The last decade has seen a nearly exponential increase in the number of molecular phylogenies published at various taxo-

American Journal of Botany 99(4): 730–750, 2012; http://www.amjbot.org/ © 2012 Botanical Society of America The last decade has seen a nearly exponential increase in the number of molecular phylogenies published at various taxonomic levels across the plant tree of life. Vast uncharted territory still remains, however, particularly for ferns. Ferns are sister to seed plants ( Pryer et al., 2001 ) and are the second largest group of vascular land plants, with ca. 12 000 species ( Smith et al., 2006 ). They inhabit a great variety of substrates, climates, and light regimes, both in habitats dominated by fl owering plants and those where few angiosperms can survive. They also represent a critical evolutionary step, bridging the functional gap between nonvascular bryophytes and seed-bearing vascular plants. Despite their ubiquity and key position in land-plant evolution, however, ferns have generally received far less attention than the megadiverse fl owering plants. Exhaustive phylogenetic studies of large fern genera, in particular, lag behind such studies for angiosperms, even though such studies can provide detailed insights into speciation, ecological diversifi cation, morphological and physiological adaptation, and biogeographic patterns. Given that ferns are sister to the seed plants ( Pryer et al., 2001 ), an increased understanding of these phenomena in ferns may help us to better understand how evolution has proceeded in angiosperms and gymnosperms. The genus Dryopteris , the woodferns, is an ideal group for such inquiries. With ca. 225 species worldwide ( Fraser-Jenkins, 1986 ), it is one of the largest genera in Dryopteridaceae, which is itself one of the largest families of leptosporangiate ferns ( Smith et al., 2006 ). The genus encompasses species with a diverse set of ranges, habitats, and morphologies, and hybridization and polyploidy appear to be common (see below). Dryopteris can thus provide a model for exploring many questions that have long been understudied in ferns, including the relative importance of dispersal vs. vicariance in shaping geographic distributions, the adaptive signifi cance of various morphological and physiological traits, and the relative importance of branching vs. reticulate evolution. Investigating such questions at a global scale will fi rst require a highly resolved, well-supported phylogeny for Dryopteris independent of the morphological, physiological, and distributional traits under study. 1 Manuscript received 29 June 2011; revision accepted 25 January 2012. The authors thank E. Alverson, S. Bornell, B. Gilman, T. Goforth, T. Grabs, A. Jandl, C. Line, S. Lorbeer, B. and A. Manierre, T. Meyer, A. Reznicek, C. Taylor, B. Vesterby, S. Wechsler, D. Werier, F. R. Wesley, and K. Woods for help in the fi eld; J. Geiger, S. Hennequin, C. Rothfels, and J. E. Watkins, Jr. for providing material; D. Giblin, M. McNamara, R. Moran, R. Olmstead, A. Smith, M. Sundue, and S. Vance for help with arranging herbarium visits; staff at herbaria BH, NY, MO, UC, US, WTU for letting us view specimens; and the Finger Lakes Land Trust, Huron Mountain Club, Fernwood Botanical Gardens, and University of Wisconsin-Madison Arboretum for allowing us to visit and collect Dryopteris in the fi eld. Profound thanks to M. Ames, B. Berger, A. Gardner, P. Gonsiska, B. Grady, J. Hunt, R. Jabaily, D. Stein, J. Wen, and especially K. Sytsma for advice and discussion. The authors are thankful for fi nancial support for this research from the National Science Foundation (DDIG award to E.B.S., T.J.G., grant DEB-1110335), the Huron Mountain Wildlife Foundation (E.B.S., T.J.G.), graduate research awards from the Botanical Society of America, American Society of Plant Taxonomists, and Torrey Botanical Society (E.B.S.), and a Smithsonian Graduate Research Fellowship (E.B.S.). 4 Author for correspondence (e-mail [email protected])