[Botany • 2022] Ridsdalea philippinensis (Rubiaceae: Gardenieae) • A New Philippine Species from Karst Vegetation in Palawan

Ridsdalea philippinensis R.Bustam. & Pelser.,

in Bustamante & Pelser, 2022.

DOI: 10.3767/blumea.2022.67.01.04

Abstract

Ridsdalea philippinensis (Rubiaceae), a new species from the karst forest in El Nido (Palawan, Philippines), is described and illustrated. It is unique among Malesian Ridsdalea species in having a corolla tube that is distinctly inflated at the apex, a character state also displayed by R. sootepensis and R. thailandica from Laos and Thailand. Amongst others, R. philippinensis, however, differs from both of these species in having smaller flowers and anthers that do not emerge from the corolla tube. An updated key for Philippine Ridsdalea is also presented.

Keywords: El Nido-Taytay Managed Resource Protected Area; Gardenieae; Malesia; Philippines; Ridsdalea; Rubiaceae

a– c, e. Ridsdalea philippinensis R.Bustam. & Pelser.
a. Flower; b. longitudinal section of flower; c. branching of twig; e. flower showing inflated apex of corolla tube.
— d, f. Ridsdalea merrillii (Elmer) J.T.Pereira. d. Flowering twig; f. flower showing the lack of an inflated apex of the corolla tube.

— Photos by: a– c, e: W. Cabanillas & L.M. Camangeg; d, f: P.B. Pelser & J.F. Barcelona.

Ridsdalea philippinensis R.Bustam. & Pelser.
a. Flowering twig; b. leaf, showing appearance of the adaxial (Ad) and abaxial (Ab) surface; c. stipule, showing appearance of the adaxial (Ad) and abaxial (Ab) surface; d. fruit; e. cross section of flower; f. indumentum at the apical part of the basal section (i.e., non-inflated part) of the corolla tube; g. anther; h. cross section of fruit.

— Drawing by J. Mansibang.

Ridsdalea philippinensis R.Bustam. & Pelser, sp. nov.

A species that is unique among all currently described species of Ridsdalea in displaying a combination of flowers with a corolla tube that is distinctly inflated at its apex and anthers that do not emerge from it.

Distribution — Ridsdalea philippinensis is endemic to El Nido, Palawan (Philippines).

Habitat & Ecology — Tower karst formation. Altitude: c. 150 m. Flowering: June.

Bustamante, R.A.A. and Pelser, P.B. 2022. A New Philippine Species of Ridsdalea (Rubiaceae, Ixoroideae) from Karst Vegetation in Palawan. Blumea - Biodiversity, Evolution and Biogeography of Plants. DOI: 10.3767/blumea.2022.67.01.04

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