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First published online July 26, 2010; doi:10.3732/ajb.1000022 American Journal of Botany 97: 1377-1390 (2010) © 2010 Botanical Society of America, Inc. |
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Systematics and Phytogeography |
2 L.H. Bailey Hortorium, Department of Plant Biology, Cornell University, Ithaca, New York 14853 USA 3 Wake Forest University, Department of Biology, Winston-Salem, North Carolina 27109 USA
ABSTRACT
• Premise of the study: Taxonomic groups have often been recognized on the basis of geographic distinctions rather than accurately representing evolutionary relationships. This has been particularly true for temperate and tropical members from the same family. Polygonaceae exemplifies this problem, wherein the woody tropical genera were segregated from temperate members of the family and placed in the subfamily Polygonoideae as two tribes: Triplarideae and Coccolobeae. Modern phylogenetic studies, especially when inferred from many lines of evidence, can elucidate more probable hypotheses of relationships. This study builds on previous work in the family and aims to test the traditional classification of the tropical woody taxa, which have been understudied and undersampled compared to their temperate relatives.
• Methods: A phylogenetic study was undertaken with expanded sampling of the tropical genera with data from five plastid markers (psbA-trnH, psaI-accD, matK, ndhF, and rbcL), nuclear ribosomal DNA (ITS) and morphology.
• Key results: Results support the placement of nine of 12 genera of the Triplarideae and Coccolobeae within Eriogonoideae, in which these genera form a paraphyletic assemblage giving rise to Eriogoneae. The remaining woody tropical genera excluded from Eriogonoideae occur in the paleotropics.
• Conclusions: Traditional characters used to delimit Coccolobeae and Triplarideae are not useful for defining monophyletic groups. The six-tepal condition is derived from the five-tepal condition, and unisexual flowers have arisen multiple times in different sexual systems. Ruminate endosperm has arisen multiple times in the family, suggesting this character is highly plastic.
Key Words: Coccoloba • Eriogonoideae • ochrea • phylogeny • Polygonaceae • ruminate endosperm
Received for publication 12 January 2010. Accepted for publication 7 June 2010.
FOOTNOTES
1 The authors acknowledge the people who helped them acquire plant material: S. Avendaño (Instituto de Ecología-Jalapa), G. Carnevali (Centro de Investigación Científica de Yucatán), G. Castillo (Instituto de Ecología-Jalapa), R. Duno (Centro de Investigación Científica de Yucatán), E. Kempton (Rancho Santa Ana Botanic Garden), S. Leython (Jardín Botánico de Caracas), J. Pale (Instituto de Ecología-Jalapa), J. Reveal (Cornell University), and S. Romero (Jardín Botánico de Caracas). They also thank staff of the herbaria A, BH, NY, GH, and US for access to material. They are grateful to Jim Reveal and one anonymous reviewer for useful improvements to the manuscript. This work was supported by funding from Wake Forest University (A.S.), Cornell University Department of Plant Biology, American Society of Plant Taxonomist, and Botanical Society of America (J.B.).
4 Author for correspondence (e-mail: jmb328{at}cornell.edu)
5 Both authors contributed equally to this manuscript.
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