Caladenia lateritica K.W.Dixon & Christenh., 2018

Dixon, Kingsley W. & Christenhusz, Maarten J. M., 2018, Endangered fairies: two new species of Caladenia (Orchidaceae; Orchidoideae; Diurideae), from the bauxite plateaux of southwestern Western Australia, Phytotaxa 334 (1), pp. 87-90 : 87-88

Caladenia lateritica K.W.Dixon & Christenh. , sp. nov. ( Fig. 1 )

Type:— AUSTRALIA . Western Australia : Waroona, Mount Nyngan, 13 km northeast of Waroona, situated between Nyngan Brook and the Murray River, 21 October 2017, Dixon 1076 (holotype: PERTH; isotypes: CANB, PERTH).

Morphologically the new species is similar to Caladenia flava but distinguished by its fragrant white versus yellow flowers with prominent red stripes and spots on the dorsal sepal and lateral petals.

Terrestrial, perennial, herbaceous geophytes with a spheroid, annually replaced tubers, situated 8–15 cm below the soil surface. Stems erect, 10–30 cm, suffused purple at the base. The leaves one per plant, emerging close to the soil surface, erect to lax, 5.0–15.0 × 0.4–0.8 cm, hairy, the apex acute-acuminate, the base clasping, sometimes with pale purple veining on the adaxial surface. Inflorescences racemose with up to three flowers, with a single, 10–15 mm long, linear bract midway, with sparse covering of fine silky hairs throughout, each flower subtended by a smaller bract. The sepals and petals spreading outward, all with acuminate apices, entirely white, with various amounts of prominent red striping on the dorsal petal and lateral sepals, often with the dorsal sepal more fully coloured comprising solid colour, spots or lines. Dorsal sepal lanceolate to broadly lanceolate, 10–21 × 2–7 mm. Lateral sepals spathulate, broadly ovate-lanceolate, 15–25 × 4–10 mm. Petals ovate, often with a single, sometimes, multiple stripes, 10–15 × 3–6 mm. Labellum 8–10 mm, prominently trilobed with a raised yellow plate near the base of the middle lobe, yellow at the base, with rows of white calli extending from either side of the plate and the lateral lobes suffused with pink. Column 8–10 mm, curved over the raised central plate, yellow, with prominent, white, lateral wings.

Distribution:— Caladenia lateritica is only found on isolated lateritic plateaux south of Dwellingup and northeast of Waroona in southwestern Western Australia , often forming extensive pure stands or co-occurring with C. rosea . They grow in shallow lateritic regolith that overlay massive bauxite, in open woodland comprising an overstory of jarrah ( Eucalyptus marginata Donn ex Sm. ), marri ( Corymbia calophylla (Lindl.) K.D.Hill & L.A.S.Johnson ; both Myrtaceae ) and parrot bush ( Banksia sessilis (Knight) A.R.Mast & K.R.Thiele ; Proteaceae ) with an understory of Conostylis setosa Lindl. (Haemordoraceae), Orthrosanthus laxus (Endl.) Benth. ( Iridaceae ), Xanthorrhoea preissii Endl. ( Asphodelaceae ), Hypocalymma robustum (Endl.) Lindl. , ( Myrtaceae ) Phyllanthus calycinus Labill. ( Phyllanthaceae ) and Stylidium Sw. ( Stylidiaceae ) species.

Ecology:— Caladenia lateritica grows with white cottonhead ( Conostylis setosa , Haemodoraceae ), with which it shares a similar stature, flower colour, scent and flowering time. The widespread and common Caladenia flava subsp. flava , to which this taxon has similarities, occurs rarely in the shallow soils, open forest and well drained plateau areas where C. lateritica occurs, indicating that the new taxon has an ecological preference for the unusual geology and climate of these high plateaux. Although the species may have occurred more extensively in the region, much of the suitable habitat of similar topography and geology in the 1000–1200 mm rainfall zone have been now mined or are currently being mined.

Etymology:— Named for the lateritic soils to which this species is restricted.

Figures

FIGURE 1. Caladenia species and the sympatric species they are putatively mimicking. A. Hypocalymma robustum (Myrtaceae). B. Caladenia rosea (Orchidaceae). C. Conostylis setosa (Haemodoraceae). D. Caladenia lateritica (Orchidaceae). E. Conostylis aculeata (Haemodoraceae). F. Caladenia flava (Orchidaceae).