PLANTS IN PERIL, 24
Yong Shik Kim and Mike Maunder
Summary. The conservation status of Abeliophyllum distichum Nakai(Oleaceae) is reviewed.
Abeliophyllum distichum(Oleaceae) is widely cultivated hardy shrub, favoured for its attractive sprays of scented white flowers in late February and early March. Abeliophyllum is a monotypic genus closely allied to Forsythia but differing in having flattened broadly winged fruits in contrast with the capsular fruits of Forsythia. A number of colour forms have been identified from wild populations(Lee, 1976) with a pink form established in cultivation as the cultivar 'Roseum'. In the wild, in the Korean peninsula, this species is scarce and threatened with extinction. The following report is derived from a joint project between the Yeungnam University and the Royal Botanic Gardens, Kew(Kim & Mike, 1995) and represents the first stages of a recovery plan for this endemic genus.
The species was first described in 1919 by Professor Takenoshin Nakai(1919) who originally collected it in the 'Chinsen(sic Chinchon) Hills of Middle Korea'(Cotton, 1948). Seeds were sent to the Arnold Arboretum in 1924 by Mr T. Ishidoya(Wilson, 1928) and live plant material sent to Kew by Nakai in 1932. According to Cotton(1948) plants were also received in the 1930s by Lord Aberconway from the Arnold Arboretum. The species rapidly became established in cultivation, with the Royal Horticultural Society awarding a Preliminary Commendation in 1936 to a plant from Lord Aberconway's collection, with a subsequent Award of Merit in 1937. A First Class Certificate was awarded in 1944 for sprays exhibited by J. Coutts of Woking. The plant was in the commercial trade by 1937, listed by the Keeper's Hill Nursery, Wimborne, Dorset. The species has become a popular component of European(Kammeyer, 1972) and American gardens(Derbyshire, 1975). It has proved cold hardy and dependable in flowering; the species' naturally layering behaviour and ease of propagation by cuttings has ensured its adoption by the commercial nursery trade.
The restricted geographical distribution and apparent rarity was commented upon by Cotton(1948): 'Its distribution was confined to an exceedingly small area, and, habit not been brought into cultivation, it was not only a species but a genus which might easily have become extinct'. Subsequently, it has been the subject of a number of reports and studies(Hwang, 1974; Lee, 1976a, 1976b, 1990;Kim & Kim, 1990); however, no comprehensive study had been undertaken to identify the plant's conservation status and management needs. A review of existing literature was undertaken followed by a field survey in 1993(Kim & Maunder, 1995). The study indicated that this species is declining in the wild and requires urgent management to reinstate regeneration in the surviving wild populations and to establish new wild populations.
Historically seven distinct localities have been recorded, all from the middle part of South Korean territory, with unconfirmed records from North Korea. These comprise three populations in the Koesan-gun area, one population at Mount Pukhan National Park, discovered in 1973 by Yong No Lee, Yong Ja Oh(Korean botanists) and Schneider in the vicinity of the Seoul metropolitan area(Lee & Kil, 1991), one population at Yongdong-up, Chungchongpuk-do, discovered in 1990 and one locality in Puan-gun, Chollapuk-do, discovered 1992. The population recorded at Chinchon-gun has been subsequently extirpated(Natural Monument No. 14). Herbarium specimens in the Kyoto University(Lee, 1987; Lee & Kil, 1991) indicate the existence of wild populations in North Korea collected by Japanese botanists, Koizumi and Saito in 1935, at Mt. Changsoo, Hwanghae-do, and by the Japanese botanists, Saito, at Nanam, Hamkyongnam-do. The population at Puan-gun has been partly destroyed by dam construction with several hundred rooted suckers translocated to a safe site in an adjacent valley during 1994 by the Department of Forest Resources, Chonpuk National University.
Abeliophyllum grows as an understory shrub in mixed deciduous woodland, often under Pinus densiflora, Quercus myrsinaefolia and Q. acutissima. It forms a low growing and open thicket of suckering growths. In early spring before leaf break the white flowers of Abeliophyllum make a spectacular show against the russets and yellows of the previous season's oak litter. Searches were undertaken during the flowering season when colonies could be readily located. The precise ecological requirements of this species are difficult to ascertain; however it is suspected that it thrives in the dappled shade of open deciduous woodland. All the extant populations (except Yongdong-gun) are subject to intensive site management or have been translocated (e.g. Puan-gun). The management of sites entails fencing, in some cases pollarding of canopy trees (for instance at the Songdok-ni site), and the clearance of shrub amongst the Abeliophyllum plants (for instance at Chujom-ni site). In addition to well-meaning habitat management the species is threatened by visitor pressure (including off-road vehicles) and the illegal collection of plants. There is no reason to assume that any of these threats will diminish. The populations, whilst all protected by the Natural monuments legislation, are under the management of a variety of authorities including private farms, country parks, university estates, etc. The future of this species accordingly depends upon the identification and implementation of correct habitat management protocols across a number of differing land management agencies.
The ecology of the species requires study; there is little evidence of seedling recruitment in wild populations, perhaps as a result of overshading and competition. In addition, preliminary studies of wild populations in Korea indicate that very little seed is produced. Observations of cultivated material suggest that the species is self incompatible, requiring pollination between differing genotypes to ensure successful seed-set. On-going studies of genetics will assess the distribution of genetic diversity within and between populations. It is suspected that the wild populations are largely clonal colonies, hence there will be little production of seed. Continuing morphological studies by one of us(YSK) indicates a wide variation in flower morphology amongst wild populations.
Abeliophyllum is cultivated in a number of Korean collections including the Chollipo Arboretum, Hantaek Botanic Garden, Keechungsan Botanic Garden, Kwanak Arboretum, Kwangnung Arboretum, and the Milim Botanic Garden(Anon., 1991). The majority of these cultivated stocks cannot be traced to any known provenance, however some collections do have stocks that are attributable through anecdote to the now extirpated population at Chinchon. One private collection cultivates samples from a number of the wild populations. The species is also known to be in cultivation in North Korea(Hwang, 1974). Only a few collections outside Korea cultivate plants of documented wild origin, for example the Arnold Arboretum and the Royal Botanic Gardens, Kew. The cultivated stocks in North American and European arboreta and botanic gardens largely clonal and, based on currently available information, duplicate both wild and cultivated genetic material in Korea.
Despite Cotton's fears(1948) Abeliophyllum has not become extinct; however it is close to extinction and qualifies for the IUCN Category of 'Critically Endangered', indicating a high risk of extinction in the near future. To ensure its survival as a wild species will requires a revision of current habitat management procedures to facilitate natural seed regeneration and the establishment of new and regenerating wild colonies. In addition it is proposed that a field gene banks should be established in Korea to hold clonal samples from the wild populations. Such a facility could access wild plants prior to developing new cultivars, notably larger flowered and good pink forms which were observed in a number of wild populations. The conservation of this species in the wild is dependent upon an understanding of the regeneration ecology and the distribution of genetic diversity within and between populations.
Abeliophyllum distichum Nakai in Bot. Mag. Tokyo 33: 153(1919. Type: Korea, 'Chinsen Hills of Middle Korea', Nakai.
DESCRIPTION. Straggling, deciduous shrubs to 1 m or more, with spreading or arching branches; young shoots dark purple, 4-angled, slightly warted. Leaves simple, entire, petiolate; petiole 5-6 mm long; lamina pubescent on both sides, lanceolate to ovate-oblong, 6-10 cm long, 3-4.5 cm wide, cuneate or rounded at base, apex narrowly acute. Inflorescence axillary racemes of 3-15 flowers, rhachis dark purple. Flowers fragrant, white or pale pink, pedicellate; pedicels 4-5 mm long, dark purple; bracts caducous, subulate, 3-5 mm long; bracteoles 2, opposite, subulate, ciliate; calyx 3-3.5 mm long, tube 1-1.5 mm long, calyx lobes 4, rounded, 2-2.5 mm long, c. 1.5 mm wide; corolla tube 4 mm long, corolla lobes 4, spreading, recurved, oblong, 6-8 mm long, 2-3 mm wide, deeply notched. Stamens 2, inserted at the base of corolla, 4.5 mm long; filaments white, slender, 3.5 mm long, anthers basifixed, extrorse, 1.5 mm long, deep yellow. Gynoecium 3-3.5 mm; ovary suborbicular, c. 1 mm long; style 1.5 mm long, stigma bifid. Fruit a circular samara, 2-3 cm in diameter, apex emarginate; seeds one per locule, pendulous.
DISTRIBUTION. Republic of Korea.
HABITAT. Mixed deciduous woodland.
CONSERVATION STATUS: Critically Endangered(sensu IUCN).
ACKNOWLEDGEMENTS. This work could not have been undertaken without the support of the British Council in funding Professor Kim's research in the UK and Mike Maunder's visit to Korea. Dr Stephen Sponberg of the Arnold Arboretum of Harvard University provided accessional information on cultivated holdings of Abeliophyllum. The assistance of Dr Chong-Min Park, Chonpuk National University and Carl Ferris Miller of the Chollipo Arboretum is gratefully acknowledged; their hospitality contributed greatly to the success and enjoyment of the field work undertaken in 1996.
Anon., (1991). A Comprehensive Bibliography of Botanical Gardens in Korea. Korean Association of Botanical Gardens.
Cotton, A. D. (1948). Abeliophyllum distichum. Curtis's Botanical Magazine 165: t. 10.
Derbyshire, E. (1975). Shrub profile: Abeliophyllum distichum. Bulletin of the Morris Arboretum 26(1): 5.
Hwang, H. J. (1974). Abeliophyllum distichum Nak., a shrub native to our country. Korean Nature 3(34): 23-24. (In Korean).
Kammeyer, H. F. (1972). Abeliophyllum, seltener Kleinsrrauch unserer Garten. Mitteilungen der Deutschen Dendrologischen Gesellschaft 64: 132.
Kim, Y. S. & Kim, T. W. (1990). The conservation of Korean rare and endangered plant species and the role of the botanic gardens and arboreta. Bulletin of the Kwanak Arboretum, Seoul National University 10: 33-47. (In Korean).
Kim, Y. S. & Maunder, M. (1995). A draft recovery plan for Abeliopyllum distichum. Unpublished report of the Yeungnam University and Royal Botanic Gardens, Kew.
Lee, T. B. (1976a). Study on the conservation of endemic plant resources(Abeliophyllum distichum Nakai). Nature Preservation 12: 6-10. (In Korean).
Lee, W. T. & Kil, B. S. (1991). The investigation of the natural growth region of Abeliophyllum distichum Nakai. Journal of Plant Taxonomy 2:1-8. (In Korean).
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Yong Shik Kim is a Professor in the Department of Landscape Architecture at Yeungnam University with specialist interests in Landscape reclamation and conservation of the Korean flora: Department of Landscape Architecture, Yeungnam University, Korea.
Mike Maunder is Head of the Conservation Unit, Living Collections Department, at Kew. He has a particular interest in the role of botanic gardens in plant conservation.
Source of the Publication:
CURTIS'S Botanical Magazine, Royal Botanic Gardens, Kew, UK. Vol. 15(2): 141-146, 1998.