The Plantsman: Clarifying the Identities of Two Nepalese Mahonia
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Since their discovery, two Nepalese mahonias have either been regarded as the same species, or been confused, by botanists and gardeners. Tony schilling and Mark WaTson conclude that they are distinct and show how to separate them. Clarifying the identities hree species of Mahonia and why the confusion came about early 19th century, based on are reported as native to initially and has persisted for so long. herbarium specimens collected by TNepal (Press et al. 2000): Following an examination of living Francis Buchanan-Hamilton (in Mark Flanagan M. acanthifolia G. Don, M. borealis and herbarium material of Nepalese 1802; see Boufford 2013) and Takeda and M. napaulensis DC. Both Mahonia, combined with our own Nathaniel Wallich (in 1818–1821) M. acanthifolia and M. napaulensis field observations, we here attempt respectively. The latter included have been in cultivation in Western to resolve this confusion. material sent to Wallich by Edward gardens since the middle of the 19th The Nepalese records of M. borealis, Gardner, the first British Resident century. However, despite the a northwest Himalayan species, have (ambassador) in Kathmandu. passing of nearly 200 years since been re-examined and are now con- Mahonia napaulensis was the first they were described, the separate sidered to be misidentifications of to be described (in 1821) by the Swiss identity and synonymy of these two M. acanthifolia, and so we recognize botanist Augustin de Candolle using taxa continue to be debated. only two species of Mahonia in Nepal. material gathered by Buchanan- In our opinion, these two Hamilton in the Kathmandu Valley. Nepalese species are clearly distinct Early taxonomic history It has leaves bearing six pairs of and readily separated, so much so Both M. acanthifolia and similarly sized leaflets and a smaller that it is difficult to understand how M. napaulensis were described in the pair of lower leaflets inserted close to 94 June 2014 PlantsmanThe of two Nepalese Mahonia Mark Watson Mahonia napaulensis (left) has significantly fewer Making taxonomic decisions based Joseph Hooker studied Mahonia leaflets per leaf thanM. acanthifolia (above) on limited or inadequate collections in Sikkim and Darjeeling in the late was clearly a problem then, and 1840s, and concluded that these two the base of the leaf (often appearing continues to be so today. Mahonias species should be united under the like stipules). are large, spiky shrubs that have earlier name of M. napaulensis Ten years later George Don tended to be avoided by collectors of (Hooker & Thomson 1855). They described M. acanthifolia. He took herbarium specimens. Furthermore, adopted a very broad species concept, up a manuscript name of Wallich, it is difficult to represent the variation writing ‘we have no hesitation in written on original labels on two seen in a large Mahonia plant on a uniting the Peninsular and Khasia specimens in the East India single herbarium sheet and so early with the Himalayan species, not- Company Herbarium, now at Royal collections can be difficult to withstanding the difference in shape Botanic Gardens, Kew (herbarium interpret. However, by combining of the berries and leaflets between code K-W). He described it as a studies in the herbarium with the extreme states of each. Dr larger shrub with a greater number of observations taken from living plants Wight informs us that he has culti- leaflet pairs, he thought up to 10. But in the field and in cultivation, we vated the Himalayan one side by side Don commented that it might be have come to a better understanding in his garden with that of the the same as M. napaulensis. of the delimitation of these species. Nilghiri, and finds them to be ➤ June 2014 95 taxonomy indistinguishable. Specimens of the Fruit collecting in Sikkim. In contrast to shrubby Sikkim plant, cultivated for a good M. napaulensis, M. acanthifolia eventually forms a plant that is sturdy enough to climb many years at Dorjiling [Darjeeling], acquired longer racemes, larger flowers, and more slender pedicels from the Kathmandu Valley. Takeda than the wild specimens in the referred all the other Mahonia in adjacent woods. The bracts are very Nepal to M. acanthifolia, a species variable organs.’ with leaves of up to 11 pairs of This early use of comparing plants leaflets, and geographically much in the wild and in cultivation is more widely spread, from northwest notable, but it is not clear if material Himalaya to east Himalaya and of M. napaulensis (in our narrow northeast India. He commented sense) from the Kathmandu Valley that ‘among the Indian species was included in these experiments. M. acanthifolia can easily be The Mahonia grown at the Calcutta distinguished by having very small Botanical Garden (‘Berberis pinnata outermost sepals [enclosing the Roxb.’, listed in the 1814 garden flower in bud], apiculate-triangular catalogue Hortus Bengalensis), was connective, and large luxuriant leaf collected by MR Smith from with numerous leaflets which are Manipur, northeast India, and so furnished with a few large teeth.’ could not have been M. napaulensis Leslie Ahrendt (1961) published as we now understand it, and was the most recent comprehensive Brian Mathew presumably M. manipurensis Takeda. monographic treatment of Mahonia in his global revision of both Berberis the Indian species, including the First monographs and Mahonia. Ahrendt agreed with south Indian M. leschenaultii (Wight At the end of the 19th century and Takeda and increased the distinction & Arn.) Tanaka ex Dunn and the first half of the 20th century there between M. napaulensis and northeast Indian M. manipurensis, was an increase in botanical M. acanthifolia by placing them in within M. napaulensis. exploration of Asia, and the first separate subsections. He highlighted monographic treatment of Old the very short, ‘insignificant’ style of Recent studies World Mahonia by Friedrich Fedde M. napaulensis as another useful Boufford (2013) recently commented: (1901). Fedde followed Hooker & distinction, as compared with the ‘the wide variation in leaf and leaflet Thomson, including M. acanthifolia 1mm style of M. acanthifolia. morphology in Mahonia napaulensis within M. napaulensis. Himalayan floristic works contin- [in the wide sense] makes it easy to Takeda (1917) took a fresh look at ued to follow this separation of the understand why so many names have the Indian species, commenting that Nepalese species until the Flora of been applied to this complex and since Hooker and Thomson ‘unhesi- Bhutan in which Grierson (1984) felt wide-ranging species. In the flowers tatingly united all Indian species … that available herbarium material and fruits and in the structure of the into a single species, M. napaulensis, was too scanty to differentiate inflorescence, however, there is … almost all the later workers have between the east Himalayan species remarkably little variation. And, indiscriminately followed this reliably. Grierson concluded that when large numbers of specimens opinion.’ Takeda set out ‘to ascertain ‘until the genus is better collected it are examined the variation in the the real M. napaulensis’, concluding seems preferable to regard Mahonia leaves can be seen to be continuous that this species had never been as being represented in this area by a and not warranting taxonomic found outside Nepal, and that single species’. The illustration recognition.’ We agree that the previous authors were misguided. provided in the Flora is reminiscent variation seen in dried material Takeda reported that the leaves of of M. napaulensis, in the narrow sense, makes it difficult to delimit species M. napaulensis had 3–7 pairs of in regard to the number of leaflet based on herbarium specimens leaflets, and was only known from a pairs. This taxonomy was followed in alone, but combined with ecology, few specimens collected by Ying et al. (2011) in Flora of China in phenology and geographic Buchanan-Hamilton and ‘Wallich’ which they also subsumed many of distribution we believe that it is 96 June 2014 PlantsmanThe Mahonia acanthifolia (top) and M. napaulensis (bottom). The leaf of M. napaulensis has leaflets at the narrower Mark Flanagan end of its variable range. possible to delimit separate species Horticultural literature species that can be cultivated in the within this complex. In the horticultural literature the open in the British Isles. It is hardy The situation may be comparable situation has been similarly confused in the southern and western parts of to Sino-Himalayan Taxus where and inconsistent, with only Herklots the country, but needs a sheltered some authors have recognized (1964) and Bean (1973) having come position. It received a First Class several species based on subtle to what we believe is the correct Certificate when shown from morphological differences and conclusion. Windsor Great Park on 25 geographic range, whereas others Geoffrey Herklots, the first November 1958. The plant in the have preferred to combine them British advisor at Godavari, Nepal’s Savill Gardens, growing on a wall near within a variable and wide-ranging national botanic garden, where he the propagating houses, is a cutting Taxus wallichiana. Recent molecular was succeeded by the first author, from the F.C.C. plant; it has attained studies analyzing the DNA of Taxus wrote: ‘I was puzzled by the fact that a height of 9ft in twelve years (1971).’ populations across the whole range the shrubs at lower elevations The following descriptions and show that this complex comprises of [M. napaulensis] – including those observations are presented in the several genetically distinct entities, wild in my garden at Godavari – hope that further misunderstanding some of which correspond to flowered in the early months of may be prevented. The main previously named species and others the year, whilst those growing differences between the two species which have now been described as between 7,000 and 8,000 feet are summarised in the table on p98.