Caladenia rosea 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 : 88

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

Type:— AUSTRALIA . Western Australia : Waroona, Mount Nyngan, 13 km NE of Waroona, situated between Nyngan Brook and the Murray River, 21 October 2017, Dixon 1077 (holotype: PERTH; isotypes: CANB, PERTH).

This pale to dark pink, fragrant fairy orchid is morphologically similar to Caladenia flava and grows sympatrically with Caladenia lateritica , but it is distinguished by the perianth being pink to dark pink with prominent red striping and spotting on the dorsal sepal and lateral petals.

Terrestrial, perennial, herbaceous geophytes with a spheroid annually replaced tuber situated 8–15 cm below the soil surface. Stems erect, 10–25 cm tall, suffused purple at the base. Leaves one per plant, erect to lax, 5.0–15.0 × 0.4–0.8 cm, hairy, usually with purple veining below, the apex attenuate, the base clasping, close to the soil surface, tinged purple. Inflorescence racemose with up to three flowers and a single linear bract midway (c. 10–15 mm long), each flower subtended by a smaller bract. Stem and bracts with a sparse, fine covering of silky hairs throughout. Sepals and petals spreading outward, the apices acuminate, pink throughout, with varying amounts of deeper pink stripes and spots. Dorsal sepal linear to ovate-lanceolate, 12–16 × 4–5 mm. Lateral sepals spathulate to ovate-lanceolate, 18–22 × 5–9 mm. Petals ovate often with a single stripe or sometimes with multiple stripes, 10–14 × 4–6 mm. The labellum, 4–5 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 4–5 mm, curved over the raised central plate, yellow with prominent white lateral wings.

Distribution:— Caladenia rosea grows sympatrically with Caladenia lateritica in shallow lateritic regolith that overlays massive bauxite. The open jarrah ( Eucalyptus marginata )—marri ( Corymbia calophylla ) woodland has an understory of Banksia sessilis ( Proteaceae ), Conostylis setosa ( Haemodoraceae ), Hypocalymma robustum ( Myrtaceae ), Orthrosanthus laxus ( Iridaceae ), Xanthorrhoea preissii ( Asphodelaceae ), Phyllanthus calycinus ( Phyllanthaceae ) and Stylidium ( Stylidiaceae ) species.

Ecology:— Caladenia rosea is putatively mimicking flowers of the Swan River myrtle ( Hypocalymma robustum ), which has a similar colour and scent. We assume that this orchid is pollinated by the same insects as Hypocalymma robustum (possibly native bees, but this is yet to be confirmed). As for Caladenia lateritica , C. rosea is restricted to the shallow soils overlaying massive bauxite in a confined, high rainfall region that is now subject to strip mining for bauxite.

Etymology:— Named for the pink colour of the flowers.

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).