Stobaea rubricaulis DC.

Karis, Per Ola & Mckenzie, Robert J., 2024, Second-step lectotypification of Stobaea rigida and reassessment of heterotypic synonyms of Berkheya rigida (Asteraceae, Arctotideae), Phytotaxa 641 (4), pp. 267-276 : 272-273

Stobaea rubricaulis DC.

The name Stobaea rubricaulis was published by Candolle (1838: 515) based on a specimen collected from Swellendam formerly in the personal herbarium of C.F. Ecklon. A specimen in Candolle’s ‘Prodromus’ herbarium (G-DC barcode G00499160) carries a label attributing it to Ecklon and bears the collection number “N. 308”, the collection locality “Swellendam et Georg”, and the Ecklon and Zeyher locality number “91”. Under ICN Art. 7.11, this specimen was effectively designated the lectotype for S. rubricaulis by Roessler (1959). The locality number “91” was used for material collected by J.L.L. Mund, who worked as a land surveyor in George and subsequently in Swellendam in the Western Cape in the late 1820s ( Glen & Germishuizen 2010). On Mund’s death in 1831, his personal herbarium passed to Ecklon, who subsequently distributed the specimens.

According to Roessler (1959), S. rubricaulis differs from B. rigida only in the somewhat coarser leaf dissection of the former. Certainly, the upper cauline leaves and involucral bracts of the central specimen on UPS-THUNB 18601 and the specimen G00499160 are morphologically consistent, with the bracts and leaves of the Thunberg specimen somewhat more densely tomentose. There is no indication that the capitula of G00499160 contained ray florets. The leaves of B. rigida vary considerably in overall dimensions, degree of dissection, and the dimensions of the apical and lateral lobes and spines. The lower cauline leaves of G00499160 are consistent with those of the most widespread form of B. rigida ( Fig. 1C ).

As cited by Roessler (1959), a specimen of B. rigida collected from Swellendam by Mund is housed in Herb. SAM (ex Herbarium Musei Austro-Africani no. 40107). In all accessible morphological characters, the SAM specimen is consistent with the G00499160 specimen and with B. rigida , although the SAM specimen is in better condition and is more complete than G00499160.

In agreement with Roessler (1959), we have found no evidence that S. rubricaulis is morphologically distinguishable from B. rigida and therefore retain the former name in the synonymy of B. rigida .

Figures

FIGURE 1. Macromorphology of Berkheya rigida. A,F,G,I. Growth habit. B. Stem base. C,J. Leaves. D,E,H,K. Compound inflorescence and capitula. Localities (all in Western Cape province): Swellendam (A,C,E); Riversdale (B,D); Cape Columbine (F–H); Scarborough, Cape Peninsula (I,K); Buffels Bay, Cape Peninsula (J). Photographs by N.A. Helme (I,K), P.O. Karis (B,F–H,J) and R.J. McKenzie (A,C–E).