Didymeles és un gènere de plantes amb flor. El sistema APG II de 2003 dóna l'opció de segregar aquesta família de la de les buxàcies i aleshores queda entre els llinatges basals dels eudicots. El gènere només compta amb dues espècies d'arbres de fulla persistent restringits a Madagascar i les Illes Comores.
Didymeles és un gènere de plantes amb flor. El sistema APG II de 2003 dóna l'opció de segregar aquesta família de la de les buxàcies i aleshores queda entre els llinatges basals dels eudicots. El gènere només compta amb dues espècies d'arbres de fulla persistent restringits a Madagascar i les Illes Comores.
Didymeles je rod vyšších dvouděložných rostlin (Rosopsida) z čeledi zimostrázovité (Buxaceae). Zahrnuje 3 druhy dvoudomých stálezelených stromů s tuhými listy a nenápadnými květy, rostoucí výhradně na Madagaskaru.
Zástupci rodu Didymeles jsou stálezelené dvoudomé stromy se střídavými kožovitými jednoduchými listy bez palistů. Čepel listů je celokrajná, se zpeřenou žilnatinou. Květy jsou jednopohlavné, uspořádané v klasech nebo latách. Okvětí je redukované na 1 až 4 kalichovité lístky (podle některých interpretací jde o listeny). Samčí květy ve zkrácených latách, se 2 tyčinkami s velmi krátkou nitkou. Samičí květy jsou v klasech, se svrchním semeníkem tvořeným jediným plodolistem a obsahujícím jediné vajíčko. Plodem je jednosemenná dužnatá peckovice.[1][2]
Rod Didymeles zahrnuje 3 druhy a vyskytuje se pouze na Madagaskaru.[3][4]
V Cronquistově systému byla čeleď Didymelaceae řazena do samostatného řádu Didymelales podtřídy Hamamelidae. Systém APG I ji ponechává nezařazenou do řádu, v systému APG II je rod Didymeles vřazen do čeledi zimostrázovité (Buxaceae).
Podle výsledků molekulárních studií je rod Didymeles bazální větví čeledi Buxaceae.[5]
Fosilie rodu Didymeles byly nalezeny na Novém Zélandu i v jiných oblastech na jižní polokouli.[2]
Obrázky, zvuky či videa k tématu Didymeles ve Wikimedia Commons
Didymeles je rod vyšších dvouděložných rostlin (Rosopsida) z čeledi zimostrázovité (Buxaceae). Zahrnuje 3 druhy dvoudomých stálezelených stromů s tuhými listy a nenápadnými květy, rostoucí výhradně na Madagaskaru.
Die Didymeles sind die einzige Pflanzengattung der Familie der Didymelaceae innerhalb der Ordnung der Buchsbaumartigen (Buxales). Zur Gattung und damit zur Familie gehören nur zwei Arten.
Die Didymeles-Arten kommen nur im nördlichen und östlichen Madagaskar und auf den Komoren vor.
Didymeles-Arten sind immergrüne Bäume. Die wechselständig und spiralig angeordneten Laubblätter sind gestielt, einfach, fiedernervig und ledrig oder papierartig. Die Blattränder sind glatt. Die Blätter werden beim Trocknen gelblich-grün. Nebenblätter fehlen.
Sie sind zweihäusig getrenntgeschlechtig (diözisch). Die kleinen, eingeschlechtigen Blüten sind reduziert. In kurzen rispigen Blütenständen stehen die männlichen Blüten zusammen. Sie enthalten aus höchstens zwei Schuppen, ein bis zwei Blütenhüllblättern und nur zwei an ihrer Basis kurz verwachsene, fertile Staubblätter vorhanden, mit höchstens kurzen Staubfäden. Der Pollen ist tricolpat. In wenigblütigen, ährigen Blütenständen stehen die weiblichen Blüten zusammen. Sie enthalten höchstens vier Schuppen, die als Hochblätter oder Blütenhüllblätter interpretiert werden und nur ein oberständiges Fruchtblatt; es enthält nur eine Samenanlage. Die lange Narbe ist zweilappig und schräg.
Es werden große, fleischige Steinfrüchte gebildet.
In der Familie gibt es nur eine Gattung mit nur zwei Arten:
Die Didymeles sind die einzige Pflanzengattung der Familie der Didymelaceae innerhalb der Ordnung der Buchsbaumartigen (Buxales). Zur Gattung und damit zur Familie gehören nur zwei Arten.
Didymeles is a genus of flowering plants. It is variously treated as the only genus of the family Didymelaceae — or in the family Buxaceae, as in the APG IV system.
The genus Didymeles is restricted to Madagascar and the Comoros. In Madagascar, the two species are found in humid montane habitats, up to 1,500 m, in two disconnected areas in the north-east and south-east of the island.[1] Fossils assignable to this genus have been found in New Zealand,[2] suggesting a much wider distribution in the past.
The conservation status of D. integrifolia has been assessed as of "least concern".[1]
Species are dioecious (i.e. "male" and "female" flowers occur on separate plants). Individual flowers have a very simple structure, without obvious petals or sepals. Female flowers have been interpreted in different ways, either as having two carpels or as occurring close together in pairs, each with a single carpel.
Didymeles species are evergreen trees. The simple leaves are leathery in texture, with untoothed (entire) margins. There are no stipules. The flowers are unisexual, with the two kinds borne on separate plants (i.e. the species are dioecious). The staminate ("male") flowers are arranged in short panicles. Each flower basically consists only of two stamens.[3] The carpellate ("female") flowers are arranged in thyrses (spike-like structures). At the base of the inflorescence there are a number of empty bracts followed by up to 15 bracts arranged in a spiral, each of which is at the base of a side branch of the inflorescence. At the apex of each side branch there is a structure made up of two larger "scales", each with a smaller "scale" at its base, and two carpels, somewhat separated from one another, often with a small "hump" in between.[4] The pollen of Didymeles is distinctive. The grain has three furrows (colpi), as is commonly the case for eudicots; but each colpus then contains two circular openings or pores.[3]
The carpellate flowers have been interpreted differently. When the genus was first described, the two carpels were considered to belong to a single flower, each "female" flower having two carpels just as the "male" flowers had two stamens. This interpretation has been accepted by some later researchers. The "scales" then correspond to tepals of the single flower. The alternative interpretation, preferred by von Balthazar et al., is that there are two flowers very close together, each with a single carpel. Only the smaller "scale" might then correspond to a tepal.[4]
Each carpel has a broad two-crested stigma on a short style, and usually contains a single ovule. The integument – the covering on the outside of the ovule – is in the form of a long coiled tube, an unusual feature in flowering plants. The fruit which forms after fertilization is a fleshy drupe, to which the stigma remains attached.[4]
The genus was first described by Louis-Marie Aubert du Petit-Thouars in 1804. He described the staminate ("male") flowers as composed only of two stamens and the pistillate (carpellate, "female") flowers as composed only of two pistils. For this reason he named the genus from the Greek διδύμος "twin" and μελὲς "members". He described the genus as containing a tree from Madagascar, but did not name the species.[5] In 1805, Jean Henri Jaume Saint-Hilaire established Didymeles integrifolia as the name of the type species of the genus.[6]
Placement in a family was uncertain for a long time: von Balthazar et al. list 9 families or orders it was placed in, or allied with, between 1873 and 1974. Placed in a family of its own, Didymelaceae, it was associated with the Buxaceae from the 1980s onwards, based on chemical, leaf, pollen and wood characters.[4] More recently, molecular phylogenetic studies have repeatedly shown that the genus is sister to the Buxaceae.[4][7][8] As of 2017, two treatments are in use. The APG III system of 2009 and the APG IV system of 2016 put Didymeles in the Buxaceae.[9][10] Other sources keep Didymelaceae as a separate family in the order Buxales.[4][11]
The genus consists of three species of evergreen trees.[12][13]
There may also be other species, undescribed as of 2013.[1]
One possible evolutionary relationship among the genera of the Buxales is shown below:[8]
BuxalesDidymeles
{{cite journal}}: CS1 maint: uses authors parameter (link) Didymeles is a genus of flowering plants. It is variously treated as the only genus of the family Didymelaceae — or in the family Buxaceae, as in the APG IV system.
The genus Didymeles is restricted to Madagascar and the Comoros. In Madagascar, the two species are found in humid montane habitats, up to 1,500 m, in two disconnected areas in the north-east and south-east of the island. Fossils assignable to this genus have been found in New Zealand, suggesting a much wider distribution in the past.
The conservation status of D. integrifolia has been assessed as of "least concern".
Didymeles, biljni rod dvosupnica smješten u vlastitu porodicu Didymelaceae, ili u porodicu Buxaceae, dio reda šimširolike. Sve vrste endemi su na Madagaskaru. [1]
Didymeles, biljni rod dvosupnica smješten u vlastitu porodicu Didymelaceae, ili u porodicu Buxaceae, dio reda šimširolike. Sve vrste endemi su na Madagaskaru.
Didymeles – rodzaj roślin należący do rodziny bukszpanowate (Buxaceae), dawniej wyodrębniany w monotypową rodzinę Didymelaceae[3][1]. Do rodzaju należą 3 gatunki występujące w północnej części Madagaskaru oraz na Komorach[4].
Zimozielone drzewa o skrętoległych, pojedynczych, całobrzegich i gładkich liściach. Kwiaty są drobne, promieniste i jednopłciowe (rośliny są dwupienne). Kwiaty pręcikowe mają zredukowany okwiat i zawierają 2 pręciki. Kwiaty słupkowe tworzą kłosy. Każdy posiada łuskowaty listek okwiatu. Zalążnia górna powstaje z jednego owocolistka. Owocem jest pestkowiec[4].
Pozycja systematyczna tych roślin długi czas była przedmiotem dyskusji systematyków. Armen Tachtadżian i później Arthur Cronquist w swoim systemie z 1981 umieścił ten rodzaj w odrębnym rzędzie Didymelales Takht. 1967. Wskazywano na pokrewieństwo tych roślin z rozmaitymi grupami systematycznymi. W końcu analizy analizujące podobieństwa chemiczne i anatomiczne wskazały na ścisłe powiązania z bukszpanowatymi. Później potwierdziły te relacje filogenetyczne także badania molekularne[4]. W systemie APG I z 1998 i APG II z 2003 rodzaj wyodrębniany był w monotypową rodzinę Didymelaceae, siostrzaną dla Buxaceae. Począwszy od systemu APG III z 2009 rodzaj włączany jest do Buxaceae[5].
Didymeles – rodzaj roślin należący do rodziny bukszpanowate (Buxaceae), dawniej wyodrębniany w monotypową rodzinę Didymelaceae. Do rodzaju należą 3 gatunki występujące w północnej części Madagaskaru oraz na Komorach.
디디멜레스속(Didymeles)은 회양목과에 속하는 속씨식물 속이다. 이 속은 적어도 지난 십여 년 이상, 상당수의 분류학자로부터 인정받아왔다. 2003년의 APG II 분류 체계에서는 과로 인정되지 않았고, 하위 종들은 회양목과에 포함되었다. 그러나 APG II 분류 체계는 조건적 분리(즉, 목(目)으로 분류하지 않지만 진정쌍떡잎식물군의 기초 계통군 속에 남겨 두는)로써, 이 과의 분리를 선택 사항으로 허락했다. 이는 같은 배치에 과로 확실하게 인정되었던, 1998년의 APG 분류 체계와 비교하여 약간의 변화를 보여 준다. 이 속은 상록수 2종을 포함하고 있으며, 마다가스카르와 코모로 제도에 제한적으로 분포한다.
디디멜레스속(Didymeles)은 회양목과에 속하는 속씨식물 속이다. 이 속은 적어도 지난 십여 년 이상, 상당수의 분류학자로부터 인정받아왔다. 2003년의 APG II 분류 체계에서는 과로 인정되지 않았고, 하위 종들은 회양목과에 포함되었다. 그러나 APG II 분류 체계는 조건적 분리(즉, 목(目)으로 분류하지 않지만 진정쌍떡잎식물군의 기초 계통군 속에 남겨 두는)로써, 이 과의 분리를 선택 사항으로 허락했다. 이는 같은 배치에 과로 확실하게 인정되었던, 1998년의 APG 분류 체계와 비교하여 약간의 변화를 보여 준다. 이 속은 상록수 2종을 포함하고 있으며, 마다가스카르와 코모로 제도에 제한적으로 분포한다.
