@ARTICLE{TreeBASE2Ref24896, author = {Paul G Wolf and Carol A Rowe and Joshua P Der and Martin P Schilling and Clayton J Visger and John A Thomson}, title = {Origins and diversity of Pteridium (Dennstaedtiaceae) on the Galapagos Islands}, year = {2015}, keywords = {Pteridium, bracken, Galapagos, allopolyploid}, doi = {}, url = {http://}, pmid = {}, journal = {AoB Plants}, volume = {}, number = {}, pages = {}, abstract = {Ferns disperse by haploid spores, which are produced in large numbers and can travel long distances in air currents. This has enabled ferns to become established on most oceanic islands. Here we follow-up on reports that Pteridium (Dennstaedtiaceae; bracken) may be represented by more than one taxon on the Galapagos Islands. We use nucleotide sequences from two plastid genes, and we developed two nuclear gene markers, to examine phylogeography of Pteridium collected at 16 sites across three of the main islands. We incorporate data from a previously published study to provide a worldwide context and to examine origins of Galapagos Pteridium. We also sampled new specimens from South and Central America. We used flow cytometry to estimate genome size of some accessions. We found that both plastid and nuclear haplotypes fall into two distinct clades, consistent with a two-diploid-species taxonomy of P. aquilinum (Northern clade) and P. esculentum (Southern clade). Furthermore, one of the putative allotetraploids, P. caudatum, possesses both northern and southern nuclear haplotypes, as predicted. Samples from the Galapagos include P. esculentum subsp. arachnoideum, P. caudatum, and possible hybrids between them. Evidence from phylogenetic analyses of nuclear and plastid haplotypes indicated multiple origins of Pteridium on the Galapagos Islands, and multiple origins of tetraploid P. caudatum. We hypothesize that ongoing hybridization contributes to the difficulty in distinguishing taxa on the basis of morphology. We also posit that P. caudatum may include recent diploid hybrids, backcrosses to P. esculentum, as well as allotetraploid plants.} }

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