Discovery of a new species of wintergreen plant from Sichuan Province, ChinaSubmitted by nordicjbotany on 17 May 2016.
By Peter W. Fritsch (author)
The species of Gaultheria series Trichophyllae (Ericaceae: Gaultherieae) comprise a clade of high-alpine creeping or mat-forming small-leaved, i.e., less than 1 cm long, shrublets.
The flowers of this group are typical for the heath family (Ericaceae) in their white to pink color and bell or urn shape. More striking, however, is the vividly colorful apparent fruit of these plants, ranging from pure white to various shades of blue or purple. The colorful portion is actually the mature fleshy calyx, which surrounds the typically pale green dry capsular fruit proper.
The group is part of the larger wintergreen genus (ca. 120 species), so-named for the production on tissue damage of methyl salicylate, i.e., oil of wintergreen, in many of its constituent species, such as the familiar teaberry (G. procumbens) in eastern North America. This compound is used in over-the-counter rubefacient pain relievers and, in lower concentrations, as a flavoring agent.
The Himalaya-Hengduan Shan (Mountains) region of East Asia, to which these plants are endemic, constitute the most plant species-rich area of the north-temperate zone, one of the most biodiverse regions worldwide, and a major global biodiversity hotspot. This, along with the spectacular and exotic setting and the horticultural potential of its flora, has long attracted plant scientists and growers to the region. As the majority of the Himalaya-Hengduan Shan lies in China, the political re-opening of China in the 1970's has impelled renewed international scientific focus on the area. This focus is embodied in the success of efforts such as the monumental Flora of China project, which treats all known vascular plant species from the Chinese part of the region, and the Biodiversity of the Hengduan Mountains Project (http://hengduan.huh.harvard.edu/fieldnotes).
Despite a storied history of scientific exploration in the Himalaya-Hengduan Shan, many plant groups in the region remain poorly understood taxonomically. This is due largely to much of the region's uncompromising environmental conditions under which scientists must work, i.e., high elevations, rugged and steep topography, heavy rainfall, poor roads, and deep snow on trails much of the year. Whereas such field conditions have undoubtedly limited progress in the Trichophyllae group, additional challenges characterize these plants in particular. They are diminutive in form and are thus often overlooked by collectors, resulting in a paucity of collections in herbaria. Their small size correlates with a reduced number of character differences among many of the species. Fruiting characters are usually masked on pressed herbarium specimens, especially in terms of color, shape, and the disposition of the calyx, i.e., whether it is open with the capsule exposed, or closed. Finally, multiple species often grow together, possibly through simultaneous animal dispersal, via droppings, of the many small seeds in each fruit, often resulting in mixed species collections and the resultant confusion in identifications. This has been found to occur even in type material.
Despite these challenges, work by me and colleagues at the Kunming Institute of Botany over the past 12 years has steadily advanced knowledge of the Trichophyllae group. Through various sources of funding by the U.S. National Science Foundation, National Natural Science Foundation of China, and the National Geographic Society, we have undertaken a number of expeditions throughout the Himalaya-Hengduan Shan to study populations of this group, including regions of Yunnan (e.g., Gaoligong Shan along the China-Burma border, Meili Xue Shan and Biluo Xue Shan along the Nujiang-Lancang Divide, Wuliang Shan in west-central Yunnan, Cang Shan west of Dali), Xizang (Tibet in the eastern edge of the Himalaya in Medog County), and western Sichuan (e.g., Erlang Shan, Gongga Shan). Through our intensive field studies in these regions, combined with the examination of critical herbarium material and the generation and analysis of DNA sequence data, the taxonomy, phylogeny, and evolution of this group are becoming much better understood. The number of currently recognized Trichophyllae species, which stood at seven just a few years ago, now numbers 18, with more new species descriptions anticipated. Part of the challenge of this group is now clearly a result of convergent evolution in what were thought to be critical species characters, such as leaf trichome length. The observation of fruit characters on live plants in the field, such as calyx and capsule color and shape, have proven critical to understanding species limits.
The species in the current NJB paper demonstrates the combined importance of herbarium specimens, field work, collaboration, and molecular data. The authors knew of unusual populations of the Trichophyllae group from two herbarium specimens collected in the 1940s by Dr. Shiu Ying Hu of Harvard University in what was then known as Sikang Province which might represent an undescribed species, but there were no flowers on the specimens, and fruits were, as usual, distorted and without color. No other information was provided on the specimen labels about these plants, and so the researchers relied on a hunch that they might be found in areas where S.Y. Hu was known to make other collections of plants.
On an expedition to one of these areas (Erlang Shan), Fritsch and his KIB colleagues rediscovered these plants and immediately upon observation realized that it was a new species to science. The plants differ from all others in the Trichophyllae group except one in having a white fleshy calyx but dark maroon fruit proper (capsule); the authors named the plant Gaultheria marronina, after the unusual capsule color.
Gaultheria marronina, sp. nov. from Sichuan, China.
The only other species with these features is G. bryoides from far western Yunnan and Myanmar, described several years earlier by Fritsch and another colleague, but this species has much smaller leaves and a closed (versus open) calyx. Molecular data have confirmed unequivocally that these species are closest relatives. We found the plants in fruit only but needed flowers for publication, which we obtained four years later. In the meantime, co-author Bo Xu from the Chengdu Institute of Biology independently discovered a population of Gaultheria about 240 km to the northeast of the Erlang Shan population in western Sichuan. Dr. Xu sent images to the KIB group who confirmed it as one and the same species as the one in Erlang Shan.
The new species is thus far known only from these two unprotected populations and is categorized as endangered in accordance with International Union for Conservation of Nature standards and recommendations (http://cmsdocs.s3.amazonaws.com/RedListGuidelines.pdf). Because species of the Trichophyllae group are often overlooked, however, we hope that more populations of this species will be found.
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