Nicotiana clarksonii M.W.Chase & Christenh., 2023

Bruhl, Jeremy J., Andrew, Damien D., Palsson, Ruth, Jobson, Richard W., Taseski, Guy M. & Samuel, Rosabelle, 2023, Nine new species of Australian Nicotiana (Solanaceae), Australian Systematic Botany 36 (3), pp. 167-205 : 168-176

Nicotiana clarksonii M.W.Chase & Christenh. , sp. nov.

( Fig. 2–6.)

Type: Queensland: Belgravia, 17.1°S, 144.4°E, 23 Apr 1998, Hyland 15763 (holo: CNS QRS115635 !; iso: CNS QRS116337 !, CNS QRS115635 !) .

Diagnosis

Nicotiana clarksonii is closely related ( Fig. 1 b) and morphologically similar to N. amplexicaulis N.T.Burb. ( Fig. 7–9), but it has flowers twice the size and a simpler (less branched) inflorescence structure and grows in limestone caves and outcrops instead of sandstone, sandstone-derived soils and clay.

Erect, herbaceous, annual to short-lived perennial herbs, forming a rosette, but with numerous large leaves in the basal portion of the stems, the main stem with major branches from near the base and fewer, shorter branches in the upper portion. Leaves with broadly winged petioles making the leaves appear sessile, the wing 1.5–3.0 cm across, blades 5.4–21.5 × 1.9–11.5 cm, ovate, widest near the base, the apex acute in the basal leaves to acuminate in those higher up, upper leaves as wide at their base as in the middle, auriculate, margins entire, sometimes toothed topped with a glandular hair, undulating, ciliate, often bullate, especially on the base, upper leaves sessile, often with a somewhat auriculate base. Vestiture composed of dense pubescence all over, short- to long-haired, all with small glands, and longest hairs somewhat twisted with swollen bases but these not glandular, leaf surfaces also densely pubescent with short glandular hairs that make leaves feel wet to the touch, calyx and peduncle similar, with long hairs and short glandular hairs. Inflorescence bracts sessile, linear lanceolate, ~ 0.5–2.3 cm long, the apex acuminate. Calyx 1.20–1.40 × 0.15–0.20 cm, one lobe slightly longer and one shorter than the others, the tips acuminate, slightly flaring, 0.3–0.5 cm longer than and persistent in the fruit, the calyx enlarged at maturity. Corolla tube 2.4–2.8 cm long (from tip of the calyx), 0.35–0.40 cm in diameter, with no throat cup and smaller in diameter at the point it meets the calyx; in some plants the floral tube is curved rather than straight, the limb 2.4–2.8 cm across, the lobes slightly cleft, cleft 0.2 cm deep, sinus 0.4 cm deep, lobes 0.8–1.0 cm long; four stamens of the same length at the throat of the floral tube and the fifth ~ 5 mm deeper in the tube, all with filaments 0.2–0.3 cm long. Fruit a capsule splitting in four lobes, 0.8–1.2 cm long at maturity.

Distribution

Known only from northern Queensland at the Mungana Caves and on Christmas Creek Station near Greenvale. In contrast, N. amplexicaulis has a range that is disjunct from N. clarksonii , occurring further south in Queensland, generally in transitional rainforest vegetation. Both species occur at sheltered sites.

Habitat and ecology

Limestone outcrops and caves in vine thickets and forests that are wet in the monsoon season but arid otherwise. These plants can grow deep inside limestone caves ( Fig. 6), in places with so little light that the only companion plants are ferns and mosses.

Phenology

Collected in flower April–December. We suspect that it could be in flower at any time of the year, depending on rainfall.

Etymology

Named for John R. Clarkson, Parks and Wildlife Service, Atherton, Queensland, who facilitated access to and accompanied us when we visited the Mungana Caves. He has a special interest in Nicotiana and described one species, namely, N. wuttkei J.R.Clarkson & Symon ( Clarkson and Symon 1991) . He is also the acclaimed, long-time Treasurer of the Australasian Systematic Botany Society.

Chromosome number

This species has the same chromosome number as does N. amplexicaulis , n = 18 ( Chase et al. 2022 b).

Notes

Nicotiana clarksonii was first collected at the Christmas Creek Station in 1975 by Thorsborne ( BRI AQ 0102628) and then at the Mungana Caves in 1982 by Goodwin ( BRI AQ 0338801). In many cases, specimens of this species have been previously identified as N. forsteri Roem. & Schult. , because of their shared sessile leaves with an auriculate leaf base, but the latter is a distantly related species ( Chase et al. 2022 b; Fig. 1) with a different floral morphology (see illustration of N. forsteri below in the section on N. gibbosa M.W.Chase, D.D.Andrew & J.J.Bruhl ). It has also been associated with N. amplexicaulis ( Fig. 7–9), to which it is sister ( Fig. 1 b), but it has flowers twice the size of the latter and grows on limestone- rather than sandstone-derived or clay soils. The Christmas Creek Station site is 650 km north of the main range of N. amplexicaulis in the areas near the Carnarvon Range, Queensland. Nicotiana clarksonii and N. amplexicaulis are highly similar, even down to their vestiture and chromosome number, but their ecology and distribution are different, which, combined with the morphological differences, justifies recognition of N. clarksonii as a distinct species. At the Mungana Caves, we observed one accession that was different from the others ( Fig. 4, 5), different enough to make us think that there might in fact be two species at Mungana (they differ mostly in the shape of the floral tube and leaf width to length ratio). However, genetically, there seems to be no differences between the two forms. We illustrate both here ( Fig. 2–5), but all other material we have examined has been like that in Fig. 2 and 3.

Selected specimens examined

QUEENSLAND. Mungana Caves, Archway Cave, 0.90 km north of Burke Developmental Road , 325 m, 17°5′34″S, 144°23′46″E, 6 Sep. 2018, Chase & Christenhusz 18151 ( BRI, CANB) ; Mungana Caves, Carpentaria Cave 1, 335 m, 17°5′41″S, 144°23′42″E, 2 May 2019, Chase & Christenhusz 19101 ( BRI) ; Mungana Caves, Carpentaria Cave 2, 335 m, 17°5′42″S, 144°23′38″E, 2 May 2019, Chase & Christenhusz 19102 ( BRI) ; Mungana Caves, outside Archway Cave, 0.9 km north of Burke Developmental Road , 360 m, 17°5′34″S, 144°23′47″E, 2 May 2019, Chase & Christenhusz 19103 ( BRI) ; Mungana Caves, Ryan Imperial Cave , 345 m, 17°5′25″S, 144°23′30″E, 2 May 2019, Chase & Christenhusz 19104 ( BRI) ; Mungana Caves, Hair Cave, Echidna’s Rest , 380 m, 17°6′10″S, 144°24′43″E, 2 May 2019, Chase & Christenhusz

19105 ( BRI); NPR 98 , Royal Archway Cave , Mungana , 80 m, 17.5°S, 144.23°E, 17 May 1997, Ford 1933 ( QRS 112344 ); Fern Cave (Spring Tower) Chillagoe, 17.13277778°S, 144.43472222°E, 11 July 1982, Godwin C 2317 ( BRI AQ0338801 ); Burdekin , Belgravia , 3 km west of Mungana , 340 m, 17.075°S, 144.375°E, 20 May 1999, Gray 7554 ( QRS 107535.3 , BRI AQ0845080 ); Burke Developmental Road, 1 km E of Chillagoe , 380 m, 17.6°S, 144.25°E, 26 July 1995, Gray 6273 ( QRS 107535.1 , QRS 107536.4 , QRS 107535.3 ); Archway Cave , Mungana National Park , 17.10°S, 144.38°E, 21 Oct 1990, Hind 6088 ( NSW 234670 ); Mungana Fern Cave , 20 miles [~ 32.2 km] west of Chillagoe, 17.0818053°S, 144.4177893°E, 30 Dec. 1982, Jacobsen 3 ( BRI AQ0339113 , BRI AQ0339515 ); Christmas Creek Station, 600 m, 15 June 1975, 19.08192453°S, 145.2508554°E, Thorsborne 76 ( BRI AQ0102628 ) .