Asteranthera

Full name and orig. publication: Asteranthera Klotzsch & Hanst. ex Hanst., Linnaea 26: 211 (April 1954, "1853").

Etymology: From the Greek άστηρ, astēr = star, and άνθηρα, and anthēra = anther, alluding to the apically coherent anthers forming a star-like figure.

Infrafamilial position: Gesnerioideae-Coronanthereae-Asterantherinae (Weber et al. 2013).

Description: Creeping-climbing shrubs. Stem and branches thin, woody, rooting at the basal nodes. Leaves opposite, small, shortly petiolate, lamina elliptic, membranous-coriaceous, dark green and hairy above, whitish and glabrous below. Flowers axillary, solitary, erect; bracteoles small, lanceolate, inserted below the calyx. Sepals nearly free to base, narrow-triangular, dentate. Corolla red, with whitish lines on tube, lobes mottled, infundibuliform-galeate; tube slightly constricted above the base and then gradually widening; limb strongly bilabiate, upper lip a long galea, consisting of two connate lobes, projecting forwards, lower lip of three spreading or slightly reflexed, ovate lobes. Stamens 4, held below the galea, filaments inserted above base of corolla tube; anthers cordate, cross-wise coherent. Disc a dorsally thickened ring, adnate to ovary base. Ovary ovoid-oblong, bilocular; style long, slender; stigma small, stomatomorphic. Fruit a fleshy berry.

Chromosome numbers: Unknown.

Type and only species: Asteranthera ovata Hanst.

Distribution: S Chile and adjacent Argentina.

Ecology: Growing as a woody climber in cool, montane rain forests. Pollination is obviously by hummingbirds (see Notes).

Notes:
(1) Salinas et al. (2010) studied and compared the growth patterns of Asteranthera, Mitraria, and Sarmienta. Asteranthera and Mitraria germinate and establish first on the forest floor and then climb up on the host trees, while Sarmienta does not root on the ground and has to be classified as a true epiphyte. The classification of Asteranthera and Mitraria as secondary epiphytes is erroneous, as the plants do not loose ground contact by a programmed death of the basal stem parts. They are simply climbers (like the ivy).
(2) The red, arcuate flowers suggest bird-pollination, particularly hummingbirds. In fact, the three Chilean gesneriads represent one of the oldest hummingbird-adapted plant groups of temperate South America, with a stem age of 26.2 my and crown age of 16.3 my (Woo et al. 2011, Abrahamczyk & Renner 2015). The only pollinator is the Green-backed Firecrown (Sephanoides sephaniodes) (Smith-Ramirez & Armesto 1994, Aizen & Vázquez 2006).

Selected references: Wiehler, Selbyana 6: 159 (1983); Zollner, Palmengarten 35: 25-27 (1991); Smith et al., Plant Syst. Evol. 261(1): 245–256 (2006), phylog.; Smith-Ramirez & Armesto, J. Ecol. 82(2): 353–365 (1994), flowering patterns Chiloe Isl.; Aizen & Vázquez Ecography. 29: 357–66 (2006), phenol., hummingbird poll.; Woo et al., Int. J. Pl. Scie. Sci. 172(3): 434-457 (2011), rev. Coronanthereae, biogeogr.; Abrahamczyk & Renner, Evol. Biol. 15:104 (2015), hummingbird/plant mutualism.

Tax. details, cytology, and bibliography: Gesneriaceae Resource Centre (GRC). Royal Botanic Garden Edinburgh.

Page content and update responsibility/contact: Anton Weber.
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