Fagopyrum longistylum M.Zhou & Y.Tang, 2021

Zhang, Kaixuan, Fan, Yu, Weng, Wenfeng, Tang, Yu & Zhou, Meiliang, 2021, Fagopyrum longistylum (Polygonaceae), a new species from Sichuan, China, Phytotaxa 482 (2), pp. 173-182 : 175-180

Fagopyrum longistylum M.Zhou & Y.Tang , sp. nov. ( Figs. 1–2 ).

Type: — CHINA. Sichuan province: Huili Co., alt ca. 1754–1780 m, 24 August 2019, Zhou & Tang s.n. (holotype CAAS2203 !) ( Fig. 1 ) .

Diagnosis: — Fagopyrum longistylum is similar to F. gracilipes , but it differs by its short-styled flower with long anther, and it is self-compatible (see Table 1).

Description: —Plants annual, herbaceous, 28–51 cm tall. Stems erect, usually branched basally, multiple branching from basal or lower nodes, branches usually horizontal or declining, some branches are long than stem. Stems terete, green, with longitudinal ribs, villose with short or long sparser hairs, all nodes leafy, nodes, internodes 0.5–3.1 cm. Leaves simple, alternate, papery, and broadly ovate, ovate, triangular, triangular-ovate or ovate-triangular (1.3–5.7 × 1.2–5.4 cm), apex acuminate, short acuminate, acute, base cordate, broad cordate, sometimes truncated or cardioid, adaxial blade surface deep green or green, abaxial blade surface green, sparsely pubescent on both surface, with 5 to 7 basal nerves and 5 to 8 pairs of lateral nerves, sunken adaxially, projecting abaxially, entire on margins, sometimes microwave, petioles 0.7–3.8 cm, green, white villous, adaxial finely grooved, villose with long erect hairs, abaxial convex, glabrous. Leaf sheaths membranous, obliquely, 3.5–7.0 mm long, with 6–11 green veins, densely or sparsely covered white long hairs, apex acuminate, long acuminate to caudate apically. Inflorescences racemose, sparse or dense, axillary or terminal, 1.7–7.0 cm long, rachis green, 4-edged, densely or sparsely covered with long and short villous; bracts funnel-shaped, oblique, 2.5–3.0 mm long, with 3–5 green veins, central vein projecting to an acuminate apex, florets 2 to 3 per bract, flowers are dense or lax on the upper or top of inflorescences rachis; pedicel linear, 1.5–3.5 mm, white, glabrous, with articulate conspicuously or inconspicuously at the apex, tepals 5 (2 smaller on the outside and 3 bigger on the inside), elliptic ovate and broadly ovoid elliptic, 1.8–2.0 × 1.2–1.6 mm, white, except greenish or pale greenish at base, apex obtuse or rounded, stamens 8, arranged in 2 whorls (5 in outer and 3 in inner), filaments 0.8–1.1 mm, white, anthers elliptic, 0.2–0.3 mm, white, ovary ovoid triangular pyramidal, 0.5–0.7 mm long, pale greenish or yellow greenish, styles 3, ca. 0.9–1.1mm, white, glabrous, stigma capitate, pistil longer than stamens, style is 0.6–0.8 mm higher than stamen ( Figs. 2A–B ). Achenes broadly ovoid triangular-pyramidal or ovoid triangular- pyramidal. The achenes are 1.7–2.2 mm long and 1.6–2.1 mm in diameter, obtuse apically, rounded basally, acute angle winged along achenes angles. The skin is brown and tan when ripe, surface smooth, lustrous, perianths closely enveloping the fruit and persistent, styles persistent, recurved ( Figs. 2C–D ).

Etymology:— The specific epithet refers to the short-styled flower with long anther.

Distribution and habitat:— Fagopyrum longistylum is known from wet sites in valleys and corn fields as a kind of wild weeds in Huili County (Liangshan State, Sichuan Province, China). It grows at elevations 1700–1800 m a.s.l.

Phenology:— Flowering time August–October; fruiting time September–November.

Conservation status:— More than 1000 individuals (three subpopulations) of Fagopyrum longistylum have been found in Huili County. On the basis of the IUCN Red List criteria ( IUCN 2019) and the available data, we can apply the criterion B1 (EOO is 3220 km 2) and assess the species as Endangered (EN).

Morphological remarks:— The flowers of Fagopyrum longistylum are dense or lax on the upper or top of inflorescences rachis, its stem is staying green. The most distinctive feature is its short-styled flower with long anther, and it is self-compatible. On the contrary F. gracilipes , the most similat species, hss homo-styled flower which is selfcompatible (see Fig. 2 and Table 1).

Chromosome number: — Fagopyrum longistylum is a diploid taxon with 2n=2x=16, whereas F. gracilipes is a tetraploid taxon with 4n=4x=32 ( Fig. 3 ).

Phylogenetic relationship based on the ITS and matK:— The lengths of ITS and matK of F. longistylum were consistent with our previous reports ( Zhou et al. 2014, Cheng et al. 2020).

ITS tree ( Fig. 4A ) shows that Fagopyrum longistylum is basal to the F. gracilipes group (including var. garcilipes and var. odontopterum ). On the other hand, in mat K tree ( Fig. 4B ), F. longistylum forms a low supported clade (bootsrap value = 19) with F. macrocarpum Ohsako et Ohnishi (1998: 85) , while F. gracilopes s.str. is sister to the group longistylum / macrocarpum . These results allowed to consider F. longistylum as a separate species.

As a whole, Fagopyrum longistylum is part, in the mat K tree ( Fig. 4B ), of large and well supported clade including F. urophyllum (bootstrap value = 94). which partially agrees with the urophyllum group sensu Zhou et al. (2014). These authors showed that this latter group (bootstrap value = 100 in Zhou et al. 2014: Fig. 2 ) includes also F. pugense , F. qiangcai , and F. leptopodum , whereas our results reveal that F. pugense and F. qiangcai (and F. caudatum , a species not studied by Zhou et al. 2014) forms a separated clade (bootstrap value = 98). In our tree, the clade pugense / qiangcai / caudatum is, in turn, sister to a low supported clade (bootstrap value = 54) including F. gilesii as basal to the clade including F. urophyllum . On the contrary, the cymosum group sensu Zhou et al. (2014) corresponds to our mat K tree where the group esculentum / cymosum / tataricum is highly supported (bootstrap value = 100). On the basis of nucleotide sequence of mat K gene, the results obtained in the present study, would led to consider up to four groups (instead of two groups by Zhou et al. 2014): cymosum clade (matching the cymosum group sensu Zhou et al. 2014), caudatum clade, urophyllum clade (partially corresponding to the urophyllum group sensu Zhou et al. 2014), and F. gilesii .

Concerning the ITS tree ( Fig. 4A ), the situation is quite different from that displyed in the mat K tree. F. urophyllum is included in a group (bootstrap value = 72) together with 4 species ( F. capillatum , F. macrocarpum , F. jinshaense , and F. qiangcai ), whereas F. cymosum is included in a large group (bootstrap value = 100) including all the other species studied by us. These two groups are different from both our mat K tree and that by Zhou et al. (2014).

Previous molecular studies of Fagopyrum (Ohnishi & Matsuoko 1996, Ohsako & Ohnishi 1998) showed the separation into two groups in agreement with Zhou et al. (2014).

To conclude, our results (sequence of mat K gene) was slightly different from the previous ones, excepting for the cymosum group, whereas our ITS tree shows a clear different configuration. We think that further studies are necessary especially to solve the urophyllum group sensu Zhou et al. (2014). Note that F. cymosum ( Yamane et al. 2003) and F. urophyllum ( Kawasaki & Ohnishi, 2006) display a considerable levels of intraspecific variation, which may influence the results in reconstructing phylogenetic trees. Besides, Baldwin et al. (1995) stated that the ITSs trees might be unstable for some of the plant interspecific classification. So, based on our results, mat K seems work better than ITSs in Fagopyrum genus. Recently, chloroplast genome was also proved as a powerful tool in Fagopyrum systematic research ( Cheng et al. 2020), cross analysis based on different molecular data may helpful to improve the authenticity of F. longistylum ’s evolutionary position in the future study.

Diagnostic keys:— We present a analytic key for the Fagopyrum species studied.

1. Perennial herbaceous tuberous plants.................................................................................................................................................2

1. Annual plants, not tuberous................................................................................................................................................................5

2. Plants more than 1 m height ...............................................................................................................................................................3

2. Plant up to 1 m height.........................................................................................................................................................................4

3. Leaf auriculate sagittate or ovate-oblong triangular, apex long acuminate or caudate; inflorescences in paniculate-spikes; achene <4 mm long...................................................................................................................................................................... F. urophyllum

3. Leaves are nearly the equilateral triangular, apex acuminate; inflorescences in corymbose cyme; achene ≥ 5 mm long................... ........................................................................................................................................................................................... F. cymosum

4. Stem and branches leafless; inflorescence terminal, heterostyle........................................................................................... F. statice

4. Stem and branches with leaves; inflorescence terminal or axillary, homostyle ....................................................... F. hailuogouense

5. Homostyle plants ................................................................................................................................................................................6

6. Plant more than 1 m tall; achene longer than 5 mm ...........................................................................................................................7

7. Perianth white or pinkish, achene smooth with angle acute...................................................................................... F. homotropicum

7. Perianth greenish, achene 3-grooved with angle obtuse .................................................................................................. F. tataricum

6. Plant less than 1 m tall; achene less than 3 mm long .........................................................................................................................8

8. Leaf surface with strong vesicular projections, margin corrugated with irregular corrugated crenation, crenation or small crenation; cymes cluster on the rachis........................................................................................................................................ F. crispatifolium

8. Leaf surface with fine lines or vesicular projections, margin entire or sinuolate; cymes are laxly or relatively laxly arranged on the rachis...................................................................................................................................................................................................9

9. Plant densely covered with hairs; the stem vigorous; leaf surface with fine lines or vesicular projections ........................................ ............................................................................................................................................................................................. F. pugense

9. Plant sparsely covered with hairs or nearly glabrous; stem thin, leaf surface smooth.....................................................................10

10. Plants creeping; achenes not winged............................................................................................................................... F. rubifolium

10. Plants erect, achenes winged ............................................................................................................................................................11

11. Achene not winged or, when occurring, the wings of young achene are green-white..................................................... F. gracilipes

11. Achene winged, the wings of young achene are red .................................................................................................. F. luojishanense

5. Heterostyle plants .............................................................................................................................................................................12

12. Heterostyly, only one type, and the pistil is longer than the stamens............................................................................ F. longistylum

12. Heterostyly, with two morphs (pistil longer or shorter than stamens) .............................................................................................13

13. Plant more than 80 cm tall................................................................................................................................................................14

14. Cultivated plants, inflorescence dense, up to 2–5 cm long; achenes longer than 5 mm, more than twice as its persistent perianthes ........................................................................................................................................................................................ F. esculentum

14. Wild plants inflorescence lax, 4–10 cm long; achene up to 3.5 mm long, slightly exceeding persistent perianthes.......................15

15. Stem erect, leaves ovate or triangular.............................................................................................................................. F. capillatum

15. Stem creeping, leaf sagittate............................................................................................................................................. F. caudatum

13. Plant up to 60 cm tall........................................................................................................................................................................16

16. Leaves cordate; inflorescence capitate ................................................................................................................................... F. gilesii

16. Leaves not cordate; inflorescence racemose, panicle or spike-like..................................................................................................17

17. Stem erect, leaves triangular or linear ..............................................................................................................................................18

18. Leaves linear with base hastate; inflorescence panicle ....................................................................................................... F. lineare

18. Leaves triangular with base truncate or sagittate .............................................................................................................................19

19. Leaves fleshy, smooth-lusterless ..................................................................................................................................... F. jinshaense

18. Leaves not fleshy, with rough surface ........................................................................................................................... F. leptopodum

17. Stem creeping or ascending, leaves triangular-sagittate, triangular-truncate or triangular-cordate .................................................20

20. Leaves triangular-sagittate, more or less fleshy, with gray-white patches on the surface; perianth more than 3.5 mm long .............. ............................................................................................................................................................................................ F. qiangcai

20. Leaves different, not fleshy, without gray-white patches on the surface; perianth less than 3 mm long.........................................21

21. Leaves triangular-truncate ....................................................................................................................................... F. gracilipedoides

21. Leaves triangular-cordate ........................................................................................................................................... F.macrocarpum

Other specimens:— CHINA. Sichuan province: Huili Co., alt ca. 1754–1780 m 28 September 2017, Zhou & Tang s.n. ( CAAS2201 !) , 20 September 2018, Tang s.n. ( CAAS2202 !) ; Huili Co., Guanhe Village , in a thick growth of maize fields, 1756 m a.s.l., 06 October 2016, Meiliang Zhou Ghassot 0299 ( CAAS1985 !) .

Figures

FIGURE 1. Fagopyrum longistylum. Drawning by Yunxiao Liu from the holotype (CAAS2203!).

FIGURE 2. Morphology of flower and seed of Fagopyrum longistylum. A–B) Morphology of short-styled flower with long anther, C–D) Morphology of immature and mature seed.

FIGURE 3. Cytogenetic analysis of Fagopyrum. A) Fagopyrum longistylum, B) Fagopyrum gracilipes.

FIGURE 4. Phylogenetic relationships of the 17 Fagopyrum species inferred from NJ analysis constructed by DNA sequence. A) Phylogenetic tree based on ITS sequence, B) Phylogenetic tree based on matK sequence.The number on the branch displayed the bootstrap support values.