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| Schols, P.; Wilkin, P.; Furness, C.; Huysmans, S.; Smets, E.. |
| 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... |
| Tipo: Article / Letter to the editor |
Palavras-chave: Dioscorea; Dioscoreaceae; Pollen; Evolution; Phylogeny. |
| Ano: 2005 |
URL: http://www.repository.naturalis.nl/record/407309 |
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| Dessein, S.; Ochoterena, H.; De Block, P.; Lens, F.; Robbrecht, E.; Schols, P.; Smets, E.; Vinckier, S.; Huysmans, S.. |
| In the 1990s Rubiaceae became a hot spot for systematists, mainly due to the comprehensive treatment of the family by Robbrecht in 1988. Next to the exploration of macromolecular characters to infer the phylogeny, the palynology of Rubiaceae finally received the attention it deserves. This article aims to present a state-of-the-art analysis of the systematic palynology of the family. The range of variation in pollen morphology is wide, and some of the pollen features are not known from other angiosperm taxa; e.g., a looplike or spiral pattern for the position of apertures in pantoaperturate grains. We compiled an online database at the generic level for the major pollen characters and orbicule presence in Rubiaceae. An overview of the variation is... |
| Tipo: Article / Letter to the editor |
Palavras-chave: Rubiaceae; Pollen morphology; Palynology; Phylogeny. |
| Ano: 2005 |
URL: http://www.repository.naturalis.nl/record/407298 |
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| Schols, P.; Furness, C.; Merckx, V.; Wilkin, P.; Smets, E.. |
| 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 J.R. & 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,... |
| Tipo: Article / Letter to the editor |
Palavras-chave: Intine; Microsporogenesis; Monocotyledons; Orbicules; Pollen ontogeny; Systematics; Tapetum; Tetrads. |
| Ano: 2005 |
URL: http://www.repository.naturalis.nl/record/407299 |
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| Merckx, V.; Schols, P.; Maas - Van de Kamer, H.; Maas, P.; Huymans, S.; Smets, E.. |
| The mycoheterotrophic Burmanniaceae are one of the three families currently recognized in the order Dioscoreales. Phylogenetic inference using nucleotide sequences of the nuclear 18S rDNA region and the mitochondrial nad1 b-c intron revealed two well-supported, major lineages within the family, corresponding to the two tribes recognized in the family: Burmannieae and Thismieae. All data supported a strong relationship between Thismieae and Tacca (Dioscoreaceae) making both Burmanniaceae and Dioscoreaceae polyphyletic. The three largest Burmanniaceae genera, Burmannia, Gymnosiphon, and Thismia, are paraphyletic. The splitting of Burmanniaceae into Burmannieae and Thismieae indicates two independent origins of mycoheterotrophy and correlated loss of... |
| Tipo: Article / Letter to the editor |
Palavras-chave: 18S rDNA; Burmanniaceae; Dioscoreales; Molecular phylogeny; Mycoheterotrophy; Nad1 b-c intron; Thismiaceae; 42.48. |
| Ano: 2006 |
URL: http://www.repository.naturalis.nl/record/422338 |
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| Wilkin, P.; Schols, P.; Chase, M.; Chayamarit, K.; Furness, C.; Huysmans, S.; Rakotonasolo, F.; Smets, E.; Thapyai, C.. |
| 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... |
| Tipo: Article / Letter to the editor |
Palavras-chave: Dioscorea; Phylogeny; Classification; Analysis; Plastid genes; RbcL; MatK; Character evolution. |
| Ano: 2005 |
URL: http://www.repository.naturalis.nl/record/407311 |
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| Merckx, V.; Schols, P.; Geuten, K.; Huysmans, S.; Smets, E.F.. |
| Amolecular phylogenetic analysis of Nartheciaceae is presented, with nine species of the family’s five genera. The main phylogenetic findings are: (a) Nietneria and Narthecium are placed in a clade sister to Lophiola; (b) sister to the Lophiola-Narthecium- Nietneria clade is a clade formed by Aletris and the monospecific Metanarthecium; (c) the inclusion of Metanarthecium luteo-viride in Aletris, as proposed by several authors, is well supported. The pollen and orbicule morphology of representatives of five genera is described. The results underline a close relationship between Nietneria, Narthecium, and Lophiola and confirm the previously reported observations of Metanarthecium pollen and the types of sexine ornamentation in Aletris. Pollen grains of... |
| Tipo: Article / Letter to the editor |
Palavras-chave: Dioscoreales Nartheciaceae Nietneria molecular phylogeny orbicules pollen morphology 42.43; 42.48; 42.57. |
| Ano: 2008 |
URL: http://www.repository.naturalis.nl/record/449539 |
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