Browsing by Author "Windham, Michael D"
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Item Open Access 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 MPolyploidy 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.Item Open Access A drought-driven model for the evolution of obligate apomixis in ferns: evidence from pellaeids (Pteridaceae).(American journal of botany, 2021-02-23) Grusz, Amanda L; Windham, Michael D; Picard, Kathryn T; Pryer, Kathleen M; Schuettpelz, Eric; Haufler, Christopher HPremise
Xeric environments impose major constraints on the fern life cycle, yet many lineages overcome these limitations by evolving apomixis. Here, we synthesize studies of apomixis in ferns and present an evidence-based model for the evolution and establishment of this reproductive strategy, focusing on genetic and environmental factors associated with its two defining traits: the production of "unreduced" spores (n = 2n) and the initiation of sporophytes from gametophyte tissue (i.e., diplospory and apogamy, respectively).Methods
We evaluated existing literature in light of the hypothesis that abiotic characteristics of desert environments (e.g., extreme diurnal temperature fluctuations, high light intensity, and water limitation) drive the evolution of obligate apomixis. Pellaeid ferns (Cheilanthoideae: Pteridaceae) were examined in detail, as an illustrative example. We reconstructed a plastid (rbcL, trnG-trnR, atpA) phylogeny for the clade and mapped reproductive mode (sexual versus apomictic) and ploidy across the resulting tree.Results
Our six-stage model for the evolution of obligate apomixis in ferns emphasizes the role played by drought and associated abiotic conditions in the establishment of this reproductive approach. Furthermore, our updated phylogeny of pellaeid ferns reveals repeated origins of obligate apomixis and shows an increase in the frequency of apomixis, and rarity of sexual reproduction, among taxa inhabiting increasingly dry North American deserts.Conclusions
Our findings reinforce aspects of other evolutionary, physiological, developmental, and omics-based studies, indicating a strong association between abiotic factors and the establishment of obligate apomixis in ferns. Water limitation, in particular, appears critical to establishment of this reproductive mode.Item Open Access A Hyb-Seq phylogeny of Boechera and related genera using a combination of Angiosperms353 and Brassicaceae-specific bait sets.(American journal of botany, 2023-10) Hay, Nikolai M; Windham, Michael D; Mandáková, Terezie; Lysak, Martin A; Hendriks, Kasper P; Mummenhoff, Klaus; Lens, Frederic; Pryer, Kathleen M; Bailey, C DonovanPremise
Although Boechera (Boechereae, Brassicaceae) has become a plant model system for both ecological genomics and evolutionary biology, all previous phylogenetic studies have had limited success in resolving species relationships within the genus. The recent effective application of sequence data from target enrichment approaches to resolve the evolutionary relationships of several other challenging plant groups prompted us to investigate their usefulness in Boechera and Boechereae.Methods
To resolve the phylogeny of Boechera and closely related genera, we utilized the Hybpiper pipeline to analyze two combined bait sets: Angiosperms353, with broad applicability across flowering plants; and a Brassicaceae-specific bait set designed for use in the mustard family. Relationships for 101 samples representing 81 currently recognized species were inferred from a total of 1114 low-copy nuclear genes using both supermatrix and species coalescence methods.Results
Our analyses resulted in a well-resolved and highly supported phylogeny of the tribe Boechereae. Boechereae is divided into two major clades, one comprising all western North American species of Boechera, the other encompassing the eight other genera of the tribe. Our understanding of relationships within Boechera is enhanced by the recognition of three core clades that are further subdivided into robust regional species complexes.Conclusions
This study presents the first broadly sampled, well-resolved phylogeny for most known sexual diploid Boechera. This effort provides the foundation for a new phylogenetically informed taxonomy of Boechera that is crucial for its continued use as a model system.Item Open Access Cheilanthes ecuadorensis: A New Species of Cheilanthes s. s. (Pteridaceae) from Northern South America(Systematic Botany, 2021-04-01) Sosa, Karla; Pryer, Kathleen M; Huiet, Layne; Yatskievych, George; Windham, Michael DOngoing research on the taxonomically complex genus Cheilanthes (Pteridaceae; Cheilanthoideae) has resulted in the identification of a new species from Loja Province in Ecuador, Cheilanthes ecuadorensis, described and illustrated herein. Originally collected in 1988 and identified as C. cf. rufopunctata, C. ecuadorensis is clearly distinct from that species in having pubescent adaxial blade surfaces and narrow, poorly-differentiated false indusia (rather than the glabrous adaxial surfaces and wide false indusia of C. rufopunctata). Among the South American species currently included in Cheilanthes, C. ecuadorensis is superficially most similar to C. pilosa. However, our molecular phylogenetic analyses indicate that C. ecuadorensis is sister to C. micropteris, the morphologically disparate generitype of Cheilanthes. Here we examine the phylogenetic relationships, morphology, cytogenetics, and geography of these four South American Cheilanthes species in a study that, once again, highlights the importance of herbaria in the process of new species discovery.Item Open Access DNA barcoding exposes a case of mistaken identity in the fern horticultural trade.(Molecular ecology resources, 2010-11) Pryer, Kathleen M; Schuettpelz, Eric; Huiet, Layne; Grusz, Amanda L; Rothfels, Carl J; Avent, Tony; Schwartz, David; Windham, Michael DUsing cheilanthoid ferns, we provide an example of how DNA barcoding approaches can be useful to the horticultural community for keeping plants in the trade accurately identified. We use plastid rbcL, atpA, and trnG-R sequence data to demonstrate that a fern marketed as Cheilanthes wrightii (endemic to the southwestern USA and northern Mexico) in the horticultural trade is, in fact, Cheilanthes distans (endemic to Australia and adjacent islands). Public and private (accessible with permission) databases contain a wealth of DNA sequence data that are linked to vouchered plant material. These data have uses beyond those for which they were originally generated, and they provide an important resource for fostering collaborations between the academic and horticultural communities. We strongly advocate the barcoding approach as a valuable new technology available to the horticulture industry to help correct plant identification errors in the international trade.Item Open Access Identifying multiple origins of polyploid taxa: a multilocus study of the hybrid cloak fern (Astrolepis integerrima; Pteridaceae).(American journal of botany, 2012-11) Beck, James B; Allison, James R; Pryer, Kathleen M; Windham, Michael DPREMISE OF THE STUDY: Molecular studies have shown that multiple origins of polyploid taxa are the rule rather than the exception. To understand the distribution and ecology of polyploid species and the evolutionary significance of polyploidy in general, it is important to delineate these independently derived lineages as accurately as possible. Although gene flow among polyploid lineages and backcrossing to their diploid parents often confound this process, such post origin gene flow is very infrequent in asexual polyploids. In this study, we estimate the number of independent origins of the apomictic allopolyploid fern Astrolepis integerrima, a morphologically heterogeneous species most common in the southwestern United States and Mexico, with outlying populations in the southeastern United States and the Caribbean. METHODS: Plastid DNA sequence and AFLP data were obtained from 33 A. integerrima individuals. Phylogenetic analysis of the sequence data and multidimensional clustering of the AFLP data were used to identify independently derived lineages. KEY RESULTS: Analysis of the two datasets identified 10 genetic groups within the 33 analyzed samples. These groups suggest a minimum of 10 origins of A. integerrima in the northern portion of its range, with both putative parents functioning as maternal donors, both supplying unreduced gametes, and both contributing a significant portion of their genetic diversity to the hybrids. CONCLUSIONS: Our results highlight the extreme cryptic genetic diversity and systematic complexity that can underlie a single polyploid taxon.Item Open Access Looking Back on 130 Years of Fern and Lycophyte Research in Glacier National Park, Montana: A Modern Taxonomic Account(American Fern Journal, 2021-11-05) Heron, Keegan; Windham, Michael D; Farrar, Donald R; Pryer, Kathleen MItem Open Access Myriopteris grusziae: A New Species from Texas and Oklahoma Segregated from the Chihuahuan Desert Taxon M. scabra (Pteridaceae)(Systematic botany., 2022-09) Windham, Michael D; Picard, Kathryn T; Pryer, Kathleen MMyriopteris scabra (until recently called Cheilanthes horridula) is a xeric-adapted fern species, endemic to the southwestern United States and northern Mexico. It is one of the most recognizable ferns in North America due to the unusual nature of the indument present on its adaxial leaf surfaces. This consists of rigid, multicellular trichomes with glassy, needle-like apices and compact conical bodies that are partially embedded in the leaf surface to form swollen, pustulate bases. Despite the seemingly distinctive nature of M. scabra, published chromosome counts indicate that collections assigned to this taxon encompass both diploids (n = 29) and tetraploids (n = 58). Here we investigate this case of cryptic diversity by integrating data from cytogenetic and spore analyses, observations of sporophyte morphology, and geographic distributions. Myriopteris scabra s.l. is shown to comprise two genetically disparate, morphologically recognizable taxa that exhibit little or no geographic overlap. The tetraploid taxon is described as a new species, M. grusziae, which completely supplants diploid M. scabra in the northeastern portion of its range (central Texas and south-central Oklahoma). This presumed allotetraploid is most like M. scabra but differs in having ultimate segments with adaxial trichomes that are longer, more flexible, mostly linear, and superficially attached. In addition, tetraploid M. grusziae has larger, more abundant scales that largely conceal the dark, sclerified leaf rachises, and it produces consistently larger spores than diploid M. scabra. We hypothesize that M. grusziae is an allotetraploid hybrid that acquired half of its chromosomes from M. scabra. However, the identity of the other diploid parent has yet to be resolved.Item Open Access Unique expression of a sporophytic character on the gametophytes of notholaenid ferns (Pteridaceae).(American journal of botany, 2012-06) Johnson, Anne K; Rothfels, Carl J; Windham, Michael D; Pryer, Kathleen MPREMISE OF THE STUDY: Not all ferns grow in moist, shaded habitats; some lineages thrive in exposed, seasonally dry environments. Notholaenids are a clade of xeric-adapted ferns commonly characterized by the presence of a waxy exudate, called farina, on the undersides of their leaves. Although some other lineages of cheilanthoid ferns also have farinose sporophytes, previous studies suggested that notholaenids are unique in also producing farina on their gametophytes. For this reason, consistent farina expression across life cycle phases has been proposed as a potential synapomorphy for the genus Notholaena. Recent phylogenetic studies have shown two species with nonfarinose sporophytes to be nested within Notholaena, with a third nonfarinose species well supported as sister to all other notholaenids. This finding raises the question: are the gametophytes of these three species farinose like those of their close relatives, or are they glabrous, consistent with their sporophytes? METHODS: We sowed spores of a diversity of cheilanthoid ferns onto culture media to observe and document whether their gametophytes produced farina. To place these species within a phylogenetic context, we extracted genomic DNA, then amplified and sequenced three plastid loci. The aligned data were analyzed using maximum likelihood to generate a phylogenetic tree. KEY RESULTS: Here we show that notholaenids lacking sporophytic farina also lack farina in the gametophytic phase, and notholaenids with sporophytic farina always display gametophytic farina (with a single exception). Outgroup taxa never displayed gametophytic farina, regardless of whether they displayed farina on their sporophytes. CONCLUSIONS: Notholaenids are unique among ferns in consistently expressing farina across both phases of the life cycle.