Hibiscus krichauffianus F.Muell., Rep.

McLay, Todd G. B., Barker, Robyn M. & Albrecht, David E., 2023, Morphological and environmental variation within Hibiscus krichauffianus (Malvaceae), and the recognition of two new species, H. verecundus and H. calcareus, Australian Systematic Botany 36 (6), pp. 457-477 : 466-467

Hibiscus krichauffianus F.Muell., Rep. pl. Babbage’s

Exped. 7–8 (Oct. 1859)

Type citation: ‘ Lake Gregory , Darling River’ . Type : So. [South] Australia, s. dat., Mr Babbage 1, Com. R. Schomburgk 9/71 (lecto, here designated: K000659853 !, Supplementary Fig. S1 , bottom right corner). Residual syntypes: Minindee Creek , River Darling [=Menindee Creek, Darling River], T. H.Goodwin s.n ( MEL 0068091 A!, excluding upper left packet and lower two fragments, Supplementary Fig. S2 ); possible syntypes: mixed collections from Herb. Mueller mounted on same sheet as the lectotype, Darling river, Near Spencer’s Gulf etc. ( K s.n., p.p.) [excluding the left-most specimen, as this is H. calcareus ; see notes below under Typification] .

Hibiscus krichauffianus F.Muell. var. krichauffianus [Autonym established by P.A.Fryxell, Proc. Linn. Soc. New South Wales 92(3): 263 (1968)].

Shrub or subshrub to 0.4–1 m tall, typically erect and ascending. Branchlets very densely covered with sessile to shortly stalked stellate hairs 0.3–0.8 mm in diameter, indumentum white, silvery-white, grey or yellowish-white. Stipules persistent or abscising with age, filiform, filiform–linear or filiform–subulate, 2.5–8 mm long, 0.16–0.4 mm wide. Mature leaves simple and unlobed, petiolate; petiole 5–25 mm long, moderately to very densely covered with sessile or shortly stalked stellate hairs; lamina mostly ovate to lanceolate or oblong, occasionally broadly ovate, flat to weakly concave or sometimes weakly folded or conduplicate, 10–55 mm long, 5–35 mm wide; base obtuse, truncate or very broadly cuneate; margins dentate to crenate; apex obtuse to broadly acute; adaxial surface whitish-silver to grey, becoming greyish-green with age, abaxial surface paler (except in young leaves); abaxial main and lateral veins raised and obvious; stellate hairs on adaxial surface dense to very dense (rarely moderate), 0.2–0.8 mm in diameter, sessile to shortly stalked, multiradiate with 7–20(–30) rays; stellate hairs on abaxial surface dense to very dense, 0.25–0.75 mm in diameter, sessile to shortly stalked, multiradiate with 10–25 rays. Flowers solitary in leaf axils, occasionally cleistogamous; combined peduncle and pedicel 5–26 mm long, usually elongating in fruit, abscission line not obvious, usually 1–2(–13) mm from base, indumentum as for young stems and petioles, broadening distally and sometimes becoming obviously flattened, occasionally recurving in fruit. Epicalyx lobes 5–8 (rarely 10), narrowly linear or subulate, 7–16 mm long, to ~ 1 mm wide, one-half to the same length as the calyx at anthesis, fused basally for 1–4 mm (fused part of epicalyx sometimes difficult to distinguish from the pedicel), straight in flower and becoming recurved (rarely incurved) in fruit, usually entire at the apex but rarely bifurcating, with moderate to dense stellate hairs abaxially on the lobes and usually very dense hairs on the fused portion. Calyx 9–18 mm long at anthesis, enlarging to 20 mm long in fruit; lobes narrowly triangular to triangular, 5–9 mm long at anthesis, enlarging to 12 mm long in fruit, abaxial indumentum of moderate to very dense stellate hairs, adaxial indumentum of appressed or ascending 1- or 2-armed hairs intermixed with stellate hairs particularly distally, obscurely 1-nerved under hairs. Petals 17–35 mm long, adnate to staminal column at base but otherwise free, pale pink or mauve (rarely white), lacking basal spot, glabrous adaxially, with sparse to moderate stellate hairs abaxially towards the margin and apex on one side, sometimes extending towards the petal base. Staminal column 10–18 mm long, apex irregularly 5-lobed, with the stamens usually distributed singly along the distal ~ 7 mm of the column but sometimes distributed along almost the full length of the column; staminal filaments 1–5 mm long; anthers yellow. Style 5-branched, with branches 1.75–4 mm long, exserted 2–9 mm beyond the apex of the staminal column. Stigmas capitate, 0.5–0.6 mm wide, distinctly hairy, hairs 0.25–0.6 mm long. Ovary 5-locular, with hairs 0.5–1 mm long. Cleistogamous flowers with a cap 3–4 mm long, with simple and stellate hairs on the apical ~1.5-mm segment, the hairs very dense. Capsule ovoid to globose, 5–12 mm long, usually beaked, beak 1–2 mm long, densely covered with simple shiny appressed hairs, the apical hairs erect, 0.5–1 mm long and extending beyond apex of capsule. Seeds reniform (rarely subangular reniform), 2–3 mm long, dark brown, with a sparse to moderate indumentum of simple, white, wispy spreading hairs 0.2–0.4 mm long; funicular remnants brown, membranous and wing-like, on either side of the himum. ( Fig. 2 a , 3 a , 4 a .)

Distribution and habitat

Hibiscus krichauffianus is widely distributed in arid Australia, predominantly occurring in southern NT, SA, south-western Qld and western NSW, with more restricted occurrences in WA near the NT border and in north-western Victoria ( Fig. 1 , grey squares). The species occurs on deep sandy substrates (yellow, brown or red) sometimes overlying limestone on sand dunes, sandy rises or sand plains. Most occurrences are in open shrublands and hummock grasslands.

Associated overstorey species include Acacia species (e.g. A. aneura F.Muell. ex Benth. , A. ligulata A.Cunn. ex Benth. , A. brachystachya Benth. and A. melleodora Pedley ), Atalaya hemiglauca (F.Muell.) F.Muell. ex Benth. , Dodonaea viscosa Jacq., Eucalyptus concinna Maiden & Blakely , Eucalyptus socialis F.Muell. ex Miq. and Grevillea stenobotrya F.Muell.

Associated shrubs and herbs include Abutilon otocarpum F.Muell. , Aluta maisonneuvei (F.Muell.) Rye & Trudgen , Aristida holathera Domin , Chrysocephalum eremaeum (Haegi) Anderb. , Crotalaria cunninghamii R.Br. , Crotalaria eremaea F.Muell. , Eremophila macdonnellii F.Muell. , Eremophila willsii F.Muell. , Gyrostemon ramulosus Desf. , Lechenaultia divaricata F.Muell. , Phyllanthus lacunellus Airy Shaw , Polycalymma stuartii F.Muell. & Sond. ex Sond. , Portulaca oleracea L., Salsola australis R.Br. , Senna artemisioides (Gaudich. ex DC.) Randell , Sida ammophila F.Muell. ex J.H.Willis , Solanum coactiliferum J.M.Black , Tribulus hystrix R.Br. , Triodia basedowii E.Pritz. and Zygochloa paradoxa (R.Br.) S.T.Blake.

Phenology

Buds, flowers or fruit were recorded in all months of the year and flowering likely occurred in response to rainfall.

Conservation status

Given the wide distribution and common occurrence of this species on sand substrates, the conservation status is of Least Concern in Australia (International Union for Conservation of Nature 2012). In Victoria, this species only occurs in Ned’s Corner in the far north-western part of the state and is therefore considered Critically Endangered in the state (Flora and Fauna Guarantee Act Threatened list issued October 2021, https://www.environment.vic.gov.au/conservingthreatened-species/threatened-list, accessed August 2023). The addition of Hibiscus calcareus and H. sp. Belele Station (D.W.Goodall 3417) to the WA flora will require reassessment of H. krichauffianus in that state, as the species may only occur on the WA–NT border.

Etymology

Named for Friedrich Eduard Heinrich Wulf Krichauff (1824– 1904), a South Australian parliamentarian and friend of Ferdinand Mueller ( O’Neill 1974). Although originally published as krichauffianus , in later references and on some specimen labels Mueller changed the spelling of the epithet to either ‘ krichauffi ’ or ‘ krichauffii ’ for unknown reasons (e.g. Mueller 1868).

Affinities

Hibiscus krichauffianus appears to be most closely allied to H. calcareus but is also similar to H. verecundus and H. sp. Belele (D.W.Goodall 3417). Features distinguishing these species from H. krichauffianus can be found in the ‘Affinities’ sections for the species, Table 1 and the key.

Populations of the highly variable species Hibiscus sturtii and H. leptocladus Benth. occur within the distributional range of H. krichauffianus and could possibly be confused with this species. Both H. sturtii and H. leptocladus represent species complexes that are currently undergoing taxonomic revision. Members of the H. sturtii complex have epicalyx lobes that are distinctly fused basally for> 4 mm (or if rarely less then the epicalyx lobes are never narrowly linear) and seed hairs that are appressed (or if rarely non-appressed then hairs dense and not wispy), whereas in H. krichauffianus the epicalyx lobes are only fused for 1–4 mm, and the seed hairs are wispy and not appressed ( Fig. 3 ). Members of the H. leptocladus complex differ from H. krichauffianus in having petals with a dark basal spot, capsules never having a dense covering of appressed hairs throughout, seeds with denser hairs and leaves that are green rather than whitish-silver to greyish-green.

Notes

We observed examples of specimens with both cleistogamous and chasmogamous flowers, indicating that the two reproductive modes can overlap on the same plant or potentially occur simultaneously. Our finding of cleistogamy being present in H. krichauffianus sens. strict. but absent in H. verecundus and only present on one specimen of H. calcareus , suggests that there may be a connection between this reproductive mode and an arid environment ( Culley and Klooster 2007).

Figures

Fig. 1. Distribution map for the four morphotypes of H. krichauffianus sens. lat. in Australia. Distributions are based only on material viewed by the authors. Morphotype A: Hibiscus krichauffianus sens. strict., grey squares; Morphotype B: Hibiscus verecundus, orange circles; Morphotype C: Hibiscus calcareus, blue triangles; Morphotype D: Hibiscus sp. Belele (voucher: D.W.Goodall 3417), black crosses.

Fig. 2. Example herbarium specimens of the four morphotypes of H. krichauffianus sens. lat. (a) Morphotype A Hibiscus krichauffianus sens. strict. (voucher: C.J.Brodie & P.J.Lang 3402, AD 249644); (b) morphotype B Hibiscus verecundus (voucher: R.J.Fensham 2991, BRI AQ653057); (c) morphotype C Hibiscus calcareus (voucher: P.Hudson s.n., AD 98321044); and (d) morphotype D Hibiscus sp. Belele (voucher: D.W.Goodall 3417, PERTH 3427285). Scale bar: 2 cm.

Fig. 3. Seeds of the four morphotypes. (a) Morphotype A Hibiscus krichauffianus sens. strict. (voucher: C.J.Brodie & P.J.Lang 3402, AD 249644); (b) morphotype B Hibiscus verecundus (voucher: R.J.Fensham 2991, BRI AQ653057); (c) morphotype C Hibiscus calcareus (voucher: P.Hudson s.n., AD 98321044); and (d) morphotype D Hibiscus sp. Belele (voucher: D.W.Goodall 3417, PERTH 3427285). Scale bar: 1 mm.

Fig. 4. Habit of morphotypes A–C. (a) Morphotype A Hibiscus krichauffianus sens. strict. (voucher: D.E.Albrecht 16356, CANB; images: Dave Albrecht); (b) morphotype B Hibiscus verecundus (voucher: T.G.B.McLay TM333, CANB; images: Mike Bayly); and (c) morphotype C Hibiscus calcareus (voucher: D.E.Albrecht 16345, CANB [holotype]; images: Dave Albrecht).