On the evolutionary history of Ephedra: Cretaceous fossils and extant molecules

Department of Botany, Stockholm University, SE-106 91 Stockholm, Sweden.
Proceedings of the National Academy of Sciences (Impact Factor: 9.67). 11/2004; 101(47):16571-6. DOI: 10.1073/pnas.0407588101
Source: PubMed


Gnetales comprise three unusual genera of seed plants, Ephedra, Gnetum, and Welwitschia. Their extraordinary morphological diversity suggests that they are survivors of an ancient, more diverse group. Gnetalean antiquity is also supported by fossil data. Dispersed "ephedroid" (polyplicate) pollen first appeared in the Permian >250 million years ago (Myr), and a few megafossils document the presence of gnetalean features in the early Cretaceous. The Cretaceous welwitschioid seedling Cratonia cotyledon dates the split between Gnetum and Welwitschia to before 110 Myr. Ages and character evolution of modern diversity are, however, controversial, and, based on molecular data, it has recently been suggested that Ephedra is very young, only 8-32 Myr. Here, we present data on the evolutionary history of Ephedra. Fossil seeds from Buarcos, Portugal, unequivocally link one type of Cretaceous polyplicate pollen to Ephedra and document that plants with unique characters, including the peculiar naked male gametophyte, were established already in the Early Cretaceous. Clades in our molecular phylogeny of extant species correspond to geographical regions, with African species in a basal grade/clade. The study demonstrates extremely low divergence in both molecular and morphological characters in Ephedra. Features observed in the fossils are present in all major extant clades, showing that modern species have retained unique reproductive characters for >110 million years. A recent origin of modern species of Ephedra would imply that the Cretaceous Ephedra fossils discussed here were members of widespread, now extinct sister lineage(s), and that no morphological innovations characterized the second diversification.

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    • "Molecular phylogenies of Ephedra by now have included 54 of the %56 species (Ickert-Bond & Wojciechowski, 2004; Rydin et al., 2004; Huang et al., 2005; Rydin & Korall, 2009; Rydin et al., 2010; Loera et al., 2015). In combination, they show that the six Mediterranean species form a grade at the base of the phylogeny, while the remaining 50 species from a wellsupported clade. "
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    ABSTRACT: Ephedra, Gnetum, and Welwitschia constitute the gymnosperm order Gnetales of still unclear phylogenetic relationships within seed plants. Here we review progress over the past 10 years in our understanding of their species diversity, morphology, reproductive biology, chromosome numbers, and genome sizes, highlighting the unevenness in the sampling of species even for traits that can be studied in preserved material, such as pollen morphology. We include distribution maps and original illustrations of key features, and specify which species groups or geographic areas are under sampled.
    No preview · Article · Jan 2016 · Journal of Systematics and Evolution
    • "support the Pachomova (1969) hypothesis that the origin and early diversification of Ephedra was in the Old World with a subsequence diversification in New World from North America to South America although the patterns are currently not fully established . It is, however, worth noting that the presence of vegetative and reproductive organs of plants related to Ephedra in the Early Cretaceous in several parts of the world including Brazil confirms the hypothesis of their Mesozoic origin (Rydin et al. 2004; Friis et al. 2011 ) and that the dispersal patterns are still uncertain and the high diversity of Gnetales pollen grains and macrofossils (Lima 1978; Osborn et al. 1993; Dilcher et al. 2005; Kerkhoff & Dutra 2007) found in the Brazilian Early Cretaceous palaeoflora suggests that the presence of this taxonomic group in Brazil is very old. We believe that this scenario suggest that north-eastern Brazil might be a plausible centre of dispersion of this group. "
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    ABSTRACT: Here we present a critical revision of the occurrence of Ephedripites pollen grains during the Cenozoic of Brazil along with a new interpretation of the palaeo-biogeographical implications regarding the distribution of E. eocenipites, E. fusiformis, E. lusaticus and E. claricristatus (=E. tertiarius) in continental and marine sediments. Morphological features of these taxa, in general terms, differ from those of Cretaceous forms by the reduced number of plicae and thinner ribs. The revision of the Brazilian literature of Ephedripites point to a Paleocene distribution restricted to 30° S palaeo-latitude, whereas from the Eocene to the Pliocene, this genus is found in higher palaeo-latitudes of south-eastern and southern Brazil, attesting its occurrence in vegetation on dry or well drained soils
    No preview · Article · Jan 2016 · Grana
    • "The Ephedra lineage has a long evolutionary history , extending at least to the late Mesozoic. Ephedra-like pollen increases in abundance in the fossil record during the Early Cretaceous (Crane & Lidgard, 1989 ) and a relatively large diversity of Ephedra-like plants has been documented in the fossil record, mainly from the Aptian (Krassilov, 1986; Yang et al., 2005; Rydin, Wu & Friis, 2006b; Wang & Zheng, 2010), including taxa that share uniquely derived features with the extant clade (Rydin, Pedersen & Friis, 2004; Rydin et al., 2006a). However, the Cretaceous diversity declined dramatically during the latter part of the period (Crane & Lidgard, 1989) and Ephedra-like megafossils are currently unknown from after the Early Cretaceous (Rydin et al., 2006b ). "
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    ABSTRACT: Pollination in gymnosperms is usually accomplished by means of wind, but some groups are insect-pollinated. We show that wind and insect pollination occur in the morphologically uniform genus Ephedra (Gnetales). Based on field experiments over several years, we demonstrate distinct differences between two Ephedra species that grow in sympatry in Greece in pollen dispersal and clump formation, insect visitations and embryo formation when insects are denied access to cones. Ephedra distachya, nested in the core clade of Ephedra, is anemophilous, which is probably the prevailing state in Ephedra. Ephedra foeminea, sister to the remaining species of the genus, is entomophilous and pollinated by a range of diurnal and nocturnal insects. The generalist entomophilous system of E. foeminea, with distinct but infrequent insect visitations, is in many respects similar to that reported for Gnetum and Welwitschia and appears ancestral in Gnetales. The Ephedra lineage is well documented already from the Early Cretaceous, but the diversity declined dramatically during the Late Cretaceous, possibly to near extinction around the Cretaceous–Palaeogene boundary. The clade imbalance between insect- and wind-pollinated lineages is larger than expected by chance and the shift in pollination mode may explain why Ephedra escaped extinction and began to diversify again.
    No preview · Article · Jan 2016 · Botanical Journal of the Linnean Society
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