Friday, April 17, 2020

[Botany • 2020] Dichaea auriculata (Orchidaceae: Zygopetalinae) • A New and Unusual Species of Dichaea from Costa Rica

Dichaea auriculata Pupulin & Karremans

in Pupulin & Karremans, 2020. 

A new and florally unusual species of the genus Dichaea is described and illustrated from Costa Rica, where it is apparently endemic, and its relationships are discussed. Dichaea auriculata is compared with the group of species close to D. graminoides, from which it can be distinguished by the lip with a long isthmus, provided with two rounded auricles at the base, instead of the sessile lip typical of the group. It is also compared with another Costa Rican endemic in the same complex, D. gracillima, from which it can be distinguished by the autogamous, mostly cleistogamous, flowers, the 3-lobed lip with rounded basal lobes, the high keel along the lip isthmus, and the bifid ligule of the column. Notes on the habitat and the ecology of the new species are provided.

Keywords: Dichaeopsis; Flora of Costa Rica; autogamy; new species; plant diversity; section Pseudodichaea

Fig. 2: Flowers of Dichaea auriculata Pupulin & Karremans (Karremans et al. 7333).
— Photos by: a. A.P. Karremans; b. F. Pupulin.

Fig. 1: Dichaea auriculata Pupulin & Karremans.
a. Habit; b. flower; c. dissected perianth; d. column and lip, lateral view (the pollinarium bent into the stigma); e. column, three views; f. anther cap and pollinarium (three views).
 — Scale bars: a = 5 cm; b– c = 5 mm; d–e = 4 mm; f = 1 mm. 
— Drawn by F. Pupulin and rendered by S. Poltronieri from the holotype.

Dichaea auriculata Pupulin & Karremans, sp. nov. 

 Species sectionis Pseudodichaeae, ab omnibus species Dichaeae Lindl. auriculis magis rotundatis et carina alta in basi labelli facile distinguenda; inter species foliis articulatis ovarioque glabro munitas (genus Dichaeopsem sensu Pfitzer vel coetum Dichaeae panamensis informaliter dictum), Dichaea gracillima C.Schweinf. in habito formaque et dimensione floris similis sed floribus plerumque autogamis labello distincte trilobo lobulis basalibus rotundatis, carina alta in isthmo labelli, ligula columnae bipartita recedit. 

Etymology. From the Latin auriculatus, provided with ears, in reference to the small, ear-like basal lobes of the lip, unique in the genus.

Habitat & Ecology — Dichaea auriculata is known from a single population, found in the constantly wet and warm region of the Río Tuis, which drains into the Caribbean. Plants of D. auriculata have been observed on shaded branches of the lower canopy, on trees of secondary mature vegetation.  

Franco Pupulin and Adam P. Karremans. 2020. A New and Unusual Species of Dichaea (Orchidaceae: Zygopetalinae) from Costa Rica. Blumea - Biodiversity, Evolution and Biogeography of Plants.  DOI: 10.3767/blumea.2020.65.01.06