevation of 50– 200 m. These valleys are surrounded by hills covered with quartz-gravel, as is typical for the area ( Schmiedel & Jürgens 1999). The relatively shallow soil (up to 40 cm deep) is soft, with few stones and consists of fine sand and silt. It has a high salinity (up to 8 mS/cm) and is neutral to slightly alkaline (pH 7–8). The high content of sulphate, calcium and sodium, which are typical for the habitats of Ruschia turgida , suggest the presence of gypsum in the soil.

Ruschia turgida is morphologically similar to Ruschia stricta ( Fig. 7 ), in that the two species share pale glaucous-green, broad leaves, which are not fused towards their bases and fall off readily in dried specimens. However, the leaves are larger in R. stricta (15–25 mm long, 7–12 mm broad and 9 mm thick vs. 10–15 mm long and 10 mm broad and thick in R. turgida ). In addition, R. turgida differs from R. stricta by its solitary flowers, which lack filamentous staminodes, whereas R. stricta forms ternate inflorescences and its flowers have filamentous staminodes.

Conservation status:— Ruschia turgida has a restricted distribution, but it is locally common. Large parts of its distribution (namely Farm Moedverloren), are protected within the Knersvlakte Nature Reserve.

Additional specimens examined: — SOUTH AFRICA. Western Cape, Vanrhynsdorp (3118): Farm Moedverloren (-- AD), 200 m, 8 August 2002, Klak 944 ( BOL) ; 16 August 2019, Schmiedel 143049 ( BOL) ; ± 3 km north of Holrivier station (-- CD), 100 m, 10 October 1998, Schmiedel 110268 ( BOL) ; between farms Quaggaskop and Moedverloren (-- DA), 200 m, 26 August 2018, Klak 2614 ( BOL) .

Figures

FIGURE 2. Ruschia stricta var. turgida, cult. Vanrhynsdorp, Frames sub BOL 19029; (drawing by B.O. Carter).

FIGURE 3. Ruschia turgida (= R. stricta var. turgida) showing the bright green leaves with translucent margins along the edges and the 6-locular fruits. Farm Moedverloren, Knersvlakte, South Africa, October 2019 (photo by U. Schmiedel).

FIGURE 4. Fruit of Ruschia turgida (=Ruschia stricta var. turgida). Top of open fruit and side view of closed fruit, Klak 2614. Scale: Distances between white lines indicate 1 mm.

FIGURE 5. Distribution of Ruschia promontorii (circle) and R. turgida (square).

FIGURE 6. Monotypic stands of Ruschia turgida (= R. stricta var. turgida) in broad valleys surrounded by low, quartz-gravel covered hills. Farm Moedverloren, Knersvlakte, South Africa, October 2019 (photo by U. Schmiedel).

FIGURE 7. Type illustration of Ruschia stricta (drawing by B.O. Carter).