Una especie nueva de Dichromanthus (Orchidaceae, Spiranthinae) de Oaxaca, México

Abstract

Dichromanthus yucundaa, a new orchid species from the Mixteca Alta region of the Sierra Madre del Sur in Oaxaca, Mexico, is described and illustrated. It is distinguished from D. cinnabarinus, the most similar species, by the more compact plants, glabrous infl orescence, prominent, broadly ovate, glabrous fl oral bracts which are abaxially glaucous, sparsely and minutely glandular-pubescent sepals (merely papillose near the apex), short column foot, viscidium sheathing the apex of the rostellum and without a retrorse prominence, and rostellum remnant stiff and pointed.

Molecular phylogenetics, floral convergence and systematics of Dichromanthus and Stenorrhynchos (Orchidaceae: Spiranthinae)

“…Therefore, inclusion of Dichromanthus aurantiacus, D. michuacanus, Deiregyne albovaginata and D. densiflora in Stenorrhynchos, as in Szlachetko et al (2005), renders Stenorrhynchos polyphyletic and results in an unnatural assemblage of species with disparate ecological preferences and overall morphology (Salazar, 2003;see below). Dichromanthus yucundaa is known only from a small area in the Mexican state of Oaxaca (Salazar & García-Mendoza, 2009), but the other three species of Dichromanthus s.l. are widespread and relatively common throughout most mountain ranges and plateaux from the southern USA (Arizona and Texas) through Mexico to northern Central America (Salazar, 2003).…”

“…The pollinator of D. yucundaa (Fig. 3C) is not known, but on account of its floral characteristics Salazar & García-Mendoza (2009) suggested that this species might also be hummingbird-pollinated. The flowers of D. michuacanus, however, differ from the previous three species in being whitish, yellow or green with dark green to brown veins on sepals and petals, and in producing an intense diurnal odour (Fig.…”

“…Lately, two contrasting views concerning the circumscription of Dichromanthus have been held by taxonomists. On the one hand, Salazar and co-workers (Salazar, Chase & Soto, 2002;Salazar, 2003Salazar, , 2009Salazar et al, 2003Salazar et al, , 2006Hágsater et al, 2005;Soto et al, 2007;Figueroa et al, 2008;Salazar & García-Mendoza, 2009;Salazar & Ballesteros-Barrera, 2010 (Salazar & García-Mendoza, 2009), based on their vegetative, reproductive and genetic similarities to D. cinnabarinus. This broader generic circumscription will be hereafter referred to as Dichromanthus s.l.…”

“…Notably, the floral characteristics shared by most species of Spiranthinae that at one time or another have been included in Stenorrhynchos, namely odour-less flowers, a tubular, showily coloured perianth in tones of red, pink, orange or yellow and a long, narrow rostellum with stiff, bristle-like rostellum remnant, seem to conform to a syndrome of pollination by hummingbirds (van der Pijl & Dodson, 1966;Dressler, 1981;Catling, 1987;Galetto, Bernardello & Rivera, 1997;Singer & Sazima, 2000). It has been suggested that the similarity in overall floral structure between the otherwise distinctive species of Dichromanthus s.l., Coccineorchis and Stenorrhynchos s.s. might have resulted from convergent adaptation to hummingbird pollination (Salazar et al, 2002Salazar, 2003Salazar, , 2005Salazar & García-Mendoza, 2009). However, previous phylogenetic studies of Spiranthinae have only sparsely sampled the species of these genera.…”

“…Lately, two contrasting views concerning the circumscription of Dichromanthus have been held by taxonomists. On the one hand, Salazar and co‐workers (Salazar, Chase & Soto, 2002; Salazar, 2003, 2009; Salazar et al ., 2003, 2006; Hágsater et al ., 2005; Soto et al ., 2007; Figueroa et al ., 2008; Salazar & García‐Mendoza, 2009; Salazar & Ballesteros‐Barrera, 2010) embraced a broader concept of Dichromanthus to include three additional species, namely D. aurantiacus (Lex.) Salazar & Soto Arenas, D. michuacanus (Lex.)…”