Der, Joshua P. , Thomson, John A. , Wolf, Paul G. .
A global phylogeographic study of the chloroplast genome in bracken (Pteridium: Dennstaedtiaceae).
PTERIDIUM is a well-defined cosmopolitan fern genus. While the validity and circumscription of the genus remains uncontroversial, systematics of infrageneric taxa has been problematic due to high levels of phenotypic plasticity, the availability of few useful morphological characters to distinguish taxa and the presence of intermediate forms between morphotypes. Pteridium has historically been classified to include a single species, Pteridium aquilinum, with two subspecies and 12 geographic varieties. More recent work using genetic and morphological data has validated two southern hemisphere allotetraploid species (P. caudatum and P. semihastatum) distinct from several diploid counterparts. Three diploid species are currently recognized: P. arachnoideum of Central and Southern America, P. esculentum of Australia and New Zealand and P. aquilinum of circumboreal and African distribution. Here we present a global phylogenetic analysis of the chloroplast of Pteridium morphotypes from throughout the range of the genus based on chloroplast trnS-rps4 intergenic spacer and rps4 gene sequence data. Plants from Europe, Africa and Asia each form distinct chloroplast groups partially characterized by the absence of one or both of two five base indels located 22 base-pairs apart in the rps4-trnS spacer. Additional groups are identified by nucleotide substitutions.
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1 - Utah State University, Department of Biology, College of Science, 5305 Old Main Hill, Logan, Utah, 84322, USA
2 - National Herbarium of NSW, Botanic Gardens Trust, Royal Botanic Gardens, Mrs Macquaries Road, Sydney, New South Wales, 2000, Australia
Presentation Type: Oral Paper:Papers for Sections
Date: Tuesday, August 1st, 2006
Time: 11:15 AM