Browsing by Subject "HYBRIDIZATION"

Now showing 1 - 4 of 4
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    A diploids-first approach to species delimitation and interpreting polyploid evolution in the fern genus astrolepis (pteridaceae)
    (Systematic Botany, 2010-04-01) Beck, James B; Windham, Michael D; Yatskievych, George; Pryer, Kathleen M
    Polyploidy presents a challenge to those wishing to delimit the species within a group and reconstruct the phylogenetic relationships among these taxa. A clear understanding of the tree-like relationships among the diploid species can provide a framework upon which to reconstruct the reticulate events that gave rise to the polyploid lineages. In this study we apply this "diploids-first" strategy to the fern genus Astrolepis (Pteridaceae). Diploids are identified using the number of spores per sporangium and spore size. Analyses of plastid and low-copy nuclear sequence data provide well-supported estimates of phylogenetic relationships, including strong evidence for two morphologically distinctive diploid lineages not recognized in recent treatments. One of these corresponds to the type of Notholaena deltoidea, a species that has not been recognized in any modern treatment of Astrolepis. This species is resurrected here as the new combination Astrolepis deltoidea . The second novel lineage is that of a diploid initially hypothesized to exist by molecular and morphological characteristics of several established Astrolepis allopolyploids. This previously missing diploid species is described here as Astrolepis obscura. © Copyright 2010 by the American Society of Plant Taxonomists.
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    Are there too many fern genera?
    (Taxon, 2018-06-01) Schuettpelz, E; Rouhan, G; Pryer, KM; Rothfels, CJ; Prado, J; Sundue, MA; Windham, MD; Moran, RC; Smith, AR
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    Deciphering the origins of apomictic polyploids in the Cheilanthes yavapensis complex (Pteridaceae).
    (American journal of botany, 2009-09) Grusz, AL; Windham, MD; Pryer, KM
    Deciphering species relationships and hybrid origins in polyploid agamic species complexes is notoriously difficult. In this study of cheilanthoid ferns, we demonstrate increased resolving power for clarifying the origins of polyploid lineages by integrating evidence from a diverse selection of biosystematic methods. The prevalence of polyploidy, hybridization, and apomixis in ferns suggests that these processes play a significant role in their evolution and diversification. Using a combination of systematic approaches, we investigated the origins of apomictic polyploids belonging to the Cheilanthes yavapensis complex. Spore studies allowed us to assess ploidy levels; plastid and nuclear DNA sequencing revealed evolutionary relationships and confirmed the putative progenitors (both maternal and paternal) of taxa of hybrid origin; enzyme electrophoretic evidence provided information on genome dosage in allopolyploids. We find here that the widespread apomictic triploid, Cheilanthes lindheimeri, is an autopolyploid derived from a rare, previously undetected sexual diploid. The apomictic triploid Cheilanthes wootonii is shown to be an interspecific hybrid between C. fendleri and C. lindheimeri, whereas the apomictic tetraploid C. yavapensis is comprised of two cryptic and geographically distinct lineages. We show that earlier morphology-based hypotheses of species relationships, while not altogether incorrect, only partially explain the complicated evolutionary history of these ferns.
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    Expression level dominance and homeolog expression bias in recurrent origins of the allopolyploid fern polypodium hesperium
    (American Fern Journal, 2019-07-01) Sigel, EM; Der, JP; Windham, MD; Pryer, KM
    © 2019 American Fern Society. All rights reserved. Allopolyploidization is a common mode of speciation in ferns with many taxa having formed recurrently from distinct hybridization events between the same parent species. Each hybridization event marks the union of divergent parental gene copies, or homeologs, and the formation of an independently derived lineage. Little is known about the effects of recurrent origins on the genomic composition and phenotypic variation of allopolyploid fern taxa. To begin to address this knowledge gap, we investigated gene expression patterns in two naturally formed, independently derived lineages of the allotetraploid fern Polypodium hesperium relative to its diploid progenitor species, Polypodium amorphum and Polypodium glycyrrhiza. Using RNA-sequencing to survey total gene expression levels for 19194 genes and homeolog-specific expression for 1073 genes, we found that, in general, gene expression in both lineages of P. hesperium was biased toward P. amorphum - both by mirroring expression levels of P. amorphum and preferentially expressing homeologs derived from P. amorphum. However, we recovered substantial expression variation between the two lineages at the level of individual genes and among individual specimens. Our results align with similar transcriptome profile studies of angiosperms, suggesting that expression in many allopolyploid plants reflects the dominance of a specific parental subgenome, but that recurrent origins impart substantial expression, or phenotypic, variation to allopolyploid taxa.