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Peirson J.A.,University of Michigan | Bruyns P.V.,University of Cape Town | Riina R.,University of Michigan | Morawetz J.J.,500 North College Ave | Berry P.E.,University of Michigan
Taxon | Year: 2013

Euphorbia subg. Athymalus consists of approximately 150 species and is one of the four main lineages that comprise the species-rich genus Euphorbia. Most species in the subgenus are stem succulents with greatly reduced leaves, but there are also leafy herbs, shrubs, trees and geophytes. The subgenus is restricted to arid regions of the Old World. Most species are found in sub-Saharan Africa, with one in Macaronesia and adjacent parts of western Africa, a few in the Arabian Peninsula (one of which extends into Iran) and one native to Madagascar. Twenty-three species are endemic to the northeastern Horn of Africa (SE Ethiopia, Socotra, Somalia), while 72 species are restricted to southern Africa (including Botswana, Lesotho, Namibia, South Africa and Swaziland). Sixty of those are endemic to South Africa alone, where they are particularly associated with the semi-arid west and south of the country in the Greater Cape Floristic Region and the Nama Karoo Region. We sampled 88 species and analyzed data from the nuclear ribosomal ITS and plastid ndhF regions. Analyses of the separate and combined datasets produced phylogenies that confirm the monophyly of E. subg. Athymalus and the placement of E. antso from Madagascar as sister to the rest of the subgenus. Our analyses also show that the subgenus consists of a grade of early-diverging lineages that are relatively poor in species and that the major radiation of succulent species in southern Africa forms a highly supported clade (E. sect. Anthacanthae). Species-level relationships within this southern African clade, however, remain largely unresolved. Our phylogenetic hypotheses allow us to propose a new classification for E. subg. Athymalus where seven sections are recognized, two of which are newly described. The large southern African E. sect. Anthacanthae is further divided into five subsections, and four series are recognized in E. subsect. Florispinae.

Fotinos T.D.,Fairchild Tropical Botanic Garden | Fotinos T.D.,Florida International University | Namoff S.,Fairchild Tropical Botanic Garden | Namoff S.,500 North College Ave | And 5 more authors.
Journal of the Torrey Botanical Society | Year: 2015

Rare plant reintroductions are designed to increase the number of individuals in the wild, but can also improve genetic diversity of populations, reducing both short-term and long-term extinction risks. We used microsatellites developed for the genus Pseudophoenix H. Wendl. ex Sarg. to determine how reintroduced plants of the endangered Pseudophoenix sargentii H. Wendl. ex Sarg. planted in the Florida Keys in the early 1990s contributes to the population genetic structure of the species. We sampled 108 individuals representing wild and reintroduced populations in the Florida Keys and from the ex situ collection at Fairchild Tropical Botanic Garden. The wild stand on Elliott Key and the reintroduced individuals on Long Key displayed evidence of genetic drift, inbreeding, and decreased gene flow. In contrast, the ex situ plants and reintroduced individuals on Elliott Key displayed low inbreeding and higher heterozygosity. All populations deviated significantly from Hardy-Weinberg equilibrium. All pairwise FST and GST values were significant except comparisons between certain age classes on Elliott Key. Analysis of molecular variance partitioned 87.8% of the genetic variation within populations. Overall, reintroduced plants have contributed to greater heterozygosity of the stand on Elliot Key. Finally, our work shows that the ex situ collection includes wild offspring of individuals that are now extirpated, supporting the ongoing importance of ex situ collections in botanic gardens. © Torrey Botanical Club.

Riina R.,University of Michigan | Peirson J.A.,University of Michigan | Geltman D.V.,RAS Komarov Botanical Institute | Molero J.,University of Barcelona | And 10 more authors.
Taxon | Year: 2013

The 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. Stemsucculents 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.

Horn J.W.,Smithsonian Institution | van Ee B.W.,Black Hills State University | Morawetz J.J.,500 North College Ave | Riina R.,University of Michigan | And 3 more authors.
Molecular Phylogenetics and Evolution | Year: 2012

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 16. kbp 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. © 2012.

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