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  • 1.
    Bolinder, Kristina
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Humphreys, Aelys M.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. Royal Botanic Gardens, UK.
    Ehrlén, Johan
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Alexandersson, Ronny
    Ickert-Bond, Stefanie M.
    Rydin, Catarina
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    From near extinction to diversification by means of ashift in pollination mechanism in the gymnosperm relict Ephedra (Ephedraceae, Gnetales)2016In: Botanical journal of the Linnean Society, ISSN 0024-4074, E-ISSN 1095-8339, Vol. 180, no 4, p. 461-477Article in journal (Refereed)
    Abstract [en]

    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.

  • 2.
    Bolinder, Kristina
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Niklas, Karl J.
    Rydin, Catarina
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    AERODYNAMICS AND POLLEN ULTRASTRUCTURE IN EPHEDRA2015In: American Journal of Botany, ISSN 0002-9122, E-ISSN 1537-2197, Vol. 102, no 3, p. 457-470Article in journal (Refereed)
    Abstract [en]

    Premise of the study: Pollen dispersal is affected by the terminal settling velocity (U-t) of the grains, which is determined by their size, bulk density, and by atmospheric conditions. The likelihood that wind-dispersed pollen is captured by ovulate organs is influenced by the aerodynamic environment created around and by ovulate organs. We investigated pollen ultrastructure and U-t of Ephedra foeminea (purported to be entomophilous), and simulated the capture efficiency of its ovules. Results were compared with those from previously studied anemophilous Ephedra species. Methods: U-t was determined using stroboscopic photography of pollen in free fall. The acceleration field around an average ovule was calculated, and inflight behavior of pollen grains was predicted using computer simulations. Pollen morphology and ultrastructure were investigated using SEM and STEM. Key results: Pollen wall ultrastructure was correlated with U-t in Ephedra. The relative proportion and amount of granules in the infratectum determine pollen bulk densities, and (together with overall size) determine U-t and thus dispersal capability. Computer simulations failed to reveal any functional traits favoring anemophilous pollen capture in E. foeminea. Conclusion: The fast U-t and dense ultrastructure of E. foeminea pollen are consistent with functional traits that distinguish entomophilous species from anemophilous species. In anemophilous Ephedra species, ovulate organs create an aerodynamic microenvironment that directs airborne pollen to the pollination drops. In E. foeminea, no such microenvironment is created. Ephedroid palynomorphs from the Cretaceous share the ultrastructural characteristics of E. foeminea, and at least some may, therefore, have been produced by insect-pollinated plants.

  • 3.
    Bolinder, Kristina
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Norbäck Ivarsson, Lena
    Humphreys, Aelys M.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. Imperial College London, UK.
    Ickert-Bond, Stefanie M.
    Han, Fang
    Hoorn, Carina
    Rydin, Catarina
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Pollen morphology of Ephedra (Gnetales) and its evolutionary implications2016In: Grana, ISSN 0017-3134, E-ISSN 1651-2049, Vol. 55, no 1, p. 24-51Article in journal (Refereed)
    Abstract [en]

    The Ephedra lineage can be traced at least to the Early Cretaceous. Its characteristically polyplicate pollen is well-represented in the fossil record and is frequently used as an indicator of paleoclimate. However, despite previous efforts, knowledge about variation and evolution of ephedroid pollen traits is poor. Here, we document pollen morphology of nearly all extant species of Ephedra, using a combination of scanning electron microscopy (SEM) and light microscopy (LM), and reconstruct ancestral states of key pollen traits. Our results indicate that the ancestral Ephedra pollen type has numerous plicae interspaced by unbranched pseudosulci, while the derived pollen type has branched pseudosulci and (generally) fewer plicae. The derived type is inferred to have evolved independently twice, once along the North American stem branch and once along the Asian stem branch. Pollen of the ancestral type is common in Mesozoic fossil records, especially from the Early Cretaceous, but it is less commonly reported from the Cenozoic. The earliest documentation of the derived pollen type is from the latest Cretaceous, after which it increases strongly in abundance during the Paleogene. The results of the present study have implications for the age of crown group Ephedra as well as for understanding evolution of pollination syndromes in the genus.

  • 4. Evkaikina, Anastasiia I.
    et al.
    Berke, Lidija
    Romanova, Marina A.
    Proux-Wéra, Estelle
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics. Stockholm University, Science for Life Laboratory (SciLifeLab). Swedish University of Agricultural Sciences, Sweden.
    Ivanova, Alexandra N.
    Rydin, Catarina
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Pawlowski, Katharina
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Voitsekhovskaja, Olga V.
    The Huperzia selago Shoot Tip Transcriptome Sheds New Light on the Evolution of Leaves2017In: Genome Biology and Evolution, ISSN 1759-6653, E-ISSN 1759-6653, Vol. 9, no 9, p. 2444-2460Article in journal (Refereed)
    Abstract [en]

    Lycopodiophyta-consisting of three orders, Lycopodiales, Isoetales and Selaginellales, with different types of shoot apical meristems (SAMs)-form the earliest branch among the extant vascular plants. They represent a sister group to all other vascular plants, from which they differ in that their leaves are microphylls-that is, leaves with a single, unbranched vein, emerging from the protostele without a leaf gap-not megaphylls. All leaves represent determinate organs originating on the flanks of indeterminate SAMs. Thus, leaf formation requires the suppression of indeterminacy, that is, of KNOX transcription factors. In seed plants, this is mediated by different groups of transcription factors including ARP and YABBY. We generated a shoot tip transcriptome of Huperzia selago (Lycopodiales) to examine the genes involved in leaf formation. Our H. selago transcriptome does not contain any ARP homolog, although transcriptomes of Selaginella spp. do. Surprisingly, we discovered a YABBY homolog, although these transcription factors were assumed to have evolved only in seed plants. The existence of a YABBY homolog in H. selago suggests that YABBY evolved already in the common ancestor of the vascular plants, and subsequently was lost in some lineages like Selaginellales, whereas ARP may have been lost in Lycopodiales. The presence of YABBY in the common ancestor of vascular plants would also support the hypothesis that this common ancestor had a simplex SAM. Furthermore, a comparison of the expression patterns of ARP in shoot tips of Selaginella kraussiana (Harrison CJ, et al. 2005. Independent recruitment of a conserved developmental mechanism during leaf evolution. Nature 434(7032): 509-514.) and YABBY in shoot tips of H. selago implies that the development of microphylls, unlike megaphylls, does not seem to depend on the combined activities of ARP and YABBY. Altogether, our data show that Lycopodiophyta are a diverse group; so, in order to understand the role of Lycopodiophyta in evolution, representatives of Lycopodiales, Selaginellales, as well as of Isoetales, have to be examined.

  • 5. Forest, Felix
    et al.
    Moat, Justin
    Baloch, Elisabeth
    Brummitt, Neil A.
    Bachman, Steve P.
    Ickert-Bond, Steffi
    Hollingsworth, Peter M.
    Liston, Aaron
    Little, Damon P.
    Mathews, Sarah
    Rai, Hardeep
    Rydin, Catarina
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. Stockholm University, Faculty of Science, The Bergius Botanical Garden Museum.
    Stevenson, Dennis W.
    Thomas, Philip
    Buerki, Sven
    Gymnosperms on the EDGE2018In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 8, article id 6053Article in journal (Refereed)
    Abstract [en]

    Driven by limited resources and a sense of urgency, the prioritization of species for conservation has been a persistent concern in conservation science. Gymnosperms (comprising ginkgo, conifers, cycads, and gnetophytes) are one of the most threatened groups of living organisms, with 40% of the species at high risk of extinction, about twice as many as the most recent estimates for all plants (i.e. 21.4%). This high proportion of species facing extinction highlights the urgent action required to secure their future through an objective prioritization approach. The Evolutionary Distinct and Globally Endangered (EDGE) method rapidly ranks species based on their evolutionary distinctiveness and the extinction risks they face. EDGE is applied to gymnosperms using a phylogenetic tree comprising DNA sequence data for 85% of gymnosperm species (923 out of 1090 species), to which the 167 missing species were added, and IUCN Red List assessments available for 92% of species. The effect of different extinction probability transformations and the handling of IUCN data deficient species on the resulting rankings is investigated. Although top entries in our ranking comprise species that were expected to score well (e.g. Wollemia nobilis, Ginkgo biloba), many were unexpected (e.g. Araucaria araucana). These results highlight the necessity of using approaches that integrate evolutionary information in conservation science.

  • 6. Han, Fang
    et al.
    Rydin, Catarina
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Bolinder, Kristina
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Dupont-Nivet, Guillaume
    Abels, Hemmo A.
    Koutsodendris, Andreas
    Zhang, Kexin
    Hoorn, Carina
    Steppe development on the Northern Tibetan Plateau inferred from Paleogene ephedroid pollen2016In: Grana, ISSN 0017-3134, E-ISSN 1651-2049, Vol. 55, no 1, p. 71-100Article in journal (Refereed)
    Abstract [en]

    Steppe vegetation represents a key marker of past Asian aridification and is associated with monsoonal intensification. Little is, however, known about the origin of this pre-Oligocene vegetation, its specific composition and how it changed over time and responded to climatic variations. Here, we describe the morphological characters of Ephedraceae pollen in Eocene strata of the Xining Basin and compare the pollen composition with the palynological composition of Late Cretaceous and Paleocene deposits of the Xining Basin and the Quaternary deposits of the Qaidam Basin. We find that the Late Cretaceous steppe was dominated by Gnetaceaepollenites; in the transition from the Cretaceous to the Paleocene, Gnetaceaepollenites became extinct and Ephedripites subgenus Ephedripites dominated the flora with rare occurrences of Ephedripites subgen. Distachyapites; the middle to late Eocene presents a strong increase of Ephedripites subgen. Distachyapites; and the Quaternary/Recent is marked by a significantly lower diversity of Ephedraceae (and Nitrariaceae) compared to the Eocene. In the modern landscape of China, only a fraction of the Paleogene species diversity of Ephedraceae remains and we propose that these alterations in Ephedreaceae composition occurred in response to the climatic changes at least since the Eocene. In particular, the strong Eocene monsoons that enhanced the continental aridification may have played an important role in the evolution of Ephedripites subgen. Distachyapites triggering an evolutionary shift to wind-pollination in this group. Conceivably, the Ephedraceae/Nitrariaceae dominated steppe ended during the Eocene/Oligocene climatic cooling and aridification, which favoured other plant taxa.

  • 7.
    Hou, Chen
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Humphreys, Aelys M.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. Imperial College London, England.
    Thureborn, Olle
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Rydin, Catarina
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    New insights into the evolutionary history of Gnetum (Gnetales)2015In: Taxon, ISSN 0040-0262, E-ISSN 1996-8175, Vol. 64, no 2, p. 239-253Article in journal (Refereed)
    Abstract [en]

    Gnetum (Gnetales: Gnetaceae) constitutes an evolutionarily isolated gymnosperm clade, comprising about 40 species that inhabit tropical areas of the world. While its closest living relative, the monotypic Welwitschia, has a well-documented fossil record from the Early Cretaceous, Gnetum-like fossils are rare and poorly understood. The phylogeny of Gnetum has been studied previously but the distant relationship to outgroups and the difficulty of obtaining plant material mean it is not yet fully resolved. Most species are tropical lianas with an angiospermous vegetative habit that are difficult to find and identify. Here a new phylogeny is presented based on nuclear and chloroplast data from 58 Gnetum accessions, representing 27 putative species, and outgroup information from other seed plants. The results provide support for South American species being sister to the remaining species. The two African species constitute a monophyletic group, sister to an Asian clade, within which the two arborescent species of the genus are the earliest diverging. Estimated divergence times indicate, in contrast with previous results, that the major lineages of Gnetum diverged in the Late Cretaceous. This result is obtained regardless of tree prior used in the BEAST analyses (Yule or birth-death). Together these findings suggest a correlation between early divergence events in extant Gnetum and the breakup of Gondwana in the Cretaceous. Compared to the old stem ages of major subclades of Gnetum, crown nodes date to the Cenozoic: the Asian crown group dates to the Cretaceous-Paleogene (K-Pg) boundary, the African crown group to the mid-Paleogene, and the South American crown group to the Paleogene-Neogene boundary. Although dispersal must have contributed to the current distribution of Gnetum, e.g., within South America and from Southeast Asian islands to the East Asian mainland, dispersal has apparently not occurred across major oceans, at least not during the Cenozoic.

  • 8.
    Hou, Chen
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Rydin, Catarina
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Proteome of pollination drops in Ephedra (Gnetales)Manuscript (preprint) (Other academic)
    Abstract [en]

    Proteins are important in many physiological and ecological processes. In pollination drops of gymnosperms, proteins take part in a number of pollen-ovule interactions and aid for example in ovule defense. Pollination drops in Ephedra (Gnetales) are secreted in large volumes and are known to be high in sucrose, but their proteomic profile has not been thoroughly studied. In this study, proteomic analysis of pollination drops of Ephedra was carried out based on four species: E. distachya, E. foeminea, E. likiangensis and E. minuta. Pollination drop samples were analyzed using gel electrophoresis (1D SDS-PAGE) and mass spectrometry (LC-MS analysis). Protein profile and putative function of proteins were assessed by searches against a set of proteomic databases. Results indicate that number of proteins as well as their amount was low, and most proteins belong to a degradome, i.e., they are remains of degrading tissue at the apex of the nucellus during formation of the pollination chamber. Variation among species was considerable. Ephedra foeminea, which is sister to all other species, contains more kinds of proteins than other investigated species. The closely related species E. likiangensis and E. minuta differ considerably in protein profiles. In E. distachya, no secretome was found; all detected proteins in this species are degradome. The observed differences between species may be related to pollination biology. Insect pollinated species, such as E. foeminea appear to have more proteins in their pollination drops than wind-pollinated species such as E. distachya. Many things are still uncertain regarding proteomics of pollination drops in Ephedra. Among other things, repeatability of results may be a problem; however, this study clearly shows that the amount of proteins in ephedran pollination drops is very low compared to other studied gymnosperms. Future studies of ovule defense in Ephedra should probably have another focus, and perhaps consider sugar content and carbohydrate metabolism rather than proteomics.

  • 9.
    Hou, Chen
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Wikström, Niklas
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. The Royal Swedish Academy of Sciences, Sweden.
    Rydin, Catarina
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. The Royal Swedish Academy of Sciences, Sweden.
    The chloroplast genome of Ephedra foeminea (Ephedraceae, Gnetales), an entomophilous gymnosperm endemic to the Mediterranean area2015In: Mitochondrial DNA, ISSN 1940-1736, E-ISSN 1940-1744, Vol. 28, no 3, p. 330-331Article in journal (Refereed)
    Abstract [en]

    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 reference-guided assembly, the length of the chloroplast genome was estimated to be 109 584 bp, comprising a large single copy region of 60 027 bp, a small single copy 8079 bp, and inverted repeat regions of 20 739 bp. In total, 118 genes were detected, including 73 protein-coding genes, eight ribosomal RNA genes, and 37 transfer RNA genes. The gene density is 1.076 (genes/kb) and the GC content is 36.7%. The genomic sequence of the entomophilous, Mediterranean species E. foeminea, differs from that of the anemophilous, Asian species E. equisetina by 1018 point mutations and 1334 indels. The detected variation is useful for future development of new plastid markers for phylogenetic purposes. Our phylogenetic analysis based on 55 protein-coding chloroplast genes resolve Ephedra as monophyletic and sister to a Gnetum-Welwitschia clade. The Gnetales are sister to Cupressophytes.

  • 10.
    Hou, Chen
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Wikström, Niklas
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. Bergius Foundation, The Royal Academy of Sciences, Sweden.
    Strijk, Joeri S
    Rydin, Catarina
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. Bergius Foundation, The Royal Academy of Sciences, Sweden.
    Resolving phylogenetic relationships and species delimitations in closely related gymnosperms using high-throughput NGS, Sanger sequencing and morphology2016In: Plant Systematics and Evolution, ISSN 0378-2697, E-ISSN 1615-6110, Vol. 302, no 9, p. 1345-1365Article in journal (Refereed)
    Abstract [en]

    Plastid genomes have been widely applied to elucidate plant evolution at higher taxonomic levels, but have rarely been considered useful for addressing close relationships. Here, we resolve the phylogeny and taxonomy of the Chinese lianoid Gnetum clade (Gnetales), using high throughput and Sanger sequencing techniques and studies of plant morphology. Despite previous efforts, relationships among taxa and the taxonomy within the clade have remained unclear. We generated 11 plastid genomes representing one arborescent and four lianoid species. Phylogenetic analyses were conducted using (a) the entire plastid genomes and (b) the protein-coding genes only. Sequence divergence among the lianoid species was substantial, with 9345 variable sites. Four variable regions were identified, targeted and sequenced for an additional 54 specimens and analyzed together with one nuclear ribosomal marker. Results from the phylogenetic analyses corroborate G. parvifolium as sister to the remaining lianoid species and support the presence of at least five additional species in the Chinese lianoid clade: G. catasphaericum, G. formosum, G. luofuense, G. montanum and G. pendulum. Following morphological investigations, G. giganteum and G. gracilipes are included in and synonymized with G. pendulum. Gnetum hainanense is included in and synonymized with G. luofuense. Two names, G. indicum and G. cleistostachyum, remain questionable. A taxonomic revision and a key to Chinese lianoid Gnetum are presented. Internal nodes in the Chinese lianoid Gnetum clade are from the Miocene and onwards and coincide with the expansion of tropical to subtropical forests in South China, which may have facilitated speciation in the clade.

  • 11.
    Humphreys, Aelys M.
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. Imperial College London, UK.
    Rydin, Catarina
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Jonsson, Knud A.
    Alsop, David
    Callender-Crowe, Leah M.
    Barraclough, Timothy G.
    Detecting evolutionarily significant units above the species level using the generalised mixed Yule coalescent method2016In: Methods in Ecology and Evolution, ISSN 2041-210X, E-ISSN 2041-210X, Vol. 7, no 11, p. 1366-1375Article in journal (Refereed)
    Abstract [en]

    There is renewed interest in inferring evolutionary history by modelling diversification rates using phylogenies. Understanding the performance of the methods used under different scenarios is essential for assessing empirical results. Recently, we introduced a new approach for analysing broadscale diversity patterns, using the generalised mixed Yule coalescent (GMYC) method to test for the existence of evolutionarily significant units above the species (higher ESUs). This approach focuses on identifying clades as well as estimating rates, and we refer to it as clade-dependent. However, the ability of the GMYC to detect the phylogenetic signature of higher ESUs has not been fully explored, nor has it been placed in the context of other, clade-independent approaches. We simulated >32000 trees under two clade-independent models: constant-rate birth-death (CRBD) and variable-rate birth-death (VRBD), using parameter estimates from nine empirical trees and more general parameter values. The simulated trees were used to evaluate scenarios under which GMYC might incorrectly detect the presence of higher ESUs. The GMYC null model was rejected at a high rate on CRBD-simulated trees. This would lead to spurious inference of higher ESUs. However, the support for the GMYC model was significantly greater in most of the empirical clades than expected under a CRBD process. Simulations with empirically derived parameter values could therefore be used to exclude CRBD as an explanation for diversification patterns. In contrast, a VRBD process could not be ruled out as an alternative explanation for the apparent signature of hESUs in the empirical clades, based on the GMYC method alone. Other metrics of tree shape, however, differed notably between the empirical and VRBD-simulated trees. These metrics could be used in future to distinguish clade-dependent and clade-independent models. In conclusion, detection of higher ESUs using the GMYC is robust against some clade-independent models, as long as simulations are used to evaluate these alternatives, but not against others. The differences between clade-dependent and clade-independent processes are biologically interesting, but most current models focus on the latter. We advocate more research into clade-dependent models for broad diversity patterns.

  • 12. Ickert-Bond, Stefanie M.
    et al.
    Rydin, Catarina
    Stockholm University, Faculty of Science, Department of Botany.
    MICROMORPHOLOGY OF THE SEED ENVELOPE OF EPHEDRA L. (GNETALES) AND ITS RELEVANCE FOR THE TIMING OF EVOLUTIONARY EVENTS2011In: International journal of plant sciences, ISSN 1058-5893, E-ISSN 1537-5315, Vol. 172, no 1, p. 36-48Article in journal (Refereed)
    Abstract [en]

    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. 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.

  • 13.
    Jörgensen, Annelie
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Rydin, Catarina
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Reproductive morphology in the Gnetum cuspidatum group (Gnetales) and its implications for pollination biology in the Gnetales2015In: Plant Ecology and Evolution, ISSN 2032-3913, E-ISSN 2032-3921, Vol. 148, no 3, p. 387-396Article in journal (Refereed)
    Abstract [en]

    Background and aims - The Gnetales include the extant genera Gnetum, Ephedra and Welwitschia. They are usually functionally dioecious, but male cones often have sterile (but pollination drop-producing) ovules in addition to male units. There are, however, exceptions, i.e. most species of Ephedra and African species of Gnetum. Furthermore, the literature contains conflicting information on the Asian Gnetum cuspidatum. One study states that sterile ovules are present in this species; another that they are absent. The latter also claims that male cones secrete nectar instead, which is interesting because nectar has only been suggested to be present in four gymnosperm species. Here we aim to elucidate whether or not sterile ovules are present in male cones of G. cuspidatum and related taxa, evaluate evidence for nectar being present in gymnosperms and discuss implications for pollination biology. Methods - Male cones from relevant taxa were examined using a dissecting microscope and scanning electron microscopy. Key results - Sterile ovules are present in G. cuspidatum and the related G. macrostachyum, G. microcarpum, G. diminutum and G. loerzingii, but they are minute, hidden among hairs, and easily overlooked. No indications of nectar or nectaries were found and their presence in Asian species of Gnetum is questioned. Conclusions - Insect pollination is probably ancestral in the Gnetales. Like most species of Gnetum, members of the G. cuspidatum group have sterile ovules in male cones, and they can thus attract pollinators to both male and female plants using sweet pollination drops. Although it is possible that these species, in addition, produce extraovular reward for pollinators, we find no such evidence. Instead, it seems plausible that pollination drops have been mistaken for (extraovular) nectar. However, African species of Gnetum have unisexual male cones. Have they developed another means of pollinator reward in male plants or are they wind-pollinated as are their ephedran analogues?

  • 14.
    Larsén, Eva
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Rydin, Catarina
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    DISENTANGLING THE PHYLOGENY OF ISOETES (ISOETALES), USING NUCLEAR AND PLASTID DATA2016In: International journal of plant sciences, ISSN 1058-5893, E-ISSN 1537-5315, Vol. 177, no 2, p. 157-174Article in journal (Refereed)
    Abstract [en]

    Premise of research. The heterosporous lycopsids of Isoetes show limited morphological and genetic variation despite a worldwide distribution and the ancient origin of the lineage. Here major relationships within the genus are clarified, using a substantially larger sampling of species than in previous studies. A first assessment of divergence times of clades is made, and the implications for dispersal mechanisms and biogeographic distribution patterns are discussed. Methodology. On the basis of sequences from three gene regions and 109 specimens representing 74 species of Isoetes, phylogeny and node ages were estimated using parsimony and Bayesian inference. Pivotal results. Three rooting approaches (outgroup analysis, midpoint rooting, and clock rooting) coherently resolved a diverse clade containing species from South Africa, India, Australia, and South America (clade A) as sister to remaining Isoetes. Analysis of divergence times of clades yielded a median age of the crown group of 147 million years ago (mya) using a birth-death tree prior and 165 mya using a Yule tree prior. Clade A was dated to 111 or 125 mya, respectively. While the earliest divergences in Isoetes appear readily explained by ancient vicariance, patterns in younger clades are consistent with dispersal processes, sometimes over long distances. Isoetes andicola (Amstutz) L.D. Gomez, once hypothesized to represent a separate lineage and assigned to the genus Stylites, is here included in a phylogenetic study for the first time. It is closely related to some other South American species, despite its peculiar morphology with a dichotomizing stem. Conclusions. Despite limited intrageneric variation at the molecular and morphological levels, node ages as well as species composition (phylogeny) indicate a Mesozoic origin of the extant clade. Biogeographic patterns appear complicated and intriguing but need more research. Tuberculate megaspore ornamentation (sensu Pfeiffer) is ancestral in the genus, as indicated by current knowledge. Other megaspore patterns appear restricted to two subclades.

  • 15.
    Norbäck Ivarsson, Lena
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Ivarsson, Magnus
    Lundberg, Johannes
    Sällstedt, Therese
    Rydin, Catarina
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Epilithic and aerophilic diatoms in the artificial environment of Kungstradgarden metro station, Stockholm, Sweden2013In: International Journal of Speleology, ISSN 0392-6672, E-ISSN 1827-806X, Vol. 42, no 3, p. 289-297Article in journal (Refereed)
    Abstract [en]

    The Kungstradgarden metro station is an artificial and urban subsurface environment illuminated with artificial light. Its ecosystem is almost completely unknown and as a first step to better understand the biology and rock wall habitats the diatom flora was investigated. A total of 12 species were found growing on the rock walls of Kungstradgarden metro station. The results show the diatom flora in Kungstradgarden to be dominated by e. g. Diadesmis contenta, Diadesmis perpusilla, Pinnularia appendiculata, Nitzschia amphibia, Nitzschia sinuata and Diploneis ovalis. One species, Caloneis cf. aerophila, has never been reported from Sweden before. Significant differences in the species composition between the sampling sites indicate Kungstradgarden metro station to be a heterogeneous habitat that provides different microhabitats.

  • 16.
    Persson, Nannie L.
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. Stockholm University, Faculty of Science, The Bergius Botanical Garden Museum.
    Rydin, Catarina
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. Stockholm University, Faculty of Science, The Bergius Botanical Garden Museum.
    Phylogenetic relationships of the 'Briza complex' to other members of the subfamily Pooideae (Poaceae)2016In: Plant Ecology and Evolution, ISSN 2032-3913, E-ISSN 2032-3921, Vol. 149, no 2, p. 216-227Article in journal (Refereed)
    Abstract [en]

    Background and aims - The species of the 'Briza complex' (Pooideae, Poaceae) are distributed in South America and Eurasia. They are relatively well-studied morphologically and have a complex taxonomic history, but only a few phylogenetic studies have been conducted using molecular data. Monophyly of the complex, which is based on presence of 'brizoid' spikelets, has not been questioned and sampling strategies in previous studies have prevented assessments thereof. Methods - We investigate phylogeny and node ages in the Briza complex and test monophyly of the group using nuclear and chloroplast data. Extensive sampling from the Briza complex and putatively related species in the subfamily Pooideae is employed. Key results - Despite morphological similarity among species, the Briza complex is polyphyletic. Members were found in three different Glades, showing the South American species, the Eurasian species and Briza humilis to be distinct groups. The South American and the Eurasian clades originated about 11 and 13 million years ago, respectively. Briza humilis diverged from Phleum (or a related genus) about 10 million years ago, whereas its crown clade is from the Pliocene-Pleistocene border. The almost simultaneous origins of these clades in the mid-Miocene coincide with temporal estimates of major diversification in grasses and formation of grassland habitats. Conclusions - Based on our results, we support the names Chascolytrum for the South American Glade and Briza for the Eurasian clade. For the Briza humilis clade, we propose the name Brizochloa. The parallel evolution of (seemingly) similar 'brizoid' spikelets in the Pooideae is surprising; however, studies have shown that floral morphology can alter dramatically by one-step mutations, causing evolutionarily distantly related species to have similar appearance. Our findings may hopefully inspire new morphological investigations of the species of the former Briza complex, as well as other poorly studied and potentially polyphyletic genera, such as Deschampsia and Echinopogon.

  • 17.
    Rydin, Catarina
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Bolinder, Kristina
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Moonlight pollination in the gymnosperm Ephedra (Gnetales)2015In: Biology Letters, ISSN 1744-9561, E-ISSN 1744-957X, Vol. 11, no 4, article id 20140993Article in journal (Refereed)
    Abstract [en]

    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.

  • 18.
    Rydin, Catarina
    et al.
    Stockholm University, Faculty of Science, Department of Botany.
    Friis, Else Marie
    Stockholm University, Faculty of Science, Department of Botany.
    Pollen germination in Welwitschia mirabilis Hook. f.: comparing differences between the polyplicate pollen producing genera of the Gnetales2005In: Grana, ISSN 0017-3134, E-ISSN 1651-2049, Vol. 44, no 3, p. 137-141Article in journal (Refereed)
    Abstract [en]

     

     

     

     

     

     

     

    Pollen grains of the seed plant genera

     

    Ephedra L. and Welwitschia

    Hook. f. (Gnetales) are of similar

    size, shape, and have a polyplicate exine with alternating thicker and thinner regions.

     

    Ephedra

    pollen is

    considered inaperturate and the exine is shed during germination, leaving the male gametophyte naked.

    The shed exine curls up and forms a characteristic structure with transverse striations. Such upcurled

    exines have been found in situ in Early Cretaceous seeds with affinities to

     

    Ephedra

    . The purpose of this

    study was to document the germination of

     

    Welwitschia

    pollen and investigate whether they also discard

    their exine during this process.

    The pollen grains of

     

    Welwitschia

    are monoaperturate with a distinct, distal sulcus. During

    germination, the sulcus splits open and the gametophyte expands to a spherical form that extends out

    of the exine. The pollen tube starts to grow one or two hours later and as in

     

    Ephedra

    , it is displaced

    towards one side. The exine is not shed but remains as a ‘‘cap’’ that partly covers the male

    gametophyte. Thus, in this respect the germination process is distinctly different from that in

     

    Ephedra

    and this study demonstrates that discharging the exine during pollen germination is unique to

     

    Ephedra

    ,

    among the polyplicate pollen producing genera in the Gnetales.

  • 19.
    Rydin, Catarina
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Hoorn, Carina
    The Gnetales: past and present2016In: Grana, ISSN 0017-3134, E-ISSN 1651-2049, Vol. 55, no 1, p. 1-4Article in journal (Refereed)
    Abstract [en]

    The present issue of GRANA is devoted to pollen morphology and diversity of the Gnetales in time and space. Three papers address fossil pollen and two papers concern pollen of the extant genus Ephedra. Together, the papers of the issue contribute new information relevant for the understanding of the fossil and evolutionary history of the Gnetales, pollination biology in the group and implications for ephedroid pollen as indicators of palaeoclimate.

  • 20.
    Rydin, Catarina
    et al.
    Stockholm University, Faculty of Science, Department of Botany. Stockholm University, Faculty of Science, The Bergius Botanical Garden Museum.
    Kainulainen, Kent
    Stockholm University, Faculty of Science, Department of Botany. Stockholm University, Faculty of Science, The Bergius Botanical Garden Museum.
    Razafimandimbison, Sylvain
    Stockholm University, Faculty of Science, Department of Botany. Stockholm University, Faculty of Science, The Bergius Botanical Garden Museum.
    Smedmark, Jenny
    Stockholm University, Faculty of Science, Department of Botany. Stockholm University, Faculty of Science, The Bergius Botanical Garden Museum.
    Bremer, Birgitta
    Stockholm University, Faculty of Science, Department of Botany. Stockholm University, Faculty of Science, The Bergius Botanical Garden Museum.
    Deep divergences in the coffee family and the systematic position of Acranthera2009In: Plant Systematics and Evolution, ISSN 0378-2697, E-ISSN 1615-6110, Vol. 278, p. 101-123Article in journal (Refereed)
    Abstract [en]

    Despite extensive efforts, there are unresolved questions on evolutionary relationships in the angiosperm family Rubiaceae. Here, information from six loci and 149 Rubiaceae taxa provide new insights. Acranthera and Coptosapelta are strongly supported as sisters. Pollen grains of Acranthera possess several features common in Rubiaceae, but amongst potential similarities with the unusual grains of Coptosapelta are the nature of the apertures andthe structure of the sexine. Luculia, Acranthera and Coptosapelta are excluded from the three subfamilies Ixoroideae, Cinchonoideae and Rubioideae. Sipaneeae and Condamineeae form a clade, sister to remaining Ixoroideae. Rondeletieae and Guettardeae are sisters to remaining Cinchonoideae. Colletoecema is sister to remaining Rubioideae, followed by the Urophylleae–Ophiorrhizeae clade. Nuclear ITS provided structured information at all phylogenetic levels, but the main gain from adding nrITS was the increased resolution. Average support values also increased but were generally high also without nrITS andthe increase was not statistically significant.

  • 21.
    Rydin, Catarina
    et al.
    Stockholm University, Faculty of Science, Department of Botany.
    Khodabandeh, Anbar
    Stockholm University, Faculty of Science, Department of Botany. Stockholm University, Faculty of Science, The Bergius Botanical Garden Museum.
    Endress, Peter K.
    The female reproductive unit of Ephedra (Gnetales): comparative morphology and evolutionary perspectives2010In: Botanical journal of the Linnean Society, ISSN 0024-4074, E-ISSN 1095-8339, Vol. 163, no 4, p. 387-430Article in journal (Refereed)
    Abstract [en]

    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.

  • 22.
    Rydin, Catarina
    et al.
    Stockholm University, Faculty of Science, Department of Botany.
    Razafimandimbison, Sylvain
    Stockholm University, Faculty of Science, Department of Botany. Stockholm University, Faculty of Science, The Bergius Botanical Garden Museum.
    Khodabandeh, Anbar
    Stockholm University, Faculty of Science, Department of Botany. Stockholm University, Faculty of Science, The Bergius Botanical Garden Museum.
    Bremer, Birgitta
    Stockholm University, Faculty of Science, Department of Botany. Stockholm University, Faculty of Science, The Bergius Botanical Garden Museum.
    Evolutionary relationships in the Spermacoceae alliance (Rubiaceae) using information from six molecular loci: insights into systematic affinities of Neohymenopogon and Mouretia2009In: Taxon, ISSN 0040-0262, E-ISSN 1996-8175, Vol. 58, no 3, p. 793-810Article in journal (Refereed)
    Abstract [en]

    Several recent phylogenetic studies of Rubiaceae have dealt with enigmatic taxa whose systematic positions have been previously unknown or controversial. We address evolutionary relationships in the Spermacoceae alliance (Rubioideae) with special emphasis on the Asian genera Mouretia and Neohymenopogon, here sequenced for the first time. Both genera belong in the tribe Argostemmateae and have persistent calyx lobeson the fruit in common with Argostemma and Mycetia. Other previous uncertainties are resolved with strong support; Saprosma is sister to Paederieae s.str. and Carpacoce is sister to remaining Anthospermeae. Our results further reveal some phylogenetic problems. Danaideae is sister to remaining taxa in the Spermacoceae alliance with high posterior probability, which contradicts results in a recent study. The uncertainty concerning evolutionary relationships of Dunnia and Theligonum is reinforced, despite a denser taxon sampling in the Spermacoceae alliance compared with earlier studies. We also demonstrate yet another example of the controversial correlation between molecular substitution rate and plant life history.

  • 23.
    Rydin, Catarina
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. Stockholm University, Faculty of Science, The Bergius Botanical Garden Museum.
    Wikström, Niklas
    Stockholm University, Faculty of Science, The Bergius Botanical Garden Museum.
    Bremer, Birgitta
    Stockholm University, Faculty of Science, The Bergius Botanical Garden Museum.
    Conflicting results from mitochondrial genomic data challenge current views of Rubiaceae phylogeny2017In: American Journal of Botany, ISSN 0002-9122, E-ISSN 1537-2197, Vol. 104, no 10, p. 1522-1532Article in journal (Refereed)
    Abstract [en]

    PREMISE OF THE STUDY: Reconstruction of plant phylogeny has heavily relied on single-gene or multigene plastid data. New sequencing methods have led to an increasing number of studies based on data from the entire plastid, but the mitochondrion has rarely been used to infer plant phylogeny because of an assumed information poverty and demonstrated lateral transfer of mitochondrial gene regions between distantly related species. METHODS: We explored phylogenetic information from the plant mitochondrion using 57 representatives of the species-rich coffee family as study system and assessed consistency with previous results based (mostly) on plastid data. KEY RESULTS: We showed that the mitochondrial genome can provide structured and statistically significant information on plant phylogeny. While most of our results are consistent with those based on plastid data, some surprising and statistically significant conflicts emerge, and our study demonstrates with striking clarity that the phylogeny of Rubiaceae is far from resolved. CONCLUSIONS: It appears unlikely that conflicts between results retrieved from the different genomic compartments would be restricted to Rubiaceae. Rather, they are probably a general phenomenon and an important factor behind longstanding difficult phylogenetic questions. The biological processes responsible for the conflicting results detected here are unclear, but some conflicts are likely caused by hybridization events that occurred tens of millions of years ago. Whether such ancient events can be reconstructed based on molecular data from extant plants remains to be seen, but future studies of the nuclear genome may provide a way forward.

1 - 23 of 23
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