Recent debates on the number of plant species in the vast lowland rain forests of the Amazon have been based largely on model estimates, neglecting published checklists based on verified voucher data. Here we collate taxonomically verified checklists to present a list of seed plant species from lowland Amazon rain forests. Our list comprises 14,003 species, of which 6,727 are trees. These figures are similar to estimates derived from nonparametric ecological models, but they contrast strongly with predictions of much higher tree diversity derived from parametric models. Based on the known proportion of tree species in neotropical lowland rain forest communities as measured in complete plot censuses, and on overall estimates of seed plant diversity in Brazil and in the neotropics in general, it is more likely that tree diversity in the Amazon is closer to the lower estimates derived from nonparametric models. Much remains unknown about Amazonian plant diversity, but this taxonomically verified dataset provides a valid starting point for macroecological and evolutionary studies aimed at understanding the origin, evolution, and ecology of the exceptional biodiversity of Amazonian forests.Amazonia | floristics | rain forests | seed plants | species diversity

Subfamily Gochnatioideae is the sister group of ∼96% of the species in Compositae (Asteraceae). It is of particular interest not only because of its position in the phylogeny, but also because, in recent molecular studies, the node it occupies is not strongly supported making difficult any inferences on the direction of character evolution in the family. The recognition of tribe Gochnatieae was one of the results of a comprehensive molecular analysis of the family that showed the traditional circumscription of the Mutisieae to be non–monophyletic. The four genera of Gochnatieae (Cnicothamnus, Cyclolepis, Gochnatia, Richterago) were defined by the presence of apiculate anther appendages and dorsally smooth style branches. Gochnatia, which contained about 70 species, was the largest and most complex genus and in the last decade some of its sections have been moved (or returned) to the rank of genus. This study includes a large selection of potential outgroups and over 60% of all species in the tribe, including all the genera and all but one of the sections of Gochnatia, to examine evolutionary relationships among the taxa. Both cpDNA and nrDNA were used in a phylogenetic analysis using parsimony, likelihood, and Bayesian approaches. The results suggest a non–monophyletic Gochnatia that is here resolved by the recognition of segregate genera. Morphological characters support these new genera and allow the adoption of a new classification for the Gochnatieae. A biogeographic analysis shows a possible southern South American/Andean origin followed by movement in three directions: into the Central Andes, into central and northern Brazil, and into Mexico and the Caribbean. The dating analysis gives an age of the split of the core Gochnatieae from the Wunderlichieae–Cyclolepis clade, and hence the age of the tribe, of 36–45 Ma and an age of 23–25 Ma for the first split within the core Gochnatieae (Andean vs. Brazil–Mexico–Caribbean). Cnicothamnus remains in Gochnatieae but Cyclolepis is designated incertae sedis.

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Athyrium filix-femina [Lady Fern) comprises a complex of homoploid (n = 40] taxa, distributed over much of the northern hemisphere and extending into South America, whose evolutionary relationships are poorly understood and whose taxonomic treatment is problematic. The A. filix-femina complex of North America comprises as many as four taxa with overlapping ranges and provides an especially suitable context for exploring patterns and processes of divergent evolution and its taxonomic consequences in ferns. We addressed differentiation of two eastern North American taxa distinguished on the basis of growth form, frond shape, and spore color, and most recently treated as varieties A. angustum and A. asplenioides (Northern and Southern Lady Fern respectively). Although, these two taxa have been long perceived as closely related, they have been known to intergrade and recombine to form a hybrid zone in their relatively narrow region of overlap. This perception is supported by the data from the present study. Collections from 17 populations, 9 of A. angustum from Quebec to Pennsylvania and 8 of A. asplenioides from New Jersey to North Carolina, were examined for spores using LM, SEM, and TEM, and/or allozymes (16 loci coding 10 enzymes). The two taxa exhibited highly distinct perispore surfaces: all A. angustum individuals had papillose surfaces, whereas most A. asplenioides individuals were rugose with a reticulum of inflated folds. Spores from the northernmost A. asplenioides population sampled (Shirley, NJ) showed varying degrees of intermediacy suggestive of introgressive hybridization with A. angustum. Levels of allozyme polymorphism in populations (means: P=36.5%, A-1.97, He = 0.129) w^ere near means for angiosperms and ferns. Genotype frequencies at most loci in all populations were in Hardy-Weinberg equilibrium indicating an outcrossing mating system. Most alleles were shared among all populations. However, at the four most polymorphic loci [Idb-1, Pgi-2, Pgm-2, and Tpi-2] allele frequencies were significantly divergent between populations o{ A. angustum and A. asplenioides, especially Idb-1 which approached fixation for alternate alleles. Values for F^j ranged from 0.008 to 0.459 for individual loci (0.255 across loci) with especially high values for Jdh-1, Pgi-2, Pgm-2, and Tpi-2. Hierarchical F^t analysis indicated that differences between the two taxa (Fxy -0-216) accounted for most allele frequency divergence among populations (FxY = 0-238). UPGMA analysis of paired Rogers' Similarity (S) values resulted in two principal clusters each comprising populations of one taxon. Populations of A. angustum and A. asplenioides were joined within their clusters at S = 0.938 and S = 0.945 respectively, while the two taxon clusters were joined at S = 0.848. The spore and isozyme data indicate substantial divergence between A. angustum and A. asplenioides, suggesting that they merit distinction at the rank of subspecies or species. Additional study of populations in their region of sympatry is required to determine the ...