Sweet-scented waxflower plant links Palawan and Borneo

The sweet scented waxflower [Hoya sipitangensis] blooms on branches and trees found within the 22,000-hectare cave systems of Puerto Princesa Subterranean River National Park in the village of Cabayugan, approximately 76 km northwest of Puerto Princesa and 360 km southwest of Manila.

A species of Hoya, also known as waxplant or waxflower, was discovered in Puerto Princesa Subterranean River National Park, highlighting the link between the Palawan province and Borneo which was connected by a land bridge during the last ice age.

Hoya sipitangensis, named after the village of Sipitang in Sabah, Malaysia–the locality in which the plant was discovered in 2002, is widespread throughout the coastal forests and low land hills of Brunei and Sabah.

The distribution of Hoya sipitangensis supporting the previous observations on the influence of Bornean biogeography on Palawan province.

For Augusto “June” Asis, 37, a forest technician at the Puerto Princesa Underground River park for more than 11 years, plants are often overlooked during the visit at the 22,000-hectare cave systems that featured limestone karst landscapes with an underground river that it emerges directly into the sea.

“Dati na naming [forest rangers] napapansin ‘yong halaman [Hoya] kasi halos pare-pareho sila. Ngayon lang nabigyan ng pansin talaga kasi may mga eksperto na nagsabi na iba pala ito, na importante,” Asis said.

The research project aimed to produce information that may serve as a reference material for plant species identification and to draft policy recommendations for conservation, management, and development of the UNESCO World Heritage Site.

The new distribution record of Hoya was published on June 14 in the scientific journal Check List by a team of scientists from the University of the Philippines Los Baños including Marjorie D. delos Angeles, Cristian C. Lucañas, and Annalee S. Hadsall.

Delos Angeles, 31, who led the scientific expedition in February 2021, described the “sweet scented” waxplant as “relatively smaller” compared to the variants found in Borneo, marking the distribution record as “significant”, citing that the location is a protected area that indicates a “high chance” that the plant species data justified that it had long existed in the Palawan province.

“It has a sweet scent. It is a unique discovery because records [of Hoya sipitangensis are isolated] in Borneo and Brunei, and we only find this plant species in Palawan,” Delos Angeles said in a phone interview.

The flowers of Hoya sipitangensis found in Puerto Princesa was measured at 4 mm, which was half of the Borneo species at 8 mm. Its yellow green leaves were around 6.62 mm long with oval to elliptic blades.

“[It is] smaller than the Borneo species. For Hoyas in general, there are morphology of flower―plants are very plastic, they adapt to its environment. As for its flower, the color of corolla is white, revolute or patupi sa loob. Leaves ay yellow green, smooth surface, no hair or trichomes,” Delos Angeles added.

The Palawan province, described as a “distinct biogeographic zone” due to its historical connections with the Greater Sunda Shelf, holds 17 species of Hoya, four of which are endemic to the island province and two are shared with the Sunda shelf.

“The low endemicity record of Palawan compared to the overall high rate of Philippine Hoya endemicity may be attributed to a dearth in data as a result of scarce botanical expeditions focusing on this genus on Palawan,” the research data said.

The discovery arose out of a research project between the University of the Philippines Los Baños in collaboration with the Puerto Princesa Subterranean River Park, through park superintendent Elizabeth Maclang and forest ranger Augusto Asis Jr., in an on-going project to document and promote fern and fern-associated flora recorded in the world-renowned park.

The research aimed to produce information that may serve as a reference material for plant species identification and to draft policy recommendations for conservation, management, and development of the UNESCO World Heritage Site.

As a one of the “women in science” since her undergraduate studies in 2010, Delos Angeles said that “no amount of money” can ever compare to the “contribution to the body of knowledge” in preserving the “floral treasures” in the country.

“It was core-funded or personal money, as help sa park [kasi] wala masyadong nagre-research sa park. Feeling ko parang passion na dine-deny ko pa dati, it is fulfilling when andoon ka na and the need to document, the need to preserve, the need to conserve. [There is] comfort in knowing that we help to conserve floral piece in park that no money or amount na kayang ibalik sa akin,” Delos Angeles said.

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