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Cytogeography of Ixeris nakazonei (Asteraceae, Lactuceae) in the Ryukyu Archipelago of Japan and Taiwan

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Abstract

The cytogeographical structures of Ixeris nakazonei, a putative hybrid between I. debilis (6x) and I. repens (2x), were investigated in the Ryukyu Archipelago and Taiwan. In the Ryukyus, I. debilis occurs on Miyakojima Island of the southern Ryukyus and northward, while I. repens occurs on all islands except for Iriomotejima and Yonagunijima Islands. I. nakazonei, comprises six polyploid cytotypes, 3x, 4x, 5x, 6x, 7x and 8x, based on x=8. Four cytotypes from 3x to 6x occur in the central Ryukyus, while four cytotypes from 5x to 8x occur in the southern Ryukyus. The higher polyploids of I. nakazonei tend to be distributed in the more southerly area. Tetraploids of I. nakazonei always co-occur with I. debilis and I. repens, supporting the hybrid origin of this cytotype. Considering the chromosome number, octoploids, which predominate in the southern Ryukyus and Taiwan, may have derived directly from hybridization between I. debilis and I. repens. Odd-numbered polyploids of I. nakazonei, 3x, 5x and 7x, are relatively rare. Their chromosome numbers indicate that triploids and heptaploids are hybrids between the tetraploid of I. nakazonei and I. repens, and between the octoploid of I. nakazonei and I. debilis, respectively. Pentaploids of I. nakazonei in the central and southern Ryukyus are, respectively, hybrids between the tetraploid of I. nakazonei and I. debilis and between the octoploid of I. nakazonei and I. repens, indicating that pentaploids of I. nakazonei have at least two independent origins.

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Acknowledgments

We wish to express our sincere gratitude to Dr. Chih-Hua Tsou (Institute of Botany, Academia Sinica, Taiwan) for her kindness in providing us the plant materials from Taiwan. We also thank Tetsuya Kudaka (Takamori Orchid Museum, Takamori, Nagano, Japan) and Tomomi Yamashiro (Okinawa Environmental Analysis Center, Ginowan, Okinawa, Japan) for collecting plants from some islands in the Ryukyus. This study was supported in part by the Grant-in-Aid for Scientific Research (C) (no. 14540648) and Grant-in-Aid for Young Scientists (B) (no. 15770061) from the Japan Society for the Promotion of Science.

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Authors and Affiliations

  1. Laboratory of Ecology and Systematics, Faculty of Science, University of the Ryukyus, 1 Senbaru, Nishihara, Okinawa 903-0213, Japan

    Tetsuo Denda & Masatsugu Yokota

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  1. Tetsuo Denda
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  2. Masatsugu Yokota
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Correspondence to Tetsuo Denda.

Appendix

Appendix

Localities and notations

Collection localities of Ixeris nakazonei and I. debilis are listed. Previous chromosome counts on the Okinawa Islands (Denda and Yokota 1999) are pooled in this list. Abbreviations of collection localities used throughout this paper are indicated. Abbreviations of inland localities are marked with asterisks. Numbers in parentheses indicate the number of individuals examined. Presence (+) or absence (−) of I. repens in coastal dune localities are also indicated. At least one specimen for each locality is deposited in the herbarium of the University of the Ryukyus (ryu).

Northern Ryukyus

Tanegashima Island (Kagoshima prefecture): TAN-1, 2 km north of Okawabana, Nishino-omote, I. debilis (5), I. repens (+); TAN-2, Hamada-hama, Minamitane, I. debilis (5), I. repens (−); TAN-3*, Nakanoshimo, Minamitane, I. debilis (3). Yakushima Island (Kagoshima prefecture): YAK-1, Tashiro-kaigan, Yaku, I. debilis (5), I. repens (−); YAK-2, Sangono-hama, Yaku, I. debilis (5), I. repens (−).

Central Ryukyus

Amamioshima Island (Kagoshima prefecture): AMA-1, Tomori-kaigan, Kasari, I. debilis (6), I. repens (+); AMA-2, Tsuchi-hama, Kasari, I. debilis (6), I. repens (+); AMA-3, Yoan-kaigan, Kasari, I. nakazonei 4x (2), 6x (1), I. debilis (2), I. repens (+); AMA-4, Tehiro-kaigan, Kasari, I. nakazonei 6x (3), I. debilis (1), I. repens (+); AMA-5, Kominato, Naze, I. nakazonei 6x (4), I. debilis (2), I. repens (+); AMA-6, Katoku-kaigan, Setouchi, I. debilis (5), I. repens (−); AMA-7, Isu, Setouchi, I. debilis (3), I. repens (−); AMA-8, Yadori-hama, Setouchi, I. debilis (3), I. repens (−); AMA-9, Sokaru, Setouchi, I. debilis (2), I. repens (−); AMA-10, Seisui-hama, Setouchi, I. debilis (6), I. repens (−); AMA-11, Kuninao-kaigan, Yamato, I. nakazonei 3x (1), 4x (6), 5x (4), 6x (5), I. debilis (2), I. repens (+); AMA-12, Ohama-kaigan, Naze, I. nakazonei 3x (3), 4x (7), 5x (1), 6x (1), I. debilis (4), I. repens (+); AMA-13, Sakihara-kaigan, Kasari, I. debilis (6), I. repens (−); AMA-14, Maehida-kaigan, Kasari, I. debilis (5), I. repens (−). Tokunoshima Island (Kagoshima prefecture): TOK-1, Yonama-hama, Amagi, I. nakazonei 4x (6), 6x (10), I. debilis (4), I. repens (+); TOK-2, Naga-hama, Tokunoshima, I. nakazonei 6x (2), I. debilis (6), I. repens (+); TOK-3, San-kaigan, Tokunoshima, I. debilis (5), I. repens (+); TOK-4, Hanatoku-kaigan, Tokunoshima, I. nakazonei 6x (3), I. debilis 6x (1), I. repens (+). Okinoerabujima Island (Kagoshima prefecture): ERA-1, north of Wadomari Port, Wadomari, I. nakazonei 4x (11), 6x (5), I. debilis (2), I. repens (+); ERA-2, Okidomari-kaigan, China, I. nakazonei 4x (3), 5x (1), 6x (2), I. debilis (5), I. repens (+). Okinawajima Island (Okinawa prefecture): OKI-1, Hedo, Kunigami, I. nakazonei 4x (6), 6x (4), I. debilis (3), I. repens (+); OKI-2, Oku, Kunigami, I. nakazonei 4x (2), 5x (3), 6x (2), I. debilis 6x (3), I. repens (+); OKI-3, Sokei, Ginoza, I. nakazonei 6x (4), I. debilis (6), I. repens (−); OKI-6, Hyakuna-kaigan, Tamagusuku, I. nakazonei 6x (3), I. debilis (7), I. repens (−); OKI-7, Komesu-kaigan, Itoman, I. nakazonei 4x (23), 5x (1), 6x (5), I. debilis (10), I. repens (+); OKI-8, Nashiro beach, Itoman, I. debilis (3), I. repens (−); OKI-9, Yokuta beach, Yomitan, I. debilis (2), I. repens (−); OKI-10, Tanchame-hama, Onna, I. nakazonei 6x (4), I. debilis (6), I. repens (−); OKI-13, Yonamine, Nakijin, I. nakazonei 4x (3), 6x (3), I. debilis (7), I. repens (+); OKI-14, Hentona, Kunigami, I. nakazonei 4x (15), 6x (10), I. debilis (5), I. repens (+). Iejima Island (Okinawa prefecture): OKI-11, Kawahira, Ie, I. debilis (9), I. repens (−); OKI-12, Ie beach, Ie, I. nakazonei 4x (10), 6x (2), I. debilis (6), I. repens (+). Ikeijima Island (Okinawa prefecture): OKI-4, Ikei, Yonashiro, I. nakazonei 4x (3), 5x (1), 6x (2), I. debilis (3), I. repens (+). Hamahigajima Island (Okinawa prefecture): OKI-5, Higa, Katsuren, I. nakazonei 6x (4), I. debilis (7), I. repens (−). Kumejima Island (Okinawa prefecture): KUM-1, Zenda-hama, Kumejima, I. nakazonei 4x (7), 6x (2), I. debilis (3), I. repens (+); KUM-2, Shimajiri, Kumejima, I. nakazonei 6x (3), I. debilis (1), I. repens (+); KUM-3, Ahra-hama, Kumejima, I. debilis (3), I. repens (+); KUM-4, Shinri-bama, Kumejima, I. debilis (8), I. repens (+); KUM-5, Mifuga, Kumejima, I. debilis (3), I. repens (−).

Southern Ryukyus and Taiwan

Miyakojima Island (Okinawa prefecture): MIY-1, western edge of Nishihennazaki, Hirara, I. nakazonei 6x (2), 7x (3), I. debilis (3), I. repens (−); MIY-2, Nishino-hama, Hirara, I. debilis (6), I. repens (−); MIY-4, south-eastern edge of Ikema-ohashi bridge, Hirara, I. debilis (2), I. repens (−); MIY-5, 5 km north of Bise-oganzaki, Hirara, I. debilis (5), I. repens (−); MIY-6, northwest of Maja Fishing Port, Hirara, I. debilis (5), I. repens (−); MIY-7, north of Takano Fishing Port, Hirara, I. nakazonei 6x (2), I. debilis (3), I. repens (−); MIY-8, Shirakawa-hama, Gusukube, I. nakazonei 6x (4), I. debilis (1), I. repens (−); MIY-9, Urasoko-kaigan, Gusukube, I. nakazonei 6x (4), I. debilis (2), I. repens (−); MIY-10, Aragusuku-kaigan, Gusukube, I. debilis (11), I. repens (−); MIY-11*, Aragusuku, Gusukube, I. debilis (5); MIY-12, Yoshino-kaigan, Gusukube, I. nakazonei 6x (2), I. debilis (3), I. repens (−); MIY-13, Higashihennazaki, Gusukube, I. nakazonei 7x (1), 8x (7), I. repens (−); MIY-14, Maiba beach, Gusukube, I. nakazonei 8x (6), I. repens (−); MIY-15*, Nanamata-kaigan, Gusukube, I. debilis (5); MIY-16, 1.5 km southwest from Iriewan inlet, Ueno, I. nakazonei 8x (3), I. repens (−); MIY-17*, Sobamine, Ueno, I. debilis (4); MIY-18, Hakuai beach, Ueno, I. nakazonei 8x (3), I. repens (−); MIY-21, Maibama, Shimoji, I. nakazonei 8x (10), I. repens (−); MIY-22, Yonaha-mae-hama, Shimoji, I. nakazonei 8x (5), I. repens (−); MIY-23, western edge of Nishihamazaki, Shimoji, I. nakazonei 8x (3), I. repens (−); MIY-24*, Painagama beach, Hirara, I. debilis (8); MIY-25, Sunayama beach, Hirara, I. nakazonei 8x (15), I. repens (−). Ikemajima Island (Okinawa prefecture): MIY-3, Ikema, Hirara, I. nakazonei 6x (10), 7x (1), 8x (3), I. debilis (4), I. repens (−). Kurimajima Island (Okinawa prefecture): MIY-19, north of Kurima Fishing Port, Shimoji, I. nakazonei 5x (1), 8x (11), I. repens (+); MIY-20, Nagama-hama, Shimoji, I. nakazonei 8x (4), I. repens (−). Irabujima Island (Okinawa prefecture): MIY-26, Nagayama-no-hama, Irabu, I. nakazonei 8x (3), I. repens (no data). Taramajima Island (Okinawa prefecture): TAR-1, north of Futenma Fishing Port, Tarama, I. nakazonei 8x (2), I. repens (no data); TAR-2, between Painuji-tsuburi and Paitsukifutsu-tsuburi, Tarama, I. nakazonei 8x (2), I. repens (no data). Ishigakijima Island (Okinawa prefecture): ISH-1, Hiranono-hama, Ishigaki, I. nakazonei 8x (5), I. repens (−); ISH-2, Akaishi, Ishigaki, I. nakazonei 8x (12), I. repens (+); ISH-3, north of Tamatorizaki, Ishigaki, I. nakazonei 5x (1), 8x (9), I. repens (+); ISH-4, Natano-hama, Ishigaki, I. nakazonei 8x (8), I. repens (−); ISH-5, Inoda-hama, Inoda, Ishigaki, I. nakazonei 5x (5), 8x (3), I. repens (+); ISH-6, Mouth of Fanangawa river, Ishigaki, I. nakazonei 8x (7), I. repens (−); ISH-7, Mouth of Torogawa river, Ishigaki, I. nakazonei 8x (3), I. repens (−); ISH-8, southeast of Mt. Karadake, Ishigaki, I. nakazonei 8x (4), I. repens (+); ISH-9, south of the mouth of Todorokigawa river, Ishigaki, I. nakazonei 8x (7), I. repens (−); ISH-10, 0.8 km south of ISH-14, Ishigaki, I. nakazonei 8x (4), I. repens (−); ISH-11, Miyara-kaigan, Ishigaki, I. nakazonei 8x (3), I. repens (−); ISH-12, Ohama-kaigan, Ishigaki, I. nakazonei 8x (5), I. repens (−); ISH-13*, Tonoshiro, Ishigaki, I. nakazonei 8x (3); ISH-14*, Funakura beach, Ishigaki 8x (3); ISH-15, Fusaki beach, Arakawa, Ishigaki, I. nakazonei 8x (8), I. repens (−); ISH-16, 1.5 km northeast of ISH-15, Ishigaki, I. nakazonei 8x (3), I. repens (−); ISH-17, south-western edge of Nagura-ohashi bridge, Ishigaki, I. nakazonei 8x (3), I. repens (−); ISH-18, 2 km north of Nagura-ohashi bridge, Ishigaki, I. nakazonei 8x (5), I. repens (−); ISH-19, west of Akasaki, Ishigaki, I. nakazonei 8x (4), I. repens (−); ISH-20, Oganzaki beach, Ishigaki, I. nakazonei 8x (5), I. repens (−); ISH-21, Sukuji beach, Ishigaki, I. nakazonei 8x (5), I. repens (−); ISH-22, Pigekage-hama, Ishigaki, I. nakazonei 8x (4), I. repens (−); ISH-23, Yonehara camping site, Ishigaki, I. nakazonei 8x (4), I. repens (−); ISH-24, southern edge of Urasoko bay, Ishigaki, I. nakazonei 8x (3), I. repens (−); ISH-25, Idona beach, Ishigaki, I. nakazonei 8x (4), I. repens (−); ISH-26, 1 km E of Nosokozaki, Ishigaki, I. nakazonei 8x (6), I. repens (−); ISH-27, 2 km E of Nosoko-ishizaki, Ishigaki, I. nakazonei 8x (5), I. repens (−); ISH-28, Mouth of Yoshinogawa river, Ishigaki, I. nakazonei 8x (4), I. repens (−); ISH-29, Mouth of Hirakubogawa river, Ishigaki, I. nakazonei 8x (5), I. repens (−). Iriomotejima Island (Okinawa prefecture): IRI-1, Mouth of Mitaragawa river, Taketomi, I. nakazonei 8x (3), I. repens (−); IRI-2, Mouth of Yonadagawa river, Taketomi, I. nakazonei 8x (4), I. repens (−); IRI-3*, Hoshidate, Taketomi, I. nakazonei 8x (8); IRI-4, Tsukiga-hama, Taketomi, I. nakazonei 8x (5), I. repens (−); IRI-5, Hoshizuna-kaigan, Taketomi, I. nakazonei 8x (3), I. repens (−); IRI-6, Nakano, Taketomi, I. nakazonei 8x (4), I. repens (−); IRI-7, Mouth of Yashigawa river, Taketomi, I. nakazonei 8x (5), I. repens (−); IRI-8, Mouth of Nadaragawa river, Taketomi, I. nakazonei 8x (5), I. repens (−); IRI-9, Mouth of Kuragawa river, Taketomi, I. nakazonei 8x (3), I. repens (−); IRI-10, 0.7 km E of Akabanari Island, Taketomi, I. nakazonei 8x (3), I. repens (−); IRI-11, Mouth of Horagawa river, Taketomi, I. nakazonei 8x (4), I. repens (−); IRI-12, Mouth of Honeragawa river, Taketomi, I. nakazonei 8x (3), I. repens (−); IRI-13, 2 km south of Nubaruzaki, Taketomi, I. nakazonei 8x (5), I. repens (−); IRI-14, Nakamazaki, Taketomi, I. nakazonei 8x (4), I. repens (−); IRI-15, Mare, Taketomi, I. nakazonei 8x (5), I. repens (−); IRI-16, Haemida-kaigan, Taketomi, I. nakazonei 8x (14), I. repens (−); IRI-17, Bora-hama, Taketomi, I. nakazonei 8x (6), I. repens (−); IRI-18, Bahari-hama, Taketomi, I. nakazonei 8x (5), I. repens (−). Yonagunijima Island (Okinawa prefecture): YON-1, Nanta-hama, Yonaguni, I. nakazonei 8x (3), I. repens (−); YON-2*, Sonai, Yonaguni, I. nakazonei 8x (6); YON-3, Ubudoumai-hama, Yonaguni, I. nakazonei 8x (4), I. repens (−); YON-4, Higawa-hama, Yonaguni, I. nakazonei 8x (8), I. repens (−); YON-5, Kataburu-hama, Yonaguni, I. nakazonei 8x (4), I. repens (−); YON-6*, Irizaki, Yonaguni, I. nakazonei 8x (3); YON-7, Nama-hama, Yonaguni, I. nakazonei 8x (8), I. repens (−); YON-8, Dannu-hama, Yonaguni, I. nakazonei 8x (4), I. repens (−). Taiwan: TAI-1, Jinshan Shiang, Taipei, I. nakazonei 8x (2), I. repens (no data); TAI- 2, Wanli Shiang, Taipei, I. nakazonei 8x (4), I. repens (no data).

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Denda, T., Yokota, M. Cytogeography of Ixeris nakazonei (Asteraceae, Lactuceae) in the Ryukyu Archipelago of Japan and Taiwan. J Plant Res 117, 3–11 (2004). https://doi.org/10.1007/s10265-003-0124-4

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