Variation of pollen morphology, and its implications in the phylogeny of Clematis (Ranunculaceae)

Clematis s.1. (including Archiclematis and Naravelia) is a genus of approximately 300 species with cosmopolitan distribution. The diversity of its pollen was surveyed in 162 taxa belonging to all infrageneric groups of Clematis s.1. Pollen morphology was investigated by use of scanning electron micr...

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Bibliographic Details
Published in:Plant systematics and evolution 2012-10, Vol.298 (8), p.1437-1453
Main Authors: Xie, Lei, Li, Liang-Qian
Format: Article
Language:English
Subjects:
Apertures
Biodiversity
Biological taxonomies
Biomedical and Life Sciences
Clematis
Evolution
Life Sciences
Mapping
Maxims
Molecular phylogenetics
Morphology
Original Article
Palynology
Phylogeny
Plant Anatomy/Development
Plant Ecology
Plant morphology
Plant Sciences
Plant Systematics/Taxonomy/Biogeography
Plants
Pollen
Scanning electron microscopy
Spinules
Taxa
Taxonomy
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Summary:Clematis s.1. (including Archiclematis and Naravelia) is a genus of approximately 300 species with cosmopolitan distribution. The diversity of its pollen was surveyed in 162 taxa belonging to all infrageneric groups of Clematis s.1. Pollen morphology was investigated by use of scanning electron microscopy to identify useful characters, test taxonomic and systematic hypotheses, and elucidate pollen character evolution on the basis of the molecular phylogeny. Clematis pollen is small to medium (14.8-32.1 μm × 14.2-28.7 μm), oblate to prolate (P/E = 0.9-1.4) in shape. The apertures may be tricolpate and pantoporate sometimes with 4-zonocolpate and pantocolpate pollen grains as transitional forms. The tricolpate pollen grains are predominant and occur in all the sections of the genus, whereas pantoporate pollen grains can be found in sect. Tubulosae, sect. Viorna, sect. Viticella, and Naravelia only. Phylogenetic mapping of aperture types reveals that the pantoporate pollen type may be the apomorphy in the genus and evolved several times. The surface ornamentation in all taxa studied is similar and characterized by microechinae evenly distributed on the microperforate tectum. The size and density of spinules on the tectum vary greatly but successive in the whole genus. According to the character syndromes of the ornamentation, separating sect. Brachiata from sect. Meclatis is supported. Though pollen morphology may contribute to investigation of problematic taxa, the taxonomic value of pollen morphology is limited at the species level.
ISSN:0378-2697
1615-6110
2199-6881
DOI:10.1007/s00606-012-0648-y