Three new species of Begonia found in Samar Island, Philippines

Being the third largest island in the Philippines and dominated by lowland evergreen rainforests and limestone forests, it is no wonder that Samar Island is one of the outstanding centers of plant diversity in the country.

The island’s intact forest provides home to many endemic and rare species and sanctuary to threatened plant species.

In fact, about 40 out of 2,400 species of flowering plants throughout the Philippines can only be found in Samar. More than 400 of these species are endemic to our country based on existing records. Adding to this list of flora are three new Begonia species recently discovered by a group of researchers from the Philippines and Taiwan.

The new species, namely, Begonia sohoton; Begonia tarangban; and Begonia burabod were found in 2018 and documented in the August 2021 issue of Phytotaxa -- a Web of Science-indexed international journal for plant taxonomy.

It is a collaborative work led by Begonia taxonomist Dr. Rosario Rubite, along with Celeena De Guzman Justo and Patricka Villaseñor from UP Manila; Asst. Prof. Marjorie Delos Angeles from UP Los Baños; Filipino botanist and Forester Danilo Tandang; and Che-Wei Lin from the Herbarium of Taiwan Forestry Research Institute.

According to Asst. Prof. Delos Angeles, she was invited by Dr. Rubite to contribute to the paper when she was working on select forests over limestone and came across the species B. burabod during one of her field works.

In the article, the authors assigned the species to the Begonia section Baryandra, which contains many flowering species that can only be found in the Philippines.

“Globally, there are 70 Begonia sections and the Philippines has two, one of which is section Baryandra. Members of this group have a rhizomatous habit, axillary inflorescences where male flowers are basal and female flowers distal, among others,” Asst. Prof. Delos Angeles said.

The researchers are proposing that two of the new Begonia species should be classified as vulnerable based on the International Union for Conservation of Nature (IUCN) Red List Categories and Criteria, which means it is “facing a high risk of extinction in the wild.”

Named after the locality of Sohoton River where it was discovered, Begonia Sohoton grows from narrow openings or cracks of limestone walls. Although the species is in a protected national park, the researchers deem tourism can have a negative impact on it. Hence, B. sohoton must be classified as vulnerable according to the researchers.

The other species is called Begonia tarangban, named after the Tarangban Falls in Calbayog City where it was discovered. It can only be spotted near the falls, growing on rocky slopes that are partially exposed to sunlight. B. tarangban is also proposed to be tagged as a vulnerable species.

Growing abundantly on shaded and moist soil slopes, the Begonia burabod was named after the local word "burabod" which means spring in Waray language. Since it can be found in different barangays in eastern Samar, the researchers proposed it to be classified in the Least Concern category of the IUCN Red List.

The discovery of these new species shows that Samar Island is indeed "one of the centers of plant endemism in the Philippines."

The unique characteristics of the new Begonia species are detailed in the article "Three new species of Begonia (section Baryandra, Begoniaceae) from Samar Island, the Philippines" published in Phytotaxa last August 26.