Hong De-Yuan

Notes on Paeonia decomposita Hand.-Mazz.

Kew Bulletin Vol 52 (4) 957-963

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Extract from the publication (abbrevated)

Summary. Paeonia decomposita, regarded as endangered in the China Plant Red Data Book, has been found to be rather common in a restricted area of NW Sichuan. Two subspecies with distinct geographical distributions can be distinguished. One of these, P. decomposita subsp. rotundiloba is described as new and illustrated here.

Introduction

Paeonia decomposita Hand.-Mazz. is a most attractive woody peony, but until the type was examined recently, (Hong et al. 1996), it has been known as P. szechuanica W.P. Fang., and was included in the China Plant Red Data Book (Hong 1992) under the latter name. It was regarded as endangered because it was known from only three localilities in a small area of the Daduhe Valley. The relationships and identity of some other collections from the adjacent Mingjiang Valley have remained uncertain until now. Recent expeditions have allowed much more detailed study and sampling of populations in both areas. The results are reported here.

Results

Plants conspecific with the collections from the Mingjiang Valley were found in seven additional localities in the valley. Further collections were also made of the taxon from the Daduhe Valley. The two differ in the number of carpels and in leaflet shape. Sixty-two individuals from six populations in the Daduhe Valley were examined. One individual had four carpels while all the rest had five. Carpel number in the Mingjiang Valley populations varied from two to five (Table 1).

Leaflets from the two populations differ in size, shape, and lobing (Fig. 1). The Mingjiang populations have wider and shorter leaflets which are acute or obtuse at the apex, rather than acuminate as in the Daduhe plants. The ratios between leaflet and lobe length and width are almost discontinuous between the two populations (Fig. 2). In view of this, subspecific rank seems most appropriate for the two populations.

Paeonia decomposita Hand.-Mazz. in Acta Horti Gothob. 13: 39 (1939); D. Y. Hong, K. Y. Pan & Y. L. Pei in Taxon 45: 68 (1995). Type: China, NW Sichuan, Chosodjo, H. Smith 4641 (UPS, holotype).

Paeonia szechuanica W.P.. Fang in Acta Phytotax. Sin. 7: 315 (1958); K. Y. Pan in W. T. Wang (ed.). Fl. Reip. Pop. Sin. 27: 45, fig.4 (1979); D. Y. Hong in L. K. Fu (ed.): China Plant Red Data Book 1: 536 - 537 (1992). Type: China, NW Sichuan. Barkam, Li Xin (H. Lee 70316) (SZ, holotype; PE, isotype).

The species is unique among woody peonies in being glabrous throughout, in the leaves being 3 or rarely 4 times compound, with (29 -)33-63 leaflets, and in the disc enveloping half to two-thirds of the carpels (neither completely enveloping them as in the P. suffruticosa complex, nor enveloping only the base as in the P. delavayi complex).

The species is listed as endangered by Hong (1992); at the time the species was known from only three localities. However, our recent studies show that it is neither endangered nor rare, although it is restricted in distribution. The only threats to it are collection of root-bark for medicine, and habitat destruction.

Table.1. Distriltution of carpel number in four populations of Paeonia decomposita in the Mingjiang Valley, Sichuan, China.

Key to subspecies of Paeonia decomposita

subsp. decomposita (Fig. 1B).

Specimens examined: ----------

chromsome Number. 2n=10 (Hong et al. 1988)

Distribution. China: Daduhe Valley of NW Sichuan.

Habitat. Thickets and young secondary forests with (Cotoneaster soongaricus, Rhamnus sp. Quercus sp., Rosa willmottiae, Berberis polyantha, Cupressus chengiana, Lespedeza sp. etc., and on cliffs and rocks in sparse conifer forests; 2050 - 3100 m.

subsp. rotundiloba D. Y. Hong subsp. nov. a subspecie typica carpellis 2 - 5 (plerumque 3 vel 4), foliolis latioribus apice acutis vel leviter obtusis lobis brevioribus latioribusque differt. Typus: China, NW Sichuan, Lixian. Hong De-yuan, Luo Yi-bo & He Yong-hua H95033 (holotypus PE, isotypi (GH/A, K, MO, US). Fig 1A.

specimens examined. ----------

chromsome Number. 2n=10 Voucher: NW Sichuan, Maoxian, 5 May 1989, Qiu Jun-Zhuan 8901 (PE)

Distribution. China: Mingjiang Valley of NW Sichuan.

Habitat. Well-developed thickets, young secondary forests, or sparse Cupressus chengiana forests, where it is usually found on rocks. Often associated with Quercus spp., Rhamnus sp., Rosa mulibracteata, Cotoneaster soongariscus, Ribes sp., Ostryopsis davidii, Cotinus coggygria, Spiraea sp., etc. 2050-3100m. Isolated from the typical subspecies by the Qionlai Range (4000m) (Map 1)