Molecular phylogenetics and classification of Euphorbia subgenus Chamaesyce (Euphorbiaceae)

Euphorbia 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.

[1]  H. Akhani,et al.  Seed morphology of Iranian annual species of Euphorbia (Euphorbiaceae) , 2011 .

[2]  R. L. Dressler.  A Synopsis of Poinsettia (Euphorbiaceae) , 1961 .

[3]  Bryan Kolaczkowski,et al.  Long-Branch Attraction Bias and Inconsistency in Bayesian Phylogenetics , 2009, PloS one.

[4]  D. Koutnik.  Chamaesyce (Euphorbiaceae) — a newly recognized genus in southern Africa , 1984 .

[5]  Ya Yang,et al.  Phylogenetics of the Chamaesyce clade (Euphorbia, Euphorbiaceae): reticulate evolution and long-distance dispersal in a prominent C4 lineage. , 2011, American journal of botany.

[6]  Robert C. Edgar,et al.  MUSCLE: multiple sequence alignment with high accuracy and high throughput. , 2004, Nucleic acids research.

[7]  F. Hellwig,et al.  Further support for the phylogenetic relationships within Euphorbia L. (Euphorbiaceae) from nrITS and trnL–trnF IGS sequence data , 2010, Plant Systematics and Evolution.

[8]  J. Molero,et al.  Euphorbia L. subsect. Esula (Boiss. in DC.) Pax in the Iberian Peninsula. Leaf surface, chromosome numbers and taxonomic treatment , 1992 .

[9]  J. Porter,et al.  Phylogenetic Relationships in Euphorbieae (Euphorbiaceae) Based on ITS and ndhF Sequence Data , 2002 .

[10]  P. Hanáček,et al.  Age and diversity in Old World succulent species of Euphorbia (Euphorbiaceae). , 2011 .

[11]  P. Rudall,et al.  Comparative ontogeny of the cyathium in Euphorbia (Euphorbiaceae) and its allies: exploring the organ-flower-inflorescence boundary. , 2007, American journal of botany.

[12]  A. Giulietti,et al.  Euphorbia flaviana, a New Species from the Inselbergs of Bahia (Brazil) and Lectotypification of E. crossadenia , 2012 .

[13]  A. P. D. Candolle.  Prodromus systematis naturalis regni vegetabilis , 1968 .

[14]  John P. Huelsenbeck,et al.  MRBAYES: Bayesian inference of phylogenetic trees , 2001, Bioinform..

[15]  G. Webster,et al.  SYSTEMATICS OF PHOTOSYNTHETIC CARBON FIXATION PATHWAYS IN EUPHORBIA , 1975 .

[16]  Joey Shaw,et al.  Comparison of whole chloroplast genome sequences to choose noncoding regions for phylogenetic studies in angiosperms: the tortoise and the hare III. , 2007, American journal of botany.

[17]  P. Rudall,et al.  Is LEAFY a useful marker gene for the flower–inflorescence boundary in the Euphorbia cyathium? , 2010, Journal of experimental botany.

[18]  D. B. Ward.  New combinations in the Florida flora , 2001 .

[19]  Alexandros Stamatakis,et al.  RAxML-VI-HPC: maximum likelihood-based phylogenetic analyses with thousands of taxa and mixed models , 2006, Bioinform..

[20]  Jeremy M. Brown,et al.  When trees grow too long: investigating the causes of highly inaccurate bayesian branch-length estimates. , 2010, Systematic biology.

[21]  Revision of the cerrado hemicryptophytic Chamaesyce of Boissier's “Pleiadeniae” (Euphorbiaceae) , 1997, Brittonia.

[22]  K. Wurdack,et al.  Phylogenetics and the evolution of major structural characters in the giant genus Euphorbia L. (Euphorbiaceae). , 2012, Molecular phylogenetics and evolution.

[23]  Mark P. Simmons,et al.  Independence of alignment and tree search. , 2004, Molecular phylogenetics and evolution.

[24]  R. Sage,et al.  The occurrence of C(2) photosynthesis in Euphorbia subgenus Chamaesyce (Euphorbiaceae). , 2011, Journal of experimental botany.

[25]  D. Marshall,et al.  Cryptic failure of partitioned Bayesian phylogenetic analyses: lost in the land of long trees. , 2010, Systematic biology.

[26]  G. Webster.  The genera of Euphorbiaceae in the southeastern United States [prim.] , 1968, Journal of the Arnold Arboretum..

[27]  Richard G. Olmstead,et al.  Combining Data in Phylogenetic Systematics: An Empirical Approach Using Three Molecular Data Sets in the Solanaceae , 1994 .

[28]  D. Maddison,et al.  MacClade 4: analysis of phy-logeny and character evolution , 2003 .

[29]  L. Croizat.  New and Critical Euphorbiaceae from Eastern Tropical Asia , 1940, Journal of the Arnold Arboretum.

[30]  G. Cremers.  Les euphorbes coralliformes de Madagascar , 1984 .

[31]  L. C. Wheeler.  Euphorbia subgenus Chamaesyce in Canada and the United States exclusive of southern Florida , 1941, Contributions from the Gray Herbarium of Harvard University.

[32]  L. C. Wheeler.  The Genera of the Living Euphorbieae , 1943 .

[33]  C. Davis,et al.  Evolutionary bursts in Euphorbia (Euphorbiaceae) are linked with photosynthetic pathway , 2014, Evolution; international journal of organic evolution.

[34]  R. Jansen,et al.  A Phylogeny of Euphorbieae Subtribe Euphorbiinae (Euphorbiaceae) Based on Molecular Data , 2007, Journal of Plant Biology.

[35]  P. Bruyns,et al.  A new subgeneric classification for Euphorbia (Euphorbiaceae) in southern Africa based on ITS and psbA-trnH sequence data , 2006 .

[36]  John P. Huelsenbeck,et al.  MrBayes 3: Bayesian phylogenetic inference under mixed models , 2003, Bioinform..