Publications


These publications acknowledge some or all of the following NSF awards:
  • DEB-9615533 to Kathleen M. Pryer;
  • DEB-9616260 to Alan R. Smith;
  • DEB-9707087 to Paul G. Wolf
  • DEB-0073036 to Raymond Cranfill

PRYER, K.M., H. SCHNEIDER, A.R. SMITH, R. CRANFILL, P.G. WOLF, J.S. HUNT, & S.D. SIPES. Horsetails and ferns are a monophyletic group and the closest living relatives to seed plants. Nature 409:618-622.

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SCHNEIDER, H. & K.M. PRYER. Structure and function of spores in the aquatic heterosporous fern family Marsileaceae. International Journal of Plant Sciences. In review.

SMITH, A.R., H. TUOMISTO, K.M. PRYER, J.S. HUNT & P.G. WOLF. 2001. Metaxya lanosa, a second species in the genus and fern family Metaxyaceae. Systematic Botany. In press.

PRYER, K.M., A.R. SMITH, J.S. HUNT, & J.-Y. DUBUISSON. 2001. rbcL data reveal two monophyletic groups of filmy ferns (Filicopsida: Hymenophyllaceae). American Journal of Botany. In press.

LUPIA, R., H. SCHNEIDER, G.M. MOESER, K.M. PRYER, & P.R. CRANE. 2000. Marsileaceae sporocarps and spores from the Late Cretaceous of Georgia, U.S.A. International Journal of Plant Sciences 161: 975-988.

PRYER, K. M. 1999. Phylogeny of marsileaceous ferns and relationships of the fossil Hydropteris pinnata reconsidered. International Journal of Plant Sciences 160: 931-954. (cover).

WOLF, P.G., S.D. SIPES, M.R. WHITE, M.L. MARTINES, K.M. PRYER, A.R. SMITH, & K. UEDA. 1999. Phylogenetic relationships of the enigmatic fern families Hymenophyllopsidaceae and Lophosoriaceae: evidence from rbcL nucleotide sequences. Plant Systematics and Evolution 219: 263-270.

WOLF, P. G., K. M. PRYER, A. R. SMITH, & M. HASEBE. 1998. Phylogenetic studies of extant pteridophytes. In Molecular systematics of plants II: DNA sequencing, eds. P. S. Soltis, D. E. Soltis, and J. J. Doyle, 541-556. Boston: Kluwer Academic Publishers.



Published Abstracts


PRYER, K.M., H. SCHNEIDER, A.R. SMITH, P. G. WOLF, R. C. CRANFILL, J. S. HUNT & S.D. SIPES. 2000. The closest living relative to seed plants: insights from four genes and morphology. American Journal of Botany 87 (Suppl): 151.
ABSTRACT: Extant vascular plants comprise free-sporing "pteridophytes" (lycopods, Psilotaceae, Equisetum, and ferns) and seed plants (gymnosperms and angiosperms). The evolution of vascular plants is mostly a 470-million-year history of pteridophytes and gymnosperms, which ultimately led to the domination of our terrestrial ecosystems by angiosperms 100 million years ago. Pteridophytes traditionally are depicted as having various paraphyletic relationships to seed plants and are often thought of as "intermediate evolutionary grades" of relatively minor significance in early land plant evolution. Phylogenetic estimates based on single genes and/or morphology yield weak evidence for the divergence and relationships among these major groups of vascular plants. This is not entirely surprising given that, with the exception of angiosperms, they all evolved in the Paleozoic and had diverged by the late Devonian (ca. 400 mya). The long independent history of each of these lineages ensures that resolving their relationships is not likely to be revealed by a single data set. Data from four genes (rbcL, atpB, rps4, nrSSU) and morphology was tested for congruence and results from the combined analysis strongly corroborate several weak inferences made from single data set trees. However, the clear resolution provided by the combined analysis for a basal dichotomy between seed plants and all other (non-lycophyte) "pteridophyte" lineages is novel. This result differs remarkably from most topologies found in the separate analyses for each of the five data sets. Robust support for Psilotaceae + Ophioglossaceae, as well as relationships among basal fern groups will also be discussed.

SCHNEIDER,H. & K.M. PRYER. 2000. Spore morphology of heterosporous ferns and its possible implications for understanding the evolution of the seed habit. American Journal of Botany 87 (Suppl): 31-32.
ABSTRACT: Heterospory has originated independently several times in vascular plant evolution, but seeds are known only from one living lineage. Although fossilized remains of seed plants from the Late Devonian and Early Carboniferous (ca. 340 mya) have provided exceptional insights into understanding the seed habit, events leading to its origin are still unclear. Monomegasporangy (single megaspore/megasporangium) is assumed to be one of the key innovations in the evolution of seed plants. This character state is found in only one other living group of vascular plants, the heterosporous ferns, which include two families with a fossil record dating back to the Early Cretaceous, Marsileaceae and Salviniaceae. Recent phylogenetic studies have demonstrated convincingly that heterosporous ferns are a monophyletic group nested within leptosporangiate ferns. Heterospory and monomegasporangy, therefore, evolved independently and at different times in the geological record in ferns and seed plants. Heterosporous ferns have an aquatic lifestyle, similar to that of Paleozoic seed plants. Comparative spore studies reveal remarkable similarities among the spores of heterosporous ferns, in particular, the presence of a gula, a modified perine structure above the aperture. The gula comprises inner and outer portions, which together enclose a chamber (= sperm lake). Each of the five extant genera (Azolla, Marsilea, Pilularia, Regnellidium, Salvinia) have their own characteristic gula, reflecting differences in ecology (e.g., amphibious versus floating growth forms). Additional differences are also found in the perine ultrastructure. Structures similar to a gula - lagenostomes - are also found in the megaspores of Paleozoic seed plants. This leads to the hypothesis that heterosporous ferns have evolved analogous megaspore structures to seed plants and these can be used as a model to better understand the biological constraints in which the seed habit evolved.

K.M. Pryer, H. Schneider, J.S. Hunt, L. Sappelsa, P.G. Wolf, S.D. Sipes, & A.R. Smith. 1999. Phylogeny of basal tracheophytes and ferns inferred from four large data sets: morphology, 18S nrDNA, rbcL, and atpB. American Journal of Botany 86: in press.
ABSTRACT: Estimates of a phylogeny for vascular plants are many and all have been contested. It is generally accepted that there were two main lines of tracheophyte evolution: one comprising lycophytes and extinct relatives, and the 99% of all other vascular plants making up its sister group, the Euphyllophytina. Phylogenetic assessments based on single genes and/or morphology have provided only weak evidence for the divergence and relationships among major groups of ferns, Psilotaceae, sphenopsids, and seed plants. Our results from phylogenetic analyses of three genes and morphology of extant species provide convincing support for a basal dichotomy in the Euphyllophytina between seed plants and all other (non-lycophyte) "pteridophyte" lineages. Robust support is also provided by these data for relationships among basal fern groups.

J.-Y. Dubuisson, J. S. Hunt, K. M. Pryer, and A. R. Smith. 1999. Phylogeny of filmy ferns (Hymenophyllaceae). American Journal of Botany 86: in press.
ABSTRACT: The Hymenophyllaceae, or "filmy ferns", are the largest (>600 species) and most diverse basal lineage of leptosporangiate ferns, displaying extreme morphological and ecological diversity. Disagreement over circumscription of genera and infrageneric taxa exceeds that in any other fern family and intrafamilial phylogenetic relationships have been, until now, completely unknown. Traditionally, two genera were recognized based on morphology of the involucre and the included receptacle: Trichomanes and Hymenophyllum. The family has been "split" into as many as 42 genera, however, and most published taxonomic treatments and classifications are in conflict over generic circumscription. We have initiated a study using morphological and chloroplast rbcL characters to resolve phylogenetic relationships among the "Copeland" genera of the Hymenophyllaceae. Our resulting best estimate of relationships indicates significant progress toward an overall phylogenetic framework for filmy ferns, which can be used to assess the evolution of characters that may have been correlated to the radiation and diversification of these ferns. This in turn permits us to rigorously address questions related to epiphytism, biogeography, and the ecological success of this group.

J.S. Hunt, K.M. Pryer, A. Vaghani, A.R. Smith, & P.G. Wolf. 1999. "Fern DNA Database": Using FileMaker Pro to coordinate DNA availability, DNA sequence data, voucher and source information for large-scale and collaborative phylogenetic studies. American Journal of Botany 86: in press.
ABSTRACT: We have implemented the computer program FileMaker Pro 4.0v1 (Claris Corp.) to create a centralized "Fern DNA Database" that is maintained online at The Field Museum. The database coordinates voucher and source information, as well as DNA-availability and DNA-sequence data for more than 700 pteridophyte specimens. The database is password-accessible to distant collaborators, which permits rigorous organization of large-scale and collaborative phylogenetic studies. Corrections and additions to the database can be suggested via online forms that are forwarded to the database manager for approval and implementation. The database is a convenient way of storing large numbers of DNA sequences that can be exported as Nexus files for phylogenetic analysis.

G.M. Moeser, R. Lupia, H. Schneider, K.M. Pryer, and P.R. Crane. 1999. Marsileaceae sporocarps and spores from the Late Cretaceous of Georgia, USA. American Journal of Botany 86: in press.
ABSTRACT: Three sporocarp specimens and several hundred dispersed megaspores were collected from the Eutaw Formation (Santonian) along Upatoi Creek, Georgia, USA. On the basis of shared morphological features of the sporocarp wall structure, and in situ megaspore and microspore ultrastructure and ornamentation, these specimens are assigned to the water fern family, Marsileaceae. If found dispersed, the megaspores would be assigned to Molaspora lobata (Dijkstra) Hall; the microspores to Crybelosporites Dettmann. Comparison of available characters in the fossil material with extant taxa of Marsileaceae reveals a remarkable similiarity to Regnellidium diphyllum Lindm. Securely linking Molaspora lobata and Crybelosporites to Marsileaceae improves our knowledge of the stratigraphic range and pattern of morphological evolution within this fern lineage.

Pryer, K.M., A.R. Smith, G. Rothwell, & P. Kenrick. 1997. Symposium: Relationships and fossil history of ferns. American Journal of Botany 84: 157-158.
ABSTRACT: Much progress has been made in the past two years to arrive at an approximate hypothesis for extant fern relationships that is based on a rigorous and explicit phylogenetic analysis of both molecular and morphological data (Amer. Fern J. 85: 134-181. 1995; Amer. Fern J. 85: 205-282. 1995). There has been little attention paid, however, to the impact of including critical fossil taxa in the estimation of a fern phylogeny (but see Rothwell, Bot. Rev., in press). Not since June 1973, at a jointly sponsored symposium of the Paleobotanical and Pteridological Sections of the Botanical Society of America and the American Fern Society, have pteridologists and paleobotanists come together to review available information and discuss the phylogeny of ferns (see symposium papers in Ann. Missouri Bot. Gard. 61: 307-482. 1974). The importance of morphological data from extant and fossil taxa to phylogenetic analysis has, in general, become eclipsed by advances in molecular sequencing. Nevertheless, in recent years, the inclusion of these data has had significant and even dramatic bearing on hypotheses of phylogeny in green plants, vertebrates, and other organisms. Many fossil taxa that are important to hypotheses of fern relationships need to be reviewed in the context of a phylogenetic analysis. The stage is now set for a synthetic approach that integrates paleobotanical and neobotanical data to understand better the evolution of ferns. The primary objective of this symposium is to introduce new ideas and approaches in a series of comprehensive talks that elaborate on important issues pertaining to a phylogenetic analysis of ferns, utilizing all available data. Topics will include: an overview of early fossil evidence relevant to fern origins and its role in clarifying relationships; an analysis of fern communities, life histories, and morphologies through geological time; the importance of including fossils in fern phylogeny analyses; a theoretical study on the use of stratigraphic data in estimating a phylogeny and the implications for combining diverse sources of data; an update on fern phylogeny using a multiple gene approach; a case study that synthesizes fossil, morphological, and molecular data to resolve relationships of tree ferns; and how a well-resolved phylogeny for ferns, which is based on all available evidence, can enable us to understand better patterns of character evolution.

Wolf, P.G., K.M. Pryer, & J.A. Irwin. 1997. Multiple gene approaches to fern phylogeny. American Journal of Botany 84: 160.
ABSTRACT: From recent studies bearing on fern relationships, it is clear that new insights will not result from the use of only one type of evidence. Progress in estimating fern phylogeny will stem from a synthetic approach that seeks to "make sense" of all the data, including information from morphology of fossil and extant ferns, and molecules. Although a workable framework of higher-level fern phylogeny based on morphology and rbcL is now in place, replacing former intuitive hypotheses of relationships founded largely on concepts of overall similarity, only a few internal nodes have robust bootstrap support: e.g., leptosporangiate ferns (89%) and "polypodiaceous" ferns (86%). Internal nodes at the base of the fern topology are very weakly supported, making it impossible to say with certainty how any of the major basal groups of ferns are related to one another. For example, what are the closest relatives to the tree ferns: heterosporous ferns, schizaeoid ferns, or the "polypodiaceous" ferns? These basal branches of the fern topology are critically important not only for stabilizing the overall framework for ferns, but also for resolving relationships among the "deep" branches of land plants (lycophytes, sphenophytes, eusporangiate ferns) and elucidating which of these are the sister group to seed plants. We report here on an ongoing, expanded molecular study to investigate further the phylogenetic relationships of extant ferns, with a particular emphasis on the basal groups, using additional chloroplast and nuclear genes. Our aim is to contribute to a robust overall framework for ferns that provides strong support for relationships at the base of the topology. Our preliminary results >from fern sequence data for newly sampled genes (e.g., 18S, atpB, 26S) suggest that we can achieve this objective. We also review approaches to analyzing combined data sets and present a preliminary analysis of combined molecular data sets for ferns. Finally, we discuss areas in which future molecular studies are likely to be most fruitful in fern phylogeny studies.

Pryer, K.M. & A.R. Smith. 1997. Character evolution and fern phylogeny. American Journal of Botany 84: 159.
ABSTRACT: A symposium entitled "Evolution of Systematic Characters in the Ferns" was held nearly 25 years ago to review the diversity of approaches and research techniques available for studies of both extant and fossil ferns, and to examine trends in various characters and their relationship to broad phylogenetic questions. Many significant advances in fern research were reported, yet pteridologists lamented the lack of a broad conceptual framework and the absence of studies correlating biological structure, function, and ecology. Due to a lack of a phylogeny for ferns, questions regarding character evolution and diversification could not be posed and tested in a rigorous fashion. Today, with the application of phylogenetic criteria, robust hypotheses of relationships enable us to begin to work toward understanding patterns and sequences of character evolution that define clades, and to identify those characters correlated with species diversification and ecological adaptation in various groups. Next to flowering plants, the Filicales is the most species-rich group of vascular plants, particularly when compared to non-angiospermous seed plants. What specific features of ferns may have promoted their diversity and ecological success? Did those apomorphies arise in the common ancestor of all ferns or in one or more subgroups within ferns? We observe that by far the greatest species diversity within ferns is concentrated in the "polypodiaceous" clade, for a total of about 80% of extant ferns. The basal clades of ferns comprise ca. 70% of the total number of fern families, but only 20% of the total number of species. Why is the "polypodiaceous" clade more speciose? Were key innovations associated with this success? Another question concerns the role of extrinsic vs. intrinsic factors in fern diversification. Using the best estimate of fern phylogeny available, we attempt to gain insight into the the origin of characters that may have been key events in the evolution and diversification of ferns, and to look for statistically significant associations with biological function and ecology.

N.B. underlined names indicate speaker.



Associated Websites


Filicopsida Website
Pryer, K.M. and A.R. Smith 1997. Filicopsida. In: Maddison, D.R. and W. P. Maddison. The Tree of Life: A distributed Internet project containing information about phylogeny and biodiversity.

Leptosporangiate Website
Pryer, K.M. and A.R. Smith 1997. Leptosporangiate Ferns. In: Maddison, D.R. and W. P. Maddison. The Tree of Life: A distributed Internet project containing information about phylogeny and biodiversity.