Bot. Mag. Tokyo 80: 345-352 (September 25, 1967)

Biosystematic Studies on Maianthemum (Liliaceae-Polygonatae) I. Somatic Chromosome Number and Morphology*

by Shoichi KAWANO* *, Masaaki IHARA* * *, Masatomo SUZUKI* * * * and Hugh H. ILTIS* * °** *

Received May 1, 1967

Abstract

A number o different clones of all three Maianthemum species (bifolium, dilatatum, canadense) from various sources were karyologically examined. All the material examined possessed 2n=36 chromosomes of basically the same or essentially very similar constitution, K (n) =18 = 2V (1V1+ 1V2) -{-8J -}-8v. Polyploidiza- tion is not apparent and did not play a role in Maianthemum speciation.

Maianthemum is a small genus belonging to the Liliaceae-Polygonatae that consists of only three species, i. e., M. bifolium (Lindl.) F. W. Schmidt of Eurasia, M. dilatatum (Wood) Nels. et Macbr. of the Pacific Northwest regions, and M. canadense Desf. of North America. Earlier investigations of Maianthemum karyology include those of Stenar1, Love and Love2>, Sato3>, Therman4>, Sokolovskaya and Strelkova5> and Sorsa6~ on M. bifolium ; Matsuura and Suto7>, Palmgren8~, Sokolovskaya9>, Sato3>, and Therman4> on M. dilatatum var. dilatatum and Sokolovskaya9~ on M. dilatatum var. vegetior Komarov ; and, Therman4> and Kawano10> on M. canadense. Although various chromosome numbers were reported by these authors for Maianthemum (Table 1), detailed karyotypic analyses were not made except for the brief descriptions of Therman4> for the three species mentioned above. As the first in a series of biosystematic studies of Maianthemum, the present study attempts a more detailed determination of the karyome of the genus, and, furthermore, re-evaluates the previ- ous cytological work of various authors.

Material and Methods

A number of different clones of M. bifolium, M. dilatatum, and M. canadense, from various sources were examined karyologically (Table 1). The clones of M. canadense were collected by Iltis and Kawano, cultivated in the Botany Department greenhouses in Madison, and studied by the first author in 1964. All the Japanese clones were collected in their native habitats in 1965, and cultivated for several months in Tokyo.

* Partially supported by NSF grant No. 21908, to Hugh H. Iltis. ** Present Address: Biology Laboratory , Seiwa Women's College, Kisaradzu, Chiba. *** Present Address : Department of General Biology, Vanderbilt University, Nashville, Tenn., U. S. A. **** Biology Laboratory , College of Education, Ibaraki University, Mito, Ibaraki. ***** Department of Botany , University of Wisconsin, Madison, Wisc., U. S. A. 346 Bot. Mag. Tokyo Vol. 80 September, 1967 KAWANO, S., et at. 347

Fig. 1. Somatic chromosomes of Maianthemum. A, M. bifolium from Fuji-Aokigahara, Yamanashi (2n=36) ; B, M. bifolium from Fuji, Motosu, Yamanashi (2n=36) ; C, M. dilatatum from Nikko, Karikomi, Tochigi (2n=36) ; D, M. canadense from Trout Lake Point, Vilas County, Wisconsin.

Fig. 2. Somatic chromosomes of M. bifolium (2n=36, from Fu ji-Aokigahara) . 348 Bot. Mag. Tokyo Vol. 80

The cytological preparations were made by using modifications of the oxy- quinoline-aceto-orcein squash method (Kawan&0~). Voucher specimens are preserved in the Herbarium of the Department of Botany, University of Tokyo (TI) and in the Herbarium of the University of Wisconsin, Madison (WIS).

Fig. 3. Somatic chromosomes of M. dilataturn (2n=36, from Fu ji-Aokigahara) .

Fig. 4. Somatic chromosomes of M. canadense (2n=36, from Trout Lake Point, Vilas County, Wisconsin). September, 1967 KAWANO, S., et al. 349 350 Bot. Mag. Tokyo Vol.. 80

Observations

1. Maianthemum bifolium (Lindl.) F. W. Schmidt (Figs. 1-A and B, and 2 ; Table 2). All the clones examined proved to possess 2n=36 chromosomes. A closer exami- nation of the karyotype of this species reveals that of the eighteen pairs in the chromosome complement., two pairs, one large and one medium-sized pair (Nos. 1 and 2), are metacentric, eight pairs are J-shaped with the constriction submedian or sub- terminal (Nos. 3-10), one pair (No. 10) of which is nucleolar chromosomes. The remaining eight pairs are contrastingly small, of which four pairs (Nos. 13, 14, 15, 16) are evidently metacentric but the remaining four pairs (Nos. 11, 12, 17, 18) possess a submedian or subterminal constriction. The karyotype of this species may roughly be expressed as follows : K(2n) = 36=4V(2V1+2V2)+16J+16v(possibly 8j+8v) (cf. Table 2).

2. Maianthemum dilatatum (Wood) Nels. et Macbr. (Figs. 1-C and 3 ; Table 2). This is an extraordinary polymorphic species in gross morphology, and various forms covering its variations were collected and examined karyologically. The results of our morphological analyses will be presented in greater detail in a forth- coming paper, but here mention should at least be made as to materials from the Island of Yakushima, Japan, and the Island of Ullung, Korea. The plants from Yakushima are an extremely dwarfish form, their leaves only 1.2-2.5 cm long and 0.8 -1.7 cm wide; in contrast , those from the Island of Ullung, Korea, represent a giant form 20-38 cm tall, with leaves from 8 to 19 cm long and 6 to 17 cm wide (our own observations in TI, TNS, and KYO, and Dr. Y. N. Lee, personal communication). All the material examined proved to be 2n=36. The plants from Ullung, Korea, were cytologically examined by Dr. Y. N. Lee, and turned out to have 2n=36 chromosomes (personal communication). The chromosome complement of this species is illustrated in Fig. 3. The basic karyotype composition is identical with that of M. bifolium described above, as follows : K(2n)=36=4V(2V1+2V2)+16J+16v(possibly 8j+8v) (cf. Table 2).

3. Maianthemum canadense Desf. (Figs. 1-D and 4). Several clones collected from Trout Lake Point, Vilas County, Wisconsin, were karyologically studied. All examined had 2n=36 chromosomes. The basic karyome constitution is essentially the same as those of M. bifolium and M. dilatatum des- cribed above, as follows : K(2n)=36=4V(2V1+2V2)+16J+16v(8j+8v).

Discussion

It was found in the present study that all plants of M. bifolium, M. dilatatum, and M. canadense that were examined possess 2n=36 chromosomes, although various chromosome numbers as described in Table 1 had been reported previously by various authors. The results obtained indicate that 2n=36 is a most prevalent number in the genus Maianthemum, and the counts such as 2n=30 or 42 made by Stenarl>, 2n=42 by Love and Love2> for M. bifolium, and 2n=32 by Matsuura and Suto7~ for M. dilatatum now are open to question. A possibility should not, however, be excluded here that they may have examined the plants belonging to entirely different groups. We are now inclined to believe the base number of the genus Maianthemum to be definitely n=18. Triploid plants with 2n=54 of M. bifolium, September, 1967 KAWANO, S., et at. 351

M. dilatatum var. dilatatum and var. vegetior were reported by Sato3~ and Sokolov- skaya8~. In the present investigation no triploid plants were detected in either M. dilatatum or in M. bifolium, though a number of clones of various origins were ex- amined. The detailed analyses of the chromosome complement of the three Maianthemum species demonstrate that all three possess an identical or at least basically very similar somatic karyome, i. e., K(n)=18=2V(1V1+ 1V2)+8J+8v(possibly 4j +4v). This fact suggests that speciation in the genus Maianthemum has taken place without any obvious material modification in karyotype appearance. However, it is not well under- stood yet as to how many pairs in the chromosome complements of three Maianthemum species are homologous each other. The mode discovered in this genus very much resembles that found in Smilacina, a genus referred to the Polygonatae as one that is most closely related to Maianthemum (Kawano and Iltisll12) ; Kawano" ; cf. Kuro- sawal4>). The basic karyome of Smilacina is known to be K(n)=18=3V+7J+8v throughout the genus, notwithstanding the fact that enormous diversities in gross morphology can be observed in the species referred to this genus (Kawano and Iltis, 1. c.; Kurosawa, 1. c.; Kawano, unpubl.). Therman4~ previously pointed out the occur rence of very characteristic satellite chromosomes in the plants belonging to the tribe Polygonatae, including Maianthemum, and Smilacina. We likewise observed a pair of nucleolar chromosomes in all three Maianthemum species (cf. Figs. 2, 3 and 4, No. 10), verifying Therman's observations. Some other problems relating to variation and evolution of the genus Maianthemum will be discussed in forthcoming papers (Kawano, Ihara and Suzuki15"6)).

Acknowledgements

The present studies were greatly facilitated with the aid and encouragement of many of our colleagues : we wish to thank Mr. Junta Sugiyama for his constant help in field work during the last two years, Dr. Y. N. Lee for his exceptional courtesy of giving us permission to use his unpublished data as to M. dilatatum from Isl. Ullung, Korea, and Dr. T. Yamazaki, Mrs. Kazue Ihara, and Mr. H. Ohashi for col- lecting material that was placed at our disposal.

References

1) Stenar, H., Ark. Bot. 26: 1-20 (1935). 1963, No. 15, Ser. Biol.: 38 (1963). 2) Love, A., and Love, D., Bot. Notis. 1942: 10) Kawano, S., Bot. Mag. Tokyo 78: 36 19 (1942). (1965). 3) Sato, D., Jap. Jour. Bot. 12: 57 (1942). 11) and Iltis, H. H., Chromosoma 4) Therman, E., Amer, Jour. Bot. 43: 134 (Ben.) 14: 296 (1963). (1956). 12) - and Iltis, 11.11., Cytologia 31: 5) Sokolovskaya, A. P., and Strelkova, O. S., 12 (1966). Bot. Zhur. SSSR. 45: 369 (1960). 13) Bot. Mag. Tokyo 78: 261 6) Sorsa, V., Ann. Acad. Fenn. Ser. A, IV. (1965). Biol. 58: 1 (1962). 14) Kurosawa, S., in The Flora of Eastern 7) Matsuura, H., and Suto, T., Jour. Fac. Himalaya, 658 (The University of Tokyo Sci. Hokkaido Univ. 5 : 33 (1935). Press, 1966). 8) Palmgren, O., Bot. Notis. 1943: 348 (1943). 15) Kawano, S., Ihara, M., and Suzuki, M., 9) Sokolovskaya, A. P., Vest Leningrad Univ. Biosystematic studies on Maianthemum 352 Bot. Mag. Tokyo Vol. 80

(Liliaceae-Polygonatae) II. Geography 16) , and ibid. III. and ecological life history (MS in pre- Variations in gross morphology (MS in paration). preparation).

摘 要

河 野 昭 一*・ 井 原 正 昭**・ 鈴 木 昌 友***・HughH.11tis****: マ イ ズ ル ソ ウ 属 の 進 化 生 物 学 的 研 究1.染 色 体 数 お よ び 核 型

マ イ ズ ル ソ ウ 属(Mα 如 窺 加 祝 π殉 は 僅 か3種,4伽'α 伽 鵬 酵o伽 祝 お よ びcα πα4飢 詔 よ り な る ユ リ科 の 小 さ な 属 で あ る.こ れ ら3種 の 染 色 体 数,核 型 を 各 地 よ り集 め た 材 料 で 調 べ た.い ず れ も2n=36の 体 細 胞 染 色 体 を も っ こ と が 明 ら か と な っ た ・ 醇o伽 祝 お よ び4π α'α伽 祝 よ り2n=30,32,42な ど の 染 色 体 数 が Stenar1),L6veandL6ve2),MatsuuraandSuto7)ら に よ り報 告 さ れ て い る が 確 認 で き な か った.ま た Sato,Sokolovskayaら に よ り3倍 体,2n=54が4伽'α 伽 初,酵oZ伽 祝 で 報 告 さ れ て い る が,発 見 で き な か っ た ・ こ れ ら3種 の 基 本 的 核 型 構 成 は 非 常 に 類 似 し て お り,K(n)=18=2V(1V1+1V2)+8J+8v(4」+4v) で 表 わ す こ とが で き る.3種 問 相 互 の 類 縁 関 係 は 未 だ は っ き り と し な い.(*清 和 女 子 短 期 大 学 生 物 学 研 究 室 ・**ヴ ア ン ダ ー ビ ル ト大 学 生 物 学 教 室 ・***茨 城 大 学 教 育 学 部 理 科 教 育 研 究 室 ・****ウ イ ス コ ン シ ン 大 学 植 物 学 教 室)