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Catarina Rydin - One of the best experts on this subject based on the ideXlab platform.

  • The chloroplast genome of Ephedra foeminea (Ephedraceae, Gnetales), an entomophilous gymnosperm endemic to the Mediterranean area.
    Mitochondrial DNA Part A, 2015
    Co-Authors: Chen Hou, Niklas Wikström, Catarina Rydin
    Abstract:

    This study presents the chloroplast genome of Ephedra foeminea, an entomophilous gymnosperm, sister to the remaining (wind-pollinated) species of Ephedra (Ephedraceae, Gnetales). Based on the refer ...

  • Moonlight pollination in the gymnosperm Ephedra (Gnetales).
    Biology Letters, 2015
    Co-Authors: Catarina Rydin, Kristina Bolinder
    Abstract:

    Most gymnosperms are wind-pollinated, but some are insect-pollinated, and in Ephedra (Gnetales), both wind pollination and insect pollination occur. Little is, however, known about mechanisms and evolution of pollination syndromes in gymnosperms. Based on four seasons of field studies, we show an unexpected correlation between pollination and the phases of the moon in one of our studied species, Ephedra foeminea. It is pollinated by dipterans and lepidopterans, most of them nocturnal, and its pollination coincides with the full moon of July. This may be adaptive in two ways. Many nocturnal insects navigate using the moon. Further, the spectacular reflection of the full-moonlight in the pollination drops is the only apparent means of nocturnal attraction of insects in these plants. In the sympatric but wind-pollinated Ephedra distachya, pollination is not correlated to the full moon but occurs at approximately the same dates every year. The lunar correlation has probably been lost in most species of Ephedra subsequent an evolutionary shift to wind pollination in the clade. When the services of insects are no longer needed for successful pollination, the adaptive value of correlating pollination with the full moon is lost, and conceivably also the trait.

  • Micromorphology of the Seed Envelope of Ephedra L. (Gnetales) and Its Relevance for the Timing of Evolutionary Events
    International Journal of Plant Sciences, 2011
    Co-Authors: Stephanie M. Ickert-bond, Catarina Rydin
    Abstract:

    Abstract Micromorphology of the seed envelope of Ephedra (Gnetales) is known to be variable, but variation patterns have 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 evolutionary patterns. 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 surface is 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. Furt...

  • The female reproductive unit of ephedra (Gnetales): comparative morphology and evolutionary perspectives.
    Botanical Journal of the Linnean Society, 2010
    Co-Authors: Catarina Rydin, Anbar Khodabandeh, Peter K. Endress
    Abstract:

    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.

  • Former diversity of Ephedra (Gnetales): evidence from Early Cretaceous seeds from Portugal and North America
    Annals of Botany, 2006
    Co-Authors: Catarina Rydin, Kaj Raunsgaard Pedersen, Peter R. Crane
    Abstract:

    • Background and Aims The extant species of the seed plant group Gnetales (Ephedra, Gnetum and Welwitschia) have been considered a remnant of a much greater, now extinct, diversity due to the pronounced differences in form and ecology among the genera. Until recently, this hypothesis has not been supported by evidence from the fossil record. This paper adds to the expanding information on Gnetales from the Early Cretaceous and describes coalified seeds from Barremian-Albian localities in Portugal and USA. • Methods The fossils were extracted from sediment samples by sieving in water. Adhering mineral matrix was removed by chemical treatment. Seeds were investigated using light and scanning electron microscopy. Morphology and anatomy of the seeds were documented and compared with those of extant species. • Key Results The fossils share characters with extant Ephedra, for example papillae on the inner surface of the seed envelope and in situ polyplicate pollen grains that shed the exine during germination. They differ from extant Ephedra seeds in morphological and anatomical details as well as in their smaller size. Two new species of Ephedra are described together with one species assigned to a new genus of Gnetales. Other Ephedra-like seeds, for which pollen and critical morphological details are currently unknown, are also present in the samples. • Conclusions These Cretaceous seeds document that key reproductive characters and pollen germination processes have remained unchanged within Ephedra for about 120 million years or more. There is sufficient variety in details of morphology to suggest that a diversity of Ephedra and Ephedra-like species were present in the Early Cretaceous flora. Their presence in Portugal and eastern North America indicates that they were widespread on the Laurasian continent. The fossil seeds are similar to seeds of Erdtmanithecales and this supports the previously suggested relationship between Erdtmanithecales and Gnetales.

Marinoni Luciane - One of the best experts on this subject based on the ideXlab platform.

Karl J. Niklas - One of the best experts on this subject based on the ideXlab platform.

  • A Biophysical Perspective on the Pollination Biology of Ephedra nevadensis and E. trifurca
    The Botanical Review, 2015
    Co-Authors: Karl J. Niklas
    Abstract:

    Previous research indicates that Ephedra nevadensis S. Wats. and E. trifurca Torr. Ex S. Watts are capable of capturing airborne pollen because of (1) the absence of foliage obstructing airflow, (2) the streamlined geometry of ovules, (3) the orientation of ovules with respect to the vertical, (4) the clustering of ovules, and (5) wind-induced oscillations of stems and pollination droplets. Wind tunnel studies and computer models also show that slightly inclined stems deflect and funnel airborne pollen upward along their leeward sides toward ovules. Additionally, the dimensions, settling velocities, and other features of Ephedra pollen in theory are compatible with long-distance wind dispersal of pollen. These features increase the efficiency of wind pollination and are consistent with anemophily. However, none of these features precludes alternative pollination mechanisms, as for example the deposition of pollen by insects foraging pollination droplets. A biophysical perspective indicates that these Ephedra species are capable of being wind pollinated but it cannot preclude the possibility of insect pollination. Frühere Forschungsarbeiten haben gezeigt, dass Ephedra nevadensis S. Wats. and E. trifurca Torr. Ex S. Wats fähig sind, durch Wind übertragene Pollen einzufangen (1) da kein Laubwerk den Luftstrom verringert, (2) wegen der stromlinienförmigen Geometrie der Samenanlagen, (3) wegen der Ausrichtung der Samenanlagen in der Vertikalen, (4) wegen des Clustering der Samenanlagen und (5) wegen der windbedingten Schwingungen von Stamm und Bestäubungstropfen. Auch zeigen Untersuchungen im Windkanal und Computermodelle, dass leicht geneigte Stämme die vom Wind angewehten Pollen ablenken und diese auf der dem Wind abgewandten Seite aufwärts in Richtung der Samenanlagen konzentrieren können. Zusätzlich sind die Größenverhältnisse, die Sinkgeschwindigkeit und weitere Eigenschaften der Ephedra Pollen theoretisch vereinbar mit einer Verbreitung der Pollen durch Wind über große Distanzen. Diese Eigenschaften verstärken die Effizienz der Windbestäubung und stehen im Einklang mit Anemophilie. Jedoch keine dieser Eigenschaften schließt alternative Mechanismen der Bestäubung aus, wie zum Beispiel das Abstreifen der Pollen von Insekten, die nach Bestäubungstropfen suchen. Eine biophysikalische Betrachtung weist darauf hin, dass Ephedra Arten die Voraussetzungen zur Windbestäubung haben, aber die Möglichkeit der Bestäubung durch Insekten kann nicht ausgeschlossen werden.

Peter R. Crane - One of the best experts on this subject based on the ideXlab platform.

  • Former diversity of Ephedra (Gnetales): evidence from Early Cretaceous seeds from Portugal and North America
    Annals of Botany, 2006
    Co-Authors: Catarina Rydin, Kaj Raunsgaard Pedersen, Peter R. Crane
    Abstract:

    • Background and Aims The extant species of the seed plant group Gnetales (Ephedra, Gnetum and Welwitschia) have been considered a remnant of a much greater, now extinct, diversity due to the pronounced differences in form and ecology among the genera. Until recently, this hypothesis has not been supported by evidence from the fossil record. This paper adds to the expanding information on Gnetales from the Early Cretaceous and describes coalified seeds from Barremian-Albian localities in Portugal and USA. • Methods The fossils were extracted from sediment samples by sieving in water. Adhering mineral matrix was removed by chemical treatment. Seeds were investigated using light and scanning electron microscopy. Morphology and anatomy of the seeds were documented and compared with those of extant species. • Key Results The fossils share characters with extant Ephedra, for example papillae on the inner surface of the seed envelope and in situ polyplicate pollen grains that shed the exine during germination. They differ from extant Ephedra seeds in morphological and anatomical details as well as in their smaller size. Two new species of Ephedra are described together with one species assigned to a new genus of Gnetales. Other Ephedra-like seeds, for which pollen and critical morphological details are currently unknown, are also present in the samples. • Conclusions These Cretaceous seeds document that key reproductive characters and pollen germination processes have remained unchanged within Ephedra for about 120 million years or more. There is sufficient variety in details of morphology to suggest that a diversity of Ephedra and Ephedra-like species were present in the Early Cretaceous flora. Their presence in Portugal and eastern North America indicates that they were widespread on the Laurasian continent. The fossil seeds are similar to seeds of Erdtmanithecales and this supports the previously suggested relationship between Erdtmanithecales and Gnetales.

Mathis, Wayne N. - One of the best experts on this subject based on the ideXlab platform.