The female reproductive unit of Ephedra (Gnetales): comparative morphology and evolutionary perspectives
2010 (English)In: Botanical journal of the Linnean Society, ISSN 0024-4074, E-ISSN 1095-8339, Vol. 163, no 4, 387-430 p.Article in journal (Refereed) Published
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 investigatedgene regions. We document morphological, anatomical and histological variation patterns in the female reproductiveunit 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 informativealthough 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.
Place, publisher, year, edition, pages
2010. Vol. 163, no 4, 387-430 p.
IdentifiersURN: urn:nbn:se:uu:diva-141812DOI: 10.1111/j.1095-8339.2010.01066.xOAI: oai:DiVA.org:uu-141812DiVA: diva2:386255