Bot. Bull. Acad. Sin. (2002) 43: 193-201

Naruhashi et al. Chromosome numbers in Rubus (Rosaceae) of Taiwan

Chromosome numbers in Rubus (Rosaceae) of Taiwan

Naohiro Naruhashi1, Yoshikane Iwatsubo1, and Ching-I Peng2,*

1Department of Biology, Faculty of Science, Toyama University, Gofuku 3190, Toyama 930-8555, Japan

2Institute of Botany, Academia Sinica, Nankang, Taipei 115, Taiwan

(Received March 27, 2001; Accepted June 3, 2002)

Abstract. Taiwan is rich in species of Rubus (Rosaceae), with 37 species known from an island of only 36,000 km2. Rubus is classified into 12 subgenera worldwide, of which subgenera Chamaebatus (1 species), Malachobatus (16 species) and Idaeobatus (20 species) occur in Taiwan. In this paper, we document the chromosome numbers of all 37 species of Rubus in Taiwan and cite vouchers for all of them. First counts are here reported for 19 of the 37 species. Based on x = 7, Chamaebatus is hexaploid; Malachobatus consists of tetraploids, hexaploids and octoploids; and Idaeobatus is uniformly diploid in Taiwan. Our results indicate that all 20 species of subgenus Idaeobatus in Taiwan have speciated at the diploid level, while the five species of section Sozostili in subgenus Malachobatus have speciated at the tetraploid level.

Keywords: Chromosome number; Polyploidy; Rosaceae; Rubus; Taiwan.

Introduction

The genus Rubus consists of about 250 sexual species and innumerable apomictic taxa (Mabberley, 1997). Focke (1910, 1911, 1914) classified the world's Rubus into 12 subgenera: Chamaemorus (Focke) Focke, Cylactis (Focke) Focke, Dalibarda (Focke) Focke, Chamaebatus Focke, Comaropsis Focke, Orobatus Focke, Dalibardastrum Focke, Malachobatus (Focke) Focke, Anoplobatus Focke, Idaeobatus (Focke) Focke, Lampobatus Focke and Rubus (Eubatus Focke). Rubus is richly represented in Taiwan, an island of ca. 36,000 km2, with 37 species in 3 subgenera: subgen. Chamaebatus, 1 sp. (R. pectinellus Maxim.); subgen. Malachobatus, 16 spp. (R. buergeri Miq., R. formosensis Kuntze, R. hayata-koidzumii Naruh., R. hui Diels, R. kawakamii Hayata, R. laciniatostipulatus Hayata ex Koidz., R. lambertianus Ser., R. liui Yuen P. Yang et S.Y. Lu, R. morii Hayata, R. nagasawanus Koidz., R. pyrifolius Sm., R. pseudobuergeri Sasaki, R. rolfei S. Vidal., R. rufus Focke, R. swinhoei Hance, R. tephrodes Hance); and subgen. Idaeobatus, 20 spp. (R. cardotii Koidz., R. corchorifolius L. f., R. croceacanthus H. Lv., R. fraxinifolius Poir., R. glandulosopunctatus Hayata, R. incanus Sasaki, R. inopertus Focke, R. linearifoliolatus Hayata, R. mesogaeus Focke, R. parviaraliifolius Hayata, R. parvifolius L., R. pinfaensis H. Lv., et Vaniot, R. piptopetalus Hayata ex Koidz., R. pungens Cambess., R. rubroangustifolius Sasaki, R. subcrataegifolius (H. Lv. et Vaniot) H. Lv. et Vaniot, R. sumatranus Miq., R. tagallus Cham. et Schltdl., R. taitoensis Hayata, R. taiwanicolus Koidz.).

Taiwan undoubtedly has one of the richest assemblages of Rubus in the world. The species richness of Rubus in Taiwan is readily seen in the fact that Japan harbors only 36 species of Rubus, yet is about ten times larger than Taiwan. Fourteen of the 37 species of Rubus in Taiwan are endemic (38%). Of the rest, 10 (27%) also occur in Japan, 19 (51%) are also found on mainland China, and 8 (22%) are also found in the Philippines.

Floristic studies of Rubus in Taiwan have been undertaken by Liu and Yang (1969), Ying (1985), Hsieh and Ohashi (1993), and Lu and Ou (1994), yet many taxonomic problems remain for this difficult genus. Cytological information often leads to a better understanding of difficult plant groups. We therefore carried out a cytological survey of all 37 species of Rubus in Taiwan, excluding only the doubtful and ambiguous taxa.

Materials and Methods

Plants of the 37 species of Rubus used in this study were grown from seeds collected from 47 localities in Taiwan. All the living specimens grown from seeds are conserved in the experimental garden of Toyama University. Voucher specimens (Table 1) made from original populations are deposited at HAST. To observe the chromosomes, root tips collected from potted plants were pretreated in a 2 mM 8-hydroxyquinoline solution for one hr at room temperature and subsequently held at 5C for 15 hr. The root tips were then fixed in a mixture of glacial acetic acid and absolute ethyl alcohol (1 : 3) for one hr, soaked in 1N HCl for a few hours, macerated in 1N HCl at 60C for 11.5 min, and then immersed in tap water. Meristematic cells were stained in 1.5% lacto-propionic orcein, and the usual squashing method was applied for the examination of somatic chromosomes in the root tip cells.

*Corresponding author. E-mail: bopeng@sinica.edu.tw


Botanical Bulletin of Academia Sinica, Vol. 43, 2002


Naruhashi et al. Chromosome numbers in Rubus (Rosaceae) of Taiwan

mosome number (2n = 28) as R. tephroides; the two were treated as synonymous by Liu and Yang (1969) and Ying (1985). Again, R. hui and R. reflexus have the same chromosome number (2n = 42). Rubus hui was thought to be a variety of R. reflexus (Metcalf, 1932; Yu and Lu, 1985; Zhang, 1985) from mainland China. However, we agree with Liu and Yang (1969), Yang (1982), Ying (1985), Hsieh and Ohashi (1993), and Lu and Ou (1994), who treated them as distinct. Rubus pseudobuergeri, with 2n = 56, is morphologically very similar to both R. buergeri (2n = 56) in Taiwan and to R. hakonensis (2n = 56) in Japan. Rubus taitoensis, a diploid with 2n = 14, is morphologically similar to R. palmatus (2n = 14), R. grayanus (2n = 14) and R. ribisoideus (2n = 14) from Japan. In morphology, the Taiwanese R. incanus and R. parviaraliifolius (subgen. Idaeobatus, sect. Thyrsidaei), both diploid with 2n = 14, resemble the mainland Chinese diploids R. innominatus and R. adenophorus respectively.

Rubus in Taiwan is represented by three of the 12 recognized subgenera: Chamaebatus, Malachobatus and Idaeobatus. Species of Chamaebatus are known to be diploid (1 sp. in North America) and hexaploid (2 spp. in Asia). Our count of 2n = 42 for the Taiwanese R. pectinellus agrees with the hexaploid reports for the mainland Chinese and Japanese species.

As summarized by Thompson (1997), all species of subgenus Malachobatus are polyploid (4x, 6x, 8x, and 14x), except for certain previous ambiguous counts . Taiwanese plants of the subgenus were also 4x, 6x, and 8x. Section Sozostili of subgen. Malachobatus is vine-like in habit. All five Taiwanese members of this section have 2n = 28 chromosomes, which suggests that they speciated at the tetraploid level.

Our study shows that all ten species of Rubus subgen. Idaeobatus sect. Rosifolii (`Rosifolius group' in Taiwan, characterized by raspberry type fruits, pinnate leaves, a stalked receptacle and inflorescences with one to a few large flowers), including R. cardotii, R. croceacanthus, R. fraxinifolius, R. glandulosopunctatus, R. linearifoliolatus, R. piptopetalus, R. rubroangustifolius, R. sumatranus, R. tagallus and R. taiwanicolus, are consistently diploid. Members of the Japanese Rosifolius group for which chromosome numbers are known (R. commersonii, R. croceacanthus, R. hirsutus, R. illecebrosus, R. minusculus, R. okinawaensis, R. sumatranus) are also all diploid (Longley, 1924; Longley and Darrow, 1924; Iwatsubo and Naruhashi, 1992, 1993, 1996; Naruhashi and Iwatsubo, 1993), indicating that polyploidization may not have occurred in the Rosifolius group in eastern Asia.

Despite the fact that plants in subgenus Idaeobatus are the most variable among the twelve subgenera of Rubus, speciation has been mainly at the diploid level (triploids and tetraploids being exceptional). Our studies of all 20 species of subgenus Idaeobatus in Taiwan revealed 2n = 14, which substantiated other cytological reports.

Acknowledgements. We thank Jr-Jen Chen, Jeun-Ching Chen, Kuo-Fang Chung, Tsai-Wen Hsu, Wei-Hsin Hu, Ya-Yi Huang, Lu-Jane Juan, Yui-Ching Kao, Chia-Hua Lin and Shu-Hui Wu

Results and Discussion

Chromosome counts of Rubus in Taiwan examined in this study are as follows: 2n = 14 in R. cardotii, R. corchorifolius, R. croceacanthus, R. fraxinifolius, R. glandulosopunctatus, R. incanus, R. inopertus, R. linearifoliolatus, R. mesogaeus, R. parviaraliifolius, R. parvifolius, R. pinfaensis, R. piptopetalus, R. pungens, R. rubroangustifolius, R. subcrataegifolius, R. sumatranus, R. tagallus, R. taitoensis and R. taiwanicolus; 2n = 28 in R. formosensis, R. hayata-koidzumii, R. kawakamii, R. lambertianus, R. liui, R. morii, R. nagasawanus, R. rufus, R. swinhoei and R. tephrodes; 2n = 42 in R. hui, R. laciniatostipulatus, R. pectinellus, R. pyrifolius and R. rolfei; 2n = 56 in R. buergeri and R. pseudobuergeri (Table 2; Figures 1- 37). Rubus is believed to have a base number of x = 7 ( Darlington and Wylie, 1955; Fedorov, 1969) . Our data are consistent with that hypothesis. On this basis, the species of Taiwan include diploids, tetraploids, hexaploids and octoploids.

As shown in Table 2, chromosome counts are reported here for the first time for 19 species: R. cardotii, R. glandulosopunctatus, R. hui, R. incanus, R. kawakamii, R. laciniatostipulatus, R. linearifoliolatus, R. liui, R. nagasawanus, R. parviaraliifolius, R. piptopetalus, R. pseudobuergeri, R. pyrifolius, R. rolfei, R. rubroangustifolius, R. rufus, R. tagallus, R. taitoensis and R. taiwanicolus. Our chromosome counts for the rest of the Taiwanese species substantiate previous reports. The count of 2n = 28 in R. formosensis agrees with a previous report by Thompson and Zhao (1993), who studied the plant deposited at the National Clonal Germplasm Repository, USA. The count of 2n = 28 in R. morii, corresponds to the meiotic chromosome report of Hsu (1968). A count of 2n = 28 in R. tephrodes agrees with the count for a plant from Hortus Academia Sinica, Peking (Vaarama, 1954); 2n = 14 in R. inopertus coincides with counts by Vaarama (1954), Britten and Hull (1957) and Thompson and Zhao (1993); 2n = 14 in R. fraxinifolius and R. pinfaensis and 2n = 28 in R. swinhoei are consistent with the reports of Thompson (1995) for the same species, collected in Guizhou; 2n = 28 in R. hayata-koidzumii agrees with the count reported by Iwatsubo and Naruhashi (1993) for a plant growing in the Botanic Garden at the University of British Columbia, Canada. Our counts of other species _ R. buergeri (2n = 56), R. corchorifolius (2n = 14), R. croceacanthus (2n =14), R. lambertianus (2n = 28), R. mesogaeus (2n = 14), R. pectinellus (2n = 42), R. pungens (2n = 14), R. subcrataegifolius (2n = 14) and R. sumatranus (2n = 14) _ all are in accordance with counts reported for plants of the same species collected in Japan (Jinno, 1951a,b, 1958a,b; Iwatsubo and Naruhashi, 1992, 1993).

Many of the first chromosome counts are the same as those observed in close relatives. The chromosome count of 2n = 28 reported here for R. kawakamii (endemic to Taiwan) is the same as that reported for R. swinhoei of mainland China, Taiwan and the Ryukyus, as these two species are morphologically very similar. Similarly, Rubus nagasawanus, also endemic to Taiwan, has the same chro


Botanical Bulletin of Academia Sinica, Vol. 43, 2002


Naruhashi et al. Chromosome numbers in Rubus (Rosaceae) of Taiwan

Figures 1-10. Microphotographs of somatic metaphase chromosomes of Taiwanese Rubus. 1: R. pectinellus (2n = 42); 2: R. kawakamii (2n = 28); 3: R. lambertianus (2n = 28); 4: R. liui (2n = 28); 5: R. morii (2n = 28); 6: R. swinhoei (2n = 28); 7: R. nagasawanus (2n = 56); 8: R. tephrodes (2n = 28); 9: R. pyrifolius (2n = 42); 10: R. buergeri (2n = 56). Scale bar equals 10 m.


Botanical Bulletin of Academia Sinica, Vol. 43, 2002

Figures 11-22. Microphotographs of somatic metaphase chromosomes of Taiwanese Rubus (Cont.). 11: R. formosensis (2n = 28); 12: R. hayata-koidzumii (2n = 28); 13: R. hui (2n = 42); 14: R. laciniatostipulatus (2n = 42); 15: R. pseudobuergeri (2n = 56); 16: R. rolfei (2n = 42); 17: R. rufus (2n = 28); 18: R. corchorifolius (2n = 14); 19: R. subcrataegifolius (2n =14); 20: R. taitoensis (2n = 14); 21: R. cardotii (2n = 14); 22: R. croceacanthus (2n = 14). Scale bar equals 10 m.


Naruhashi et al. Chromosome numbers in Rubus (Rosaceae) of Taiwan

Figures 23-37. Microphotographs of somatic metaphase chromosomes of Taiwanese Rubus (Cont.). 23: R. fraxinifolius (2n = 14); 24: R. glandulosopunctatus (2n = 14); 25: R. linearifoliolus (2n = 14); 26: R. piptopetalus (2n = 14); 27: R. ruburoangustifolius (2n = 14); 28: R. sumatranus (2n = 14); 29: R. tagallus (2n = 14); 30: R. taiwanicolus (2n = 14); 31: R. inopertus (2n = 14); 32: R. pinfaensis (2n = 14); 33: R. pungens (2n = 14); 34: R. incanus (2n = 14); 35: R. parviaraliifolius (2n = 14); 36: R. mesogaeus (2n = 14); 37: R. parvifolius (2n = 14). Scale bar equals 10 m.


Botanical Bulletin of Academia Sinica, Vol. 43, 2002

for field assistance. This study was supported in part by research grants from Academia Sinica and the Council of Agriculture, Taiwan to Ching-I Peng.

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Naruhashi et al. Chromosome numbers in Rubus (Rosaceae) of Taiwan