Paeonia Newsletter [vol.30/4]/Paeonia newsletter
Volume 30, No. 4
Fall 2000
Editor and Publisher:
Donald R. Smith 46 Exeter Street W. Newton, MA 02465
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Table of Contents:
The World of Tree Peonies According to Hong and Hong.....................................
Classification Tree for Paeonia Section Moutan.........................................
p.1 p. 4
Recent Developments Concerning the Classification of Section Moutan or (The World of Tree Peonies According to Hong and Hong)
by D. R. Smith
Two recent studies by Hong et al. (1997, 1998) have shed new light on the classification of Pceonia, section Moutan. The first of these studies deals primarily with the taxonomic status of P. lutea var. ludlowii, while the second addresses the sub-division of the delavayanae sub-section of section Moutan. Although the results of these studies are not nearly as definitive as those for section Pceonia recently reported by
Tao Sang (see previous issue of the newsletter, V30, N3), they are nonetheless based on extensive field observations, population sampling and analysis of several plant characteristics. Together, these studies arrive at several new and interesting conclusions that are well worth summarizing here.
Compared to section Pceonia (which contains approx. 28 species), I would have assumed that classification of sectio n Moutan (with only ~ 6-9 species) would be considerably easier. In practice, however, this has not proved to be the case.
Section Moutan is composed of a relatively small group of woody peonies that are endemic to China. This section is divided into two subsections (Pelavayanae and Vaginatae). Within each of these sub-sections are smaller groups of
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Paeoniaallied "species" sometimes referred to as complexes.
One such group is the Delavayi complex with members that are endemic to southwestern China. This complex includes P. lutea, P. delavayii and P. potaninii. Another such group is the Suffruticosa complex, which includes P. rockii, P. ostii and P. qiui, etc. This group is endemic to north-central China.
Classification of the Pceonia delavayi complex has been especially problematic due to a significant lack of agreement among the taxonomists who have studied the complex. Some taxonomists recognize one species with three infraspecific taxa, while others accept only two species, and yet others accept three species with two infraspecific taxa. Hong's results show that the complex is extremely variable both within and between populations in the number, length, and width of leaf segments and in the number, size and color of the floral parts. Hong and Hs co-workers concluded that only one species should be recognized, without any infraspecific taxa. As a result Pceonia lutea and Pceonia potaninii are reduced to synonymy of Pceonia delavayi.
In all, eighteen populations were studied in the field. From these extensive field studies, the following observations were made.
Plants of the Pceonia delavayi complex are always dwarf shrubs. The tallest being less than 6 feet in height while the shortest rarely reach 3 feet. Seedlings were very rarely found in the field indicating that vegetative reproduction is probably predominant in the Pceonia delavayi complex. Cloning by stolens, however, was very common and was found in every population visited.
P. potaninii (along with its two varieties alba and trollioides) has long been considered to be a separate species within the delavayi complex. One of the main justifications for treating P. potaninii as a separate species was that it was considered to have narrower leaf segments than P.
delavayii and P. lutea. However, leaf segments were found to vary greatly within the delavayi complex and plants of P. potaninii were found to fall in the middle of the overall variation range in the complex. The same situation was found for the length of the leaf segment as well. Therefore, it would appear that P. potaninii is rather similar to P. delavayii and P. lutea in this regard, and thus this character cannot be used to justify a species status for this taxon.
The major conclusions of the Hong et al. study on the taxonomy of the delavayi complex are quoted below:
"In summary, the Pceonia delavayi complex exhibits tremendous and continuous variation in characters of the leaves (number, length, and width of segments), bracts (number), and floral parts (color and number). Except for the very weak correlation between petal color and geography, the variation in these characters is clearly insignificant taxonomically. Therefore, none of these characters can be considered as justifying the subdivision of this complex, which we thus consider as comprising only one species, without infraspecific taxa."
Another problem with the classification of section Moutan is the taxonomic rank of P. lutea var. ludlowii. Although this "variety" has long been considered to be a sub-species or variety of P. lutea, according to Stern and Taylor (1951, 1953), this taxon is distinctly different from variety lutea, especially in plant height, size of flowers and number and size of follicles. Examination of plants in five populations by Hong (1997), have confirmed these differences. These observations indicated that plants of P. ludlowii are tall (6-11 feet), caespitose, and have larger, pure yellow flowers, yellow filaments, acuminate leaf segments and lobes, and mostly one carpel per flower (more than 97% of the flowers examined had a single carpel and less than 3% had two carpels). Furthermore, P. ludlowii produces very large follicles (up to 3" long) that contain the largest seeds (ca. 1.3 cm diameter) in the genus. In contrast, plants of P. delavayi are not caespitose, have much shorter stems, acute leaf
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Paeonia 2segments and lobes, more or less pendulous and
smaller flowers on curved pedicels, yellow petals These species are:
nearly always red-blotched at the base, purple-red
filaments, and 3 or 4 (but rarely 2) much smaller
carpels. In addition P. ludlowii was found to be
obligately sexual with no vegetatively produced
individuals or plantlets found in any of the
populations. This is in sharp contrast to P.
delavayi, which reproduces both sexually and
vegetatively. Furthermore, in several delavayi
populations no seedlings were found, indicating
that these populations were formed primarily by
cloning. It is Hong's opinion that these
differences clearly support the recognition of
variety ludlowii as a distinct species (i.e., P.
ludlowii).
1. P. jishanensis
2. P. ostii
3. P. rockii
4. P. yananensis
Based on Hong's extensive observations, a brief description of P. ludlowii highlighting the major differences with P. delavayii/lutea is given below:
P. ludlowii is a tall shrub that often forms large and dense clumps with dozens of stems. Ludlowii is distinguished by its long, commonly unbranched stems to 8 feet (vs. 5 feet in variety luted) larger and more open flowers (up to 5" vs. 3" for luted), and up to 2 carpels twice as large as those of variety lutea. There are usually 4 flowers to a stem.
The situation in sub-section Vaginatae is only slightly less complicated. Here again, recent developments have dramatically changed the "generally accepted" picture of this group of peonies. Until quite recently, it was though that only one species, namely P. suffruticosa, existed within this sub-section. In 1992, however, a group from the Chinese Academy of Forestry in Beijing led by Professor Hong Tao (not to be confused with Hong De-yuan mentioned earlier) proposed a radically new classification system for tree peonies. Hong's principal assertion is that numerous plants previously designated as P. suffruticosa are in fact really cultivars developed in China and Japan over several centuries and were derived from various crosses between four wild species (now expanded to 6 or 7) newly described by him and his associates.
To these should be added P. szechuanica and another recently discovered tree peony with red flowers, P. qiui. This new species was recently described by Pei and Hong (1995). There may also be a seventh species, P. yunnanensis first described by Fang in 1958, but this may also be synonymous with P. yananesis listed above. The classification tree for section Moutan based on the recent work of Hong and Hong is shown in Fig. 1.
References:
Hong De-yuan, Pan Kai-yu, and Yu Hong, Taxonomy of the Pceonia Delavayi Complex (P^ONIACEAE), Ann. Missouri Bot. Gard., 85 (4), 554-564, 1998.
Hong De-yuan, Pceonia (Pseoniaceae) in Xizang (Tibet), NOVON, 7 (2), 156-161, 1997.
Stern, F. C. and G. Taylor, A new peony from S. E. Tibet, J. Royal Hort. Soc., 76, 216-217, 1951.
Hong Tao, Zhang, J.X., Li, J.J., Zhao, W.Z. and Li, M.R., Study on the Chinese Wild Woody Peonies II. New Taxa of Pceonia L. Sect. Moutan D.C. Bulletin of Botanical Research, Harbin 12 (3), 223-234, 1992.
Hong Tao and Osti, G.L., Study on the Chinese Wild Woody Peonies I. New Taxa of Pceonia L. Sect. Moutan D.C. OP. Cit.14 (3), 237-240, 1994.
Pei, Yan-Long and Hong, De-yuan, Pseonia qiui-A new woody species of Pseonia from Hubei, China. Acta Phytotaxonomica Sinica, 33 (1), 91-93, 1995.
Fang, Wen-Pei, Notes on Chinese Peonies. Acta Phytotaxonomica Sinica, 7 (4), 297-323, 1958.
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Paeonia 3Section
Sub-section
Species
Delavayanae
Moutan
Vaginatae
P. delavayii
P. ludlowii
P. rockii
P. ostii
P. qiui
P. jishanensis
P. szechanensis
P. yananensis
Fig. 1 Phylogenetic tree of Pceonia section Moutan based on the studies of Hong1 and Hong2 et al. 1Tao;2De-yuan
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Paeonia 4