Revision clarifies identities and conservation of three Thai Garcinia trees

A specimen-based taxonomic revision has clarified the identities of three evergreen Garcinia trees found in Peninsular Thailand and assigned conservation categories to each species. The study examined Garcinia bancana, G. costata and G. parvifolia, members of section Brindonia in the Clusiaceae family. It formalized six lectotypifications, clarified the morphological characters separating the three taxa, documented their distributions and habitats, and assessed their conservation status.

The revision is a treatment of plant taxonomy and distribution rather than a field trial of their edible fruits or timber. The investigation combined historical literature, original type material, herbarium collections, digital specimen databases, field observations and geographic analyses. The author examined specimens held by AAU, BK, BKF, BM, C, CMUB, K, P, PSU and SING, then consulted digitized material from BO, CAL, E, L, MEL and U.

Records were also checked through the Global Biodiversity Information Facility and JSTOR, while taxonomic histories were compiled from IPNI, Plants of the World Online and World Flora Online. Historical and newly collected specimens supported descriptions of morphology, distribution, habitat, ecology, phenology and uses. Conservation categories followed the IUCN Red List Categories and Criteria and incorporated GeoCAT analyses and field data.

This scope allowed the study to connect names published in the nineteenth century with modern observations, although the assessments remain constrained by the locations and specimens available to the author. Garcinia bancana is an evergreen, dioecious tree distributed from Peninsular Thailand through Peninsular Malaysia and Singapore to Sumatra and Borneo. Thai records come from Surat Thani, Krabi, Satun, Songkhla, Yala and Narathiwat provinces.

The species occurs in tropical lowland evergreen rainforest, often beside streams and in peat swamp forests, from near sea level to 300 metres above sea level. Trees generally reach 7–20 metres, with a maximum of 25 metres in the description, although specimens in Peninsular Malaysia have been reported at up to 33 metres. The leaves are glossy, decussate and elliptic, obovate or oblanceolate-obovate, measuring 10–23 by 4–11.5 centimetres.

Its axillary inflorescences bear four-part flowers, and the smooth, unlobed fruits become yellow or orangish yellow at maturity. Each berry contains 8–12 seeds, although one to three may be aborted, and cutting the fruit releases sticky yellow exudate. The sour fruits are eaten, while the wood is used locally for indoor construction in Peninsular Thailand.

The analysis confirmed that four names are based on the same species: Garcinia bancana, G. oxyedra, G. lamponga and G. leucandra. Original collections showed that the latter three names cannot be distinguished from G. bancana, supporting the earlier treatment by Vesque. The study designated one lectotype for each of these four names, thereby fixing each botanical name to a specific specimen from the material cited in the original descriptions.

For G. bancana, the selected lectotype is a complete Teijsmann sheet from Bangka, the type locality in Indonesia, preserved at Kew. The study also examined type material of G. oxyphylla and G. cymulosa and found them distinct from G. bancana, whereas the type of G. hookeri was not examined. It further treated the name G. bancana var. curtisii as a synonym of G. oliveri because the two could not be morphologically distinguished in the cited studies and examined material.

Garcinia costata has a much smaller documented distribution, extending only through Peninsular Thailand and three Malaysian states: Kedah, Perak and Pahang. Its confirmed Thai range comprises Trang, Satun and Songkhla. The species inhabits tropical lowland evergreen rainforest at approximately 100–200 metres above sea level and flowers from December through March, with fruiting recorded in March.

It is a dioecious tree generally 8–15 metres tall, although the description permits a maximum of 20 metres. Its large leaves are 16–26 by 7–13 centimetres and conspicuously ribbed, a feature reflected in the Latin epithet costata, meaning “ribbed” or “with prominent ribs or a midrib.” Staminate flowers reach 2.5–3 centimetres across, with four white petals and numerous stamens united around a central pistillode. The fruit changes from green to pink or red and forms a depressed globose berry 4–5 by 5–8 centimetres, with 8–12 pronounced vertical lobes and grooves.

The authors assessed G. costata as Vulnerable under criterion D1 because of its restricted global distribution, limited known localities and small number of mature individuals. Its global extent of occurrence was calculated as 17,253.89 square kilometres, while its area of occupancy was 24 square kilometres. The corresponding Thai estimates were 496.92 square kilometres for extent of occurrence and 12 square kilometres for area of occupancy.

The assessment retained the Vulnerable category reached in an earlier evaluation, but changed the criterion from D2 to D1. The lectotype for G. costata was not designated in the present study: Nazre and colleagues had already selected the specimen G. King’s Collector 5375 from Maxwell’s Hill, Perak, in 2018.

The present revision located that lectotype at Kew and examined additional isolectotypes. No use was recorded in Thailand, although the fruits were reported as eaten in Peninsular Malaysia. Garcinia parvifolia has the broadest range among the three species, extending from Peninsular Thailand through Peninsular Malaysia and Singapore to Sumatra, Java, the Lesser Sunda Islands, Sulawesi, Maluku and Borneo, and onward to New Guinea.

Thai records exist in Ranong, Surat Thani, Phangnga, Krabi, Nakhon Si Thammarat, Trang, Satun, Songkhla and Narathiwat provinces. The trees can reach 30 metres, and large individuals may have buttressed trunks. Their relatively small leaves measure 5–13 by 2–4.5 centimetres and taper into a long blunt tip; the name parvifolia derives from Latin elements meaning “small-leaved.” The species grows in tropical lowland evergreen forest, sometimes beside streams and in forest with bamboo, from near sea level to 350 metres.

Published records indicate occurrence in peat swamp forest in Narathiwat, although the author did not examine Thai specimens from that habitat; peat swamp records also exist in Johor, Peninsular Malaysia. Flowering occurs from February to May and fruiting from April to July. Garcinia parvifolia was assessed as Least Concern because it has a wide geographic range, occurs at many localities, and has no known or immediate threats to the species or its habitat.

Its global extent of occurrence is 7,560,436.72 square kilometres and its area of occupancy 836 square kilometres. In Thailand, where its distribution is confined to the peninsula, the corresponding estimates are 58,159.96 and 60 square kilometres. The study’s second set of two lectotypifications concerned the basionym Rhinostigma parvifolium and the synonym Garcinia globulosa.

The selected Rhinostigma parvifolium lectotype is Diepenhorst HB2093 from Priaman, Sumatra, preserved at Utrecht, while Ridley 9195 from Singapore’s Garden Jungle was designated as the lectotype of G. globulosa. These choices attach definitive reference specimens to names that had been supported by multiple original gatherings. The revised diagnoses show that the three species are readily separable when leaves, flowers, fruits and inflorescence structure are considered together.

G. bancana has unlobed, rough stigmas and smooth, globose or subglobose fruits, with leaves ranging from elliptic to obovate or oblanceolate-obovate. G. costata is distinguished by its strongly ribbed leaves, much larger staminate flowers, a pistillode surrounded by fused stamens, and a fruit with eight to 12 vertical grooves and a radiate, lobed persistent stigma. G. parvifolia has smaller elliptic or narrowly elliptic leaves, staminate flowers without a pistillode and smooth, unlobed stigmas, together with depressed fruits measuring 2–3 by 1.5–3 centimetres and usually containing two to five seeds.

These are taxonomic distinctions, not evidence that the species were formerly combined into a single variable taxon. Recorded Thai vernacular names include cha muang ka and cha muang pa for G. bancana, mang khut pa for G. costata, and cha muang lek for G. parvifolia. The work does not establish clinical effects from consuming the fruits, nor does it test cultivation or yield.

Instead, it addresses a core taxonomic problem within a section recently expanded to 91 recognized species: approximately 11 section Brindonia species had been reported from Thailand, but many identifications had depended primarily on published literature because a comprehensive national revision was lacking.

Subject of Research: Taxonomic revision and conservation assessment of three Peninsular Thai Garcinia trees

Article Title: Taxonomic treatment of three Thai Garcinia species (section Brindonia , Clusiaceae ), with six lectotypifications and conservation status assessments

Article References: Ngernsaengsaruay, C. (2026). Taxonomic treatment of three Thai Garcinia species (section Brindonia, Clusiaceae), with six lectotypifications and conservation status assessments. PhytoKeys, 275, 27-46. https://doi.org/10.3897/phytokeys.275.188257

Image Credits: AI Generated

DOI: 10.3897/phytokeys.275.188257

Keywords: Garcinia, plant taxonomy, Thailand, lectotypification, conservation status, IUCN assessment, Peninsular Thailand, herbarium specimens, Clusiaceae, wild fruit trees, Taxonomic, treatment