Euphorbia Subg Research Articles

A worldwide molecular phylogeny and classification of the leafy spurges, Euphorbia subgenus Esula (Euphorbiaceae)

AbstractThe leafy spurges, Euphorbia subg. Esula, make up one of four main lineages in Euphorbia. The subgenus comprises about 480 species, most of which are annual or perennial herbs, but with a small number of dendroid shrubs and nearly leafless, pencil–stemmed succulents as well. The subgenus constitutes the primary northern temperate radiation in Euphorbia. While the subgenus is most diverse from central Asia to the Mediterranean region, members of the group also occur in Africa, in the Indo–Pacific region, and in the New World. We have assembled the largest worldwide sampling of the group to date (273 spp.), representing most of the taxonomic and geographic breadth of the subgenus. We performed phylogenetic analyses of sequence data from the nuclear ribosomal ITS and plastid ndhF regions. Our individual and combined analyses produced well–resolved phylogenies that confirm many of the previously recognized clades and also establish a number of novel groupings and placements of previously enigmatic species. Euphorbia subg. Esula has a clear Eurasian center of diversity, and we provide evidence for four independent arrivals to the New World and three separate colonizations of tropical and southern Africa. One of the latter groups further extends to Madagascar and New Zealand, and to more isolated islands such as Réunion and Samoa. Our results confirm that the dendroid shrub and stem–succulent growth forms are derived conditions in E. subg. Esula. Stem–succulents arose twice in the subgenus and dendroid shrubs three times. Based on the molecular phylogeny, we propose a new classification for E. subg. Esula that recognizes 21 sections (four of them newly described and two elevated from subsectional rank), and we place over 95% of the accepted species in the subgenus into this new classification.

Molecular phylogenetics and classification of Euphorbia subgenus Chamaesyce (Euphorbiaceae)

AbstractEuphorbia subg. Chamaesyce contains around 600 species and includes the largest New World radiation within the Old World–centered genus Euphorbia. It is one of the few plant lineages to include members with C3, C4 and CAM photosynthesis, showing multiple adaptations to warm and dry habitats. The subgenus includes North American–centered groups that were previously treated at various taxonomic ranks under the names of “Agaloma,,, “Poinsettia”, and “Chamaesyce”. Here we provide a well–resolved phylogeny of Euphorbia subg. Chamaesyce using nuclear ribosomal ITS and chloroplast ndhF sequences, with substantially increased taxon sampling compared to previous studies. Based on the phylogeny, we discuss the Old World origin of the subgenus, the evolution of cyathial morphology and growth forms, and then provide a formal sectional classification, with descriptions and species lists for each section or subsection we recognize.

Notes on six endemic or rare species ofEuphorbiasubg.Esula (Euphorbiaceae)in Iran

Pahlevani A. H., Maaroofi H. & Joharchi M. R.: Notes on six endemic or rare species of Euphorbia subg. Esula (Euphorbiaceae) in Iran. — Willdenowia 41: 267–276. December 2011. — Online ISSN 1868-6397; © 2011 BGBM Berlin-Dahlem. Stable URL: http//dx.doi.org/10.3372/wi.41.41208In the course of the revision of the genus Euphorbia in Iran, E. grisophylla and E. sogdiana are reported as new for the country. E. erythradenia, E. malleata and E. spartiformis are confirmed as rare localised endemics and an epitype is selected for the name E. spartiformis. E. polycaulis is shown to be the correct name for the more widespread Iranian endemic so far known as E. decipiens and E. sparsiglandulosa is sunk into the synonymy of this species. All species but E. polycaulis are illustrated and the following information is given for each of them: synonymy, description, delimitation from similar species, distribution and specimens examined.

Giants and dwarfs: Molecular phylogenies reveal multiple origins of annual spurges within Euphorbia subg. Esula

Euphorbia (Euphorbiaceae) comprises over 2150 species and is thus the second-largest genus of flowering plants. In Europe, it is represented by more than 100 species with highest diversity in the Mediterranean area; the majority of taxa belong to subgenus Esula Pers., including about 500 taxa. The few available phylogenetic studies yielded contrasting results regarding the monophyly of subg. Esula, and the phylogenetic relationships among its constituents remain poorly understood. We have sampled DNA sequences from the nuclear ribosomal internal transcribed spacer (ITS) and the plastid trnT- trnF region from about 100, predominantly European taxa of subg. Esula in order to infer its phylogenetic history. The plastid data support monophyly of subg. Esula whereas the ITS phylogeny, which is generally less resolved, is indecisive in this respect. Although some major clades have partly incongruent positions in the ITS and plastid phylogenies, the taxonomic content of the major terminal clades is congruent in both trees. As traditional sectional delimitations are largely not corroborated, an improved classification is proposed. Character state reconstruction illustrates that the annual life form developed independently several times in different clades of subgenus Esula from perennial ancestors, and that several morphological traits used in previous classifications of Euphorbia developed in parallel in different lineages.

A new subgeneric classification for Euphorbia (Euphorbiaceae) in southern Africa based on ITS and psbA-trnH sequence data

AbstractWe use data from the internal transcribed spacer (ITS) region of the nuclear rDNA cistron and the chloroplast psbA–trnH intergenic spacer to reconstruct the phylogenetic relationships among southern African species of Euphorbia. The results indicate that major re–organization is necessary of the groupings within Euphorbia that have been recognised in the past, since most of them turn out to be polyphyletic. Furthermore, in its present circumscription, Euphorbia itself is not monophyletic, nor do the southern African species form a monophyletic group. Both datasets show that the southern African species fall into four major groups, which we recognise as subgenera: Chamaesyce Raf., Esula Pers., Euphorbia and Rhizanthium (Boiss.) Wheeler. To accommodate the southern African species, subg. Chamaesyce is divided into sect. Chamaesyce, sect. Frondosae Bruyns, sect. nov., sect. Articulofruticosae Bruyns, sect. nov. and sect. Espinosae Pax & Hoffm. Subgenus Euphorbia is divided into sect. Euphorbia, sect. Monadenium (Pax) Bruyns, sect. Goniostema H. Baill. ex Boiss. and sect. Tirucalli Boiss. To re–establish the monophyly of Euphorbia, the genera Endadenium L. C. Leach, Monadenium Pax and Synadenium Boiss. are reduced to synonymy under Euphorbia subg. Euphorbia sect. Monadenium and the species are all transferred to Euphorbia. Consequently the subtribe Euphorbiinae now consists of the single, very large, very widely distributed and very diverse genus Euphorbia. Three of the subgenera (Chamaesyce, Esula, Euphorbia) are nearly cosmopolitan, showing the great age and wide extent of the radiation that has occurred within Euphorbia. The remaining subg. Rhizanthium is mainly African.

Pollen morphology of Euphorbia subgenus Agaloma section Tithymalopsis and related species (Euphorbiaceae)

The pollen morphology of seven species of Euphorbia subg. Agaloma sect. Tithymalopsis (Euphorbiaceae), and ten more species added by a later worker, has been examined with light and scanning electron microscopy. Three poorly differentiated exine sculpturing patterns have been observed within the 17 species. Species of sect. Tithymalopsis do not have pollen that could be distinguished from pollen of the 10 related species of subg. Agaloma. The present results do not support the monophyly of sect. Tithymalopsis proposed by morphological and isozymic data.

A Preliminary Classification of Euphorbia Subgenus Euphorbia

During preparation of the Euphorbieae for the Flora of Tropical East Africa, most of the 250 plus species in Euphorbia subg. Euphorbia were examined, resulting in a new approach to their classification. Comments are offered on the principal systems to date, all of which have been based on vegetative characters. In the newly proposed system, certain character changes linked with increasing succulence and a reduction in size are used to indicate development from trees, to shrubs, and then herbs, as an advancement in adaptation toward survival in arid conditions. Features of the inflorescence, capsules, and seeds are considered to be the most important in deciding relationships between groups, while vegetative features are used as indicators of development within the groups. A system of two sections based on seed characters is proposed, and the relationships between groups, while vegetative features are used as indicators of development within the groups

On the Identity of Euphorbia wightiana Hook.f.

J. D. Hooker, while describing the new species Euphorbia wightiana (1887: 248) from the Deccan Peninsula, remarked that 'my only materials for this very curious species are bad specimens in Herb. Wallich and a drawing marked "Madras, R. W. 446"'. He placed this species in Sect. Anisophyllum which is characterized by opposite, stipulate and oblique leaves, involucral glands with petaloid limbs, ecarunculate seeds, etc. This species has not been reported by later workers and thus the present author was prompted to look for it in the field, herbaria and literature. As a consequence, the following facts have come to light. Although J. D. Hooker was well aware of the name Euphorbia wightiana Boiss. (Cent. Euphorb.: 37 (1860)) which he (1887: 264) gave as a synonym of E. rothiana Spreng., nevertheless he still used the same name for his new species, which name is therefore an illegitimate later homonym. A critical examination of the photographs of the type material (Wight in Wall. Cat. 7692) and iconotype (Madras: R. W. 446) and the original description (leaves linear to ovate with margins entire to serrulate; involucre minute, puberulous; glands transversely oblong, unwinged; capsules oblong, puberulous; seeds bluish, oblong, mottled with a furrow on one side) of E. wightiana Hook.f. revealed that it is none other than E. agowensis Hochst. ex Boiss., an Ethiopian species recently reported from the 'Deccan Peninsula' by Kumari & Subbarao (Bull Bot. Surv. India 15: 126 (1973) (1976)) and Raju & Rao (1979: 42). While describing the species (though based on bad material) Hooker f. failed to recognise the significance of: (i) phyllotaxis spiral, opposite or ternate; (ii) the modification of the stipules into minute glands; (iii) the absence of limbs on the cyathial glands; and (iv) the presence of a caruncle on the seeds. Of course, he did note the mottled nature of the seeds and the presence of a furrow on one side, but his errors led him to place the species in the Sect. Anisophyllum (= Euphorbia Subg. Chamaesyce) to which it does not belong. In recent times (e.g. Raju & Rao, 1.c.) the diversity noted in the leaves of E. agowensis Hochst. ex Boiss. led to an explanation of the discrepancy recorded by Hooker f. in this regard for E. wightiana wherein three forms exist based on leaf-outline. One form has obovate leaves (Wall. Cat. 7692-the three small twigs near the bottom on the right hand side of the sheet) (Fig. lA). Another form has lanceolate leaves (R. W. 446) and resembles E. dracunculoides Lam. in habit (Fig. 1B). These two forms were collected by Raju (Raju & Rao, 1.c.) from Srisailam (Andhra Pradesh) in southern India. The third form is intermediate between the first two (Wall. Cat. 7692-the top four big twigs (Fig.