Vanoverberghia Merr. (1912)

Docot, R. V. A., Banag, C. I., Tandang, D. N., Funakoshi, H. & Poulsen, A. D., 2019, Recircumscription and revision of the genus Vanoverberghia (Zingiberaceae), Blumea 64 (2), pp. 140-157 : 146

Vanoverberghia Merr. (1912) 76. — Type: Vanoverberghia sepulchrei Merr.

Terrestrial herb in loose clumps. Rhizome 1– 4 cm across, red or reddish green to yellowish brown, scales thick or thin, brown. Leafy shoot erect to arching, pseudostem terete, base bulbose; sheath glabrous or pubescent, mid-green to reddish; ligule ovate to oblong, if ovate, entire or bilobed, coriaceous to subcoriaceous, glabrous to densely pubescent; lamina subsessile to petiolate, oblong, apex caudate. Inflorescence a terminal raceme, pendulous, with 1–3 persistent brown bracts; floral bract absent or spathaceous, if spathaceous, tubular at the base; bracteole absent; flowers one per fertile bract, congested or laxly arranged along the rachis, pedicellate, opening in succession from base to top; calyx in bud cylindrical, at anthesis funnel-shaped or spathaceous, if spathaceous, laterally split to the base, apex 1–3-dentate; corolla lobes linear-oblong, white or mid-green, apices rounded, cucullate, glabrous to pubescent; labellum connate to base of lateral corolla lobes, free part bifid, the lobes subulate or deltate, if deltate, petaloid and crisped, white; lateral staminodes filiform, pubescent; stamen curved at anthesis; filament canaliculate and enclosing the style up to almost half its length, spirally coiled after anthesis; anther oblong or linear, sericeous, thecae dehiscing throughout their entire length, pubescent, crest absent or present, if present, emarginate and pubescent; style glabrous to pubescent; stigma cupular, ostiole elliptic, margin pubescent or hispid; epigynous glands two, compressed, oblong or subglobose; ovary subglobose to globose, glabrous or densely pubescent, green, yellow, or deep red, trilocular with axile placentation. Fruit ellipsoid to subglobose to oblong, indehiscent, calyx persistent. Seed subglobose, black or brown with white aril.

Distribution, habitat, and species richness Vanoverberghia was endemic to the Philippines until V. sasakiana was described based on a collection from Lanyu Island, Taiwan. The extension of distribution of V. sasakiana to the Philippines supports Luzon Island as the center of diversity of

Vanoverberghia , specifically within the Cordillera Mountains, a 320 km long mountain range in Luzon Island situated from the province of Ilocos Norte down to Pangasinan ( Map 1 ). The type species, V. sepulchrei , as well as V. diversifolia , and V. vanoverberghii were actually discovered within this mountain range. Vanoverberghia rubrobracteata occurs in eight provinces in the Philippines, making it the most widespread species of the genus. In fact, V. rubrobracteata distribution extends to the Visayas including the islands of Negros and Panay ( Map 1 ).

Vanoverberghia species usually inhabit shaded montane forest above 800 m but some also favour lowland forest (e.g., V. diversifolia was recorded as low as at 100 m). Their most preferred habitat appears to be near streams and ravines where the soil is humid, although some species occupy pine forest (e.g., V. sepulchrei ).

Floral biology, pollination and seed dispersal Observation in the field and data gathered from herbarium sheets and photographs with dates from the internet (e.g., Pelser et al. 2011 onwards: ‘ Co’s Digital Flora website’) document that flowering occurs between September and January (wet season) while their closely related Alpinia species (subclade B in Fig. 1) flower in the dry season between March and May. The epigynous glands of Vanoverberghia are located at the base of the 12 –20 mm long corolla tube, and therefore the pollinator needs to have a long proboscis. Those species flowering at night (e.g., V. sepulchrei ) are most likely to be pollinated by moths but butterflies and bees are also likely when anthesis occurs by day. Furthermore, the fruits of Vanoverberghia are indehiscent and contain arillate seeds with a sweet-sour flavour. This indicates that seed dispersal may be by birds or bats but this needs further field observation.

Figures

Map 1 Distribution of Vanoverberghia diversifolia Elmer (▲), V. rubrobracteata Docot & Ambida (★), V. sasakiana Funak. & H.Ohashi (◆); V. sepulchrei Merr. (■) and V. vanoverberghii (Merr.) Funak. & Docot (●).