<p>Members of Zygophylloideae are shrubs, shrublets and herbs of arid and semiarid areas of almost all continents, and many of the species are major components of the vegetation in their areas of distribution. A phylogenetic analysis of Zygophylloideae based on noncoding <i>trnL</i> plastid DNA sequences and morphological data, indicates that the currently recognised genera <i>Augea</i>, <i>Tetraena</i>, and <i>Fagonia</i>, are embedded in <i>Zygophyllum</i>. A new generic classification based on six monophyletic and morphologically distinctive entities is proposed here: <i>Augea</i>, <i>Fagonia</i>, <i>Melocarpum</i>, <i>Roepera</i>, <i>Tetraena</i> and <i>Zygophyllum</i>. </p><p>The taxonomy of the genus <i>Fagonia</i> is revised in detail. A key to the 34 species recognised is presented, as well as descriptions and distribution maps for each species. Five new species are described and illustrated, <i>F. densispina</i>, <i>F. gypsophila</i> and <i>F. latistipulata </i>from Somalia, and <i>F. hadramautica</i> and <i>F. mahrana</i> from the southern part of the Arabian peninsula. Of the accepted species, 26 are restricted to the Old World and eight to the New World. The names of all four species of <i>Fagonia</i> currently on the IUCN Red List of Threatened Plants are put into synonymy. Instead, eight other species are proposed for this list.</p><p>Relationships within <i>Fagonia</i> are inferred from analysis of plastid <i>trnL</i> intron and nuclear ribosomal ITS sequences. The phylogenetic analysis is performed using parsimony and Bayesian model averaging. All species of <i>Fagonia</i> in the Old World, except <i>F. cretica</i>, form a weakly supported clade, and all <i>Fagonia</i> species of the New World, except <i>F. scoparia</i>, form a second, well supported clade, sister to the Old World clade. <i>Fagonia scoparia</i>, endemic to northeastern Mexico,<i> </i>is sister to all other <i>Fagonia</i> species. Vicariance-dispersal analysis indicated that the occurrences of <i>Fagonia</i> in South America and southern Africa are due to dispersals, and that the ancestor of <i>Fagonia</i> had a distribution in agreement with the boreotropics hypothesis.</p>
| Identifer | oai:union.ndltd.org:UPSALLA/oai:DiVA.org:uu-3634 |
| Date | January 2003 |
| Creators | Beier, Björn-Axel |
| Publisher | Uppsala University, Department of Systematic Botany, Uppsala : Acta Universitatis Upsaliensis |
| Source Sets | DiVA Archive at Upsalla University |
| Language | English |
| Detected Language | English |
| Type | Doctoral thesis, comprehensive summary, text |
| Relation | Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, 1104-232X ; 898 |
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