Thursday, March 10, 2016

[Botany • 2016] New Orchid Species of Stigmatodactylus (Orchidoideae; Diurideae) from central Palawan, Philippines; Stigmatodactylus dalagangpalawanicum & S. aquamarinus

Stigmatodactylus aquamarinus  A.S.Rob. & E.Gironella, 2016
FIGURE 4. Stigmatodactylus aquamarinus growing in situ in the Mount Victoria massif.

Two new species of Stigmatodactylus from Palawan Island in the Philippines are described and illustrated. The taxa, which represent the first records for the genus Stigmatodactylus in the Philippines, are restricted to the ultramafic peaks of central Palawan. Cryptostylis carinata, originally described from New Guinea, is also documented, representing a first record for this species in Palawan.

Keywords: Acianthinae, Diurideae, Malesia, Orchidoideae, Philippine flora

Stigmatodactylus dalagangpalawanicum A.S.Rob., 2016
FIGURE 2. Stigmatodactylus dalagangpalawanicum growing in situ in the Mount Victoria massif.

Stigmatodactylus dalagangpalawanicum A.S.Rob., 2016

Conservation status: This species is known from three small populations across a 2 km transect in closed canopy upper montane forest. The total population across all three sites comprises ca. 18 mature individuals. Direct observations satisfy the IUCN Red List Criteria B2ac(iv);D (IUCN, 2001) as CR (Critically Endangered). The occurrence of this taxon in the surrounding forest above 1400 metres can be inferred, potentially satisfying the criteria for an EN assessment, but the ephemeral nature of Stigmatodactylus populations and their apparent sensitivity to environmental disturbance nonetheless puts them at high risk.

Distribution and Ecology: Growing terrestrially in humus layer overlying ultramafic rock in upper montane, closed canopy forest below summit scrub zone. The known populations of Stigmatodactylus dalagangpalawanicum comprise fewer than 20 documented individuals growing within a narrow elevational range of 1400–1700 m. Plants grow singly or in sparsely scattered groups beneath stunted summit trees, 2.0–3.5 m tall. June temperatures achieve 25 ºC in the shade during the day, 12–14 ºC at night, with frequent clouds and periodic rains (pers. obs.). Associated genera
include Leptospermum (Myrtaceae), Vaccinium (Ericaceae), Rhododendron (Ericaceae) and Quercus (Fagaceae).

Phenology: Inflorescences bearing flowers observed in June, July, October, November and December, suggesting a tendency to flower following the rainy spring months into the start of the dry season, which is most pronounced from January through to April. Exploratory root excavation in October showed no apparent tubers, although they have been noted at other times of year, suggesting that these are newly produced at the end of each growing season; the noted absence of tubers in other perennating Stigmatodactylus taxa (Kores 1991, Schlechter 1911) may thus be a function of timing, although this cannot be stated with certainty in the absence of multiple observations.

Etymology: The specific epithet, dalagangpalawanicum, is the Tagalog (Filipino) words dalaga ng Palawan (Maiden of Palawan), a reference to the pretty and diminutive form of the plants and a name now adopted by the local Tagbanua tribe for the plant since our research began. This designation is made in particular honour to the second author, Elizabeth Gironella, in the year following her official retirement after decades of work as curator of the herbarium at Palawan State University

Stigmatodactylus aquamarinus A.S.Rob. & E.Gironella, 2016
FIGURE 4. Stigmatodactylus aquamarinus growing in situ in the Mount Victoria massif.

Stigmatodactylus aquamarinus A.S.Rob. & E.Gironella, 2016

Conservation status: This species is known from three small populations of just 1–2 individuals each. Direct observations satisfy the IUCN Red List Criteria B2ac(iv);D (IUCN, 2001) as CR (Critically Endangered). Despite numerous visits with successful sightings of its sister taxon, Stigmatodactylus dalagangpalawanicum, S. aquamarinus has not yet been observed at the same location more than once.

Distribution and Ecology: Growing terrestrially in moss pads overlying matted tree roots or steeply inclined ultramafic rock, generally occurring singly beneath closed canopy forest of upper montane trees 4–6 m tall or climbing bamboo; or in ultramafic rubble in open summit scrub, sheltered by large boulders. The known populations of Stigmatodactylus aquamarinus occur between 1430–1680 m.

Phenology: Plants and inflorescences bearing flowers observed in October, November and December, during the latter part of the wet season. Vegetative parts have been notably absent at other times of year, and the recurrence of plants at the same site in consecutive years has yet to be documented. This may suggest ephemeral colonisation of suitable sites, but data are too scant to be conclusive.

Etymology: The specific epithet, aquamarinus, is derived from the Latin aqua (water) and marinus (of the sea) = aquamarine, a reference to the unusual bluish to turquoise colour of the petals and sepals.

Alastair S. Robinson, Elizabeth P. Gironella and Jehson M. Cervancia. 2016. New Orchid Species of Stigmatodactylus (Orchidoideae; Diurideae) and A New Record of Cryptostylis carinata from central Palawan, Philippines. Phytotaxa. 252(2): 99–113. DOI:   10.11646/phytotaxa.252.2.2

Buod (Pilipino)
Inilarawan at iginuhit sa artikulong ito ang dalawang bagong species ng Stigmatodactylus mula sa isla ng Palawan sa Pilipinas. Ito ang pinakaunang tala ng genus Stigmatodactylus sa Pilipinas at matatagpuan lamang sa ultramafic na bundok sa gitnang Palawan. Ang ultramafic na bundok ay may mataas na mga sangkap na Magnesium at Iron. Inihayag rin sa sulating ito ang unang tala sa Palawan ng 1 species na Cryptostylis carinata, na unang naitalâ sa bansang New Guinea.