Th(^ nK)n()|)livtv and pin lot^cnctic relati()nslii|ts iif the Irihe Kii|)h^nized jicneia. subgenera, and sections within the Euplunbieae and 1 oulj^roup taxa from \\\v tribe lli[)[>otnaneae (Knpliorbiac(^ae). I^'>ll' tl><' I 1'^ ^>'i*' ^^^fhV aiial}ses suppitrl the innnophvly of Kuphorbieae in adiy Ijefore the !>reaku|) of (ittudwanaland. at whiih time the major lineages of subtril)e ' We are extremely gratehil to all those who have assist^^l with this research. In particular we thank Susan (barter, J. Travis Columbus, FdizalxMh Kriar. Victoria llnllowell. (,ordnn MePherson. and Oady Webster for critically reviewing the manuscri]tt. For permission to examine tluir c(j|lectiotr^ and to sam[)lc herbarium uialerial, we thank the curators and staffs at MUZ. CAS. I)A\. FNCB. K CB. K. MO, NY. USA. SCO, Sl\ and TEX. The following institntions ami inilividuals extended assistance by permitting access to their living collections: Dylan llannon; Chuck Hanson of Arid bands (weenhouses; Mark Mayfield; Meetia Singh; S<'ymonr bindf^n; John Trager and Jot-ChMuents of the llnntington Botanical Carden; I'rs Eggli of Snkkulenten-Sammlung /ihich: and Herman Schwartz. Cordon McTherson and Sebastian Teillier collected material (A' .W'of^iiillaandnid itcopalnt and Kupliorlmi grtfiKiitui, respecti\ ely. Fieldwork, herbarium visits, and laboiatory use and materials were made possible by the giMu-rous support of the Andrew W. M<'llon Fonnihition, the American Socii'tv of IMarit Taxonomists, the Howard and Phoebe Brown Scholarship, and the Hardman Native FMant Besearch Award. I.anren Baz jirovided ITS secjucnees for Cluimui'syce degcneri, C, hyper'uljoiia, and C prnslnita. Kenneth Wnrdack gave useful information about outgroup selection. We are Indebted to ihe staff and graduate students at tlte Hancho Santa Ana Botanic Carden for enconragement and support, especiall} Eric Uoalson for his (n)ntinuous hclji and ad\ice. M^ancho Santa Ana Botanic C...

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.

Euphorbia subg. Euphorbia is the largest and most diverse of four recently recognized subgenera within Euphorbia and is distributed across the tropics and subtropics. Relationships within this group have been difficult to discern due mainly to homoplasious morphological characters and inadequate taxon sampling in previous phylogenetic studies. Here we present a phylogenetic analysis of E. subg. Euphorbia, using one nuclear and two plastid regions, for the most complete sampling of molecular sequence data to date. We assign 661 species to the subgenus and show that it is comprised of four highly supported clades, including a single New World clade and multiple independent lineages on Madagascar. Using this phylogenetic framework we discuss patterns of homoplasy in morphological evolution and general patterns of biogeography. Finally, we present a new sectional classification of E. subg. Euphorbia comprising 21 sections, nine of them newly described here.

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RESUMENSe calcula que en México las Euphorbiaceae están representadas por 43 géneros y 782 especies, más 32 taxa intraespecíficos: 8 subespecies y 24 variedades. Se propone una lista preliminar de la familia para el país. Los géneros más grandes son Euphorbia (241 spp., 31%), Croton (124 spp., 16%), Acalypha (108 spp., 14%), Jatropha (48 spp., 6%) y Phyllanthus (41 spp., 5%). Juntos representan 72% de las especies de las Euphorbiaceae conocidas de México. Hay un género endémico del país, Enriquebeltrania y se estima que 57% de las especies mexicanas son endémicas a su territorio. Empleando el concepto de Megaméxico, este valor aumenta a 78%. Los taxa introducidos están representados por un género (Ricinus) y 10 especies. Se destacan dos centros de diversidad que corresponden con las vertientes pacífica y atlántica. A nivel de género, las euforbiáceas mexicanas muestran una gran afinidad con las de Centro y Sudamérica; a nivel de especie, en su mayoría son endémicas, pero de las que no lo son, 200 existen también en Centroamérica, 138 en los Estados Unidos, 85 en Sudamérica y 55 en las Antillas. Casi ninguna de las especies mexicanas se encuentra de manera natural en el Viejo Mundo. A pesar de su gran importancia, tanto sistemática como florística, el conocimiento de las Euphorbiaceae en México es aún sumamente pobre.Palabras clave: diversidad, Euphorbiaceae, México. ABSTRACTIt is estimated that in Mexico the Euphorbiaceae are represented by 43 genera and 782 species. In addition, there are 32 infraspecific taxa: 8 subspecies and 24 varieties. A preliminary list of the taxa is provided. The most diverse genera are Euphorbia (241 spp., 31%), Croton (124 spp., 16%), Acalypha (108 spp., 14%), Jatropha (48 spp., 6%), and Phyllanthus (41 spp., 5%). Together, these represent 72% of the species present in Mexico. There is one endemic genus, Enriquebeltrania. It is estimated that 57% of the Mexican species are endemic to the country. Employing the concept of Megamexico, 78% of the species are endemic. There are ten introduced species and one introduced genus (Ricinus). Within the country, the family is most diverse along the Pacific and Atlantic slopes. At the level of genus, the Mexican Euphorbiaceae show a strong affinity with Central and South America. At the level of species, most Mexican Euphorbiaceae are endemic, but of the species that are not, 200 also occur in Central America, 138 in the United States, 85 in South America, and 55 in the Antilles. Almost no Mexican species are found naturally in the Old World. Despite their great systematic and floristic importance, an adequate understanding of the Mexican Euphorbiaceae is still lacking.

Malpighiaceae possess flowers with a unique bilateral symmetry (zygomorphy), which is a hypothesized adaptation associated with specialization on neotropical oil bee pollinators. Gene expression of two representatives of the CYC2 lineage of floral symmetry TCP genes, CYC2A and CYC2B, demarcate the adaxial (dorsal) region of the flower in the characteristic zygomorphic flowers of most Malpighiaceae. Several clades within the family, however, have independently lost their specialized oil bee pollinators and reverted to radial flowers (actinomorphy) like their ancestors. Here, we investigate CYC2 expression associated with four independent reversals to actinomorphy. We demonstrate that these reversals are always associated with alteration of the highly conserved CYC2 expression pattern observed in most New World (NW) Malpighiaceae. In NW Lasiocarpus and Old World (OW) Microsteria, the expression of CYC2-like genes has expanded to include the ventral region of the corolla. Thus, the pattern of gene expression in these species has become radialized, which is comparable to what has been reported in the radial flowered legume clade Cadia. In striking contrast, in NW Psychopterys and OW Sphedamnocarpus, CYC2-like expression is entirely absent or at barely detectable levels. This is more similar to the pattern of CYC2 expression observed in radial flowered Arabidopsis. These results collectively indicate that, regardless of geographic distribution, reversals to similar floral phenotypes in this large tropical angiosperm clade have evolved via different genetic changes from an otherwise highly conserved developmental program.

The study of traits that play a key role in promoting diversification is central to evolutionary biology. Floral nectar spurs are among the few plant traits that correlate with an enhanced rate of diversification, supporting the claim that they are key innovations. Slight changes in spur morphology could confer some degree of premating isolation, explaining why clades with spurs tend to include more species than their spurless close relatives. We explored whether the cyathial nectar spur of the Pedilanthus clade (Euphorbia) may also function as a key innovation. We estimated the phylogeny of the Pedilanthus clade using one plastid (matK) and three nuclear regions (ITS and two G3pdh loci) and used our results and a Yule model of diversification to test the hypothesis that the cyathial spur correlates with an increased diversification rate. We found a lack of statistical support for the key innovation hypothesis unless specific assumptions regarding the phylogeny apply. However, the young age (hence small size) of the group may limit our ability to detect a significant increase in diversification rate. Additionally, our results confirm previous species designations, indicate higher homoplasy in cyathial than in vegetative features, and suggest a possible Central American origin of the group.

Cubanthus (Euphorbiaceae) has traditionally been recognized as a small genus of three similar species restricted to Cuba and Hispaniola. In this study we used DNA sequence data from the nuclear ITS and chloroplast ndhF gene regions to investigate its systematic position and the position of four other shrubby Euphorbia species endemic to Cuba: E. cubensis, E. helenae, E. munizii, and E. podocarpifolia. The results demonstrate that all of these taxa belong to a well-supported Antillean clade nested within Euphorbia that also includes E. punicea and E. gymnonota. For that reason, we treat Cubanthus as a section of Euphorbia instead of a separate genus. Euphorbia sect. Adenorima is relegated to a synonym of sect. Cubanthus. New names are proposed for Cubanthus brittonii and Cubanthus linearifolius (Euphorbia millspaughii and E. scutiformis, respectively), and a new combination is made for Cubanthus umbelliformis (Euphorbia umbelliformis). Section Cubanthus belongs to clade C of Euphorbia and is part of a New World assemblage that includes members of sections Euphorbiastrum, Pteroneurae, Portulacastrum, Stachydium, and the former genus Pedilanthus. Based on both the molecular results and morphological differences, two subsections are proposed: subsect. Cubanthus and subsect. Moa. The molecular phylogeny supports the hypothesis that section Cubanthus radiated entirely within the Antilles and the nearby Bahamian archipelago.