Polhillia connata (Harv.) C.H.Stirt.

du Preez, B., Dreyer, L. L., Stirton, C. H. & Muasya, A. M., 2021, A monograph of the genus Polhillia (Genisteae: Fabaceae), South African Journal of Botany 138, pp. 156-183 : 173-174

6. Polhillia connata (Harv.) C.H.Stirt. ( Fig. 15 ), S. Afr. J. Bot. 52: 2 (1986).

Type: Cap. Bon. Spei, without precise locality, Thom 37 ( K, holo.!) .

Argyrolobium connatum Harv., Fl. Cap. 2: 72 (1862). Genista connata (Harv.) Briq., Etude Cytises Alpes Mar. 119 (1894).

Polhillia canescens C.H.Stirt. S Afr. J. Bot. 52: 2 (1986), syn. nov. Type: South Africa, Western Cape, 3420 (Bredasdorp): Adamskop, north of Bredasdorp, 23 Sept 1982, Bayer 3104 (NBG, holo.!; K, iso.!).

Erect, lax, multi-stemmed shrubs up to 1.8 m tall, sprouting from woody rootstock. Branches greyish-brown, young stems sericeousvillous, old stems glabrescent, lenticels prominent. Stipules 5.0 — 10.0 mm long, silvery. Lea fl ets oblanceolate, grey, canescent-sericeous, conduplicate, flattened during wet season, apex acute-apiculate, base cuneate, terminal leaflet 7.0 — 21.0 X 2.0 — 5.0(— 7.0) mm, lateral leaflets 6.0 — 21.0 X 2.0 — 5.0(— 7.0) mm; leaves subsessile. In fl orescence 2 — 4 flowered terminal cluster, subsessile; pedicel to 4.0 mm long; bract 1.0 — 1.5 mm long, linear. Flowers yellow, 11.5 — 13.0 mm long. Calyx 6.0 — 7.5 mm long, yellow-green, sericeous; tube 3.0 — 4.0 mm long; dorsal teeth triangular, 3.0 — 3.5 mm long, fused for less than one third of lobe length, tips acute; ventral teeth narrowly triangular-ensiform, 3.0 — 3.5 mm long, fused to ± half of lobe length, converging, apex acute-apiculate. Standard 11.5 — 14.0 mm long; claw linear, 3.0 — 4.5 mm long; lamina broadly ovate, 8.5 — 11.0 X 10.0 — 14.0 mm, apex emarginate, base cordate, adaxial surface shortly and sparsely pilose, back sericeous all over except along basal flanks. Wing petals 10.5 — 12.0 mm long, equal to or slightly longer than keel; claw 3.5 — 4.0 mm long; lamina oblong-lunate, 8.5 — 10.0 X 4.0 — 5.5 mm, pilose along midline to completely glabrous, apex acute-obtuse, base minutely auriculate; oval and lunulate depression with lamellate sculpturing. Keel petals 10.0 — 11.8 mm long; claw 3.5 — 5.0 mm long; lamina lunate-oblanceolate, rostrate, 7.5 — 8.0 X 3.5 — 4.5 mm, sericeous on fore half, apex sub-rostrate, base truncate-auriculate. Stamens basifixed anthers 2.4 — 2.5 mm long, carinal anther 2.2 — 2.4 mm long, dorsifixed anthers 1.2 — 1.3 mm long; staminal tube 8.4 — 9.2 mm long, unfused portion remaining closely united, tightly arranged around style. Pistil 9.3 — 10.7 mm long; ovary 5.4 — 6.0 X 1.2 — 1.4 mm, ovules 9; style usually at 80 — 90̊ angle, height of curvature 4.8 — 5.8 mm, sericeous, becoming glabrous towards apex. Fruit indehiscent, non-plicate, straight to slightly falcate, tapering towards apex and base, sericeous, pale-brown, 30.0 — 45.0 X 4.0 — 5.0 mm. Seed ovate-reniform; testa olive-green to dark-brown, rarely marbled pale-orange, smooth; 2.3 — 2.7 X 1.9 — 2.4 mm, 1.7 — 1.9 mm thick.

Etymology

The specific epithet “connata ” refers to the stipules that are connate and sheath the stems in this species, despite this being typical of all other Polhillia species.

Diagnostic characters

Polhillia connata is easily distinguished from all other Polhillia species, except P. canescens , by its erect, sparingly branched, lax growth form (versus more densely branched, rounded erect shrubs in other species); rostrate-beaked keel (versus rounded, lunate in other species); large leaves up to 7.0 mm wide (versus leaves usually less than 3.5 mm wide).

We are, however, of the opinion that P. connata is identical to P. canescens . Having studied the type specimens of P. connata and P. canescens , as well as material collected during the extensive fieldwork for this study, it became apparent what caused the taxonomic confusion between these two species. In P. connata leaf size is very variable, influenced by plant age and season. The type material of P. connata is almost 200 years old and appears to have been collected from a depauperate plant with fairly small, closed leaves while the type of P. canescens was collected from a healthy individual with large, open leaves. Flower morphological features were difficult to assess due to the age of the type specimens and the lack of available flowers, but comparable traits were similar. The calyces of the two taxa were identical, with the unique ventral calyx teeth narrowly triangular-ensiform, 3.0 — 3.5 mm long, fused to ± half of lobe length, and the tips converging on one another. The exact locality of type specimen of P. connata collected by the Scottish missionary Rev. George Thom is unknown. However, the collection was probably made between 1818, when he was appointed pastor of the Dutch Reformed Church in Caledon and 1823 when he moved to his last Ministry at Tulbagh. It is plausible that he would have travelled in the wider southern Overberg area and probably came across this species in either the Bredasdorp or Riversdale areas. Stirton (1986a) speculated that the collection may have come from near Caledon, where Rev. Thom was based, but no Polhillia has been recorded from this area. Based on this evidence, in combination with the morphological similarities and the observed natural environmental leaf size variation, we here reduce P. canescens into synonymy under P. connata .

Distribution, ecology and conservation status

Polhillia connata flowers from September to October. It is endemic to the Overberg region, where it is known from six localities north of Bredasdorp ( Fig. 6B ). It grows on shale-derived soils in Central and Eastern Ruens ^Shale Renosterveld (FRs 12 & FRs 13) on rocky slopes ( Mucina and Rutherford, 2006). Plants were found on most aspects but appeared to favour northerly facing slopes and gullies. A thorough assessment of the population located roughly 1500 plants. The P. connata populations in the Riversdale area remain a mystery, both in terms of its taxonomy and whether these populations still exist. Only 3 collections were made in this area, the most recent in 1925. All collections are without precise locality details. John Muir collected this species on both sides of the Langeberg Mountains during the 1920’s. Despite extensive searches in the course of this study, none of these populations could be relocated. The majority of the lowland Renosterveld in the area has been ploughed for agriculture and it is likely that these populations have become extinct since the last collection in 1925. Rebelo et al. (1991) discussed the differences between the Agulhas Plain and the Riversdale Plain which both harbour Polhillia and pointed out that these communities have different structures, the latter still poorly known. Isolated within a broad western Renosterveld zone of the Riversdale Plain there are small patches of silcrete and calcrete cappings (Their Fig. 2 ); habitats not dissimilar to those of the main distribution of Polhillia in the Agulhas Plain. Such areas might be best to survey further for this species. The Red Data List status of this species is proposed as Vulnerable (VU A2c; B 1ab(iii, iv,v)+ B 2ab(iii,iv,v); C2a(i)) following the latest IUCN categories and criteria ( IUCN, 2012).

Additional specimens examined

South Africa. WESTERN CAPE: 3321 (Ladismith): Hills at Waterval in Klein Karoo, north of Langeberg (— CD), Sept 1925, Muir 3745 (BOL, PRE). 3420 (Bredasdorp): Rooivlei, Bredasdorp (— AC), 16 Oct 1982, Bayer 3183 (NBG); Rooivlei farm, Swellendam area (— AC), 13 Oct 2003, CREW 30 (NBG); 21 May 2017, B. du Preez 287 (BOL); 15 Oct 2017, B. du Preez 388 (BOL); Rooivlei farm, 0.5 km east of trig beacon 172 (— AC), 12 Sept 2000, Helme 1752 (NBG); About 12 km NE Bredasdorp on Adoons Kop (— AC), 1 Aug 2001, Helme 2062 (NBG); Adoonskop farm just off R319 (— AC), 15 Oct 2017, B. du Preez 390 (NBG, PRE); Adoonskop, north of Bredasdorp (— AC), 9 Oct 1986, B.- E. van Wyk 2093 (JRAU), 2094 (JRAU); Overberg region, San Souci farm off R319 (— AC), B.A. Walton 498 (NBG); Haasiesdrif farm, just off R319 (— AC), 14 Oct 2017, B. du Preez 383 (BOL); Rooivlei farm, 20 miles north of Bredasdorp (— AC), 1 Oct 2012, Stirton 13721 (BOL); 1 Nov 20111, Stirton 14347 (BOL); Beyersdal farm (— AD), 13 Oct 2017, B. du Preez 382 (BOL, PRU); Beyersdal farm, above Zoutrivier (— AD), 12 Jul 2017, B. du Preez 519 (BOL). 3421 (Riversdale): Riversdale, Hills near Riversdale (— AB), Oct 1923, Muir 2803 (BOL); Flats near Riversdale (— AB), Muir 2817 (PRE).

Figures

Fig. 15. Composite plate of Polhillia connata. 1 — Flower front view; 2 — Flower side view; 3 — Flower bottom view; 4 — Calyx; 5 — Wing petals; 6 — Keel petals; 7 — Androecium; 8 — Gynoecium; 9 — Fruit; 10 — Close-up of leaves and stipules; 11 — Close-up of a single leaf and stipules; 12 — Habit. Scale bars: 4 mm (except images 9 and 10 — Scale bars: 10 mm). Photographs by B. du Preez

Fig. 6. Map showing distribution of Polhillia in the Western Cape Province, South Africa.A — Distribution of extra Overberg species; B — Species within and just outside of the Overberg region. Note expansion of square in A to map in B.

Fig. 2. Cross-sections through the leaves of the Overberg Polhillia species, with abaxial surface on left side of image. 1 — P. brevicalyx (isobilateral, spongy centre); 2 — P. connata (isobilateral, spongy centre); 3 — P.curtisiae (bifacial); 4 — P. pallens (bifacial); 5 — P. stirtoniana (bifacial); 6 — P. xairuensis (isobilateral, spongy only). Note the substantially different mesophyll arrangement of P. brevicalyx compared to other species within the Overberg, but note the similarity with P. involucrata (Fig. 3.5 & 3.6). Images taken at 400 X magnification.Scale bars: 50 µm.