Phylogenetics and the evolution of major structural characters in the giant genus Euphorbia L. (Euphorbiaceae)

Department of Botany, Smithsonian Institution, NMNH MRC-166, P.O. Box 37012, Washington, DC 20013-7012, USA.
Molecular Phylogenetics and Evolution (Impact Factor: 3.92). 01/2012; 63(2):305-26. DOI: 10.1016/j.ympev.2011.12.022
Source: PubMed


Euphorbia is among the largest genera of angiosperms, with about 2000 species that are renowned for their remarkably diverse growth forms. To clarify phylogenetic relationships in the genus, we used maximum likelihood, bayesian, and parsimony analyses of DNA sequence data from 10 markers representing all three plant genomes, averaging more than 16kbp for each accession. Taxon sampling included 176 representatives from Euphorbioideae (including 161 of Euphorbia). Analyses of these data robustly resolve a backbone topology of four major, subgeneric clades--Esula, Rhizanthium, Euphorbia, and Chamaesyce--that are successively sister lineages. Ancestral state reconstructions of six reproductive and growth form characters indicate that the earliest Euphorbia species were likely woody, non-succulent plants with helically arranged leaves and 5-glanded cyathia in terminal inflorescences. The highly modified growth forms and reproductive features in Euphorbia have independent origins within the subgeneric clades. Examples of extreme parallelism in trait evolution include at least 14 origins of xeromorphic growth forms and at least 13 origins of seed caruncles. The evolution of growth form and inflorescence position are significantly correlated, and a pathway of evolutionary transitions is supported that has implications for the evolution of Euphorbia xerophytes of large stature. Such xerophytes total more than 400 species and are dominants of vegetation types throughout much of arid Africa and Madagascar.

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    • "Molecular phylogenetic studies (the most recent and comprehensive by Horn et al., 2012) have revealed four main evolutionary lineages in Euphorbia, corresponding to the four subgenera currently recognized. Most species in Europe belong to Euphorbia subgenus Esula Pers., which is sister to all other subgenera (Horn et al., 2012). It comprises roughly 480 species and represents the most significant radiation of the genus in temperate areas of the Old World, with highest diversity in the Mediterranean and the Irano-Turanian regions (Riina et al., 2013). "
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    ABSTRACT: The leafy spurges, Euphorbia subgenus Esula, have one of their diversity centres in the Mediterranean, which is considered to be one of the 25 biodiversity hot-spots. The eastern Mediterranean, in particular, is characterized by its high species richness and is therefore considered to be a cradle for lineage diversification. However, the area remains neglected in phylogenetic studies. Using nuclear ribosomal internal transcribed spacer (ITS) and plastid trnT-trnF sequences, we explored the phylogenetic relationships in the predominantly eastern Mediterranean E. hierosolymitana group, which is characterized by a woody habit. The widespread shrublets E. acanthothamnos, E. glabriflora and E. spinosa, which are similar in habit, are not most closely related, the last two forming a sister clade to other taxa. From the E. acanthothamnos alliance, dendroid shrubs evolved at least two, but possibly four, times, giving rise to widespread E. bivonae and E. hierosolymitana, the Cretan endemic E. sultan-hassei and the here newly described and genetically most divergent E. lemesiana, endemic to Cyprus. We provide a taxonomic treatment and morphological comparison with the similar, but not most closely related, E. hierosolymitana. Our study underlines the phytogeographical peculiarity of Cyprus and contributes to our current knowledge on the diversification patterns in the eastern Mediterranean. © 2015 The Linnean Society of London, Botanical Journal of the Linnean Society, 2015, ●●, ●●–●●.
    Botanical Journal of the Linnean Society 09/2015; 179(2). DOI:10.1111/boj.12319 · 2.53 Impact Factor
    • "either segregated from or included within Euphorbia. Recent phylogenetic studies (Horn et al. 2012, Yang et al. 2012, Dorsey et al. 2013, Peirson et al. 2013, Riina et al. 2013) have resulted in a new subgeneric classification in which 4 subgenera and 65 sections are proposed. Euphorbia subg. "
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    ABSTRACT: Two new species of Euphorbia subg. Chamaesyce sect. Anisophyllum are described and illustrated. Both are endemic to the Sonoran Desert of Baja California Sur, Mexico, and were previously determined as Euphorbia polycarpa. Their recognition is highly supported by both molecular and morphological data. Euphorbia vizcainensis occurs in the Vizcaíno and Magdalena subdivisions at elevations from 20 to 250 m. It differs from E. polycarpa in having rugose seeds with transverse ridges (vs. smooth seeds). It is most similar to E. pondii from which it is separated by features of the stipules, involucral appendages, and seeds. Euphorbia cerralvensis is restricted to the Cerralvo Island in the municipality of La Paz of the Central Gulf Coast subdivision, and occurs at elevations from 10 to 300 m. It also differs from E. polycarpa by having seeds with transverse ridges. Morphologically it is very distinct from other Euphorbia species in the region. Phylogenetic evidence suggests that it belongs to a clade with E. dentosa, E. leucophylla, E. petrina, and E. brandegeei, species from which it is distinguished by its suffrutescent ascending habit (vs. herbaceous prostrate habit).
    Phytotaxa 08/2015; 221(3):265-278. DOI:10.11646/phytotaxa.221.3.4 · 1.32 Impact Factor
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    • "The genus is renowned for its remarkable morphological diversity and diverse growth forms and is characterized by the cyathium, a pseudanthial inflorescence unique in Angiosperms, which consists of four or five staminate cymules surrounding a terminal pistillate flower within a cup-like involucre formed by the fusion of bracts from the staminate cymules. The cyathium has glands along its rim, and the glands can sometimes have appendices (Webster 1994, Radcliffe–Smith 2001, Horn et al. 2012, Yang et al. 2012). The cyathium is taxonomically very important for the identification of species and was once used to segregate genera within subtribe Euphorbiineae (Webster 1994, Radcliffe-Smith 2001). "
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    ABSTRACT: Euphorbia is the largest genus of Euphorbiaceae and is among the giant genera of Angiosperms. In the state of São Paulo, the genus is represented by 23 species occurring in savannas, high altitude fields, and anthropic areas. This work includes an identification key, photographs, and comments on morphology, habitat, and geographical distribution. We reestablish Euphorbia chrysophylla and recognize Leptopus brasiliensis as a synonym of Euphorbia sciadophila. Six new records for the state of São Paulo are presented: Euphorbia adenoptera, E. bahiensis, E. chrysophylla, E. cordeiroae, E. foliolosa and E. ophthalmica. Eight lectotypes are designated.
    Phytotaxa 09/2014; 181(4):193-215. DOI:10.11646/phytotaxa.181.4.1 · 1.32 Impact Factor
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