The rosid clade (70,000 species) contains more than one-fourth of all angiosperm species and includes most lineages of extant temperate and tropical forest trees. Despite progress in elucidating relationships within the angiosperms, rosids remain the largest poorly resolved major clade; deep relationships within the rosids are particularly enigmatic. Based on parsimony and maximum likelihood (ML) analyses of separate and combined 12-gene (10 plastid genes, 2 nuclear; >18,000 bp) and plastid inverted repeat (IR; 24 genes and intervening spacers; >25,000 bp) datasets for >100 rosid species, we provide a greatly improved understanding of rosid phylogeny. Vitaceae are sister to all other rosids, which in turn form 2 large clades, each with a ML bootstrap value of 100%: (i) eurosids I (Fabidae) include the nitrogen-fixing clade, Celastrales, Huaceae, Zygophyllales, Malpighiales, and Oxalidales; and (ii) eurosids II (Malvidae) include Tapisciaceae, Brassicales, Malvales, Sapindales, Geraniales, Myrtales, Crossosomatales, and Picramniaceae. The rosid clade diversified rapidly into these major lineages, possibly over a period of <15 million years, and perhaps in as little as 4 to 5 million years. The timing of the inferred rapid radiation of rosids [108 to 91 million years ago (Mya) and 107-83 Mya for Fabidae and Malvidae, respectively] corresponds with the rapid rise of angiosperm-dominated forests and the concomitant diversification of other clades that inhabit these forests, including amphibians, ants, placental mammals, and ferns. community assembly ͉ divergence time estimates ͉ phylogeny ͉ rapid radiation G reat progress has been made in elucidating deep-level angiosperm relationships during the past decade. The eudicot clade, with Ϸ75% of all angiosperm species, comprises several major subclades: rosids, asterids, Saxifragales, Santalales, and Caryophyllales (1-3). Investigations have converged on the branching pattern of the basalmost angiosperms, revealing that Amborellaceae, Nymphaeales [in the sense of APG II (3) and including Hydatellaceae (4)], and Austrobaileyales are successive sisters to all other extant angiosperms (reviewed in ref.2). Analyses of complete plastid genome sequences have resolved other problematic deep-level relationships, suggesting that Chloranthaceae and magnoliids are sister to a clade of monocots and eudicots plus Ceratophyllaceae (5, 6). Likewise, progress has been made in clarifying relationships within the large monocot (7) and asterid (8) clades.Despite these successes, the rosids stand out as the largest and least-resolved major clade of angiosperms; basal nodes within the clade have consistently received low internal support (1, 2, 9, 10). The rosid clade comprises Ϸ70,000 species and 140 families (2, 11). Containing more than a quarter of total angiosperm and Ϸ39% of eudicot species diversity, the rosid clade is broader in circumscription than the traditional Rosidae or Rosanae (e.g., 12; reviewed in ref.2). The oldest fossil flowers conforming to the rosids are from the late S...

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. Molecular phylogenetics has revolutionized our understanding of the Caryophyllales, and yet many relationships have remained uncertain, particularly at deeper levels. We have performed parsimony and maximum likelihood analyses on separate and combined data sets comprising nine plastid genes (;12,000 bp), two nuclear genes (;5000 bp), and the plastid inverted repeat (;24,000 bp), giving a combined analyzed length of 42,006 bp for 36 species of Caryophyllales and four outgroups. We have recovered strong support for deep-level relationships across the order. Two major subclades are well supported, the noncore and core Caryophyllales; Rhabdodendron followed by Simmondsia are sisters to the core Caryophyllales, Limeum and Stegnosperma are successive sisters to the ''globular inclusion'' clade, Gisekia is a distinct lineage well separated from Rivina within the ''raphide'' clade, and Rivina and Phytolaccaceae are disparate lineages, with Rivina sister to Nyctaginaceae. The placement of Sarcobatus and relationships within the portulacaceous cohort remain problematic. Within the latter, Halophytum is sister to Basellaceae and Didiereaceae, and the clade comprising Portulaca, Talinum, and Cactaceae is well supported. Classical hypotheses argued that the early Caryophyllales had evolved in open, dry, marginal environments at a time when pollinators were scarce, and, as such, the ancestral caryophyllid flower was wind pollinated with an undifferentiated perianth. We reevaluated these hypotheses in light of our phylogeny and find little support for anemophily as the ancestral condition; however, the early caryophyllid flower is suggested to have possessed an undifferentiated perianth. A subsequent minimum of nine origins of differentiated perianth is inferred. We discuss the evidence for independent origins of differentiated perianth and highlight the research opportunities that this pattern offers to the field of evolutionary developmental genetics.