Radek Walkowiak

הצטרף ב:פבר' 14, 2019 פעילות אחרונה: אוק' 29, 2020

Scientific Member, Program Manager and Botanist at The International Equisetological Association (IEA), World Equisetum Program, Research Service .. Passionate about plant biology, specifically in plant systematics, phylogenetic taxonomy of Equisetum, Equisetaceae, Tortula muralis complex, Marchantia polymorpha complex, botanical nomenclature and history of botanical explorations and discovery, conservation biology, in vitro plant breeding ..

“Equisetum is the single surviving genus of a class of ancient vascular plants that dates back to the mid-Devonian period (350 + million years ago). Species (no hybrids): 15 (18), nearly worldwide. Plants with jointed stems and distinct nodes. Leaves small, fused into sheaths, tips remaining free, toothlike. Sporangia borne on peltate sporophylls aggregated in cones. Spores green, rather white in hybrids. Gametophytes green, terrestrial, unisexual, male gametophytes smaller than female” ..

“The fossil record suggests that species morphologically of modern aspect appeared in the Mesozoic and all the characteristic synapomorphies of living Equisetum had evolved by the Lower Cretaceous 136 Ma ago” ..

‘’†Equisetum thermale [Channing, Zamuner, Edwards et Guido] confirms the hypothesis that Equisetum was established prior to the Cenozoic and have a history extending back to the Late Jurassic (Equisetum had developed the suite of adaptations required to colonize hot spring–influenced settings in Late Jurassic times and has maintained them for over 150 million years)’’ ..

It is believed that the genus Equisetum developed in the Tertiary, arising from the much older genus Equisetites, originating in the Paleozoic era - Permian or Carboniferous. The Triassic species Equisetites arenaceus was initially included in the genus Equisetum. Some fossil species of the genus Equisetites resemble modern horsetails so much that the generic distinction between Equisetum and Equisetites was questioned and it was suggested that Equisetum may be considered the oldest modern vascular plant” ..

“According to phylogenetic analyzes carried out by Jean-Michel Guillon, the most basal representative of the genus is Equisetum bogotense. Incorporating it in the Equisetum subgenus not including the Hippochaete subgenus makes this subgenus a paraphyletic taxa” ..

“Equisetaceae [Michx. ex DC.] The only modern representative is the genus Equisetum [L.] Fossil plants of this family are usually classified as Morphotaxon Equisetites. These include morphologically diverse plants known from different continents, found mainly in Triassic and younger rocks, rarely already Carboniferous” ..

“The first Equisetum-Equisetites species appeared in the upper Devon about 375 million years ago. The genus Equisetum can therefore be called living fossils” ..

“Equisetales [DC. ex Bercht. & J. Presl] Four families, of which only Equisetaceae have modern representatives. These plants occur on Earth from the Devonian, but played a special role in the Carboniferous vegetation. Plants of various sizes, from small herbaceous plants to extinct calamites reaching about 20 (30) m high. The following taxa are distinguished: Calamitaceae (+Asterocalamitaceae), Equisetaceae, Tchernoviaceae, Gondwanostachyaceae (Formerly: +Phyllothecaceae, +Schizoneuraceae). Fossil taxa with an unclear taxonomic position: Annularia, Schizoneura, Neocalamites, Spaciinodum” ..

“Equisetopsida [C. Agardh] The class is fossil, living representatives are classified in one genus - Equisetum. Taxonomy: Equisetidae [(Warm.) / Engl. & Gilg], Equisetales [(Dumort.) / DC. ex Bercht. & J. Presl], Equisetineae [Rabenh.], Equisetaceae [Michx. ex DC.], Equisetum [L.] /// Hyeniales, Hyeniaceae /// Sphenophyllales [Seward], Sphenophyllaceae, Cheirostrobaceae /// Calamitales, Calamitaceae [Unger]” ..

“Equisetophyta [D. H. Scott / B. Boivin] The group is fossil, living representatives are classified in one genus - Equisetum. Taxonomy: Equisetophytina [Reveal], Equisetopsida [C. Agardh]” ..

“Horsetails, Equisetophyta emerged from one trunk of Trimerophytes, Trimerophyta” ..
/ Radosław Janusz Walkowiak, 2008

“Trimerophyta is a cluster of fossil plants, very old terrestrial vascular plants that lived from early to middle Devonian. This group is paraphyletic; that is, it does not include all the descendants of a common ancestor. Trimerophytes were characterized by leafless shoots dividing pseudomonopodially, dichotomously or trichotomously, but one branch was more developed than the other, forming a sort of principal axis. The dichotomous branches shortened as they moved away from the main axis, creating tufted sporangia at the ends of only the side branches. Conductive bundles in trimerophytes were thicker than in rhyniophytes. Trimerophytes reached 1 m in height. Large trimerophytes were among the largest plants of the early Devonian. Trimerophytes descended from the oldest terrestrial plants - rhyniophytes, and gave rise to the extinct Cladoxylophyta, Psilotopsida, Polypodiopsida, Equisetopsida and extinct Progymnospermophyta. Classification of this group, orders: Pertica, Psilophyton, Trimerophyton, Dawsonites” ..

The genus Equisetum [L.] is divided into three distinct lineages, which are usually treated as three subgenus. Hybridization has only been recorded between members of the same subgenus.

Subgenus Paramochaete [Christenh. & Husby]

E. bogotense [Kunth] Andean horsetail, upland South America up to Costa Rica.
The most basal (phylogenetics) representative of the genus. 10–40 cm.

Subgenus Equisetum [L.]

E. arvense [L.] Field horsetail, common horsetail.
The plant is widespread. 10–100 cm.

Equisetum diffusum [D.Don.] Himalayan horsetail. Himalayan India
and China and adjacent nations above-about 450 m. 10–90 cm.

Equisetum fluviatile [L. em. Ehrh.] Water horsetail.
Temperate zone, mainly in the Northern Hemisphere.
30-150 cm.

Equisetum palustre [L.] Marsh horsetail. It is widespread,
mainly in cooler regions of Eurasia and North America.
10-60(80) cm.

Equisetum pratense [Ehrh.] Meadow horsetail, Shade horsetail, Shady horsetail.
The plant is widespread but is usually quite rare. 10-30(50) cm.

Equisetum sylvaticum [L.] Wood horsetail. Northern Hemisphere,
Eurasia and North America. 30-60 cm.

Equisetum telmateia [Ehrh.] Great horsetail, northern giant horsetail.
Europe, Asia Minor, North Africa and west coast of North America.
30-150(250) cm.
Equisetum telmateia [Ehrh.] subsp. telmateia. Great horsetail. Europe, western Asia, northwest Africa. Main stem is pale greenish white.
= Equisetum telmateia [Christenhusz et al. 2019]
Equisetum telmateia subsp. braunii [(Milde) Hauke] Northern giant horsetail. Western North America, from southeastern Alaska and western British Columbia south to California. Main stem is green.
= Equisetum braunii [Christenhusz et al. 2019]

Subgenus Hippochaete [(Milde) Baker]

Equisetum giganteum [L.] Southern giant horsetail. 200-500 cm.
South America and Central America, from central Chile east to Brazil and north to southern Mexico. Populations from northern Chile with very stout stems up to 3.5 cm diameter are treated as a separate species Equisetum xylochaetum [Mett.] / [Christenhusz et al. 2019]

Equisetum hyemale [L.] Rough horsetail, rough scouring rush. scouringrush horsetail (snake grass). Holarctic Kingdom, Europe, northern Asia and North America, Mexico, Central America in Guatemala. 30-150 cm.
The North American subspecies Equisetum hyemale ssp./var. affine [(Engelm.) A.A.Eat.] may be treated as a separate species Equisetum prealtum [Raf.] / [Christenhusz et al. 2019]

Equisetum laevigatum [A.Braun] Smooth horsetail, smooth scouring rush. 30-150 cm.
Native to much of North America except for northern Canada and southern Mexico.
It is usually found sandy and gravelly substrates.

Equisetum myriochaetum [Schltdl. & Cham.] Mexican giant horsetail. 450-800 cm.
Nicaragua, Costa Rica, Colombia, Venezuela, Ecuador, Peru, cental Mexico.
It is the largest horsetail species.

Equisetum ramosissimum [Desf.] Branched horsetail. 20-80(100) cm.
Asia, Europe, Africa, southwest Pacific islands.
E. ramosissimum [Desf.] subsp./var. ramosissimum is native through much of Asia, Europe, and Africa, with an introduced population in the southeast United States.
E. ramosissimum [Desf.] subsp. debile [(Roxb. ex Vaucher) Hauke] is found in southeast Asia and some Pacific islands
= E. ramosissimum [Desf.] var. huegelii [(Milde) Christenh. & Husby, 2019]
The type subspecies has more obvious branching from the aerial stem than subspecies debile.

Equisetum scirpoides [Michx.] Dwarf scouring rush, dwarf horsetail.
North Eurasia and North America, cool temperate zones. 3-30 cm.
It is the smallest horsetail species.
Equisetum scirpoides [Michx.] ssp. scirpoides (5-30 cm)
Equisetum scirpoides [Michx.] ssp. walkowiaki [R. J. Walkowiak, 2008]; (3-15/20 cm)

Equisetum variegatum [Schleich. ex F.Weber & D.Mohr] including ssp./var. alaskanum [A.A.Eat.] / [Christenhusz et al. 2019] Variegated horsetail, variegated scouring rush. 30-80 cm. It has a circumpolar distribution in the northern hemisphere (cool temperate zones), in the northern Europe, Asia, North America, Greenland, Iceland, Faroe Islands, in the Pyrenees, Apennines in Europe, Mongolia, Japan. It occurs in dune slacks, mountain flushes and beside lakes, rivers and canals.

Very well-researched † extinct species:

†Equisetum dimorphum [Elgorriaga] is an extinct horsetail species of the family Equisetaceae, and one of the oldest records of the genus Equisetum. It was found in rocks from the Lower Jurassic of Chubut, Argentina, among other plants as ferns, conifers and pteridosperms. Most closely related to a Equisetum laterale Phillips and Equisetites ferganensis Seward. Temporal range: Pliensbachian. This species was described in 2015 by a team led by Andres Elgorriaga. Morphological curiosity, the species to some extent similar to modern E. hyemale.

†Equisetum thermale [Channing, Zamuner, Edwards & Guido] is an extinct horsetail species in the family Equisetaceae described from a group of whole plant fossils including rhizomes, stems, and leaves. It is a near‐complete Equisetum-species of Late Jurassic age with excellent anatomical preservation. The species is known from Middle to Late Jurassic sediments exposed in the province of Santa Cruz, Argentina. It is one of several extinct species placed in the living genus Equisetum. Temporal range: Callovian – Tithonian. Fossils specimens of Equisetum thermale are highly detailed and complete. Channing and his team published their 2011 type description for E. thermale. The etymology of the chosen specific name thermale is in recognition of both the geology of the type location and as a reference to the original habitat of a hot spring. E. thermale show infrequent branching of the stems, a feature found only in Equisetum-Hippochaete. The stems of E. thermale grew up to 10 cm, and each of the nodes on the stem have up to twelve single veined leaves which correspond to the number of ridges on the stem. Morphological curiosity, the species to some extent similar to modern E. bogotense.

Well-researched hybrids:

Subgenus Equisetum:

Equisetum × bowmanii [C.N.Page]; (Equisetum sylvaticum × Equisetum telmateia)
Equisetum × dycei [C.N.Page]; (Equisetum fluviatile × Equisetum palustre)
Equisetum × font-queri [Rothm.]; (Equisetum palustre × Equisetum telmateia)
Equisetum × litorale [Kühlew ex Rupr.]; (Equisetum arvense × Equisetum fluviatile)
Equisetum × mchaffieae [C.N.Page]; (Equisetum fluviatile × Equisetum pratense)
Equisetum × mildeanum [Rothm.]; (Equisetum pratense × Equisetum sylvaticum)
Equisetum × robertsii [Dines]; (Equisetum arvense × Equisetum telmateia)
Equisetum × rothmaleri [C.N.Page]; (Equisetum arvense × Equisetum palustre)
Equisetum × willmotii [C.N.Page]; (Equisetum fluviatile × Equisetum telmateia)

Subgenus Hippochaete:

Equisetum × ferrissii [Clute]; (Equisetum hyemale affine × Equisetum laevigatum)
Equisetum × moorei [Newman]; (Equisetum hyemale × Equisetum ramosissimum)
Equisetum × nelsonii [(A.A.Eaton) Schaffn.]; (Equisetum laevigatum × Equisetum variegatum)
Equisetum × schaffneri [Milde]; (Equisetum giganteum × Equisetum myriochaetum)
Equisetum × trachyodon [(A.Braun) W.D.J.Koch]; (Equisetum hyemale / affine × Equisetum variegatum)

(c) IEA, Radosław Janusz Walkowiak, 2008 - 2020

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