-RESEARCH-

[Systematics and Evolution of Aquatic Plants]

• Alisma (Alismataceae) Ito et al. (in prep.)
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• Q: Do hybridization and polyploidy play important roles in the evolution of Alisma?
• A: Yes.
• Sagittaria (Alismataceae) Ito et al. (2020)
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• Sagittaria is a genus of ca. 40 species in the aquatic plant family Alismataceae with a nearly global distribution, and a center of diversity in the New World. Two thirds of the known species are native to the Americas, while only a few species are distributed in Africa, Asia and Europe. A previous biogeographic analysis of the genus suggested an African origin for the genus with subsequent dispersal to North America and then to East Asia. Here we expanded the taxon sampling with a focus on the New World taxa and applied species delimitation and biogeographic analyses to revise the knowledge of the phylogeny and evolution of the genus. We obtained largely similar topologies from the chloroplast DNA and nuclear DNA (ITS) data sets. The 74 accessions sampled for our analyses were delimited into 29 species and several cryptic taxa were revealed in widely distributed species. Biogeographic analysis supported basal diversification in South America and subsequent colonization to North America and Asia.
• Monochoria (Pontederiaceae) Ito et al. (in prep.)
• Elatine (Elatinaceae) Ito et al. (in prep.)
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• Q: Can dispersal be roled out in the biogeography of Elatine as Cai et al. (2016) concluded?
• A: No. Dispersal plays an important role in the evolution of Elatine gratioloides from Australasia.
• Ottelia (Hydrocharitaceae) Ito et al. (2019)
• Eriocaulon (Eriocaulaceae) Larridon et al. (2019)
• Callitriche (Plantaginaceae) Ito et al. (2017)
• Najas (Hydrocharitaceae) Ito et al. (2017) | Ito et al. (2018)
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• Q: An infrasubgeneric classification of four sections in Najas subgen. Cauinia?
• A: Section Euvaginatae was resolved as non-monophyletic; a classification of two sections is proposed.
• A: A revised key to sections of Najas subgen. Caulinia is provided.
• A: Najas subgenus Caulinia section Caulinia (Tzvelev) Yu Ito, stat. nov. - Caulinia sect. Caulinia Tzvel., Novosti Sist. Vyssh. Rast. 13: 18. (1976); Tzvel., Fl. Evropeiskoi Chasti SSSR 4: 201. (1979) - Najas subgen. Caulinia “unranked” Euvaginatae Magn., Beitr. Kenntn. Najas 57. (1870) - Najas subgen. Caulinia section Nudae Rendl., Trans. Linn. Soc. London, Bot. 399 (1899), syn. nov. (Lectotype here designated: Najas graminea Del.) - Najas subgen. Caulinia section Spathaceae Rendl., Trans. Linn. Soc. London, Bot. 398 (1899), syn. nov. (Lectotype here designated: Najas indica (Willd.) Cham.)
• Limosella (Scrophulariaceae) Ito et al. (2017)
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• Q: If/which dispersal play important roles in shaping the worldwide but discontinuous distribution of Limosella?
• A: Relatively recent continental dispersal from southern Africa to the north into Eurasia via tropical Africa.
• A: Historical trans-oceanic dispersal from Eurasia to Australia.
• A: Current latitudinal trans-oceanic dispersal in the Southern Hemisphere.
• Althenia (Potamogetonaceae) Ito et al. (2016)
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• Q: Afro-Eurasian Althenia seems to be closely related to Australasian Lepilaena?
• A: Lepilaena is non-monophyletic and Althenia is nested within the group.
• A: Synapomorphies and a revised key to species of Althenia s.l. are provided.
• A: Althenia F.Petit,, Ann. Sci. Observ. 1: 451. (1829) = Lepilaena J. Drumm. ex Harv., Hooker's J. Bot. Kew Gard. Misc. 7: 57 (1855), syn. nov.
• A: Althenia marina (E.L. Robertson) Yu Ito, comb. nov. ≡ Lepilaena marina E.L. Robertson, H. B. S. Womersley, Mar. Benth. Fl. South Australia 1: 80. (1984) = Lepilaena patentifolia E.L. Robertson, Fl. S.Austral. 4: 1736. (1986), syn. nov.
• A: Its disjunct distribution most likely originated in Australasia (Miocene), followed by dispersal to Afro-Eurasia.
• Ruppia (Ruppiaceae) Ito et al. (2010) | Ito et al. (2013) | Ito et al. (2015) | Ito et al. (2017)
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• Q: The cosmopolitan genus Ruppia with one species? two? many more?
• A: Four species and one species complex comprising of nine entities.
• A: Ruppia bicarpa Yu Ito et Muasya, sp. nov.---TYPE: SOUTH AFRICA. Western Cape: Cape Town Dist., Jakkalsfontein Private Nature Reserve, 33°24'09"S, 18°15'07"E, Brackish pool, 12 Nov 2014, Y. Ito & A.M. Muasya YI01979 (holotype: BOL!; isotype: TNS!)
• Q: Polyploidy event(s) in Ruppia occur once? twise? many times?
• A: Tetraploidy evolves at least twise ("Tetraploid_α" and "Tetraploid_γ").
• A: "Tetraploid_β" is best explained by chloroplast capture between "Tetraploid_α" and "Tetraploid_γ".
• Q: Morphologically ambiguous collections to be explained by hybridization?
• A: "Triploid" occurs between "Occidentalis" and "Tetraploid_α".
• A: Ruppia megacarpa and "Occidentalis" hybridized in Hokkaido, Japan.
• Q: Anything else?
• A: Disjunct distribution between Australasia and East Asia (Ruppia megacarpa and "Tetraploid_α")
• A: Siblings: "Utahensis" (inland salinity water) and "Occidentalis" (inland fresh alkaline water).
• Q: Nomenclature notes:
• A: Ruppia maritima L., Sp. Pl. 127. 1753 ? Lectotype (designated by Setchell in Proc. Calif. Acad. Sci. ser. 4, 25: 470. 1946): [illustration in] Micheli, Nov. Pl. Gen., pl. 72, tab. 35. 1729 - Buccaferra cirrhosa Petagna, Instit. Bot. 5: 1826. 1787 (syn. nov.) - Ruppia cirrhosa (Petagna) Grande in Bull. Orto Bot. Regia Univ. Napoli 5: 58. 1918 (syn. nov.) Lectotype (designated here): [illustration in] Micheli, Nov. Pl. Gen., pl. 72, tab. 35. 1729
• A: Ruppia spiralis L. ex Dumort., Fl. Berg. 164. 1827 ? Lectotype (designated here): origin unknown (LINN 176.2 [digital image!])
• Sparganium (Typhaceae) Ito et al. (2016)
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• Q: Varieties of Sparganium emersum seem not to be close each other?
• A: Sparganium emersum s.l. revised to be non-monophyletic; S. acaule from North America resurrected.
• Q: Morphologically ambiguous collections to be explained by hybridization?
• A: Sparganium acaule × S. fluctuans hybridized in North America
• A: Sparganium emersum × S. glomeratum hybridized in Europe
• A: Sparganium fallax × S. japonicum hybridized in Japan
• A: Sparganium glomeratum × S. gramineum hybridized in Japan
• Q: Anything else?
• A: Siblings: Sparganium androcladum (emergent) and S. fluctuans-S. gramineus (floating-leaved).
• A: Siblings: Sparganium acaule (emergent) and S. glomeratum (amphibium).
• A: Siblings: Sparganium emersum (amphibium) and S. angustifolium (floating-leaved).
• Potamogeton (Potamogetonaceae) Ito et al. (2007) | Ito & Tanaka (2013) | Ito et al. (2014) | Ito et al. (2016)
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• Q: Morphologically ambiguous collections to be explained by hybridization?
• A: Potamogeton ×inbaensis occurs between P. wrightii and P. lucens in China and Japan.
• A: Potamogeton distinctus × P. nodosus hybridized in Myanmar.
• A: Potamogeton ×malainoides occurs between P. wrightii and P. distinctus in Myanmar.
• A: Potamogeton pusillus s.l. × P. illinoensis hybridized in Argentina.
• Isolepis (Cyperaceae) Ito et al. (2016) | Yano et al. (2016)
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• Q: Varieties of Isolepis fluitans seem not to be close each other?
• A: Isolepis fluitans s.l. revised to be non-monophyletic; I. lenticularis from Australasia resurrected.
• Q: Morphologically ambiguous collections to be explained by hybridization?
• A: Isolepis crassiuscula × I. lenticularis hybridized in New Zealand.
• Q: Anything else?
• A: Colonization into Australasia from South Africa occurred twise, followed by cladogenesis radiation
• A: Isolepis crassiuscula distributed disjunctively between Australasia and East Asia
• A: Isolepis fluitans distributed disjunctively between Europe and South Africa
• Halodule (Cymodoceaceae) Ito & Tanaka (2011)
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• Q: Morphologically ambiguous collections to be explained by hybridization?
• A: Halodule uninervis x I. pinifolia hybridized in Okinawa, Japan.