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Micromorphology of the seed envelope of Ephedra L. (Gnetales) and its relevance for the timing of evolutionary events
University of Alaska, Fairbanks.
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Systematic Biology.
2011 (English)In: International journal of plant sciences, ISSN 1058-5893, Vol. 172, no 1, 36-48 p.Article in journal (Refereed) Published
Abstract [en]

Micromorphology of the seed envelope of Ephedra (Gnetales) is known to be variable, but variation patternshave never been systematically documented. We test the usefulness of this feature for species determination and subclade delimitation in Ephedra and investigate the relationship of this character to infrageneric evolutionarypatterns. Most species have a basically smooth seed envelope, which in some species appears slightly striate or reticulate due to convex or depressed outer periclinal cell walls. Ephedra rhytidosperma from China and Ephedra torreyana from North America have transverse lamellae formed by the epidermis. A papillate surfaceis found in respective close relatives of these two species. Micromorphology of the seed envelope is generally not useful for species identification or subclade delineation. The amount of variation is low, and intraspecific variation, which in some cases seems to be correlated with hybridization and/or introgression, complicates species recognition. Furthermore, parallel evolution of similar micromorphological patterns in unrelated subclades of Ephedra is evident and cannot be explained by similar seed dispersal mechanisms. The Asian species with transverse lamellae or papillae on the seed are dispersed by frugivores whereas similar American species are anemochoric. Transverse ridges occur in several Early Cretaceous fossil seeds with affinity to Ephedra. However, our results indicate that the resemblance between these fossils and extant taxa with similar features is superficial and convergent. In line with other recent studies, we find that Cretaceous ephedroids are extinct stem relatives to the extant clade.

Place, publisher, year, edition, pages
2011. Vol. 172, no 1, 36-48 p.
National Category
Natural Sciences
URN: urn:nbn:se:uu:diva-141820DOI: 10.1086/657299OAI: oai:DiVA.org:uu-141820DiVA: diva2:386270
Available from: 2011-01-12 Created: 2011-01-12 Last updated: 2013-09-18Bibliographically approved

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