From a Sri Lankan rainforest, a new species of orchid blooms

From a Sri Lankan rainforest, a new species of orchid blooms

3 May 2020 07:53 pm

By Dilrukshi Handunnetti

COLOMBO — A rare new orchid described from a tropical lowland rainforest in Sri Lanka now bears the name of two of the island’s pioneering forest ecologists.

A new paper published in the journal Biotaxa identifies the new discovery as Gastrodia gunatillekeorum, a species found in just three small populations comprising fewer than 100 mature individuals. That makes it both habitat specific and endangered.

In naming the petite orchid, researchers dedicated it to two of the island’s top ecologists, Nimal Gunatilleke and Savitri Gunatilleke from the University of Peradeniya. “This is our humble tribute to this unique couple for their immense contribution in the field of ecology and for encouraging, mentoring and nurturing future ecologists of Sri Lanka,” said study’s lead author  Champika Bandara from the Faculty of Applied Sciences of the Uva Wellassa University, Badulla.

Gastrodia are mycotrophic plants — those that rely on fungus for their nutrition — and as such occur in highly specific locations, given that fungi are also highly specific to the habitat where they grow, Bandara said this new species was discovered in the Sinharaja lowland rainforest, an area dominated by Mesua and Shorea trees.

The small orchid bears a close resemblance to G. spatulata, a flower endemic to Indonesia, because they both have white, wide-open and backward-reflexed flower fronts. In G. gunatillekeorum, however, the petals are as long as the outer part of the flower, known as the perianth, while in G. spatulata there are free linear petals inside the perianth tube.

Rising out of leafy litter and a bed of wet soil in the Sinharaja lowland rainforest, the new orchid is limited to three small populations and considered endangered. Image courtesy of Champika Bandara.

There are some 90 Gatrodia species, or potato orchids, known to science, with a range across much of the Ind0-Pacific, from Africa to New Zealand, and as far north as Siberia. For all its biological richness, Sri Lanka had only one species of the plant — G. zeylanica — before the recent discovery. The new orchid can be easily distinguished from G. zeylanica by its shorter stature of the whole plant, yellow-orange color inside the perianth tube, and shorter lip. And G. gunatillekeorum is unique also because it has a short flowering and fruiting season each year: between February and April.

It was during an ecological field survey in April 2018 that lead author Champika Bandara observed a few flowering individuals of Gastrodia within the biodiversity-rich Sinharaja Man and Biosphere Reserve, just above the Beverly Estate tea plantation near the town of Deniyaya in the southern district of Matara.

In March 2019, Bandara spotted some more at the Center for Tropical Forest Science and Forest Global Earth Observatory located within Sinharaja, this time closer to Ratnapura district, and again the following month in the same western region of Sinharaja.

Having discovered only the three distinct populations within the western and southern regions of Sinharaja rainforest, conservation efforts for the new species may have to be location specific, the researchers say.

Researchers have named the new orchid after two of Sri Lanka’s leading forest ecologists, Nimal and Savithri Gunatilleke, in recognition of their decades-long contribution to science. Image courtesy of Champika Bandara.

All three orchid populations were found amid thick leaf litter and decaying stumps and stems. Given the small size of the population and habitat specialty, any change in the habitat condition will bring change to the fungus community — and the orchid populations that depend on these fungi may perish in their absence, Bandara told Mongabay.

Two populations were found within protected areas inside the Sinharaja evergreen rainforest in Deniyaya while the third fell within a protected area under the Department of Forest.

All three populations are located in long-term forest observation plots, so the researchers plan to conduct further research into population dynamics and pollination studies.

Though the current distribution of the new species appears restricted to the lowland tropical rainforest, the researchers are open to the possibility that the species may occur in adjacent areas that have not yet been fully explored, said Pankaj Kumar, co-author and botanist with the Hong Kong-based Kadoorie Farm and Botanical Garden.