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Chloroplast-DNA Phylogenetics and Biogeography in a Reticulating Group: Study in Poa (Poaceae)

Robert J. Soreng
American Journal of Botany
Vol. 77, No. 11 (Nov., 1990), pp. 1383-1400
Stable URL: http://www.jstor.org/stable/2444749
Page Count: 18
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Chloroplast-DNA Phylogenetics and Biogeography in a Reticulating Group: Study in Poa (Poaceae)
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Abstract

Cladistic analysis of Poa chloroplast DNA (cpDNA) restriction sites tested previously hypothesized relationships within the genus. Forty-six taxa representing 19 sections or groups and three subgenera of Poa and two out-group genera, Puccinellia and Bellardiochloa, are analyzed. Five major and several minor cpDNA groups are identified. The cpDNA cladogram is generally congruent with the subgeneric taxonomy of Poa. Exceptions are reclassified or are discussed in terms of character incompatibilities and possible reticulation events. The cpDNA tree detected relationships among sections that were unresolved using traditional character sets and provides a basis for polarization of morphological character states. An assessment of biogeographic events based on the cpDNA tree suggests: 1) Poa originated in Eurasia; 2) at least six groups of species independently colonized North America; and 3) two of the latter groups colonized South America, and one closely related group colonized New Zealand and Australia. The cpDNA tree provided a conservative estimate of the number of amphi-neotropical disjunctions when compared to the known number of species disjunctions.

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