Salicornia decussata (S.Steffen, Mucina & G.Kadereit) Piirainen & G.Kadereit

Steffen, S., Mucina, L. & Kadereit, G. (2009). Three new species of Sarcocornia (Chenopodiaceae) from South Africa. Kew Bulletin 64: 447. https://doi.org/10.1007/s12225-009-9127-1

Type

South Africa, Western Cape, Reddelingshuys (N of Piketberg), 18°37′53.7″E, 32°31′19.0″ S. Steffen & Mucina 260306/10 (holotypus NBG!; isotypus MJG!).

Morphology General Habit

Erect subshrub up to 50 cm tall, branches 6 – 23 mm thick, rough, laterally compressed, gnarled, often breaking up; ramification strictly regular, with a pair of branches arising from each node

Morphology General

Segments strongly succulent, boat-shaped, laterally compressed, 3 – 5 mm long, 4 – 7 mm wide, old segments corky, dead cortex adhering to younger branches, but older branches often without cortex, leaf apex strongly keeled, leaf margin strongly spreading, concave, segments not flattened in herbarium material-Inflorescences terminal and lateral, spike-like thyrses, 5 – 48 mm long, 2 – 4 mm in diam., cylindrical in flower and fruit, with 3 – 16 fertile segments

Morphology Reproductive morphology Inflorescences

Flowers 3 per cyme in a row, 1/3 of the flowers hidden by the subtending bract, central flower c. 2 mm, slightly longer than the lateral ones

Morphology Reproductive morphology Flowers Perianth

Perianth tube with 4 lobes, stamens 2, adaxial, anthers c. 1 mm long, stigmas bifid, plumose, spreading

Morphology Reproductive morphology Seeds

Seeds not seen at maturity, testa of immature (!) seeds rugose.

Distribution

South Africa, Western Cape, endemic to the West Coast, Piketberg region

Ecology

Sarcocornia decussata occurs at altitudes of 120 – 160 m in three types of habitats all linked to the Porterville Formation (Boland Subgroup of the Malmesbury Group (Namibian Erathem). One type of habitat is quartz patches, a unique southern African habitat, which originated through weathering of softer shale (mudstones, siltstones, sandstones) layers leaving behind hard quartzitic veins which, after disintegration, form an almost continuous quartzite rubble layer (Schmiedel 2002; Mucina et al.2006a). The other habitat type is large erosion scars in the soft layers of the Malmesbury shales. From this habitat S. decussata expanded marginally into immediately adjacent alluvia built of heavy, clayey soils derived from the local shales. The obvious salinity of all the listed habitats relates to salt-bearing layers within the Malmesbury shales. Climatically the distribution area of S. decussata falls within winter-rainfall region and it is characterised by local mean annual precipitation (MAP) fluctuating around 300 mm, and dropping as low as 250 mm of MAP in the rain shadow of the closely-situated Piketberg Mountains.

Conservation

The species shows very restricted distribution, only six larger populations (accompanied by a number of closely-situated small satellite populations) are known. The largest known population is shared by the Farms Draaihoek and Uitkoms near Eendekuil (Piketberg region, West Coast) and counts around 10,000 individuals. Regeneration (young saplings) has also been observed, especially in shallow “dongas” (erosion ditches). The current extent of the ploughed quartz patches on both farms suggests that nearly half of the habitat must have been lost to grain cultivation in the course of the last 3 – 4 years. The existence of the species is, however, not immediately under threat (unless the habitat destruction continues) and therefore we can rank the current conservation status of this taxon as Vulnerable (VU), according to the criteria of IUCN (2001).

Note

The specific epithet has been chosen because of the very strict (and well-pronounced) decussate ramification of this species. The major population occurring near Eendekuil was known to several botanists (N. Helme, J. C. Manning, pers. comm.) in the past, having been previously considered as an outlier locality of Sarcocornia xerophila (Tölken) A. J. Scott, known from similar habitats (quartz patches) of the Knersvlakte (southern Namaqualand), situated some 200 km to the north of the northernmost localities of S. decussata. Sarcocornia xerophila and S. decussata are not closely related (Steffen 2006); the latter belongs to the S. mossiana clade (Steffen 2006). This taxon has also been recognised by Goldblatt et al. (2005) as “Sarcocornia sp. 1”. Mucina et al. (2006a: 277) named this taxon “Sarcocornia sp. nov”. (Mucina 200103/8 NBG), one of the dominants in the vegetation unit called SKk 8 Piketberg Quartz Succulent Shrubland.