Browsing by Author "Hunt, JS"

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    Horsetails and ferns are a monophyletic group and the closest living relatives to seed plants.
    (Nature, 2001-02) Pryer, KM; Schneider, H; Smith, AR; Cranfill, R; Wolf, PG; Hunt, JS; Sipes, SD
    Most of the 470-million-year history of plants on land belongs to bryophytes, pteridophytes and gymnosperms, which eventually yielded to the ecological dominance by angiosperms 90 Myr ago. Our knowledge of angiosperm phylogeny, particularly the branching order of the earliest lineages, has recently been increased by the concurrence of multigene sequence analyses. However, reconstructing relationships for all the main lineages of vascular plants that diverged since the Devonian period has remained a challenge. Here we report phylogenetic analyses of combined data--from morphology and from four genes--for 35 representatives from all the main lineages of land plants. We show that there are three monophyletic groups of extant vascular plants: (1) lycophytes, (2) seed plants and (3) a clade including equisetophytes (horsetails), psilotophytes (whisk ferns) and all eusporangiate and leptosporangiate ferns. Our maximum-likelihood analysis shows unambiguously that horsetails and ferns together are the closest relatives to seed plants. This refutes the prevailing view that horsetails and ferns are transitional evolutionary grades between bryophytes and seed plants, and has important implications for our understanding of the development and evolution of plants.
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    Metaxya lanosa, a second species in the genus and fern family Metaxyaceae
    (Systematic Botany, 2001-10-11) Smith, AR; Tuomisto, H; Pryer, KM; Hunt, JS; Wolf, PG
    We describe and illustrate Metaxya lanosa, the second known species in the genus and the fern family Metaxyaceae (Pteridophyta). It is currently known from four different watersheds in Amazonian Peru and Venezuela. It can be distinguished readily from M. rostrata by the noticeably woolly-hairy stipes and rachises (hairs red-brown or orange-brown and easily abraded), broader, more elliptic pinnae, cartilaginous and whitish pinna margins, more distinct veins abaxially, and longer pinna stalks, especially on the distal pinnae, rbcL data from a very limited sampling are ambiguous but do not reject support for the recognition of at least two species within Metaxya.
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    rbcL data reveal two monophyletic groups of filmy ferns (Filicopsida: Hymenophyllaceae).
    (American journal of botany, 2001-06) Pryer, KM; Smith, AR; Hunt, JS; Dubuisson, JY
    The "filmy fern" family, Hymenophyllaceae, is traditionally partitioned into two principal genera, Trichomanes s.l. (sensu lato) and Hymenophyllum s.l., based upon sorus shape characters. This basic split in the family has been widely debated this past century and hence was evaluated here by using rbcL nucleotide sequence data in a phylogenetic study of 26 filmy ferns and nine outgroup taxa. Our results confirm the monophyly of the family and provide robust support for two monophyletic groups that correspond to the two classical genera. In addition, we show that some taxa of uncertain affinity, such as the monotypic genera Cardiomanes and Serpyllopsis, and at least one species of Microtrichomanes, are convincingly included within Hymenophyllum s.l. The tubular- or conical-based sorus that typifies Trichomanes s.l. and Cardiomanes, the most basal member of Hymenophyllum s.l., is a plesiomorphic character state for the family. Tubular-based sori occurring in other members of Hymenophyllum s.l. are most likely derived independently and more than one time. While rbcL data are able to provide a well-supported phylogenetic estimate within Trichomanes s.l., they are inadequate for resolving relationships within Hymenophyllum s.l., which will require data from additional sources. This disparity in resolution reflects differential rates of evolution for rbcL within Hymenophyllaceae.