Browsing by Author "Yatskievych, G"

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    Patterns of diversification in the xeric-adapted fern genus myriopteris (Pteridaceae)
    (Systematic Botany, 2014-01-01) Grusz, AL; Windham, MD; Yatskievych, G; Huiet, L; Gastony, GJ; Pryer, KM
    Strong selective pressures imposed by drought-prone habitats have contributed to extensive morphological convergence among the 400 + species of cheilanthoid ferns (Pteridaceae). As a result, generic circumscriptions based exclusively on macromorphology often prove to be non-monophyletic. Ongoing molecular phylogenetic analyses are providing the foundation for a revised classification of this challenging group and have begun to clarify its complex evolutionary history. As part of this effort, we generated and analyzed DNA sequence data for three plastid loci (rbcL, atpA, and the intergenic spacer trnG-trnR) for the myriopterid clade, one of the largest monophyletic groups of cheilanthoid ferns. This lineage encompasses 47 primarily North and Central American taxa previously included in Cheilanthes but now placed in the recircumscribed genus Myriopteris. Here, we infer a phylogeny for the group and examine key morphological characters across this phylogeny. We also include a brief discussion of the three well-supported Myriopteris subclades, along with a review of reproductive mode and known ploidy levels for members of this early diverging lineage of cheilanthoid ferns. © Copyright 2014 by the American Society of Plant Taxonomists.
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    Refining the phylogeny of cheilanthoid ferns: The resurrection and recircumscription of Myriopteris (Pteridaceae)
    (Systematic Botany, 2013) Grusz, AL; Pryer, KM; Yatskievych, G; Huiet, RL; Gastony, GJ; Windham, MD
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    Species relationships and farina evolution in the cheilanthoid fern genus Argyrochosma (Pteridaceae)
    (Systematic Botany, 2011-07-01) Sigel, EM; Windham, MD; Huiet, L; Yatskievych, G; Pryer, KM
    Convergent evolution driven by adaptation to arid habitats has made it difficult to identify monophyletic taxa in the cheilanthoid ferns. Dependence on distinctive, but potentially homoplastic characters, to define major clades has resulted in a taxonomic conundrum: all of the largest cheilanthoid genera have been shown to be polyphyletic. Here we reconstruct the first comprehensive phylogeny of the strictly New World cheilanthoid genus Argyrochosma. We use our reconstruction to examine the evolution of farina (powdery leaf deposits), which has played a prominent role in the circumscription of cheilanthoid genera. Our data indicate that Argyrochosma comprises two major monophyletic groups: one exclusively non-farinose and the other primarily farinose. Within the latter group, there has been at least one evolutionary reversal (loss) of farina and the development of major chemical variants that characterize specific clades. Our phylogenetic hypothesis, in combination with spore data and chromosome counts, also provides a critical context for addressing the prevalence of polyploidy and apomixis within the genus. Evidence from these datasets provides testable hypotheses regarding reticulate evolution and suggests the presence of several previously undetected taxa of Argyrochosma. © 2011 by the American Society of Plant Taxonomists.
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    Using Plastid and Nuclear DNA Sequences to Redraw Generic Boundaries and Demystif Species Complexes in Cheilanthoid Ferns.
    (AMERICAN FERN JOURNAL, 2009-04-01) Windham, MD; Huiet, L; Schuettpelz, E; Grusz, AL; Rothfels, C; Beck, J; Yatskievych, G; Pryer, KM