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  • 1
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    Selection on length mutations after frameshift can explain the origin and retention of the AP3/DEF-like paralogues in Impatiens (2008)
    In:  Journal of Molecular Evolution vol. 66 no. 5, pp. 424-435
    Details
    Publication Date: 2024-01-12
    Description: Evolution of class B genes through gene duplication has been proposed as an evolutionary mechanism that contributed to the enormous floral diversity. Frameshift mutations are a likely mechanism to explain the divergent C-terminal sequences of MIKC gene subfamilies. So far, the inferences for frameshifts and selective pressures on the C-terminal domain are made for old duplications for which the exact selective pressures are obscured by evolutionary time. This motivated us to study an example of a recent duplication, which allows us to consider in more detail the selective pressures that are involved after duplication. We find that after duplication and frameshift of Impatiens class B genes, the individual codons show no evidence for adaptive selection. It is rather the length of the C-terminal domain that either is strictly conserved or varies strongly. This suggests a role for the length of the C-terminal domain in the retention of duplicated genes.
    Keywords: APETALA3 /DEFICIENS ; C-terminal domain ; frameshift ; gene duplication ; impatiens ; selection ; indels
    Repository Name: National Museum of Natural History, Netherlands
    Type: info:eu-repo/semantics/article
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  • 2
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    Systematic palynology in Ebenaceae with focus on Ebenoideae: Morphological diversity and character evolution (2009)
    Elsevier
    Details
    Publication Date: 2009-02-01
    Print ISSN: 0034-6667
    Electronic ISSN: 1879-0615
    Topics: Geosciences
    Published by Elsevier
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  • 3
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    Are the genera Hallea and Mitragyna (Rubiaceae-Coptosapelteae) pollen morphologically distinct? (1994)
    In:  Blumea - Biodiversity, Evolution and Biogeography of Plants (0006-5196) vol.39 (1994) nr.1/2 p.321
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    Publication Date: 2015-03-06
    Description: Recent literature is controversial as regards the segregation of Hallea and Mitragyna, and pretends that the two genera show pollen morphological differences. In the present study the pollen morphology of all ten species of the complex is described on the basis of light and scanning electron microscopy (including examination of broken grains, which were obtained with a technique never applied in palynology, viz. shaking with glass beads). The two genera have 3-zonocolporate grains with compound apertures (endoapertures are always H-shaped, sometimes incompletely so). While Hallea showed to be stenopalynous (sexine always tectate-perforate), Mitragyna is more variable (sexine microreticulate or tectate-perforate), and several of its species have pollen similar to that of Hallea. Numerical analysis was used to evaluate the palynological observations in the light of the macromorphological variation in the complex. It is concluded that both Hallea and Mitragyna deserve generic recognition, but are not fully distinct pollen morphologically.
    Repository Name: National Museum of Natural History, Netherlands
    Type: Article / Letter to the editor
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  • 4
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    Are the genera Hallea and Mitragyna (Rubiaceae-Coptosapelteae) pollen morphologically distinct? (1994)
    In:  Blumea: Biodiversity, Evolution and Biogeography of Plants vol. 39 no. 1/2, pp. 321-340
    Details
    Publication Date: 2024-01-12
    Description: Recent literature is controversial as regards the segregation of Hallea and Mitragyna, and pretends that the two genera show pollen morphological differences. In the present study the pollen morphology of all ten species of the complex is described on the basis of light and scanning electron microscopy (including examination of broken grains, which were obtained with a technique never applied in palynology, viz. shaking with glass beads).\nThe two genera have 3-zonocolporate grains with compound apertures (endoapertures are always H-shaped, sometimes incompletely so). While Hallea showed to be stenopalynous (sexine always tectate-perforate), Mitragyna is more variable (sexine microreticulate or tectate-perforate), and several of its species have pollen similar to that of Hallea.\nNumerical analysis was used to evaluate the palynological observations in the light of the macromorphological variation in the complex. It is concluded that both Hallea and Mitragyna deserve generic recognition, but are not fully distinct pollen morphologically.
    Repository Name: National Museum of Natural History, Netherlands
    Type: info:eu-repo/semantics/article
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  • 5
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    A Plastid Gene Phylogeny of the Yam Genus, Dioscorea: Roots, Fruits and Madagascar (2005)
    In:  Systematic Botany vol. 30 no. 4, pp. 736-749
    Details
    Publication Date: 2024-01-12
    Description: 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.
    Keywords: Dioscorea ; phylogeny ; classification ; analysis ; plastid genes ; rbcL ; matK ; character evolution
    Repository Name: National Museum of Natural History, Netherlands
    Type: info:eu-repo/semantics/article
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  • 6
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    Pollen Evolution in Yams (Dioscorea: Dioscoreaceae) (2005)
    In:  Systematic Botany vol. 30 no. 4, pp. 750-758
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    Publication Date: 2024-01-12
    Description: 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 than once and is particularly characteristic in the Malagasy clade. Sexine ornamentation in the Stenophora clade is diverse. The endemic allotetraploid D. pyrenaica is characterized by large, monosulcate, gemmate pollen. The Dioscorea B clade is characterized by pollen with small, dense perforations. Orbicules occur in all Dioscorea species, but are absent in most of the outgroup taxa.
    Keywords: Dioscorea ; Dioscoreaceae ; pollen ; evolution ; phylogeny
    Repository Name: National Museum of Natural History, Netherlands
    Type: info:eu-repo/semantics/article
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  • 7
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    Palynological Characters and Their Phylogenetic Signal in Rubiaceae (2005)
    In:  The Botanical Review vol. 71 no. 3, pp. 354-414
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    Publication Date: 2024-01-12
    Description: 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 presented here and illustrated per character: dispersal unit, pollen size and shape, aperture number, position and type, sexine ornamentation, nexine pattern, and stratification of the sporoderm. The presence/absence and morphological variation of orbicules at the generic level is provided as well. The systematic usefulness of pollen morphology in Rubiaceae is discussed at the (sub)family, tribal, generic, and infraspecific levels, using up-to-date evolutionary hypotheses for the different lineages in the family. The problems and opportunities of coding pollen characters for cladistic analyses are also treated.
    Keywords: Rubiaceae ; pollen morphology ; palynology ; phylogeny
    Repository Name: National Museum of Natural History, Netherlands
    Type: info:eu-repo/semantics/article
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  • 8
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    Micromorphology and systematic distribution of pit membrane thickenings in Oleaceae: Tori and pseudo-tori (2008)
    In:  IAWA Journal vol. 29 no. 4, pp. 409-424
    Details
    Publication Date: 2024-01-12
    Description: Recent studies on the functional significance of pit membranes in water conducting cells have renewed general interest in their micromorphology. At least two types of pit membrane thickenings have been described in angiosperm families, i.e. genuine tori and pseudo-tori. This study explores the distribution and morphology of pit membrane thickenings in 69 species and 23 genera within Oleaceae using light and electron microscopy. Torus-bearing pit membranes are confirmed for Osmanthus, and new records are reported for Chionanthus retusa, Picconia azorica, and P. excelsa, but not for the other species studied of Chionanthus. This infrageneric variation suggests that tori represent a plastic feature that has evolved more than once within the family as the result of functional adaptation to efficient and safe water transport. Pseudo-tori are observed in species of Abeliophyllum, Fontanesia, Forsythia, Jasminum, Ligustrum, Menodora, and Syringa. Based on structural differences, we state that tori and pseudo-tori can be distinguished as non-homologous features.
    Keywords: electron microscopy ; pit aperture ; pit membrane ; plasmodesmata ; pseudo-torus ; torus ; tracheid ; vessel element
    Repository Name: National Museum of Natural History, Netherlands
    Type: info:eu-repo/semantics/article
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  • 9
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    Pollen morphological variation in Vanguerieae (Ixoroideae - Rubiaceae) (2000)
    In:  Grana vol. 39, pp. 90-102
    Details
    Publication Date: 2024-01-12
    Description: The Vanguerieae is a large tribe of the subfamily Ixoroideae (Rubiaceae) and consists of about 500 species in 27 genera. This study gives a detailed pollen morphological description of 30 species from 16 genera, based on light microscopy and scanning electron microscopy. The Vanguerieae are considered to be stenopalynous, although there is some evidence to question this. First, there is a difference in sexine types that clearly de\xc2\xae nes Keetia and Psydrax ( both reticulate) , and Canthium and Vanguerieae (both perforate with very small perforations) from the other Vanguerieae investigated. Second, pollen grains corroborate the subgeneric delimitations of Canthium sensu Bridson. Pollen morphologically the tribe is characterised by ( 1) the shape of the ectoapertures which is intermediate between a colpus and a porus, and ( 2) the presence of a costa oriented perpendicular to the ectoaperture and has a form which is correlated with the shape of the costa.
    Keywords: Vanguereae ; Ixoroideae ; Rubiaceae ; pollen ; morphological variation ; stenopalynous
    Repository Name: National Museum of Natural History, Netherlands
    Type: info:eu-repo/semantics/article
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  • 10
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    Floral ontogeny of the Afro-Madagascan genus Mitrasacmopsis with comments on the development of superior ovaries in Rubiaceae (2007)
    In:  Annals of Botany vol. 100, pp. 41-49
    Details
    Publication Date: 2024-01-12
    Description: Background and Aims Members of Rubiaceae are generally characterized by an inferior ovary. However, Mitrasacmopsis is cited in the literature as having a semi-inferior to superior ovary. It has previously been hypothesized that the gynoecial development of Rubiaceae with semi-inferior to superior ovaries takes place in the same way as in Gaertnera, one of the most commonly cited rubiaceous genera with a superior ovary. To test this hypothesis, a floral ontogenetic study of Mitrasacmopsis was carried out with special attention paid to the gynoecial development.\n\nMethods Floral ontogeny and anatomy of Mitrasacmopsis were examined using scanning electron and light microscopy.\n\nKey Results At an early developmental stage, a concavity becomes visible in the centre of the floral apex simultaneously with the perianth initiation. A ring primordium surrounding this concavity expands vertically forming the corolla tube (early sympetaly). Stamen primordia develop inside the corolla. From the bicarpellate gynoecium only two carpel tips are visible because the ovary is formed by a gynoecial hypanthium. In the basal part of each carpel, a placenta primordium is initiated. Two septa divide the ovary into two locules. In each locule, the placenta becomes mushroom shaped and distinctly stalked. Eventually, the inferior ovary of Mitrasacmopsis develops into a beaked capsule. Only very late in the fruiting stage, the continuously expanding ovary is raised above the insertion point of the persistent calyx, changing the ovary position of Mitrasacmopsis from basically inferior to secondarily semi-inferior.\n\nConclusions Mitrasacmopsis follows an epigynous pattern of floral development. However, the presence of a prominent beak in the fruiting stage gives the whole ovary a semi-inferior appearance. This kind of secondarily semi-inferior ovary is shown to be different from the secondarily superior ovary observed in Gaertnera.
    Keywords: Mitrasacmopsis quadrivalvis ; Gaertnera ; floral ontogeny
    Repository Name: National Museum of Natural History, Netherlands
    Type: info:eu-repo/semantics/article
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