Showing papers by "Carol A. Furness published in 2005"
TL;DR: A phylogenetic analysis based on sequence data from the plastid genes rbcL and matK is presented, using 67 species of Dioscorea and covering all the main Old World and selected New World lineages, and finds that a clade of rhizomatous taxa is sister to the rest of Diocorea.
Abstract: Following recent phylogenetic studies of the families and genera of Dioscoreales, the identification of monophyletic infrageneric taxa in the pantropical genus Dioscorea is a priority. A phylogenetic analysis based on sequence data from the plastid genes rbcL and matK is presented, using 67 species of Dioscorea and covering all the main Old World and selected New World lineages. The analysis used 14 outgroup taxa, including Trichopus Gaertn., Tacca J.R. & G. Forster, Stenomeris Planch., Burmannia L. and Thismia Griff. The main findings are: a) that a clade of rhizomatous taxa is sister to the rest of Dioscorea; b) the main Old World groups (such as the right-twining D. sect. Enantiophyllum) are monophyletic and c) there are two distinct lineages among the endemic Malagasy taxa. The consequences of the results for infrageneric classification of Dioscorea is considered, in particular the possibility of greatly simplifying the classifications of Knuth and Burkill. The results are also used to present novel hypotheses of character evolution in selected underground.
116 citations
TL;DR: Pollen character evolution in yams (Dioscorea: Dioscoreaceae) was investigated in relation to the phylogeny obtained from a recent combined analysis of rbcL and matK gene sequences as discussed by the authors.
Abstract: Pollen character evolution in yams (Dioscorea: Dioscoreaceae) was investigated in relation to the phylogeny obtained from a recent combined analysis of rbcL and matK gene sequences. The following characters were evaluated: pollen size, aperture number, sexine ornamentation, perforation density, and orbicule presence or absence. Continuous characters were coded using the gap weighting method. Each character was optimized using MacClade onto a tree selected at random from analyses based on molecular data of Wilkin et al. The results indicate that in Dioscorea pollen size decreases in the more derived clades. The latter observation may be related to the evolution of annually replaced tubers. Aperture number increases from one in the monosulcate Stenophora clade (sister to the rest of Dioscorea) to two in other Dioscorea clades. This may be related to the presence of simultaneous microsporogenesis in Dioscorea. A perforate sexine is plesiomorphic in Dioscorea and a striate pattern has evolved more th...
31 citations
TL;DR: In this paper, the ontogeny of three genera of Dioscoreales, Narthecium ossifragum Huds (Nartheciaceae), Tacca artocarpifolia Seem and Tacca chantrieri Andre (Dioscoreaceae), and Diocorea communis communis (L) Caddick & Wilkin, were described and illustrated using LM, SEM, and TEM.
Abstract: Pollen and orbicule ontogeny in representatives of three genera of Dioscoreales—Narthecium ossifragum Huds (Nartheciaceae), Tacca artocarpifolia Seem and Tacca chantrieri Andre (Dioscoreaceae), and Dioscorea communis (L) Caddick & Wilkin (Dioscoreaceae)—is described and illustrated using LM, SEM, and TEM The main difference is in microsporogenesis, which is successive in Narthecium Huds and simultaneous in Tacca JR & G Forst and Dioscorea L This is reflected in the tetrad configuration but not in the apertures: Narthecium and Tacca are monosulcate, while Dioscorea has two equatorial apertures Other features of pollen development are similar in all three genera Exine development starts at the proximal pole, and during the tetrad stage, the exine remains thicker at this pole Intine development begins before mitosis A conspicuously channeled intine forms beneath the aperture(s) in all three genera, and in Tacca it also occurs in nonapertural regions After mitosis, the generative cell is situat
13 citations