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Trichome types, foliar indumentum, and epicuticular wax in the Mediterranean ‘Gall Oaks’, Quercus subsectio Galliferae (Spach) Guerke (Fagaceae): implications for taxonomy, ecology, and evolution
Stockholm University, Faculty of Science, Department of Botany.
Swedish Museum of Natural History, Department of Palaeobotany.
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Trichome characters are often considered taxonomically important in oak species. Here, we investigated a group of Mediterranean oaks, Quercus subsectio Galliferae and Q. pubescens, using a large dataset and covering the entire distribution range of the group. Due to different interpretations of terms in previous studies, trichome terminology was re-assessed aiming at a practicable nomenclature. In contrast to previous studies, we found that acicular, bifurcate, fasciculate, stellate, uniseriate and capitate trichomes are represented in all taxa. One exception is the lack of bifurcate trichomes in Quercus canariensis. This suggests that seemingly taxonomically informative presence/absence data for trichome types as reported previously may be a result of too small sample size and hence unrepresentative. In combination with other morphological characters (leaf shape, size and texture), features of the indumentum, such as the floccose, easily removable trichomes in Quercus canariensis can be important in species delimitation. Making use of trichome characteristics in Quercus subsectio Galliferae requires exhaustive sampling of all taxa in order to extract reproducible taxonomic signal from quantitative characters. This would be the prerequisite for building datasets that could be used for phylogenetic studies, investigations of character evolution and comparative morphological studies.

Keyword [en]
Quercus, trichomes, trichome classification, foliar indumentum, epicuticular wax, taxonomy, ecological significance, evolution
National Category
Natural Sciences
Research subject
Plant Ecology; Plant Morphology; Plant Systematics
URN: urn:nbn:se:su:diva-62715OAI: diva2:444095
Available from: 2011-09-27 Created: 2011-09-27 Last updated: 2011-09-29Bibliographically approved
In thesis
1. Comparative morphological studies of fossil and living plane trees (Platanaceae) and oaks (Quercus): taxonomy, ecology, evolution
Open this publication in new window or tab >>Comparative morphological studies of fossil and living plane trees (Platanaceae) and oaks (Quercus): taxonomy, ecology, evolution
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Morphological characters are essential for flowering plant identification, but also provide information about diversity patterns and ecological adaptation. In woody plant species, characters of the leaf are among the most useful and can be examined on fossils as well. In this thesis, I studied leaf architecture, epidermal anatomy and reproductive structures of some fossil Platanaceae (plane trees) and an extant group of Quercus (oak) both qualitatively and quantitatively. The aim of this study was to understand past and present patterns of distribution in these taxa, their morphological variability and possible species delimitations. Platanaceae constitute today a relict taxon with a disjunct distribution, but were a taxonomically and morphologically diverse group in the geological past. The presence of the modern genus Platanus in the Late Cretaceous of Central Germany could be demonstrated through the combined analysis of leaves, flowers, fruits and pollen. The extinct genus Credneria is only represented by leaf fossils, but a unique combination of characters proved its affinity with the Platanaceae. Although several species had been described previously, a statistical analysis showed that the observed leaf polymorphism is due to environmental constraints, pointing towards a single species, Credneria denticulata. Quercus subsection Galliferae is a small group of white oaks with a disjunct distribution in the Mediterranean region, which show a high morphological variability within and low differentiation between the species. Samples from the entire distribution range were subjected to a morphological and quantitative analysis. The results demonstrated that the established species, except for Q. canariensis, are linked by clinal variation, which in turn corresponds to geographical gradients. An evaluation of epidermal characters revealed them to be of restricted use for taxon delimitation in the group. Instead, leaf and epidermal morphology provide extensive information about the ecology and biogeographic history of oaks.

Place, publisher, year, edition, pages
Stockholm: Department of Botany, Stockholm University, 2011. 53 p.
Platanaceae, Platanus, Credneria, Quercus, Galliferae, leaf architecture, epidermal anatomy, comparative morphology, character variation, variability, sample size, diversity patterns, species concepts, ecology, biogeography, evolution, plant fossils
National Category
Research subject
Plant Ecology
urn:nbn:se:su:diva-62707 (URN)978-91-7447-369-8 (ISBN)
Public defence
2011-10-28, Föreläsningssalen, Botanicum, Lilla Frescativägen 5, Stockholm, 13:00 (English)
At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Manuscript. Paper 3. Manuscript. Paper 4. Manuscript. Available from: 2011-10-06 Created: 2011-09-27 Last updated: 2011-10-07Bibliographically approved

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Tschan, Georg Florian
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