Phylogeny of the Clusioid Clade ( Malpighiales ) : Evidence from the Plastid and Mitochondrial Genomes 1

American Journal of Botany 98(2): 306–325, 2011; http://www.amjbot.org/ © 2011 Botanical Society of America morphologically heterogeneous and ecologically diverse. Growth forms include large tropical rainforest trees, temperate and high altitude tropical herbs and shrubs, and aquatic plants of swiftfl owing rivers and streams. Although their distribution is nearly cosmopolitan, their greatest species diversity is in the tropics. This well-supported clade contains fi ve families ( APG III, 2009 ; Wurdack and Davis, 2009 ) representing 94 genera and ~1900 species ( Kato, 2006 ; Cook and Rutishauser, 2007 ; Stevens, 2007a , b ; Weitzman et al., 2007 ; Thiv et al., 2009 ; Koi and Kato, 2010 ; Tippery et al., in press ): Bonnetiaceae, Calophyllaceae, Clusiaceae s.s., Hypericaceae, and Podostemaceae. The clusioids, excluding Podostemaceae, are an important component of tropical forests and comprise ~3% of the total species diversity in the Center for Tropical Forest Science ’ s global network of tropical forest research plots ( CTFS, 2009 ). Podostemaceae, the largest strictly aquatic fl owering plant family, play a key role in river systems — especially through their impact on the ecology and nutrition of fi sh and invertebrates ( Allan, 1995 ; Machado-Allison et al., 2003 ). This family occupies a unique ecological niche for angiosperms: growing fi rmly attached to solid substrates in swift-fl owing, nutrientpoor rivers and waterfalls ( Philbrick and Novelo, 2004 ). Their ability to attach to substrates in these harsh environments is facilitated by biofi lms partially composed of cyanobacteria, which may function as an important source of nitrogen for the plants The clusioids are a clade of fl owering plants in the large rosid order Malpighiales ( Savolainen et al., 2000 ; Soltis et al., 2000 ; Wurdack and Davis, 2009 ). Species in this clade are