Bot. Bull. Acad. Sin. (1996) 37(4): 281-285

Hsieh and Chaw — Osteomeles of Taiwan

Osteomeles schwerinae C. K. Schneid. (Rosaceae): a new record for the flora of Taiwan

Chang-Fu Hsieh¹ and Shu-Miaw Chaw^2,3

¹Department of Botany, National Taiwan University, Taipei, Taiwan 106, Republic of China

²Institute of Botany, Academia Sinica, Taipei, Taiwan 115, Republic of China

(Received April 25, 1996; Accepted September 17, 1996)

Abstract. Osteomeles schwerinae C. K. Schneid. is reported for the first time from Taiwan. A key and several useful features that differentiate the present species from its only congener in Taiwan, O. anthyllidifolia var. subrotunda, are presented. A taxonomic treatment of the two species in Taiwan and a line-drawing which illustrates the present new record are provided.

Keywords: Osteomeles; O. anthyllidifolia var. subrotunda; O. schwerinae; Rosaceae; Taxonomy; Taiwan.

On a field trip to Nantou County made by the senior author in 1993, an unknown taxon assignable to the genus Osteomeles Lindl. (Liu & Hsieh 267) was collected and sent to the junior author for identification. It turned out that this collection represents O. schwerinae C. K. Schneid., a species not previously reported in the literature relating to the flora of Taiwan. Osteomeles schwerinae might be indigenous to Taiwan but avoided collection until recently because the collection locale (Figure 1) is not easily accessible. The population is large with more than 300 individuals, and the species is commonly found at higher elevations in the provinces Gansu, Guizhou, Sichuan, and Yunnan of mainland China.

Osteomeles, characterized by pinnately compound leaves and stony pomes, is a small genus of about five species, native to eastern Asia and Polynesia (Yu and Ku 1974; Liu and Su, 1977; Yu et al., 1985). Three species were previously described from central and southern mainland China, of which O. anthyllidifolia (Sm.) Lindl. var. subrotunda (C. Koch) Masamune (Ohashi, 1993) was the only species previously known to occur also in Taiwan. After a preliminary survey of the genus Osteomeles based on specimens from HAST, TAI, and KYO, we found that the identities and nomenclatures within the genus are highly confused and a comprehensive revisional study is definitely demanded. The distribution ranges of the genus are wide; the number of the leaflets per leaf and their shapes, sizes, and pubescent states within an individual species or even among the same collection number are highly variable; and the herbarium specimens available are geographically incomplete, especially those from mainland China and Polynesia. It is, therefore, our intention to do a thorough monographic study. At this time, we present only a taxonomical treatment of the two indigenous species in Taiwan, based on specimens available from HAST,

KYO, and TAI. The nomenclature, descriptions, and useful diagnostic characters of the two species are given as follows. In addition, the collection place and illustration of the new record are provided.

Key to the Osteomeles Species in Taiwan

1a. Stem prostrate; leaves with (7-)11_15 leaflets; leaflets coriaceous, obovate to obovate-oblong, ca. 6_10 mm long, apex rounded or slightly emarginate, abaxial surface moderately to densely pilose; calyx tube and lobe densely hirtellous 1. O. anthyllidifolia var. subrotunda

1b. Stem erect; leaves with 19_31 leaflets; leaflet chartaceous to subcoriaceous when mature, elliptic to obovate, ca. 3_5 mm long, apex abruptly acuminate, abaxial surface sparsely hirtellous; calyx tube and lobe sparsely hirtellous. 2. O. schwerinae

1. Osteomeles anthyllidifolia (Sm.) Lindl. var. subrotunda (C. Koch) Masam. in Ann. Rep. Taihoku Bot. Gard. 2: 124. 1932; Ohashi in Fl. Taiwan 2nd ed. Vol. 3, p. 84.

O. subrotunda C. Koch in Miq., Ann. Bot. Lugd.-Bat. 1: 250. 1864.

O. anthyllidifolia f. subrotunda (C. Koch) Koidz. in J. Coll. Sci. Univ. Tokyo 34(2): 44. 1913.

O. anthyllidifolia auct. non Lindl.: Hayata, Icon. Pl. Form. 3: 101. 1913; Li, Woody Fl. Taiwan 276. 1963; Liu & Su in Fl. Taiwan 3: 71. 1977.

Prostrate shrub, much-branched; young branches polished. Leaves odd-pinnate, 2_3.5 cm long, 1.5_2.0 cm wide; leaflets (7-) 11_15, coriaceous, obovate to obovate-oblong, 6_10 mm long, 4_6 mm wide, rounded or obscurely to slightly emarginate at apex, rounded to obtuse at base, margins entire and revolute, upper surface rugose

³Corresponding author. Fax: 886-02-7827954. E-mail: bochaw@ ccvax.sinica.edu.tw.

Botanical Bulletin of Academia Sinica, Vol. 37, 1996

Figure 1. Detailed collection locale (solid triangle) of Osteomeles schwerinae in Taiwan

and sparsely pilose, then glabrate, lower surface moderately to densely pilose; petioles 5_8 mm long; stipules subulate, 3_4 mm long, caducous. Inflorescences cymose, 4_5-flowered; petals white, broadly ovate. Fruits globose, about 5 mm in diameter, crowned with persistent sepals.

Specimens examined. TAITUNG HSIEH: Lanyu, Yehyu to Langtao, Hsu 9482 (TAI), Leu et al. 2176 (HAST); without further locality, Sasaki s.n. in 1942 (TAI).

Notes. The cited collections were made on coral rocks near the sea. Koch originally described O. subrotunda on the basis of Bürger's collection (n. v.) from the islands in the south of Japan proper. He also noted that no flowers or fruits were available for study. Masamune (1932) treated Koch's species as a variety of O. anthyllidifolia. Earlier, Hemsley (1900) had reported that O. subrotunda also occurs in Guandong Province on mainland China. Obviously, Yu and Ku (1974) adopted Hemsley's view that O. subrotunda is specifically distinct from the O. anthyllidifolia and extended the definition of the species to include also the taxa from the Ryukyus, the Bonin Islands, and the Philippines. We have examined a number of collections from the former two islands and found that

their style bases are villous rather than glabrous as illustrated by Hemsley in his plate 2644 and mentioned by Yu and Ku in their key and specific description. Unfortunately, no materials from Guandong Province assignable to O. subrotunda are available for further scrutiny, and the species from the Bonin Islands are especially variable. Again, we urge a critical revisional study of the genus.

2. Osteomeles schwerinae C. K. Schneid. Ill. Handb. Laubh. 1: 763. t. 430 m, 431 o-r. 1906 & In Fedde, Repert. Spec. Nov. Regni Veg. 3: 222. 1906; E. Wils. in Sarg. Pl. Wilson. 1: 184. 1912; Hand.-Mazz. Symb. Sin. 7: 461. 1933; Iconogr. Commoph. Sinic. 2: 207. t. 2143. 1972; Fl. Reipub. Popul. Sin. tomus 36: 208, f. 24: 1-5. 1974; Yu et al. in Woody Fl. China 990. 1985.

O. chinensis Lingelsh. & Borza in Fedde, Repert. Spec. Nov. Regni Veg. 13: 386. 1914.

O. anthyllidifolia auct. non Lindl.: Franch. Pl. Delavay. 227. 1890; Hook. f. In Curtis's Bot. Mag. 120: t. 7354. 1894. Figures 1 and 2

Hsieh and Chaw — Osteomeles of Taiwan

Figure 2. Osteomeles schwerinae (from Liu & Hsieh 267). A, habit; B, portion of leaf (adaxial view), showing the winged rachis and the unequal-sided leaflets at their bases; C, longitudinal section of flower; D, a petal; E, mature fruit.

Botanical Bulletin of Academia Sinica, Vol. 37, 1996

Erect, deciduous to semi-evergreen shrub, up to 4 m tall; young branchlets slender, aggregated, terete, sparsely hirtellous and glabrescent; stipules linear to lanceolate, ca. 4 mm long, caducous but the base persistent; leaves odd-pinnate, ca. 3 cm long, 1 cm wide, clustered at the lateral short branches, the rachis winged, sulcate above; petioles slender, ca. 5 mm long, densely sericeous; leaflets 19_31, subsessile, elliptic to oblong-obovate (except the topmost which are usually angular-obovate), 3_5 mm long, 2_3 mm wide, sparsely hirtellous on the lower part of adaxial midrib and sparsely hirtellous on abaxial surface, obtuse and mucronulate at apex, unequal-sided at base; flowers often 3 (-5) forming a corymbose inflorescence at lateral short branch, each flower subtended by two subulate bracteoles, flowers sometimes solitary, the peduncle and the pedicels densely sericeous, the latter 3_7 mm long; calyx tube and lobes sparsely sericeous outside, glabrous inside, the lobes 5, lanceolate, ca. 2.5 × 1 mm, gradually acuminate at apex; petals white, obovate to elliptic, ca. 5 × 3 mm; stamens 15_21, the filaments 3_5 mm long; gynoecium of 5 pistils, the style linear, ca. 4 mm long, villose basally, connate and adnate to hypanthium; ovary 5-celled; mature peduncle 1_1.5 cm long; fruit ovoid to globose, sparsely sericeous at tip, ca. 5_8 mm in diam, crowned by the persistent calyx (which reflexed), filaments, and styles, pyrenes 5.

Specimens examined. NANTOU HSIEN: at the 6K mark of the Tanta Logging Way, Liu & Hsieh 267 (HAST, TAI).

Notes. The voucher specimen was collected in the upper-stream area of the Tsoshui River, Nantou Hsien, Taiwan (Figure 1). The population of O. schwerinae is situated on a southwest-facing slope at an elevation of approximately 1,000 meters. The inclination of the slope was more than 45 degrees. Rock types in the habitat were mainly argillite and slate complex of Lushan Formation of the Miocene Age (Ho, 1944). Apparently, the soils were prominently of slate pale colluvial type. The mean annual rainfall and temperature were estimated as 2,300 mm and 17.4°C, respectively (based on data by the Central Weather Bureau, 1985_1989).

The whole area, covered by a wide spectrum of shrubs and young trees, appeared to be a slope that naturally re-vegetated following a slide occurrence. The population

of O. schwerinae was composed of more than three hundred individuals up to 4 meters high. Associated plants, mainly pioneer and light-demanding, consisted of Cyclobalanopsis glauca, Pistacia chinensis, Liquidambar formosana, Zelkova serrata, Spiraea tarokoensis, Glochidion rubrum, Pittosporum illicioides, Morus australis and Acer albopurpurascens. Flowering of O. schwerinae occurred in April, and fruiting lasted to the end of May. Both flowers and fruits were abundant in 1992 and 1993.

Acknowledgments. We thank Zhen-Yu Li (PE) for the verification of our voucher collection and the administrators of HAST, KYO, and TAI who kindly made their loan available to us. We also gratefully acknowledge the critical reading of Dr. D. Boufford and one anonymous reviewer. This work is supported in part by an Academia Sinica grant to SMC.

Literature Cited

Central Weather Bureau. 1985_1989. Annual Report of Climatological Data. Central Weather Bureau, Taiwan.

Hemsley, W. B. 1900. Osteomeles subrotunda C. Koch. In Hooker's Icones Plantarum. Vol. 27, plate 2644. Dulau & Co., London

Ho, C. S. 1944. Explanatory Text of the Geological Map of Taiwan. Central Geological Survey Institute, Taiwan, Taipei, pp. 61_63.

Li, H.-L. 1963. Woody Flora of Taiwan. Livinston Publ. Co., Narberth, Pennsylvania.

Liu, T.-S. and H.-J. Su. 1977. Rosaceae. In H.-L. Li, T.-S. Liu, T.-C. Huang, T. Koyama, and C. E. Devol (eds.), Flora of Taiwan, Vol. 4, Epoch Publ. Co., Taipei, pp. 551_616.

Masamune, G. 1932. Genera Plantarum Formosanarum. I. Saururaceae - Rosaceae. Ann. Rep. Taihoku Bot. Gard. 1: 124.

Ohashi, H. 1993. Rosaceae. In T.C. Huang et al. (eds.), Flora of Taiwan. 2nd ed. Vol. 3: 84. Department of Botany, National Taiwan University, Taipei.

Yu, T.-T. and T.-C. Ku. 1974. In T.-T. Yu et al. Flora Reipublicae Popularis Sinicae. Vol. 36, pp. 207_210.

Yu, T.-T., C.-L. Li, S.-C. Nie, L.-T. Lu, T.-C. Ku, C. Ma, and C.-S. Sung. 1985. Rosaceae. In W. C. Cheng, (ed.), Sylva Sinica, Chinese Forestry Publ. House, Beijing, pp. 990_991. (in Chinese).