Phylogenetic relationships and evolution of extant horsetails, Equisetum, based on chloroplast DNA sequence data (rbcL and trnL-F)

dc.contributor.author

Des Marais, DL

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Smith, AR

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Britton, DM

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Pryer, KM

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2020-12-05T17:46:06Z

dc.date.available

2020-12-05T17:46:06Z

dc.date.issued

2003-01-01

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2020-12-05T17:46:06Z

dc.description.abstract

Equisetum is a small and morphologically distinct genus with a rich fossil record. Two subgenera have been recognized based principally on stomatal position and stem branching: subg. Equisetum (eight species; superficial stomates; stems branched) and subg. Hippochaete (seven species; sunken stomates; stems generally unbranched). Prior attempts at understanding Equisetum systematics, phylogeny, and character evolution have been hampered by the high degree of morphological plasticity in the genus as well as by frequent hybridization among members within each subgenus. We present the first explicit phylogenetic study of Equisetum, including all 15 species and two samples of one widespread hybrid, Equisetum x ferrissii, based on a combined analysis of two chloroplast markers, rbcL and trnL-F. Our robustly supported phylogeny identifies two monophyletic clades corresponding to the two subgenera recognized by earlier workers. The phylogenetic placement of Equisetum bogotense, however, is ambiguous. In maximum likelihood analyses, it allies with subg. Hippochaete as the most basal member, while maximum parsimony places it as sister to the rest of the genus. A consensus phylogeny from the two analyses is presented as a basal trichotomy (E. bogotense, subg. Hippochaete, subg. Equisetum), and morphological character evolution is discussed. We detected rate heterogeneity in the rbcL locus between the two subgenera that can be attributed to an increased rate of nucleotide substitution (transversions) in subg. Hippochaete. We calculated molecular-based age estimates using the penalized likelihood approach, which accounts for rate heterogeneity and does not assume a molecular clock. The Equisetum crown group appears to have diversified in the early Cenozoic, whereas the Equisetaceae total group is estimated to have a Paleozoic origin. These molecular-based age estimates are in remarkable agreement with current interpretations of the fossil record.

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1058-5893

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1537-5315

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https://hdl.handle.net/10161/21862

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en

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University of Chicago Press

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International Journal of Plant Sciences

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10.1086/376817

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Science & Technology

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Life Sciences & Biomedicine

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Plant Sciences

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divergence times

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Equisetum

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fossil record

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horsetails

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likelihood ratio test

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molecular clock

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morphological character evolution

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penalized likelihood

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phylogeny

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CLOSEST LIVING RELATIVES

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SUBGENUS EQUISETUM

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SEXUAL-BEHAVIOR

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REPRODUCTIVE-BIOLOGY

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LIKELIHOOD APPROACH

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DIVERGENCE TIMES

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GENUS EQUISETUM

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SEED PLANTS

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GAMETOPHYTES

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ORIGIN

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Phylogenetic relationships and evolution of extant horsetails, Equisetum, based on chloroplast DNA sequence data (rbcL and trnL-F)

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Journal article

duke.contributor.orcid

Pryer, KM|0000-0002-9776-6736

pubs.begin-page

737

pubs.end-page

751

pubs.issue

5

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Trinity College of Arts & Sciences

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Biology

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Duke Science & Society

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Duke

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Initiatives

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Institutes and Provost's Academic Units

pubs.publication-status

Published

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164

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