Saturday 13 August 2022

Cyne barcelonae: A new species of Showy Mistletoe from the Philippines.

Showy Mistletoes, Loranthaceae, are specialist members of the Sandlewood order, Santalales, which superficially resemble the Mistletoes of the northern temperate regions (to which they were formerly thought to be related), but with a distribution in the Southern Hemisphere and tropical regions, and more showy and brightly coloured flowers. Like the True Mistletoes, the Showy Mistletoes are hemiparasitic, which is to say they produce chlorophyll and photosynthesise for themselves, but obtain many of their nutrients by sinking their roots into the xylem of other Plants.

In a paper published in the journal Phytotaxa on 11 August 2022, Daniel Nickrent of the Plant Biology Section at Cornell University, and Mark Gregory Rule of the Department of Environmental Studies at Mindanao University and the Philippine Taxonomic Initiative describe a new species of Showy Mistletoe from Dinagat and Bucas Grande Island off the northeast coast of Mindanao. 

The new species is placed in the genus Cyne, which has previously been found in the Philippines, the Moluccas Islands, and New Guinea, and given the specific name barcelonae, in honour of the Filipina botanist Julie Fenete Barcelona, for her work on Pteridophytes and Rafflesia

Cyne barcelonae. (A) Habit of mistletoe parasitic on Myrsine sp. (B) A young haustorial connection to host branch. Arrow indicates a new vegetative shoot forming on the flank of the haustorium. Note that no epicortical roots are present. (C) Terminal portion of vegetative shoot showing two lateral and the central stems assuming a pseudo-whorled appearance. Note the connation of the leaf bases. (D) Non-connate leaves subtending to young shoots with connate leaves, still unopened. (E) Young inflorescence with one of the connate leaves removed. Although two pairs of triads can be discerned, their decussate nature is obscure. (F) Flowering shoots of plant photographed on Dinagat Island. Meljan Demetillo & Mark Gregory Rule in Nickrent & Rule (2022).

Cyne barcelonae produces a stem directly from its host without epicortical runners (visible external roots). This stem then typically divides to form two branches. The bark darkens to reddish brown as it ages, leaves are waxy and oval. The branch tips have two terminal leaves, each surrounding two triads of flowers. These flowers are green and tubular, with red tips. Fruits are a orange-brown in colour.

Cyne barcelonae. (A) Flowers at anthesis. Note the green corolla with a dilated base as well as stamens with filaments. (B) Fruits young and mature with persistent calyculus and style base. (C) Young fruit longitudinal section showing seed inside ovary wall. (D) Capitulum arising from corky periderm of receptacle. Note the bracts and bracteoles adpressed to calyculus/ovary. (E) Portion of inflorescence with two triads, one with calyculus/ovaries removed to show the laciniate bracts and bracteoles. (F) Corky periderm removed from receptacle. Nickrent & Rule (2022).

This Mistletoe has been observed growing on trees belonging to the genera MyrsineSterculia, and  Timonius, always on ultramafic soils within 20 m of a stream; other Mistletoes were observed in the same areas targeting the same host-trees. The species was found on two islands. Bucas Grande is part of the Siargao Islands Protected Landscape and Seascape, and in theory enjoys a high level of protection. However, the area where Cyne barcelonae was found growing as actually a fragment of remnant forest within a community-operated resort, and while their are regulations on Human activities here, firewood-collection and commercial tree cultivation do occur. Furthermore, the Plants were observed before the passage of Typhoon Rai through the area in December 2021, and has not been revisited by scientists since. Dinagat Island is currently considered to be severely threatened by mining, despite being recognised as an area of great importance for Plant biodiversity, with about half of the island's forests in areas which are currently covered by Mineral Production Sharing Agreements. Some protection may be offered by the Dinagat Island Conservation Program, which has recently been initiated by the provincial government, and which is intended to exclude areas of great biological significance from mineral extraction.

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