Once more unto the breach, dear friends: Resolving the origins and relationships of the Pellaea wrightiana hybrid complex.

PREMISE: The taxonomic status of Wright's cliff brake fern, Pellaea wrightiana, has been in dispute ever since it was first described by Hooker in 1858. Previously published evidence suggested that this "taxon" may represent a polyploid complex rather than a single discrete species, a hypothesis tested here using a multifaceted analytical approach. METHODS: Data derived from cytogenetics, spore analyses, leaf morphometrics, enzyme electrophoresis, and phylogenetic analyses of plastid and nuclear DNA sequences are used to elucidate the origin, relationships, and taxonomic circumscription of P. wrightiana. RESULTS: Plants traditionally assigned to this taxon represent three distinct polyploids. The most widespread, P. wrightiana, is a fertile allotetraploid that arose through hybridization between two divergent diploid species, P. truncata and P. ternifolia. Sterile triploids commonly identified as P. wrightiana, were found to be backcross hybrids between this fertile tetraploid and diploid P. truncata. Relatively common across Arizona and New Mexico, they are here assigned to P. ×wagneri hyb. nov. In addition, occasional sterile tetraploid plants assigned to P. wrightiana are shown here to be hybrids between the fertile allotetraploid and the tetraploid P. ternifolia subsp. arizonica. These tetraploid hybrids originated independently in two regions of parental sympatry (southern Arizona and west Texas) and are here assigned to P. ×gooddingii hyb. nov. CONCLUSIONS: Weaving together data from a diversity of taxonomic approaches, we show that plants identified as P. wrightiana represent three morphologically distinguishable polyploids that have arisen through repeated hybridization events involving the divergent sexual taxa P. ternifolia and P. truncata.

Polyploidy in gymnosperms - Insights into the genomic and evolutionary consequences of polyploidy in Ephedra.

While polyploidization is recognized as a major evolutionary driver for ferns and angiosperms, little is known about its impact in gymnosperms, where polyploidy is much less frequent. We explore Ephedra to evaluate (i) the extent of genome size diversity in the genus and the influence polyploidy has had on the evolution of nuclear DNA contents, and (ii) identify where shifts in genome size and polyploidy have occurred both temporally and spatially. A phylogenetic framework of all Ephedra species together with genome sizes and karyotypes for 87% and 67% of them respectively, were used to explore ploidy evolution and its global distribution patterns. Polyploidy was shown to be extremely common, with 41 species (83%) being polyploid (up to 8×) or having polyploid cytotypes - the highest frequency and level reported for any gymnosperm. Genome size was also diverse, with values ranging ~5-fold (8.09-38.34 pg/1C) - the largest range for any gymnosperm family - and increasing in proportion to ploidy level (i.e. no genome downsizing). Our findings provide novel data which support the view that gymnosperms have a more conserved mode of genomic evolution compared with angiosperms.

Diversification and reticulation in the circumboreal fern genus Cryptogramma.

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.

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.

BACKGROUND: The nitrogen isotope ratio (expressed as delta(15)N) of red blood cells (RBCs) is highly correlated with the RBC long-chain omega-3 (n-3) fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in Yup'ik Eskimos. Because delta(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 delta(15)N in hair and RBCs and then evaluated the relations between hair delta(15)N and RBC EPA and DHA. We also assessed the agreement in carbon isotope ratios (delta(13)C) between hair and RBCs, because delta(13)C has been proposed as a dietary biomarker in other populations. DESIGN: We assessed relations between hair and RBC delta(15)N and delta(13)C in a community-based sample of 144 Yup'ik Eskimos and examined the correlations between delta(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 delta(15)N (r = 0.91) and delta(13)C (r = 0.87). Hair isotope ratios were greater than RBC ratios by 1.5 per thousand for delta(15)N and by 2.3 per thousand for delta(13)C. There were strong correlations between hair delta(15)N and RBC EPA and DHA (r = 0.83 and 0.84, respectively). CONCLUSIONS: These results support the use of hair delta(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.

A molecular phylogeny of scaly tree ferns (Cyatheaceae).

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.

Tree ferns: monophyletic groups and their relationships as revealed by four protein-coding plastid loci.

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.