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Corymbieae
Abstract and Figures
The generic name Corymbium was employed by Linnaeus in Corollarium Generum Plantarum (Linnaeus 1737), Hortus Cliff ortianus (Linnaeus 1738), and Genera Plantarum ed. 2 (Linnaeus 1742) and ascribed to Gronovius (in Burman's Rariorum Africanarum Plantarum, 1738–39). With valid pub-lication in Species Plantarum (Linnaeus 1753) the offi cial name became Corymbium L. Linnaeus placed the genus in his Syngenesia Monogamia together with Jasione, Lobelia, Viola and Impatiens on account of the unusual capitular and fl oral morphology, but in his outlines of a natural system he placed the genus with the other members of Compositae. Thus in the Fragmenta Methodi Naturalis, which appeared as an appendix in the Paris edition of the Genera Plantarum (1743), he placed Corymbium in "XXI Ordo", comprising all genera that he would later refer to as Compositae. Cassini (1818, 1829) referred Corymbium without hesi-tation to Vernonieae, where it has since traditionally been placed (Lessing 1832; De Candolle 1836; Harvey 1865; Bentham 1873a, b; Hoff mann 1890–1894; Jones 1977; Weitz 1989, 1990), although the genus has never fi t com-fortably in that tribe. Bentham (1873b) noted that the pistil of Corymbium has a distinct ovary that is long, cylindrical, and densely hirsute, and very short style branches, while in typical Vernonieae the ovary is not densely hirsute and the style branches are long and slender (Jones 1977). Bolick (1978) also noted that Corymbium pollen diff ered from that of other Vernonieae. Based on signifi cant diff er-ences in sesquiterpene lactones and diterpenes, Bohlmann and his collaborators (Zdero and Bohlmann 1988; Bohl-mann and Jakupovic 1990) suggested Corymbium be re-moved from Vernonieae. Bremer (1994) in a cladistic analysis of Compositae found Corymbium morphologi-cally anomalous in Vernonieae and removed it from the tribe. In his treatment Corymbium was placed in subfamily Cichorioideae but without a tribal assignment. Similarly, Robinson (1996) excluded Corymbium from Vernonieae based on the chemistry and morphology, but proposed no other tribal placement. Molecular data (Panero and Funk 2002, 2008) refl ect the morphological, palynological and chemical disparities noted by earlier workers (described above). Sequence in-formation showed that Corymbium did not belong in any existing tribe or subfamily and so was placed in its own tribe, Corymbieae, and its own subfamily, Corymbioideae (Panero and Funk 2002) (see the metatree in Chapter 44). In addition, Corymbium was strongly supported as the sis-ter group to the entire subfamily Asteroideae which con-tains 65% of the genera within the family. The removal of Corymbium from Vernonieae has been accepted by the systematic community (Nordenstam 2007) and the re-cent molecular phylogeny of Vernonieae by Keeley et al. (2007) did not include this genus.
Chromosome number changes during the evolution of angiosperms are likely to have played a major role in speciation. Their study is of utmost importance, especially now, as a probabilistic model is available to study chromosome evolution within a phylogenetic framework. In the present study, likelihood models of chromosome number evolution were fitted to the largest family of flowering plants, the Asteraceae. Specifically, a phylogenetic supertree of this family was used to reconstruct the ancestral chromosome number and infer genomic events. Our approach inferred that the ancestral chromosome number of the family is n = 9. Also, according to the model that best explained our data, the evolution of haploid chromosome numbers in Asteraceae was a very dynamic process, with genome duplications and descending dysploidy being the most frequent genomic events in the evolution of this family. This model inferred more than one hundred whole genome duplication events, however it did not find evidence for a paleopolyploidization at the base of this family, which has previously been hypothesized on the basis of sequence data from a limited number of species. The obtained results and potential causes of these discrepancies are discussed.
It is shown that there is a wide range of structural variation in the habit of the Arundineae and Ehrharteae of the fynbos of the Cape Floristic Region (Cape Province, South Africa). Structural differences in the bases of the fynbos grasses have been classified into four groups: swollen, knotty tillering, weak and annual. Variation in the position of the innovation buds occurs with one group having basal perennating buds, implying that all the culm material is annual, while the second group has cauline innovation buds, leading to the development of a divaricate perennial herb. The recognition of caducous, mesic (orthophyllous) and sclerophyllous leaf blades is also possible, based on leaf morphology and anatomy. These variations in growth forms allow the classification of the Cape grasses into five guilds adapted for survival in the dense fynbos vegetation that develops between the well-spaced fires in these heathlands. The following guilds have been recognized: competition avoiders that grow on rock ledges and outcrops where competition from shrubby vegetation is reduced; reseeders, that survive the protracted interfire period as seed; geophytes, that survive this period as underground organs; coppicers, that survive as small plants; and competitors, that grow tall by means of cauline innovation buds, and so are able to compete with the shrubby heath vegetation.
Variation in the fire-survival strategy of the fynbos, legume tribesPodalyrieae andLiparieae was studied, since it is often the only conspicuous difference between morphologically similar taxa. Two main strategies are apparent: sprouters, taxa which are able to sprout from a woody rootstock after fire and non-sprouters, those which only recruit from seed after fire. In fynbos legumes sprouting and non-sprouting taxa differ in their habitat specificity, population densities, relative regional abundance, and in seed germination tempo. Speciation patterns, as inferred from an analysis of the geographical distribution and habitat specificity of the species, are discussed. Problems relating to the use of sprouting versus non-sprouting as a taxonomic character in fynbos legumes are addressed and possible solutions are given.
The Cape Peninsula, a 470 km2 area of rugged scenery and varied climate, is located at the southwestern tip of the Cape Floristic Region, South Africa. The Peninsula is home to 2285 plant species and is a globally important hot-spot of biodiversity for higher plants and invertebrates. This paper provides a broad overview of the physiography, biological attributes and history of human occupation of the Peninsula. The Peninsula is characterized physiographically by extremely high topographical heterogeneity, very long and steep gradients in annual rainfall, and a great diversity of nutrient-poor soils. Thus, the Peninsula supports a high number of habitats and ecological communities. The predominant vegetation is fynbos, a fire-prone shrubland, and 12 broadly characterized fynbos types have been described on the Peninsula. Animal community structure, especially with regard to invertebrates, is poorly known. Vertebrate community structure is probably strongly influenced by nutrient poverty and recurrent fire. Generally, most vertebrates are small and typically occur in low numbers. Some invertebrates play keystone roles in facilitating ecological processes. Human occupation of the Peninsula was limited, until relatively recently, by nutrient poverty. After Dutch colonization in 1652, direct and indirect impacts on the natural ecosystems of the Peninsula escalated dramatically, and by 1994, some 65% of original natural habitat was either transformed by urbanization and agriculture, or invaded by alien plants. Nonetheless, there is still excellent potential to conserve the Cape Peninsula's remaining biodiversity.
A revision of the genus Corymbium L. (Asteraceae; Vernonieae) is presented in which nine species, four subspecies and five varieties are recognized. C. elsiae Weitz and C. laxum subsp. bolusii Weitz are described as new taxa and several new combinations are made. Full descriptions, synonymy, distribution data, maps, illustrations, and a key to the species are provided. Remarks on diagnostic features, ecology and a brief historical review are given.
The roots of Corymbium villosum afforded nine new simple ent-labdane derivatives two in which two diterpene units are combined via malonic acid and two in which the hydroxy groups are connected via malonic acid forming macrolide systems. The structures were elucidated by high field NMR spectroscopy and a few chemical transformations. The chemotaxonomic relevance of the results is discussed briefly.
Molecular studies of the flowering plant family Compositae (Asteraceae) based on comparative DNA sequence data of chloroplast genes provide new insights into the evolution and radiation of the family. The results support the creation of new groups to maintain a classification that reflects evolutionary history. We are proposing the following new names: subfamilies Corymbioideae, Gochnatioideae, Gymnarrhenoideae, Hecastocleoideae, and Pertyoideae; tribes Athroismeae, Corymbieae, Dicomeae, Gochnatieae, Gymnarrheneae, Hecastocleideae, Polymnieae; subtribe Rojasianthinae. The totals now stand at 11 subfamilies and 35 tribes. Only one tribe, the Mutisieae, is non-monophyletic having two branches. Most of the new groups are derived from taxa included in tribe Mutisieae, long suspected to be a paraphyletic group. Molecular studies that support these changes are discussed elsewhere but a summary of their results is presented.
This paper provides a general survey of the occurrence of diterpenes in the Asteraceae. Data on 4351 botanical occurrences were obtained from the literature. These were grouped by skeleton for each genus. Then, the genera were grouped by subtribes, which, in turn, were gathered in tribes, followed by subfamilies. In spite of the low number of species containing diterpenes, it was possible to describe some structural features of these compounds, i.e. the skeletal types in various taxa and the positions in some skeletons that are always oxidized or never undergo oxidation in some genera. Thus, it was verified that: in the subfamily Cichorioideae, only a few of the studied species possess diterpenes, wherein kaurane is the most frequent diterpene skeleton. In the Asteroideae, the presence of diterpenes is much greater than that in the Cichorioideae and Carduoideae. At tribal taxonomic level, for example, the Astereae produce labdanes and clerodanes; Heliantheae and Eupatorieae produce kauranes and labdanes, respectively; and Calenduleae produce pimaranes. Some taxonomic implications are presented. © 2005 The Linnean Society of London, Botanical Journal of the Linnean Society, 2005, 147, 291–308.
In fynbos vegetation of the southwestern Cape Province, South Africa, plant species diversity relations (alpha and beta diversity) are studied in a local context of variation across two interacting gradients, a temporal gradtent (age after fire) and an altitudinal gradient.
Alpha diversity is lower in the older fynbos at high and low altitudes. This can be related to the nature of succession in fynbos. The lowest alpha diversity occurs in the low altitude old vegetation. This appears to occur because of the decrease of understory cover due to overtopping by tall shrubs and tall restioids.
Beta diversity is due more to the altitude factor than to fire. This can also be related to the nature of fynbos succession. In general the trends shown by alpha and beta diversity can be explained with reference to fynbos succession, the regenerating strategies after fire (seed vs. vegetative) and the effect of the overstory on the understory.
Two basic patterns of exine ultrastructure are found in theCompositae, the caveate Helianthoid pattern and the non-caveate Anthemoid pattern. TheHeliantheae, Astereae, Inuleae, Sececioneae, Calenduleae andEupatorieae all have pollen with caveate exines. TheMutisiseae, Vernonieae andCardueae have predominately Anthemoid pollen. TheAnthemideae, Arctoteae andLactuceae have pollen with exines of both patterns. Recent investigations of pollen in theVernonieae suggest that these exine ultrastructures in the family have evolved in response to mechanical stresses on the wall which are caused by changes in volume of the grain as it loses or gains water from its environment.
The Vernonieae is one of the major tribes of the largest family of flowering plants, the sunflower family (Compositae or Asteraceae), with ca. 25,000 species. While the family's basal members (the Barnadesioideae) are found in South America, the tribe Vernonieae originated in the area of southern Africa/Madagascar. Its sister tribe, the Liabeae, is New World, however. This is the only such New/Old World sister tribe pairing anywhere in the family. The Vernonieae is now found on islands and continents worldwide and includes more than 1500 taxa. The Vernonieae has been called the "evil tribe" because overlapping character states make taxonomic delimitations difficult at all levels from the species to the subtribe for the majority of taxa. Juxtaposed with these difficult-to-separate entities are monotypic genera with highly distinctive morphologies and no obvious affinities to any other members of the tribe. The taxonomic frustration generated by these contrary circumstances has resulted in a lack of any phylogeny for the tribe until now. A combined approach using DNA sequence data from two chloroplast regions, the ndhF gene and the noncoding spacer trnL-F, and from the nuclear rDNA ITS region for 90 taxa from throughout the world was used to reconstruct the evolutionary history of the tribe. The data were analyzed separately and in combination using maximum parsimony (MP), minimum evolution neighbor-joining (NJ), and Bayesian analysis, the latter producing the best resolved and most strongly supported tree. In general, the phylogeny shows Old World taxa to be basal and New World taxa to be derived, but this is not always the case. Old and New World species are found together in two separate and only distantly related clades. This is best explained by long-distance dispersal with a minimum of two trans-oceanic exchanges. Meso/Central America has had an important role in ancient dispersals between the Old and New World and more recent movements from South to North America in the New World.
The largest family of flowering plants Asteraceae (Compositae) is found to contain 12 major lineages rather than five as previously suggested. Five of these lineages heretofore had been circumscribed in tribe Mutisieae (Cichorioideae), a taxon shown by earlier molecular studies to be paraphyletic and to include some of the deepest divergences of the family. Combined analyses of 10 chloroplast DNA loci by different phylogenetic methods yielded highly congruent well-resolved trees with 95% of the branches receiving moderate to strong statistical support. Our strategy of sampling genera identified by morphological studies as anomalous, supported by broader character sampling than previous studies, resulted in identification of several novel clades. The generic compositions of subfamilies Carduoideae, Gochnatioideae, Hecastocleidoideae, Mutisioideae, Pertyoideae, Stifftioideae, and Wunderlichioideae are novel in Asteraceae systematics and the taxonomy of the family has been revised to reflect only monophyletic groups. Our results contradict earlier hypotheses that early divergences in the family took place on and spread from the Guayana Highlands (Pantepui Province of northern South America) and raise new hypotheses about how Asteraceae dispersed out of the continent of their origin. Several nodes of this new phylogeny illustrate the vast differential in success of sister lineages suggesting focal points for future study of species diversification. Our results also provide a backbone exemplar of Asteraceae for supertree construction.
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