Discussion
Sagittaria aginashi is remarkably peculiar because of the following characteristics: obtuse apex of basal lobes of sagittate leaves (
Fig. 2F), small numerous tubercles at the base within the vagina of petioles (
Fig. 2G), and no stolon (
Fig. 2I) (
Makino, 1901;
Kadono, 2014). However, almost all specimens identified as
S. aginashi did not have these key characters (T. Shiga, pers. obs.). Based on the Korean literature (e.g.,
Shin et al., 1997;
Choi, 2000;
Lee, 2003;
Kim and Choi, 2007;
Lee, 2007),
S. aginashi probably have not been identified clearly in Korea. In fact, the photographs of
S. aginashi in
Lee (2003) and
Lee (2007) are actually those of
S. trifolia.
Sagittaria aginashi has sometimes been treated taxonomically as the same as
S. trifolia (
Keener, 2005). The ITS sequences distinguish the species of the genus
Sagittaria and demonstrate that the sequences of
S. aginashi are clearly different from those of
S. trifolia (
Table 1). We conclude that
S. aginashi is rare, but clearly is distributed in Korea. We confirm that the ITS sequences of
S. aginashi are uniform in the current preliminary genetic study (
Tables 1,
2). To clarify the historical biogeography of this species, further genetic research is required based on samples from the entire distributional range using multiple polymorphic markers.
In Korea,
S. aginashi often has not been distinguished taxonomically with narrow-leaved
S. trifolia and is believed to be a relatively common species. Although we have not surveyed on habitats of Jeju Island, we show that the number of populations of
S. aginashi is quite low and that population sizes are extremely small in Korea (
Fig. 1,
Table 1). The lowland populations of the species may have become extinct mainly by human disturbance. The total number of flowering individuals in the three localities is <50, whereas that of immature individuals is <2,000 (
Table 1). The effective population sizes of Korean
S. aginashi may be quite small. The present status of
S. aginashi indicates that this species should be listed as an endangered species in the Korean Red List and requires urgent protection by conservation programs including the extensive surveys on its additional natural habitats. Because
S. aginashi reproduces asexually by numerous tubercles, intra-population genetic diversity may be at quite a low level. An evaluation of the genetic diversity using polymorphic markers, such as microsatellite markers, is needed to formulate an appropriate conservation program.
Furthermore,
S. aginashi (sequence type A) is closely related to the Chinese endemic species
S. tengtsungensis (sequence type B) and
S. lichuanensis (sequence type C) (
Table 2). The genetic diversity and genetic relationships among Chinese endemic
Sagittaria species including
S. tengtsungensis,
S. lichuanensis, and
S. potamogetifolia have been investigated well using multiple genetic markers (
Du et al., 1998;
Keener, 2005;
Chen et al., 2012;
Liao et al., 2016).
Liao et al. (2016) revealed that
S. tengtsungensis,
S. lichuanensis,
S. potamogetifolia, and
S. pygmaea form a monophyletic group and that
S. lichuanensis, consisting of many sequence types, is a genetically polymorphic species. These species, except for
S. pygmaea, are distinguishable from other
Sagittaria species by forming numerous tubercles at the base of the petiole (
Chen et al., 1984;
Chen, 1989;
Wang and Chen, 1996;
Wang et al., 2010). To clarify the phylogenetic relationships and taxonomic status of
S. aginashi among these Chinese endemic species, phylogenetic studies based on the DNA sequences of multiple loci and detailed morphological studies are needed.
Taxonomic treatment
Sagittaria aginashi Makino, Bot. Mag. (Tokyo) 15: 104, 1901;
S. sagittifolia L. var.
aginashi Makino, Bot. Mag. (Tokyo) 6: 49, 1892. —TYPE: Japan, Honshu, Prov. Iwaki (Fukushima Prefecture), Maniwa near Sakamoto in Watarigori, 17 Aug 1890,
Makino s.n. [Lectotype designated by
Tanaka (2005): MAK77766!] (
Fig. 2).
Description: Perennial, glabrous herbs, 30–70 cm tall (29–150 cm —morphological variation ranges including Japanese plants indicated in parentheses); rhizomes erect, thick, densely rooting; stolon absent; corm absent; numerous tubercles on the inside of the sheath at base; tubercles 0.4–0.8 (0.3–1.0) cm long, 0.2–0.4 (0.2–0.7) cm wide. Leaves radical, fasciculate, erect, strongly nervate, petiolate; petioles 23–46 (23–83) cm long; blades lanceolate to linear or sagittate; leaves from spring to early summer and in juvenile plants lanceolate to linear without basal (lateral) lobes; basal lobes of sagittate leaves 7–12 (5–25) cm long; remainder of blade (middle lobe) 6–12 (4–20) cm long, 0.6–4.5 (0.6–9.8) cm wide; apex of basal lobes obtuse; latex seeping from scratches. Scapes erect, emersed, 30–71 (29–152) cm, taller than the leaves; inflorescence usually paniculate, in 4 to many whorls of (2 or) 3 flowers, lowest whorl rarely branched; female flowers on lowest 1 (or 2) whorls; bracteoles free or connate toward the base, 0.5–1.0 cm long. Flowers unisexual, the female flower below and male one above. Sepals 3, ovate to oblong, obtuse, entire, light green shaded with red, persistent, ca. 5–8 mm long. Petals 3, suborbicular, 8–13 mm long. Stamens 23 (18–24); anthers yellow. Ovaries numerous, apocarpous, crowded in a spherical head. Achenes 15–17 mm long, narrowly winged, with a short beak. Flower and fruit Jul–Aug. 2
n = 22 (
Harada, 1956).
Korean name: Bo-pul.
Distribution and habitat: Japan (Hokkaido, Tohoku, Kanto, Chubu, Kinki, Chugoku, Shikoku, Kyushu) and Korea (Gyeonggi, Gyeongnam, Jeju) (
Fig. 1). In ponds, lakes, marshes, moors, and paddy fields.
Specimens examined: KOREA. Gyeonggi: Taereung, 8 Sep 1940, H-D. Jang 1135, 1142 (OSA227615, 227616); Ansansi, Sangnok-gu, 17 Sep 2009, E. S. Jeon 91244 (KH1269331). Ulsan-si: Ulju-gun, Somdong-myeon, Mujechi-neup, 17 Aug 2006, S. H. Park & G. H. Nam 61296 (KH1120514–1120516); 1 Sep 2016, K. Tsubota et al. 44, 45 (Niigata University = NGU4126, 4491); Buk-gu, Maegok-dong, Doltimi-neup, 1 Sep 2016, K. Tsubota et al. 46–52 (NGU4127, 4492–4497). Gyeongnam: Yangsan-si, Wondong-myeon, Dae-ri, 2 Sep 2016, K. Tsubota et al. 53–57 (NGU4128, 4498–4501). Jeju: Seogwipo-si, Namwon-eup, 23 Aug 2001, Y. J. Kang s.n. (KH1058229, 1058866, 1058867).
JAPAN. Hokkaido Pref.: Tomakomai-shi, 14 Aug 2016, K. Tsubota et al. 34–38 (NGU4124, 4484–4487). Aomori Pref.: Higashidori-mura, 5 Aug 2016, S. Nemoto 3369 (NGU4123); Goshogawara-shi, 14 Sep 2016, K. Tsubota & A. Matsumoto 70–72 (NGU4132, 4512, 4513). Akita Pref.: Mitane-cho, 15 Sep 2016, K. Tsubota 73–77 (NGU4133, 4514–4517). Iwate Pref.: Takizawa-shi, 13 Sep 2016, K. Tsubota & T. Shiga 65–69, 83 (NGU4131, 4507–4511); Isawa-cho, 1 Sep 1985, Y. Kadono 770 (Kobe University). Miyagi Pref.: Osaki-shi, 12 Sep 2016, K. Tsubota & T. Shiga 62–64 (NGU4130, 4505, 4506). Fukushima Pref.: Kitashiobara-mura, 27 Sep 2016, K. Tsubota & K. Shutoh 81, 82 (NGU4135, 4520); Tamakawamura, 1 Aug 2016, K. Tsubota et al. 27–29 (NGU4121, 4479, 4480); Iwaki-shi, 1 Aug 2016, K. Tsubota et al. 24–26 (NGU4122, 4477, 4478). Tochigi Pref.: Nasukarasuyama-shi, 29 Jul 2016, K. Tsubota et al. 17–22 (NGU4118–4120, 4474–4476); Hongo-mura, 15 Aug 1953, K. Ogawa s.n. (OSA). Niigata Pref.: Sado-shi, 16 Jul 2016, K. Tsubota 5-9 (NGU4117, 4470–4473); Gosen-shi, 25 May 2016, K. Tsubota 1–3 (NGU4466–4468), 7 Sep 2016, K. Tsubota 58–61 (NGU4129, 4502, 4504); Sanjo-shi, 25 May 2016, K. Tsubota 4 (NGU4469); Joetsu-shi, 25 Sep 2016, K. Tsubota et al. 78– 80 (NGU4134, 4518, 4519), 9 Sep 2013, T. Shiga 7518 (NGU297, 298, 300), 24 Sep 2008, T. Shiga & S. Takebayashi 6388 (OSA239165). Nagano Pref.: Hakuba-mura, 19 Aug 1975, K. Seto 21626, 21627 (OSA28426, 28427). Aichi Pref.: Toyoake-shi, 8 Sep 1968, S. Hamashima s.n. (OSA185419). Shiga Pref.: Koka-cho, 29 Aug 2001, K. Seto 55464 (OSA161116); Makino-cho, 30 Aug 1966, T. Kodama 10864 (OSA3472). Kyoto Pref.: Miyazu-shi, 14 Jun 2001, S. Fujii et al. 8624 (OSA206370), 15 Sep 1995, K. Seto 44829 (OSA101400–101402). Nara Pref.: 9 Aug 1948, M. Hutoh 1084 (OSA198806); Nara-shi, 26 Sep 1965, K. Seto 14928 (OSA1743), 9 Jun 1963, K. Seto 12293 (OSA198809); Tenrishi, 3 Sep 1999, N. Morimoto 4482 (OSA244026), 26 Sep 1997, K. Seto 48119 (OSA104917); Kitakatsuragi-gun, 1 Aug 1951, T. Kodama s.n. (OSA198808); Soni-mura, 24 Aug 2011, N. Morimoto 11924 (OSA188309); Tsukigase-mura, 14 Jun 2003, K. Seto 59208 (OSA165643). Osaka Pref.: Izumi-shi, 8 Sep 1985, C. Shimizu s.n. (OSA204544), 13 Oct 1983, C. Shimizu s.n. (OSA204561); Sakai-shi, 20 Aug 1933, O. Kishimoto 1083 (OSA); Shijonawate-shi, 26 Aug 1999, M. Tanaka s.n. (OSA148585), Aug 1931, Kira s.n. (OSA204041); Shijonawate-cho, 24 Sep 1963, K. Seto 12974 (OSA); 24 Sep 1963, M. Kuwashima s.n. (OSA); Senpoku-gun, 22 Sep 1960, K. Seto 10407 (OSA58620). Mie Pref.: Shimagahara-mura, 23 Sep 1999, K. Seto 51559 (OSA156483); Yokkaichi-shi, 2 Aug 1951, N. Yasui s.n. (OSA); 13 Aug 1950, N. Yasui s.n. (OSA); Ueno-shi, 21 Aug 2003, K. Seto 59676 (OSA), 3 Oct 1999, S. Fujii 7182 (OSA201287); Nabari-shi, 7 Aug 1992, K. Seto 38848–38851 (OSA93981–93984). Hyogo Pref.: Kumobemura, 1 Jul 1928, S. Yonezawa s.n. (OSA180470); Takarazukashi, 13 Sep 1998, K. Seto 49823 (OSA152575); 14 Sep 1997, K. Seto 48062 (OSA150060). Wakayama Pref.: Wakayamashi, 19 Sep 2000, S. Fujii 8278 (OSA203436); Ono-shi, 17 May 2016, Y. Kadono s.n. (NGU4481–4483), 30 Sep 1998, T. Fujii 10508 (OSA210073); Kato-shi, 11 Oct 2014, T. Shiga 8299 (NGU2775). Hiroshima Pref.: Higashihiroshima-shi, 22 Sep 2013, T. Shiga 7594 (NGU299). Kagawa Pref.: Mannoucho, 19 Aug 2016, T. Shiga et al. s.n. (NGU4125, 4488–4490). Kumamoto Pref.: Arao-shi, 10 Aug 1934, H. Arao 692 (Herb. of Kumamoto Pref. Matsubase Store House = NB, 21-000681), 17 Oct 1933, H. Arao 694, 695 (NB21-000683, 000684), 18 Sep 1932, H. Arao 696, 697 (NB21-000685, 000686); Minamioguni-machi, 18 Jul 1993, T. Maeda s.n. (NB21- 114265), H. Nobukuni 4416 (NB21-006292); Ashikita, 1953, M. Maeda s.n. (NB21-050593); Kuma-mura, 16 Aug 1917, S. Tokunaga s.n. (NB21-050597); Aso-shi, 30 Sep 1906, H. Kozuma s.n. (NB21-050594).