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Publications by Jordan Metzgar

Research paper thumbnail of Diversification and reticulation in the circumboreal fern genus Cryptogramma

Molecular Phylogenetics and Evolution, 2013

We investigated the evolutionary complexity that resulted from cryptic diversification and polypl... more We investigated the evolutionary complexity that resulted from cryptic diversification and polyploidy in parsley ferns (Cryptogramma). A total of 14 species were included in our data set, with six outgroup species and eight Cryptogramma species. DNA sequence data from six plastid loci (rbcL, rbcL–accD, rbcL–atpB, rps4–trnS, trnG–trnR and trnP–petG) were analyzed using maximum likelihood and Bayesian methods to provide the first rigorous assessment of diversification in the genus, including testing the monophyly of the genus and sections. Cryptogramma and Coniogramme are recovered as reciprocally monophyletic sister genera. We established the monophyly of both sections within Cryptogramma. Furthermore, our sequence data reveal that described species reflect mostly allopatric reciprocally monophyletic lineages that are independent evolutionary trajectories. Using sequence data from the nuclear locus (gapCp) we find that the European C. crispa is an autotetraploid with a partially diploidized genome, while the North American tetraploid Cryptogramma sitchensis is an allopolyploid derived from C. acrostichoides and C. raddeana. Subsequent backcrossing between C. sitchensis and C. acrostichoides has allowed the introgression of C. raddeana alleles into northern populations of C. acrostichoides.► Cryptogramma is monophyletic based on plastid sequence data. ► Most described Cryptogramma species are taxonomically valid monophyletic lineages. ► European Cr. crispa is an ancient autotetraploid. ► New World tetraploid Cr. sitchensis formed by Cr. acrostichoides and Cr. raddeana. ► Nuclear sequence data in Cr. acrostichoides complex exhibit signs of introgression.

Papers by Jordan Metzgar

Research paper thumbnail of Autoplolyploid origin of the octoploid Turkish parsley fern (Cryptogramma bithynica): Insights from chloroplast and nuclear markers

Polyploidy is a common phenomenon in plants, with autopolyploids originating from genome compleme... more Polyploidy is a common phenomenon in plants, with autopolyploids originating from genome complements of two different species, and allopolyploids resulting from genome doubling within a single species. Speciation via polyploidy is one of the main modes of sympatric speciation in plants. Ferns are well known for having a high degree of polyploidy. A new octoploid species of parsley fern was discovered in Turkey last year (Cryptogramma bithynica), although its origins were unknown. Cryptogramma is a member of the Pteridaceae family and consists of nine species found across the Northern Hemisphere in boreal habitats and southern South America, with C. bithynica found only in the mountains of northwestern Turkey. It often grows near populations of the tetraploid C. crispa, and its morphology is very similar to C. crispa, although C. bithynica differs from C. crispa in overall smaller plant size and minor differences in the shape of the sterile leaves. Larger spores and the octoploid chr...

Research paper thumbnail of Morphologically diverse but with surprisingly little genetic structure: the evolutionary history of three closely related species of Therorhodion

We looked at the phylogenetic relationships and morphology among dwarf rhododendron (Therorhodion... more We looked at the phylogenetic relationships and morphology among dwarf rhododendron (Therorhodion camtschaticum Small, T. glandulosum Standley ex Small and T. redowskianum Hutch.) in the heath family (Ericaceae, subfamily Rhodoreae). Therorhodion was originally considered part of the genus Rhododendron but was described as its own genus by Small in 1914. Only recently has this distinction been more widely recognized and substantiated by genetic data. Therorhodion camtschaticum is restricted to southeast Alaska and the Aleutian chain extending into Kamtschatka and Japan, while T. glandulosum is today found only on the Seward Peninsula and lower Yukon in North America, but broadly distributed in the Russian Far East. The third species T. redowskianum is distinct morphologically from the former two and restricted to eastern Asia. When in sympatry the species are well marked morphologically. While Therorhodion camtschaticum and T. glandulosum are similar in size, T. redowskianum is smal...

Research paper thumbnail of The Paraphyly of <I>Osmunda</I> is Confirmed by Phylogenetic Analyses of Seven Plastid Loci

Systematic Botany, 2008

To resolve phylogenetic relationships among all genera and subgenera in Osmundaceae, we analyzed ... more To resolve phylogenetic relationships among all genera and subgenera in Osmundaceae, we analyzed over 8,500 characters of DNA sequence data from seven plastid loci (atpA, rbcL, rbcL-accD, rbcL-atpB, rps4-trnS, trnG-trnR, and trnL-trnF). Our results confirm those from earlier anatomical and single-gene (rbcL) studies that suggested Osmunda s.l. is paraphyletic. Osmunda cinnamomea is sister to the remainder of Osmundaceae (Leptopteris, Todea, and Osmunda s.s.). We support the recognition of a monotypic fourth genus, Osmundastrum, to reflect these results. We also resolve subgeneric relationships within Osmunda s.s. and find that subg. Claytosmunda is strongly supported as sister to the rest of Osmunda. A stable, well-supported classification for extant Osmundaceae is proposed, along with a key to all genera and subgenera.

Research paper thumbnail of Evolutionary relationships within the Neotropical, eusporangiate fern genus Danaea (Marattiaceae)

Molecular Phylogenetics and Evolution, 2008

Genera within the eusporangiate fern family Marattiaceae have long been neglected in taxonomic an... more Genera within the eusporangiate fern family Marattiaceae have long been neglected in taxonomic and systematic studies. Here we present the first phylogenetic hypothesis of relationships within the exclusively Neotropical genus Danaea based on a sampling of 60 specimens representing 31 species from various Neotropical sites. We used DNA sequence data from three plastid regions (atpB, rbcL, and trnL-F), morphological characters from both herbarium specimens and live plants observed in the field, and geographical and ecological information to examine evolutionary patterns. Eleven representatives of five other marattioid genera (Angiopteris, Archangiopteris, Christensenia, Macroglossum, and Marattia) were used to root the topology. We identified three well-supported clades within Danaea that are consistent with morphological characters: the ''leprieurii'' clade (containing species traditionally associated with the name D. elliptica), the ''nodosa'' clade (containing all species traditionally associated with the name D. nodosa), and the ''alata'' clade (containing all other species). All three clades are geographically and ecologically widely distributed, but subclades within them show various distribution patterns. Our phylogenetic hypothesis provides a robust framework within which broad questions related to the morphology, taxonomy, biogeography, evolution, and ecology of these ferns can be addressed.

Research paper thumbnail of Tree ferns: Monophyletic groups and their relationships as revealed by four protein-coding plastid loci

Molecular Phylogenetics and Evolution, 2006

Tree ferns are a well-established clade within leptosporangiate ferns. Most of the 600 species (i... more 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 Kubitzki, 1990) 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.

Research paper thumbnail of Phylogeny and Divergence Time Estimates for the Fern Genus Azolla (Salviniaceae)

International Journal of Plant Sciences, 2007

A phylogeny for all extant species of the heterosporous fern genus Azolla is presented here based... more 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 þ A: rubra lineage from the A. caroliniana þ A: microphylla þ A: mexicana complex).

Research paper thumbnail of Relation between stable isotope ratios in human red blood cells and hair: implications for using the nitrogen isotope ratio of hair as a biomarker of eicosapentaenoic acid and docosahexaenoic acid

American Journal of Clinical Nutrition, 2009

Background: The nitrogen isotope ratio (expressed as d 15 N) of red blood cells (RBCs) is highly ... more Background: The nitrogen isotope ratio (expressed as d 15 N) of red blood cells (RBCs) is highly correlated with the RBC long-chain x23 (n23) fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in Yup'ik Eskimos. Because d 15 N can also be measured in hair samples, it could provide a noninvasive, retrospective biomarker for EPA and DHA intakes. Objectives: We investigated the agreement between d 15 N in hair and RBCs and then evaluated the relations between hair d 15 N and RBC EPA and DHA. We also assessed the agreement in carbon isotope ratios (d 13 C) between hair and RBCs, because d 13 C has been proposed as a dietary biomarker in other populations. Design: We assessed relations between hair and RBC d 15 N and d 13 C in a community-based sample of 144 Yup'ik Eskimos and examined the correlations between d 15 N and RBC EPA and DHA in a subset of these participants (n = 44). Results: We showed a 1:1 relation with good agreement between hair and RBC d 15 N (r = 0.91) and d 13 C (r = 0.87). Hair isotope ratios were greater than RBC ratios by 1.5‰ for d 15 N and by 2.3‰ for d 13 C. There were strong correlations between hair d 15 N and RBC EPA and DHA (r = 0.83 and 0.84, respectively). Conclusions: These results support the use of hair d 15 N values as a biomarker of EPA and DHA intakes. Because hair collection is noninvasive and the samples require no special processing, studies of EPA and DHA intakes in large populations could use biomarkers rather than self-reports to assess these fatty acids.

Research paper thumbnail of A molecular phylogeny of scaly tree ferns (Cyatheaceae)

American Journal of Botany, 2007

Tree ferns recently were identified as the closest sister group to the hyperdiverse clade of fern... more 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) þ 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.

Research paper thumbnail of Diversification and reticulation in the circumboreal fern genus Cryptogramma

Molecular Phylogenetics and Evolution, 2013

We investigated the evolutionary complexity that resulted from cryptic diversification and polypl... more We investigated the evolutionary complexity that resulted from cryptic diversification and polyploidy in parsley ferns (Cryptogramma). A total of 14 species were included in our data set, with six outgroup species and eight Cryptogramma species. DNA sequence data from six plastid loci (rbcL, rbcL–accD, rbcL–atpB, rps4–trnS, trnG–trnR and trnP–petG) were analyzed using maximum likelihood and Bayesian methods to provide the first rigorous assessment of diversification in the genus, including testing the monophyly of the genus and sections. Cryptogramma and Coniogramme are recovered as reciprocally monophyletic sister genera. We established the monophyly of both sections within Cryptogramma. Furthermore, our sequence data reveal that described species reflect mostly allopatric reciprocally monophyletic lineages that are independent evolutionary trajectories. Using sequence data from the nuclear locus (gapCp) we find that the European C. crispa is an autotetraploid with a partially diploidized genome, while the North American tetraploid Cryptogramma sitchensis is an allopolyploid derived from C. acrostichoides and C. raddeana. Subsequent backcrossing between C. sitchensis and C. acrostichoides has allowed the introgression of C. raddeana alleles into northern populations of C. acrostichoides.► Cryptogramma is monophyletic based on plastid sequence data. ► Most described Cryptogramma species are taxonomically valid monophyletic lineages. ► European Cr. crispa is an ancient autotetraploid. ► New World tetraploid Cr. sitchensis formed by Cr. acrostichoides and Cr. raddeana. ► Nuclear sequence data in Cr. acrostichoides complex exhibit signs of introgression.

Research paper thumbnail of Autoplolyploid origin of the octoploid Turkish parsley fern (Cryptogramma bithynica): Insights from chloroplast and nuclear markers

Polyploidy is a common phenomenon in plants, with autopolyploids originating from genome compleme... more Polyploidy is a common phenomenon in plants, with autopolyploids originating from genome complements of two different species, and allopolyploids resulting from genome doubling within a single species. Speciation via polyploidy is one of the main modes of sympatric speciation in plants. Ferns are well known for having a high degree of polyploidy. A new octoploid species of parsley fern was discovered in Turkey last year (Cryptogramma bithynica), although its origins were unknown. Cryptogramma is a member of the Pteridaceae family and consists of nine species found across the Northern Hemisphere in boreal habitats and southern South America, with C. bithynica found only in the mountains of northwestern Turkey. It often grows near populations of the tetraploid C. crispa, and its morphology is very similar to C. crispa, although C. bithynica differs from C. crispa in overall smaller plant size and minor differences in the shape of the sterile leaves. Larger spores and the octoploid chr...

Research paper thumbnail of Morphologically diverse but with surprisingly little genetic structure: the evolutionary history of three closely related species of Therorhodion

We looked at the phylogenetic relationships and morphology among dwarf rhododendron (Therorhodion... more We looked at the phylogenetic relationships and morphology among dwarf rhododendron (Therorhodion camtschaticum Small, T. glandulosum Standley ex Small and T. redowskianum Hutch.) in the heath family (Ericaceae, subfamily Rhodoreae). Therorhodion was originally considered part of the genus Rhododendron but was described as its own genus by Small in 1914. Only recently has this distinction been more widely recognized and substantiated by genetic data. Therorhodion camtschaticum is restricted to southeast Alaska and the Aleutian chain extending into Kamtschatka and Japan, while T. glandulosum is today found only on the Seward Peninsula and lower Yukon in North America, but broadly distributed in the Russian Far East. The third species T. redowskianum is distinct morphologically from the former two and restricted to eastern Asia. When in sympatry the species are well marked morphologically. While Therorhodion camtschaticum and T. glandulosum are similar in size, T. redowskianum is smal...

Research paper thumbnail of The Paraphyly of <I>Osmunda</I> is Confirmed by Phylogenetic Analyses of Seven Plastid Loci

Systematic Botany, 2008

To resolve phylogenetic relationships among all genera and subgenera in Osmundaceae, we analyzed ... more To resolve phylogenetic relationships among all genera and subgenera in Osmundaceae, we analyzed over 8,500 characters of DNA sequence data from seven plastid loci (atpA, rbcL, rbcL-accD, rbcL-atpB, rps4-trnS, trnG-trnR, and trnL-trnF). Our results confirm those from earlier anatomical and single-gene (rbcL) studies that suggested Osmunda s.l. is paraphyletic. Osmunda cinnamomea is sister to the remainder of Osmundaceae (Leptopteris, Todea, and Osmunda s.s.). We support the recognition of a monotypic fourth genus, Osmundastrum, to reflect these results. We also resolve subgeneric relationships within Osmunda s.s. and find that subg. Claytosmunda is strongly supported as sister to the rest of Osmunda. A stable, well-supported classification for extant Osmundaceae is proposed, along with a key to all genera and subgenera.

Research paper thumbnail of Evolutionary relationships within the Neotropical, eusporangiate fern genus Danaea (Marattiaceae)

Molecular Phylogenetics and Evolution, 2008

Genera within the eusporangiate fern family Marattiaceae have long been neglected in taxonomic an... more Genera within the eusporangiate fern family Marattiaceae have long been neglected in taxonomic and systematic studies. Here we present the first phylogenetic hypothesis of relationships within the exclusively Neotropical genus Danaea based on a sampling of 60 specimens representing 31 species from various Neotropical sites. We used DNA sequence data from three plastid regions (atpB, rbcL, and trnL-F), morphological characters from both herbarium specimens and live plants observed in the field, and geographical and ecological information to examine evolutionary patterns. Eleven representatives of five other marattioid genera (Angiopteris, Archangiopteris, Christensenia, Macroglossum, and Marattia) were used to root the topology. We identified three well-supported clades within Danaea that are consistent with morphological characters: the ''leprieurii'' clade (containing species traditionally associated with the name D. elliptica), the ''nodosa'' clade (containing all species traditionally associated with the name D. nodosa), and the ''alata'' clade (containing all other species). All three clades are geographically and ecologically widely distributed, but subclades within them show various distribution patterns. Our phylogenetic hypothesis provides a robust framework within which broad questions related to the morphology, taxonomy, biogeography, evolution, and ecology of these ferns can be addressed.

Research paper thumbnail of Tree ferns: Monophyletic groups and their relationships as revealed by four protein-coding plastid loci

Molecular Phylogenetics and Evolution, 2006

Tree ferns are a well-established clade within leptosporangiate ferns. Most of the 600 species (i... more 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 Kubitzki, 1990) 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.

Research paper thumbnail of Phylogeny and Divergence Time Estimates for the Fern Genus Azolla (Salviniaceae)

International Journal of Plant Sciences, 2007

A phylogeny for all extant species of the heterosporous fern genus Azolla is presented here based... more 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 þ A: rubra lineage from the A. caroliniana þ A: microphylla þ A: mexicana complex).

Research paper thumbnail of Relation between stable isotope ratios in human red blood cells and hair: implications for using the nitrogen isotope ratio of hair as a biomarker of eicosapentaenoic acid and docosahexaenoic acid

American Journal of Clinical Nutrition, 2009

Background: The nitrogen isotope ratio (expressed as d 15 N) of red blood cells (RBCs) is highly ... more Background: The nitrogen isotope ratio (expressed as d 15 N) of red blood cells (RBCs) is highly correlated with the RBC long-chain x23 (n23) fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in Yup'ik Eskimos. Because d 15 N can also be measured in hair samples, it could provide a noninvasive, retrospective biomarker for EPA and DHA intakes. Objectives: We investigated the agreement between d 15 N in hair and RBCs and then evaluated the relations between hair d 15 N and RBC EPA and DHA. We also assessed the agreement in carbon isotope ratios (d 13 C) between hair and RBCs, because d 13 C has been proposed as a dietary biomarker in other populations. Design: We assessed relations between hair and RBC d 15 N and d 13 C in a community-based sample of 144 Yup'ik Eskimos and examined the correlations between d 15 N and RBC EPA and DHA in a subset of these participants (n = 44). Results: We showed a 1:1 relation with good agreement between hair and RBC d 15 N (r = 0.91) and d 13 C (r = 0.87). Hair isotope ratios were greater than RBC ratios by 1.5‰ for d 15 N and by 2.3‰ for d 13 C. There were strong correlations between hair d 15 N and RBC EPA and DHA (r = 0.83 and 0.84, respectively). Conclusions: These results support the use of hair d 15 N values as a biomarker of EPA and DHA intakes. Because hair collection is noninvasive and the samples require no special processing, studies of EPA and DHA intakes in large populations could use biomarkers rather than self-reports to assess these fatty acids.

Research paper thumbnail of A molecular phylogeny of scaly tree ferns (Cyatheaceae)

American Journal of Botany, 2007

Tree ferns recently were identified as the closest sister group to the hyperdiverse clade of fern... more 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) þ 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.