Browsing by Author "Schneider, H"

Now showing 1 - 13 of 13

Open Access
A classification for extant ferns
(Taxon, 2006-01-01) Smith, AR; Pryer, KM; Schuettpelz, E; Korall, P; Schneider, H; Wolf, PG
We present a revised classification for extant ferns, with emphasis on ordinal and familial ranks, and a synopsis of included genera. Our classification reflects recently published phylogenetic hypotheses based on both morphological and molecular data. Within our new classification, we recognize four monophyletic classes, 11 monophyletic orders, and 37 families, 32 of which are strongly supported as monophyletic. One new family, Cibotiaceae Korall, is described. The phylogenetic affinities of a few genera in the order Polypodiales are unclear and their familial placements are therefore tentative. Alphabetical lists of accepted genera (including common synonyms), families, orders, and taxa of higher rank are provided.
Open Access
A molecular phylogeny of scaly tree ferns (Cyatheaceae).
(American journal of botany, 2007-05) Korall, P; Conant, DS; Metzgar, JS; Schneider, H; Pryer, KM
Tree ferns recently were identified as the closest sister group to the hyperdiverse clade of ferns, the polypods. Although most of the 600 species of tree ferns are arborescent, the group encompasses a wide range of morphological variability, from diminutive members to the giant scaly tree ferns, Cyatheaceae. This well-known family comprises most of the tree fern diversity (∼500 species) and is widespread in tropical, subtropical, and south temperate regions of the world. Here we investigate the phylogenetic relationships of scaly tree ferns based on DNA sequence data from five plastid regions (rbcL, rbcL-accD IGS, rbcL-atpB IGS, trnG-trnR, and trnL-trnF). A basal dichotomy resolves Sphaeropteris as sister to all other taxa and scale features support these two clades: Sphaeropteris has conform scales, whereas all other taxa have marginate scales. The marginate-scaled clade consists of a basal trichotomy, with the three groups here termed (1) Cyathea (including Cnemidaria, Hymenophyllopsis, Trichipteris), (2) Alsophila sensu stricto, and (3) Gymnosphaera (previously recognized as a section within Alsophila) + A. capensis. Scaly tree ferns display a wide range of indusial structures, and although indusium shape is homoplastic it does contain useful phylogenetic information that supports some of the larger clades recognised.
Open Access
A molecular phylogeny of the fern family Pteridaceae: assessing overall relationships and the affinities of previously unsampled genera.
(Molecular phylogenetics and evolution, 2007-09) Schuettpelz, E; Schneider, H; Huiet, L; Windham, MD; Pryer, KM
The monophyletic Pteridaceae accounts for roughly 10% of extant fern diversity and occupies an unusually broad range of ecological niches, including terrestrial, epiphytic, xeric-adapted rupestral, and even aquatic species. In this study, we present the results of the first broad-scale and multi-gene phylogenetic analyses of these ferns, and determine the affinities of several previously unsampled genera. Our analyses of two newly assembled data sets (including 169 newly obtained sequences) resolve five major clades within the Pteridaceae: cryptogrammoids, ceratopteridoids, pteridoids, adiantoids, and cheilanthoids. Although the composition of these clades is in general agreement with earlier phylogenetic studies, it is very much at odds with the most recent subfamilial classification. Of the previously unsampled genera, two (Neurocallis and Ochropteris) are nested within the genus Pteris; two others (Monogramma and Rheopteris) are early diverging vittarioid ferns, with Monogramma resolved as polyphyletic; the last previously unsampled genus (Adiantopsis) occupies a rather derived position among cheilanthoids. Interestingly, some clades resolved within the Pteridaceae can be characterized by their ecological preferences, suggesting that the initial diversification in this family was tied to ecological innovation and specialization. These processes may well be the basis for the diversity and success of the Pteridaceae today.
Open Access
Comparative morphology of reproductive structures in heterosporous water ferns and a reevaluation of the sporocarp
(International Journal of Plant Sciences, 2006-07-01) Nagalingum, NS; Schneider, H; Pryer, KM
Heterosporous water ferns (Marsileaceae and Salviniaceae) are the only extant group of plants to have evolved heterospory since the Paleozoic. These ferns possess unusual reproductive structures traditionally termed "sporocarps." Using an evolutionary framework, we critically examine the complex homology issues pertaining to these structures. Comparative morphological study reveals that all heterosporous ferns bear indusiate sori on a branched, nonlaminate structure that we refer to as the sorophore; this expanded definition highlights homology previously obscured by the use of different terms. By using a homology-based concept, we aim to discontinue the use of historically and functionally based morphological terminology. We recognize the sorophore envelope as a structure that surrounds the sorophore and sori. The sorophore envelope is present in Marsileaceae as a sclerenchymatous sporocarp wall and in Azolla as a parenchymatous layer, but it is absent in Salvinia. Both homology assessments and phylogenetic character-state reconstructions using the Cretaceous fossil Hydropteris are consistent with a single origin of the sorophore envelope in heterosporous ferns. Consequently, we restrict the term "sporocarp" to a sorophore envelope and all it contains. Traditional usage of "sporocarp" is misleading because it implies homology for nonhomologous structures, and structures historically called sporocarps in Salviniaceae are more appropriately referred to as sori. © 2006 by The University of Chicago. All rights reserved.
Open Access
Evolution of vascular plant body plans: a phylogenetic perspective
(Developmental genetics and plant evolution, 2002) Schneider, H; Pryer, KM; Cranfill, R; Smith, AR; Wolf, PG
Open Access
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.
Open Access
Is morphology really at odds with molecules in estimating fern phylogeny?
(Systematic Botany, 2009-07-01) Schneider, H; Smith, AR; Pryer, KM
Using a morphological dataset of 136 vegetative and reproductive characters, we infer the tracheophyte phylogeny with an emphasis on early divergences of ferns (monilophytes). The dataset comprises morphological, anatomical, biochemical, and some DNA structural characters for a taxon sample of 35 species, including representatives of all major lineages of vascular plants, especially ferns. Phylogenetic relationships among vascular plants are reconstructed using maximum parsimony and Bayesian inference. Both approaches yield similar relationships and provide evidence for three major lineages of extant vascular plants: lycophytes, ferns, and seed plants. Lycophytes are sister to the euphyllophyte clade, which comprises the fern and seed plant lineages. The fern lineage consists of five clades: horsetails, whisk ferns, ophioglossoids, marattioids, and leptosporangiate ferns. This lineage is supported by characters of the spore wall and has a parsimony bootstrap value of 76%, although the Bayesian posterior probability is only 0.53. Each of the five fern clades is well supported, but the relationships among them lack statistical support. Our independent phylogenetic analyses of morphological evidence recover the same deep phylogenetic relationships among tracheophytes as found in previous studies utilizing DNA sequence data, but differ in some ways within seed plants and within ferns. We discuss the extensive independent evolution of the five extant fern clades and the evidence for the placement of whisk ferns and horsetails in our morphological analyses. © 2009 by the American Society of Plant Taxonomists.
Open Access
Marsileaceae sporocarps and spores from the late cretaceous of Georgia, U.S.A.
(International Journal of Plant Sciences, 2000-01-01) Lupia, R; Schneider, H; Moeser, GM; Pryer, KM; Crane, PR
A new species provisionally assigned to the extant genus Regnellidium Lindm. (Regnellidium upatoiensis sp. nov.) is established for isolated sporocarps assignable to the heterosporous water fern family Marsileaceae. Three sporocarps and hundreds of dispersed megaspores were recovered from unconsolidated clays and silts of the Eutaw Formation (Santonian, Late Cretaceous) along Upatoi Creek, Georgia, U.S.A. The sporocarps are ellipsoidal and flattened, contain both megasporangia and microsporangia, and possess a two-layered wall - an outer sclerenchymatous layer and an inner parenchymatous layer. In situ megaspores are spheroidal, with two distinct wall layers - an exine, differentiated into two layers, and an outer ornamented perine also differentiated into two layers. The megaspores also possess an acrolamella consisting of six (five to seven) triangular lobes that are twisted. In situ microspores are trilete and spheroidal, with a strongly rugulate perine, and show modification of the perine over the laesura to form an acrolamella. Comparison of the fossil sporocarps with those of four extant species of Marsileaceae reveal marked similarity with Regnellidium diphyllum Lindm., particularly in megaspore and microspore morphology. If found dispersed, the in situ megaspores would be assigned to Molaspora lobata (Dijkstra) Hall and the microspores to Crybelosporites Dettmann based on their size, shape, and ornamentation. Regnellidium upatoiensis sp. nov. extends the stratigraphic range of the genus back to the Santonian, nearly contemporaneous with the first evidence of Marsilea, and implies that the diversification of the Marsileaceae into its extant lineages occurred in the mid-Cretaceous.
Open Access
Molecular phylogenetic relationships and morphological evolution in the heterosporous fern genus Marsilea
(Systematic Botany, 2007-01-01) Nagalingum, NS; Schneider, H; Pryer, KM
Using six plastid regions, we present a phylogeny for 26 species of the heterosporous fern genus Marsilea. Two well-supported groups within Marsilea are identified. Group I includes two subgroups, and is relatively species-poor. Species assignable to this group have glabrous leaves (although land leaves may have a few hairs), sporocarps lacking both a raphe and teeth, and share a preference for submerged conditions (i.e., they are intolerant of desiccation). Group II is relatively diverse, and its members have leaves that are pubescent, sporocarps that bear a raphe and from zero to two teeth, and the plants are often emergent at the edges of lakes and ponds. Within Group II, five subgroups receive robust support: three are predominantly African, one is New World, and one Old World. Phylogenetic assessment of morphological evolution suggests that the presence of an inferior sporocarp tooth and the place of sporocarp maturation are homoplastic characters, and are therefore of unreliable taxonomic use at an infrageneric level. In contrast, the presence of a raphe and superior sporocarp tooth are reliable synapomorphies for classification within Marsilea. © Copyright 2007 by the American Society of Plant Taxonomists.
Open Access
On the phylogenetic position of Cystodium: It's not a tree fern - It's a polypod!
(American Fern Journal, 2006-04-01) Korall, P; Conant, DS; Schneider, H; Ueda, K; Nishida, H; Pryer, KM
The phylogenetic position of Cystodium J. Sm. is studied here for the first time using DNA sequence data. Based on a broad sampling of leptosporangiate ferns and two plastid genes (rbcL and atpB), we show that Cystodium does not belong to the tree fern family Dicksoniaceae, as previously thought. Our results strongly support including Cystodium within the large polypod clade, and suggest its close relationship to the species-poor grade taxa at the base of the polypod topology (Sphenomeris and Lonchitis, or Saccoloma in this study). Further studies, with an expanded taxon sampling within polypods, are needed to fully understand the more precise phylogenetic relationships of Cystodium.
Open Access
Phylogeny and divergence time estimates for the fern genus Azolla (Salviniaceae)
(International Journal of Plant Sciences, 2007-10-22) Metzgar, JS; Schneider, H; Pryer, KM
A phylogeny for all extant species of the heterosporous fern genus Azolla is presented here based on more than 5000 base pairs of DNA sequence data from six plastid loci (rbcL, atpB, rps4, trnL-trnF, trnG-trnR, and rps4-trnS). Our results are in agreement with other recent molecular phylogenetic hypotheses that support the monophyly of sections Azolla and Rhizosperma and the proposed relationships within section Azolla. Divergence times are estimated within Azolla using a penalized likelihood approach, integrating data from fossils and DNA sequences. Penalized likelihood analyses estimate a divergence time of 50.7 Ma (Eocene) for the split between sections Azolla and Rhizosperma, 32.5 Ma (Oligocene) for the divergence of Azolla nilotica from A. pinnata within section Rhizosperma, and 16.3 Ma (Miocene) for the divergence of the two lineages within section Azolla (the A. filiculoides + A. rubra lineage from the A. caroliniana + A. microphylla + A. mexicana complex). © 2007 by The University of Chicago. All rights reserved.
Open Access
Structure and function of spores in the aquatic heterosporous fern family Marsileaceae
(International Journal of Plant Sciences, 2002-01-01) Schneider, H; Pryer, KM
Spores of the aquatic heterosporous fern family Marsileaceae differ markedly from spores of Salviniaceae, the only other family of heterosporous ferns and sister group to Marsileaceae, and from spores of all homosporous ferns. The marsileaceous outer spore wall (perine) is modified above the aperture into a structure, the acrolamella, and the perine and acrolamella are further modified into a remarkable gelatinous layer that envelops the spore. Observations with light and scanning electron microscopy indicate that the three living marsileaceous fern genera (Marsilea, Pilularia, and Regnellidium) each have distinctive spores, particularly with regard to the perine and acrolamella. Several spore characters support a division of Marsilea into two groups. Spore character evolution is discussed in the context of developmental and possible functional aspects. The gelatinous perine layer acts as a flexible, floating organ that envelops the spores only for a short time and appears to be an adaptation of marsileaceous ferns to amphibious habitats. The gelatinous nature of the perine layer is likely the result of acidic polysaccharide components in the spore wall that have hydrogel (swelling and shrinking) properties. Megaspores floating at the water/air interface form a concave meniscus, at the center of which is the gelatinous acrolamella that encloses a "sperm lake". This meniscus creates a vortex-like effect that serves as a trap for free-swimming sperm cells, propelling them into the sperm lake.
Open Access
Tree ferns: monophyletic groups and their relationships as revealed by four protein-coding plastid loci.
(Molecular phylogenetics and evolution, 2006-06) Korall, P; Pryer, KM; Metzgar, JS; Schneider, H; Conant, DS
Tree ferns are a well-established clade within leptosporangiate ferns. Most of the 600 species (in seven families and 13 genera) are arborescent, but considerable morphological variability exists, spanning the giant scaly tree ferns (Cyatheaceae), the low, erect plants (Plagiogyriaceae), and the diminutive endemics of the Guayana Highlands (Hymenophyllopsidaceae). In this study, we investigate phylogenetic relationships within tree ferns based on analyses of four protein-coding, plastid loci (atpA, atpB, rbcL, and rps4). Our results reveal four well-supported clades, with genera of Dicksoniaceae (sensu ) interspersed among them: (A) (Loxomataceae, (Culcita, Plagiogyriaceae)), (B) (Calochlaena, (Dicksonia, Lophosoriaceae)), (C) Cibotium, and (D) Cyatheaceae, with Hymenophyllopsidaceae nested within. How these four groups are related to one other, to Thyrsopteris, or to Metaxyaceae is weakly supported. Our results show that Dicksoniaceae and Cyatheaceae, as currently recognised, are not monophyletic and new circumscriptions for these families are needed.

Browsing by Author "Schneider, H"

Results Per Page

Sort Options