Research Article |
Corresponding author: Alexander P. Sukhorukov ( suchor@mail.ru ) Academic editor: Eric Roalson
© 2018 Alexander P. Sukhorukov, Maya V. Nilova, Anastasiya A. Krinitsina, Maxim A. Zaika, Andrey S. Erst, Kelly A. Shepherd.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Sukhorukov AP, Nilova MV, Krinitsina AA, Zaika MA, Erst AS, Shepherd KA (2018) Molecular phylogenetic data and seed coat anatomy resolve the generic position of some critical Chenopodioideae (Chenopodiaceae – Amaranthaceae) with reduced perianth segments. PhytoKeys 109: 103-128. https://doi.org/10.3897/phytokeys.109.28956
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The former Chenopodium subgen. Blitum and the genus Monolepis (Chenopodioideae) are characterised in part by a reduced (0–4) number of perianth segments. According to recent molecular phylogenetic studies, these groups belong to the reinstated genera Blitum incl. Monolepis (tribe Anserineae) and Oxybasis (tribe Chenopodieae). However, key taxa such as C. antarcticum, C. exsuccum, C. litwinowii, C. foliosum subsp. montanum and Monolepis spathulata were not included and so their phylogenetic position within the Chenopodioideae remained equivocal. These species and additional samples of Blitum asiaticum and B. nuttallianum were incorporated into an expanded phylogenetic study based on nrDNA (ITS region) and cpDNA (trnL-trnF and atpB-rbcL intergenic spacers and rbcL gene). Our analyses confirm the placement of C. exsuccum, C. litwinowii and C. foliosum subsp. montanum within Blitum (currently recognised as Blitum petiolare, B. litwinowii and B. virgatum subsp. montanum, respectively); additionally, C. antarcticum, currently known as Oxybasis antarctica, is also placed within Blitum (reinstated here as B. antarcticum). Congruent with previous studies, two of the three accepted species of Monolepis – the type species M. trifida (= M. nuttalliana) as well as M. asiatica – are included in Blitum. The monotypic genus Carocarpidium described recently with the type C. californicum is not accepted as it is placed within Blitum (reinstated here as B. californicum). To date, few reliable morphological characters have been proposed that consistently distinguish Blitum (incl. two Monolepis species) from morphologically similar Oxybasis; however, two key differences are evident: (1) the presence of long-petiolate rosulate leaves in Blitum vs. their absence in Oxybasis and (2) a seed coat structure with the outer wall of the testa cells lacking stalactites (‘non-stalactite seed coat’) but with an obvious protoplast in Blitum vs. seed coat with the outer walls of the testa cells having stalactites (‘stalactite seed coat’) and a reduced protoplast in Oxybasis. Surprisingly, the newly sequenced North American Monolepis spathulata nested within the tribe Dysphanieae (based on ITS and trnL-trnF + rbcL + atpB-rbcL analyses).The phylogenetic results, as well as presence of the stalactites in the outer cell walls of the testa and lack of the rosulate leaves, confirm the distinctive nature of Monolepis spathulata from all Blitum and, therefore, the recent combination Blitum spathulatum cannot be accepted. Indeed, the morphological and molecular distinctive nature of this species from all Dysphanieae supports its recognition as a new monotypic genus, named herein as Neomonolepis (type species: N. spathulata). The basionym name Monolepis spathulata is also lectotypified on a specimen currently lodged at GH. Finally, while Micromonolepis pusilla is confirmed as belonging to the tribe Chenopodieae, its position is not fully resolved. As this monotypic genus is morphologically divergent from Chenopodium, it is retained as distinct but it is acknowledged that further work is required to confirm its status.
Blitum , Chenopodioideae , Chenopodium , Oxybasis , new genus, taxonomy
The family Chenopodiaceae Vent. comprises ~1500 species distributed worldwide (
Some of the most recent and drastic taxonomic changes have been proposed by
Further changes were subsequently proposed by
The recent split of Chenopodiumsensu lato into genera belonging to different tribes as suggested by
It has become apparent in recent years that fruit and seed characters are also useful in distinguishing members of the former Chenopodium, particularly amongst groups that are quite morphologically similar (
Amongst the species of the former Chenopodium or Monolepis investigated carpologically but not included in recent molecular phylogenetic studies, two taxa are of special interest. The first, Monolepis spathulata, is endemic to western states of USA and North Mexico and was transferred to Blitum (as B. spathulatum) due to morphological affinities with other species of the genus. The second taxon, Chenopodium antarcticum, is another poorly known taxon endemic to Tierra del Fuego (southernmost parts of Argentina and Chile) that still occupies a pending position within Chenopodioideae. Previously, it was described as Blitum antarcticum Hook.f. (
To resolve this issue, we have included these two species, in addition to several accessions of taxa sampled for the first time [Chenopodium antarcticum, C. exsuccum (C.Loscos) Uotila, C. litwinowii (Paulsen) Uotila, C. foliosum subsp. montanum Uotila and Monolepis spathulata], as well as an additional sample of Blitum asiaticum (Fisch. & C.A.Mey.) S.Fuentes, Uotila & Borsch. in expanded molecular analyses based on nrDNA (ITS region) and cpDNA (atpB-rbcL intergenic spacers + rbcL and trnL-trnF intergenic spacer + rbcL, hereafter as atpB-rbcL and trnL-trnF, respectively) to determine their phylogenetic position within the Chenopodioideae. Furthermore, we discuss the role of fruit and seed characters for delimitating morphologically similar but phylogenetically distant taxa and conclude with proposed taxonomic changes that reflect our findings.
Several new taxa were included in the phylogenetic analysis for the first time: Chenopodium antarcticum (Hook.f.) Hook.f. [≡ Oxybasis antarctica (Hook.f.) Mosyakin: Chile, Tierra del Fuego, December 1971, Moore & Goodall s.n. (LE)]; C. exsuccum (C.Loscos) Uotila: Algeria, Zenina, July 1968, V.P. Boczantsev 681 (LE); C. foliosum subsp. montanum Uotila: Iran, prov. Tehran, Elburz, June 1977, K.-H. Rechinger 57243 (B); C. litwinowii (Paulsen) Uotila: Afghanistan, Parwan prov., Salang, 8 August 1969, J.E. Carter 602 (LE); Monolepis spathulata A.Gray: USA, California, Susanville, August 1983, I.Yu. Koropachinsky & al. 404 as Monolepis nuttalliana (MHA). Additionally, we have included a new accession of Blitum asiaticum (Fisch. et C.A.Mey.) S.Fuentes, Uotila et Borsch (Russia, Yakutiya, Ust-Yansky distr., August 1976, E.V. Ter-Grigoryan 1009, MHA). The taxa included in the molecular analyses and their GenBank accession numbers are given in the Table
Voucher information and GenBank accession numbers for the species of Chenopodioideae and outgroups included in the phylogenetic analysis (arranged in alphabetical order). The newly sequenced samples are highlighted in bold. Some vouchers in GenBank may be stored under old names.
Species | Old names (if applicable) | GenBank accession number | |||
---|---|---|---|---|---|
ITS | rbcL | trnL-trnF | atpB-rbcL | ||
Atriplex hortensis | – | HM005854 | KX678160 | HE577500 | – |
Atriplex patula | – | HE577358 | MG249776 | HE577498 | HM587650 |
Atriplex spongiosa | – | – | AY270060 | – | HM587661 |
Atriplex undulata | – | – | AY270061 | – | HM587665 |
Atriplex phyllostegia | – | HM005870 | HM587590 | – | HM587651 |
Atriplex peruviana | – | HM005867 | – | – | – |
Atriplex watsonii | – | HM005871 | – | – | – |
Atriplex rusbyi | – | HM005865 | – | – | – |
Atriplex patagonica | – | HM587541 | – | – | – |
Atriplex lentiformis | – | HM005872 | – | – | HM587637 |
Atriplex cinerea | – | HM587491 | – | – | – |
Atriplex centralasiatica | – | DQ086481 | HM587583 | – | HM587621 |
Atriplex suberecta | – | HM005863 | – | – | – |
Axyris amaranthoides | – | AM849227 | KX678411 | HE577510 | – |
Axyris hybrida | – | HE577371 | – | HE577511 | – |
Blitum antarcticum | Chenopodium antarcticum (Oxybasis antarctica) | MH155315 | MH632743 | MH632745 | MH152573 |
Blitum asiaticum | Monolepis asiatica | MH150882 | MH731231 | MH731229 | – |
Blitum bonus-henricus | Chenopodium bonus-henricus | HE577372 | KF613023 | HE577512 | HM587670 |
Blitum californicum | Chenopodium californicum | HE577376 | MF963177 | HE577516 | – |
Blitum capitatum | Chenopodium capitatum | KJ629064 | MG249277 | HE577513 | – |
Blitum litwinowii | Chenopodium litwinowii | MH153781 | MH632744 | MH632746 | MH632749 |
Blitum nuttallianum | Monolepis nuttalliana | HE577375 | JX848452 | HE577515 | HM587702 |
Blitum petiolare | Chenopodium exsuccum | MH150883 | – | MH632747 | MH152574 |
Blitum virgatum L. | Chenopodium foliosum | JF976147 | AY270081 | HE577518 | HM587673 |
Blitum virgatum subsp. montanum | Chenopodium foliosum subsp. montanum | MH155242 | – | – | – |
Ceratocarpus arenarius | – | AY556430 | HM587594 | HE577505 | – |
Chenopodiastrum coronopus | Chenopodium coronopus | HE577403 | HM587595 | HE577543 | HM587671 |
Chenopodiastrum hybridum | Chenopodium hybridum | HE577530 | – | HE577530 | – |
Chenopodiastrum murale | Chenopodium murale | HE577392 | HM849890 | HE577531 | HM587675 |
Chenopodium album | – | JF976146 | JF941270 | HE577609 | MF073794 |
Chenopodium atrovirens | – | KP226648 / | KX679232 | HE577587 | – |
Chenopodium auricomum | – | KP226671 | – | – | – |
Chenopodium bengalense | Chenopodium giganteum | HE577458 | – | – | – |
Chenopodium berlandieri var. boscianum | – | HE577426 | MG249740 | HE577564 | – |
Chenopodium berlandieri var. zschackei | – | HE577425 | – | – | – |
Chenopodium desertorum | – | HE577417 | AY270042 | HE577555 | HM587672 |
Chenopodium desiccatum | – | HE577412 | KX678128 | HE577550 | – |
Chenopodium ficifolium | – | HE577466 | KM360714 | HE577606 | – |
Chenopodium fremontii | – | HE577408 | KX679065 | HE577572 | – |
Chenopodium hians | – | HE577470 | MG248000 | HE577610 | – |
Chenopodium iljinii | – | HE577468 | – | – | – |
Chenopodium incanum | – | HE577410 | MG246401 | HE577548 | – |
Chenopodium leptophyllum | – | HE577428 | MG248863 | HE577566 | – |
Chenopodium neomexicanum | – | KJ629054 | – | – | – |
Chenopodium nevadense | – | HE577411 | – | – | – |
Chenopodium opulifolium | – | HE577454 | MG248036 | HE577594 | – |
Chenopodium pallescens | – | HE577409 | – | – | – |
Chenopodium pallidicaule | – | KJ629055 | – | – | – |
Chenopodium nutans | Einadia nutans | – | KM896090 | – | HM587686 |
Chenopodium parabolicum | Rhagodia parabolica | – | KU564859 | – | HM587704 |
Chenopodium quinoa | – | HE577443 | KY419706 | – | KY419706 |
Chenopodium standleyanum | – | KJ629051 | MG249838 | HE577560 | – |
Chenopodium subglabrum | – | HE577465 | MG249459 | HE577605 | – |
Chenopodium vulvaria | – | HE577407 | JN892907 | HE577591 | – |
Chenopodium watsonii | – | HE577462 | MG246238 | HE577602 | – |
Cycloloma atriplicifolium | – | HQ218998 | HM587598 | – | HM587681 |
Dysphania ambrosioides | Chenopodium ambrosioides | DQ005963 | MG249540 | HE577493 | HM587682 |
Dysphania botrys | Chenopodium botrys | KJ629068 | MG247946 | DQ499383 | HM587683 |
Dysphania cristata | Chenopodium cristatum | KJ629066 | AY270046 | – | HM587684 |
Dysphania glomulifera | Chenopodium glomuliferum | – | AY270086 | HM587685 | |
Dysphania pumilio | Chenopodium pumilio | HE577343 | MG248652 | HE577485 | – |
Dysphania schraderiana | Chenopodium schraderianum | HE577349 | – | – | – |
Exomis microphylla | – | – | HM587601 | – | HM587687 |
Grayia brandegeei | – | HM005845 | HM587604 | HE577497 | HM587690 |
Grayia spinosa | – | HM005844 | HM587605 | HE577496 | HM587691 |
Halimione verrucifera | Atriplex verrucifera | HM587575 | HM587606 | – | HM587695 |
Halimione pedunculata | Atriplex pedunculata | HM587573 | AY270093 | – | HM587694 |
Holmbergia tweedii | – | HM005842 | AY270100 | – | HM587696 |
Krascheninnikovia ceratoides | – | HE577367 | AY270105 | HE577507 | HM587697 |
Krascheninnikovia ceratoides subsp. lanata | Krascheninnikovia lanata | HE577368 | MG248963 | HE577508 | HM587698 |
Lipandra polysperma | Chenopodium polyspermum | KJ629061 | KX677934 | HE855686 | – |
Micromonolepis pusilla | – | – | HM587608 | – | HM587701 |
Neomonolepis spathulata | Monolepis spathulata (Blitum spathulatum) | MH675518 | MH731232 | MH731230 | MH152575 |
Oxybasis glauca | Chenopodium glaucum | KJ629060 | MG249300 | HE577527 | MF073807 |
Oxybasis rubra | Chenopodium rubrum | HE577381 | MG249329 | HE577525 | – |
Oxybasis urbica | Chenopodium urbicum | KJ629057 | MG246691 | HE577524 | HM587678 |
Oxybasis micrantha | – | KU359325 | – | – | – |
Spinacia oleracea | – | EU606218 | – | AJ400848 | – |
Suckleya suckleyana | – | HE577347 | – | – | – |
Teloxys aristata | Chenopodium aristatum; Dysphania aristata | KJ629070 | AY270140 | – | HM587708 |
Outgroups | – | ||||
Bassia laniflora | Kochia laniflora | KF785942 | – | – | – |
Bassia prostrata | Kochia prostrata | KF785963 | AY270104 | HE577478 | KF785926 |
Beta vulgaris | – | AY858597 | – | – | DQ074969 |
Hablitzia tamnoides | – | AY858590 | AY270092 | HE577475 | JQ407841 |
Polygonum aviculare | – | – | MF158792 | HQ843161 | JN234937 |
Polygonum aviculare subsp. buxiforme | – | GQ339988 | – | – | – |
Total genomic DNA was extracted from herbarium samples according to
PCRs for two chloroplast markers (atpB-rbcL and trnL-trnF) and nrDNA (ITS region) were carried out in a Thermal Cycler T100 (Bio-Rad, USA) using primers and cycler programmes listed in Table
Marker | Primer sequences and combination | Reference | Cycler programmer |
---|---|---|---|
ITS | ITS5 5'-GGA AGT AAA AGT CGT AAC AAG G-3' |
|
95 °C for 5 min, 33 cycles of amplification (95 °C for 15 s, 55 °C for 30 s, 72 °C for 40 s), 72 °C for 5 min |
ITS4 5'-TCC TCC GCT TAT TGA TAT GC-3' | |||
rbcL (partial) | rbcLaF 5'- ATG TCA CCA CAA ACA GAG ACT AAA GC-3' |
|
95 °C for 5 min, 35 cycles of amplification (95 °C for 10 s, 55 °C for 30 s, 72 °C for 40 s), 72 °C for 5 min |
rbcLaR 5'-GTA AAA TCA AGT CCA CCR CG-3' |
|
||
atpB-rbcL spacer | atpB-rbcL F 5'-GAA GTA GTA GGA TTG ATT CTC-3' |
|
95 °C for 5 min, 35 cycles of amplification (95 °C for 20 s, 56 °C for 30 s, 72 °C for 60 s), 95 °C for 20 s, 56 °C for 80 s, 72 °C for 8 min |
atpB-rbcL R 5'-CAA CAC TTG CTT TAG TCT CTG-3' | |||
trnL-F | Tab C 5'-CGA AAT CGG TAG ACG CTA CG-3' |
|
95 °C for 5 min, 35 cycles of amplification (95 C for 1 min, 50 °C – 65 °C (increasing in 0.3 C per cycle) for 1 min, 72 °C for 4 min), 72 °C for 5 min |
Tab D 5'-GGG GAT AGA GGG ACT TGA AC-3' | |||
Tab E 5'- GGT TCA AGT CCC TCT ATC CCC-3' | |||
Tab F 5'ATI' TGA ACT GGT GAC ACG AG 3' |
Sequencing was performed following Sanger methods on an Applied Biosystems 3730 DNA Analyser using ABI PRISM BigDye Terminator v. 3.1 (Center of Collective Use “Genome”, Institute of Molecular Biology, Moscow, Russia). The sequencing primers were the same as the amplification primers.
The raw forward and reverse sequences were checked and combined in BioEdit sequence alignment editor v. 7.0.5.3 (
To show the relationships between taxa, we reconstructed various phylogenies using Bayesian analysis, maximum likelihood (ML) and maximum parsimony (MP) methods for the ITS and combined trnL-trnF + rbcL + atpB-rbcL datasets. Models of nucleotide substitution were selected using the MrModeltest 2.1.7 (
The carpology of the tribe Chenopodioideae was described in detail in a previous study by
The cross-sections of the seeds were prepared using a rotary microtome Microm HM 355S (Thermo Fisher Scientific, USA) and then examined using a Nikon Eclipse Ci (Nikon Corporation, Japan) light microscope and photographed using a Nikon DS-Vi1 camera (Nikon Corporation, Japan) at the Department of Higher Plants, Lomonosov Moscow State University. Before sectioning, the seeds were soaked in water:alcohol:glycerine (1:1:1) solution, dehydrated in ethanol dilution series and embedded in the Technovit 7100 resin (Heraeus Kulzer, Germany).
The phylogenetic analysis based on nrDNA (ITS) and combined cpDNA analyses (trnL-trnF + rbcL + atpB-rbcL) revealed that the tribes Axyrideae, Chenopodieae s.str., Anserineae and Dysphanieae are well-supported within Chenopodioideae and congruent with previous molecular analyses by
In the ITS analysis (Figure
Like the ITS phylogenetic analysis, the combined trnL-trnF + rbcL + atpB-rbcL tree (Figure
This study highlighted the fact that these species, with the exception of Monolepis spathulata, possess the same fruit and seed anatomy as other Blitum species such as a mamillate pericarp (Figure
Additional noteworthy characters evolved in Blitum and Oxybasis. This table summarises life history and carpological data from
Taxon/Character | Life history | Perianth segments | Cells of the outer pericarp layer | Pericarp adherence to the seed coat | Seed shape and colour | Seed surface | Seed keel | Thickness of seed-coat testa (µm) | Acicular outgrowths of the testa cells | Presence of spatial heterospermy | Seed embryo position |
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Blitum antarcticum | short-lived perennial herb | basally connate | spongy | scraped off the seed | roundish, red | alveolate | – | 12–20 | – | – | vertical |
B. asiaticum | annual | free | not spongy | easily ruptured | roundish, red | undulate | + | 7–10 | – | – | vertical |
B. atriplicinum | annual or short-lived perennial herb | basally connate | not spongy | hardly removed | roundish, red | alveolate, with hairy-like outgrowths | – | 17–25 | + | – | vertical |
B. bonus-henricus | perennial herb | basally connate | spongy | scraped off the seed | roundish, red | smooth | – | 37–45 | – | + | vertical, rarely horizontal |
B. californicum | perennial herb | basally connate | spongy | scraped off the seed | roundish, red | alveolate | – | 25–30 and 37–45 (heterospermous) | – | + | vertical |
B. capitatum | annual or short-lived perennial herb | basally connate | not spongy | hardly removed | ovate, red | undulate | + (two keels and a groove between them) | 12–15 | – | + | vertical |
B. hastatum | annual or short-lived perennial herb | connate to 1/3 | not spongy | hardly removed | ovate, red | undulate | + (two keels and a groove between them | 15–18 | – | + | vertical |
B. korshinskyi | annual or short-lived perennial herb | almost free | not spongy | hardly removed | ovate, red | undulate | + (two keels and a groove between them) | 10–12 | – | – | vertical |
B. litwinowii | annual or short-lived perennial herb | basally connate | not spongy | hardly removed | ovate, red | alveolate | + (two keels and a groove between them) | 10–12 | – | – | vertical |
B. nuttallianum | annual | free, or perianth absent | not spongy | hardly removed | roundish, red | alveolate, with hairy-like outgrowths | – | 8–10 | + | – | vertical |
B. petiolare | annual or short-lived perennial herb | basally connate | not spongy | hardly removed | ovate, red | alveolate | + (two keels and a groove between them) | 15–17 | – | – | vertical |
B. virgatum | annual or short-lived perennial herb | basally connate | not spongy | hardly removed | ovate, red | undulate | + (two keels and a groove between them) | 10–12 | – | + | vertical |
Oxybasis chenopodioides | annual | fused in almost all flowers, free only in some flowers | not spongy | easily ruptured | roundish, red | minutely pitted | – | 10–15 | + | vertical and horizontal | |
O. glauca | annual | basally connate | not spongy | easily ruptured | roundish, red | minutely pitted | – | 10–15 and 17–25 (heterospermous) | + | + | vertical and horizontal |
O. gubanovii | annual | basally connate | not spongy | hardly removed | roundish, red | smooth (minutely pitted) | + (one keel) | 12–15 | + | – | vertical |
O. macrosperma | annual | connate to the middle or almost to the top | spongy | scraped off the seed | roundish, red | reticulate with minutely pitted dots | – | 12–20 | + | – | vertical and horizontal |
O. mexicana | annual | basally connate | not spongy | easily ruptured | roundish, red | reticulate with minutely pitted dots | – | 20–25 | + | + | vertical and horizontal |
O. micrantha | annual | basally connate | not spongy | scraped off the seed | roundish, red | minutely pitted | + (one keel) | 12–15 | + | – | horizontal, rarely vertical |
O. rubra | annual | basally connate | not spongy | easily ruptured | roundish, red | reticulate with minutely pitted dots | – | 10–15 | + | vertical and horizontal | |
O. urbica | annual | basally connate | papillate | scraped off the seed | roundish, black | minutely pitted | – | 42–50 | + | – | horizontal |
The phylogenetic position of Chenopodium foliosum subsp. montanum [≡ Blitum virgatum subsp. montanum (Uotila) S.Fuentes, Uotila et Borsch], C. exsuccum [= Blitum petiolare Link] and C. litwinowii [≡ B. litwinowii S.Fuentes, Uotila et Borsch] within Blitum as proposed by
The importance of morphological characters used to delineate species within the genus Chenopodium that are now considered to belong to either Blitum or Oxybasis have been discussed by various authors (e.g.
In the absence of molecular phylogenetic data, it is clear that carpological characters must be taken into consideration when determining the generic placement of taxa in either Blitum or Oxybasis. Molecular data from this study and previous investigations (
This species was initially described as Monolepis pusilla Torr. ex Watson (
Recently, Monolepis spatulata was transferred to Blitum (as B. spathulatum) based on its resemblance to other species of the genus due to the presence of a reduced number of perianth segments (
Neomonolepis spathulata (A.Gray) Sukhor., comb. nov.
Annual, glabrous, branched or not; lateral branches if present ascending; leaves cauline (rosulate leaves absent), densely located, spatulate-oblong, with a short petiole up to 1 cm or sessile, entire; inflorescence leafy (bracts similar to stem leaves); flowers sessile or shortly pedicellate, unisexual intermixed in small glomerules (Figure
≡ Monolepis spathulata A.Gray, Proc. Amer. Acad. Arts 7: 389 (1868). Lectotype (Sukhorukov, designated here): [USA, California, Sierra Nevada], Mono Pass, 1866, H.N. Bolander 6373 lower right-hand specimen (GH00037208 [image]!, isolectotypes MO-216255 [image]! NY01085540 [image]! US00921387 [image]! YU064591 [image]!).
≡ Blitum spathulatum (A.Gray) S.Fuentes, Uotila et Borsch, Willdenowia 42(1): 17 (2012).
As Neomonolepis is a monotypic genus, the description of N. spathulata corresponds to the generic description above. Neomonolepis spathulata is morphologically distant from all Dysphanieae (Teloxys, Suckleya A.Gray, Dysphania R.Br. and Cycloloma Moq.) in being glabrous in all parts (vs. glandular and/or simple hairs), having unisexual flowers (vs. bisexual or polygamous) and ‘stalactite’ seed-coat testa (vs. ‘non-stalactite’). For this reason, we prefer to refer to the clade with the above-mentioned genera as the ‘Dysphanieae + Neomonolepis’ clade.
The type specimen lodged at GH contains several plants collected from different areas in California and almost all of them were collected after the description of Monolepis spathulata (
South-western North America (USA, North Mexico).
The new generic name is composed by the prefix “neo” (new) and the core name Monolepis.
In the Chenopodioideae, some phylogenetically distant taxa often look similar due to convergence of various morphological characters, some of which were previously thought to be diagnostic such as the number of perianth segments. A remarkable example is highlighted by the different phylogenetic positions occupied by members of the former genus Monolepis, which are currently included in Anserineae (M. nuttalliana ≡ Blitum nuttallianum; M. asiatica ≡ B. asiaticum), Dysphanieae (Neomonolepis spathulata ≡ Monolepis spathulata) and Chenopodieae (Monolepis pusilla ≡ Micromonolepis pusilla). This study shows that fruit and seed characters such as seed-coat structure are valuable traits for taxonomic study. These features are particularly useful in distinguishing the morphologically similar but phylogenetically distinct genera Blitum and Oxybasis.
We thank Eric H. Roalson and anonymous reviewers for the comments on the previous draft of the paper and Igor Pospelov and Steve Matson for the excellent images of Blitum asiaticum and Micromonolepis pusilla, respectively. The Russian Science Foundation (project 1450-00029: carpological research), Scientific programme АААА-А16-116021660045-2 of the Department of Higher Plants, Lomonosov Moscow State University (revision of the herbaria in Moscow and St.-Petersburg) and Russian Foundation for Basic Research (project 18-04-00029: revision of the herbarium collection in UK) supported the study of AS, MN and AK. The study of AE was financially supported by the Scientific programme АААА-А17-117012610055-3 of the Central Siberian Botanical Garden, SB RAS (sampling herbarium specimens from NS) and Tomsk State University competitiveness improvement programme (sampling herbarium specimens from TK).