Vanilla subgen. Vanilla

1. Vanilla subgen. Vanilla

= Vanilla subgen. Xanata Soto Arenas & Cribb (2010: 359) .

Type species: — Vanilla planifolia Andrews (1808 View in CoL : t. 538).

= Vanilla subsect. Papillosae Portères (1951: 290) , nom. inval. nud. (Art. 39.1; Turland et al. 2018).

= Vanilla subsect. Lamellosae Portères (1951: 291) . nom. inval. nud. (Art. 39.1; Turland et al. 2018).

= Vanilla subsect. Papillosae Portères (1954: 141) , nom. inval. nud. (Art. 39.1; Turland et al. 2018).

= Vanilla subsect. Lamellosae Portères (1954: 148) , nom. inval. nud. (Art. 39.1; Turland et al. 2018).

Description:—Members of Vanilla subgen. Vanilla are nomadic or epiphytic vines, germinating in decomposing organic matter on the ground or epiphytically. Leaves usually well-developed and thick coriaceous. Inflorescence racemose, mainly axillary, occasionally apical, producing two to many flowers, the floral bracts usually small, typically differing notoriously from the leaves. Some species offer floral fragrances and thus can be highly aromatic. The sepals and petals are coppery, greenish, yellowish or whitish, narrow and often similar in color to the lip. In fragrant species the sepals thickened, often warty near the apex. Petal with a prominent abaxial keel, apical margins often minutely serrulate. The lip forming a distinct floral tube, with the lip margins fused to the column for more than half of its length to form a narrow, papillose-hirsute, dry, basal nectary; the flowers appear, however, nectarless (except in V. hartii ). The lip blade usually with three distinct sites of ornamentation: a papillae-rich basal claw, a distinct penicillate callus of retrorse scales (except in V. bicolor Lindley 1838 : misc. 37 and V. palmarum Lindley 1840 : pl. 436) placed above the middle of the blade, just below the rosteller flap of the column, and clumps of warts or papillae on a thickened plate or forming elevated keels near the apex of the lip. The column is straight or bent, often with a hirsute ventral surface, with a well-developed rostellum and another flap-like, retrorse proximal stigma lobe. Pollen in monads, forming two easily disrupted masses. The fruits calyculate, either dehiscent or indehiscent, sometimes differing within the same species, non-aromatic ( V. sect. Palmarum ) or aromatic ( V. sect. Vanilla ), the latter containing vanillic and anisic aromatic compounds.

Discussion:— Vanilla subgen. Vanilla includes 40 species and two nothospecies divided into two sections: Vanilla sect. Vanilla , including all commercially grown, aromatic vanilla, and Vanilla sect. Palmarum Karremans , Damián & Pupulin. Our circumscription of Vanilla subgen. Vanilla aligns completely with Vanilla sect. Xanata sensu Soto Arenas & Cribb (2010) and is strongly supported by multiple lines of evidence: biogeographically, through its exclusively Neotropical distribution; ecologically, by its predominantly allogamous breeding system and reliance on euglossine bees for pollination; and by DNA data across multiple scales. We tentatively include their so-called ‘ V. penicillata group’, made up of the cryptic V. calamitosa and V. penicillata Garay & Dunst. (in Dunsterville & Garay 1965: 324), in this subgenus pending further studies. These two species are odd among Neotropical Vanilla in that they are the only ‘leafless’ species occurring on the mainland, featuring the reduced or scale-like leaf habit. Soto Arenas & Cribb (2010) listed the group among the relatives of V. planifolia on account of the presence of the tubular lip adnate to the column, the blade with a penicillate callus, and calyculate fruits, and we agree with this interpretation. However, the greenish-cream flowers with brown keels and slightly curved fruits are reminiscent of some members of V. subgen. Tethyos , which often also have a penicillate callus. DNA data would be critical to confirm the phylogenetic relationships of these two taxa, which might represent an interesting case of convergent evolution.