Der, Joshua P. , Thomson, John A. , Stratford, Jeran K. , Wolf, Paul G. .
Global chloroplast phylogeny and biogeography of bracken (Pteridium: Dennstaedtiaceae).
Bracken ferns (genus Pteridium) represent an ancient species complex with a natural worldwide distribution. Pteridium has historically been treated as comprising a single species, but recent treatments recognize several related species. Phenotypic plasticity, geographically-structured morphological variation, and geographically biased sampling have all contributed to taxonomic confusion in the genus. We sampled bracken specimens worldwide and used variable regions of the chloroplast genome to investigate phylogeography and reticulate evolution within the genus. Our results distinguish two major clades within Pteridium, a primarily northern hemisphere Laurasian/African clade which includes all taxa currently assigned to P. aquilinum, and a primarily southern hemisphere Austral/South American clade which includes P. esculentum and P. arachnoideum. All European accessions of P. aquilinum ssp. aquilinum appear in a monophyletic group and are nested within a clade containing the African P. aquilinum taxa (P. a. ssp. capense and P. a. ssp. centrali-africanum). Our results allow us to hypothesize the maternal progenitors of two allotetraploid bracken species, P. caudatum and P. semihastatum. We also discuss the biogeography of bracken in the context of the chloroplast phylogeny. Our study is one of the first to take a worldwide perspective in addressing variation in a broadly distributed species complex.
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1 - Utah State University, Department of Biology, 5305 Old Main Hill, Logan, UT, 84322-5305, USA
2 - National Herbarium of NSW, Botanic Gardens Trust, Royal Botanic Gardens, Mrs Macquaries Road, Sydney, New South Wales, 2000, Australia
Presentation Type: Poster:Posters for BSA Sections
Location: Event Tent/Cliff Lodge
Date: Monday, July 27th, 2009
Time: 5:30 PM