Current address: Department of Systematic Botany, University of Stockholm, SE-106 91 Stockholm, Sweden.
The female reproductive unit of Ephedra (Gnetales): comparative morphology and evolutionary perspectives
Article first published online: 25 AUG 2010
© 2010 The Linnean Society of London
Botanical Journal of the Linnean Society
Volume 163, Issue 4, pages 387–430, August 2010
How to Cite
RYDIN, C., KHODABANDEH, A. and ENDRESS, P. K. (2010), The female reproductive unit of Ephedra (Gnetales): comparative morphology and evolutionary perspectives. Botanical Journal of the Linnean Society, 163: 387–430. doi: 10.1111/j.1095-8339.2010.01066.x
- Issue published online: 25 AUG 2010
- Article first published online: 25 AUG 2010
- Received 2 February 2010; revised 2 February 2010; accepted for publication 9 June 2010
- character evolution;
- reproductive morphology;
- seed plants
Morphological variation in Ephedra (Gnetales) is limited and confusing from an evolutionary perspective, with parallelisms and intraspecific variation. However, recent analyses of molecular data provide a phylogenetic framework for investigations of morphological traits, albeit with few informative characters in the investigated gene regions. We document morphological, anatomical and histological variation patterns in the female reproductive unit and test the hypothesis that some Early Cretaceous fossils, which share synapomorphies with Ephedra, are members of the extant clade. Results indicate that some morphological features are evolutionarily informative although intraspecific variation is evident. Histology and anatomy of cone bracts and seed envelopes show clade-specific variation patterns. There is little evidence for an inclusion of the Cretaceous fossils in the extant clade. Rather, a hypothesized general pattern of reduction of the vasculature in the ephedran seed envelope, probably from four vascular bundles in the fossils, to ancestrally three in the living clade, and later to two, is consistent with phylogenetic and temporal analyses, which indicate that extant diversity evolved after the Cretaceous–Tertiary boundary. Notwithstanding striking similarities between living and Cretaceous Ephedra, available data indicate that the Mesozoic diversity went almost entirely extinct in the late Cretaceous causing a bottleneck effect in Ephedra, still reflected today by an extraordinarily low level of genetic and structural diversity. © 2010 The Linnean Society of London, Botanical Journal of the Linnean Society, 2010, 163, 387–430.