Biogeography of cedrela (meliaceae, sapindales) in central and South america.

Dated phylogenies have helped clarify the complex history of many plant families that today are restricted to the world's tropical forests, but that have Eocene, Oligocene, and Miocene fossils from the northern hemisphere. One such family is the Meliaceae. Here we infer the history of the neotropical Meliaceae genus Cedrela (17 species), the sister clade of which today is restricted to tropical Asia. Sequences from the nuclear ribosomal spacer region and five plastid loci obtained for all ingroup species and relevant outgroups were used to infer species relationships and for molecular-clock dating under two Bayesian relaxed clock models. The clock models differed in their handling of rate autocorrelation and sets of fossil constraints. Results suggest that (1) crown group diversification in Cedrela started in the Oligocene/Early Miocene and intensified in the Late Miocene and Early Pliocene, and (2) Central American Cedrela species do not form a clade, implying reentry into Central America after the closure of the Panamanian Isthmus. At present, Cedrela is distributed in both dry and humid habitats, but morphological features suggest an origin in dry forest under seasonal climates, fitting with Miocene and Pliocene Cedrela fossils from deciduous forests.

Molecular phylogenetics of Neotropical Cedreleae (mahogany family, Meliaceae) based on nuclear and plastid DNA sequences reveal multiple origins of "Cedrela odorata".

This study focuses on the 17 Neotropical species described in Cedrela (Meliaceae; Cedreleae), in particular C. odorata, which has been shown in past population genetic studies to be more variable than other tree species. We sampled two sets of molecular markers, nuclear ribosomal spacers (nrITS), and several plastid regions (the psbB, psbN, psbT exons and the trnS-trnG spacer). Both sets of markers produced congruent results using parsimony, maximum likelihood and Bayesian methods for a set of taxa that include outgroups (outside Cedreleae) as well as other members of the related genera within Cedreleae. All results confirm current delimitation of Cedreleae and genetic distinctiveness for four new species with divergent morphologies. Our study also provides evidence that there are several genetic entities among the accessions of C. odorata that have distinct ranges or habitat preferences. These entities may constitute new species, are morphologically cryptic and require a great deal more investigation to delimit their ranges. Our results have important implications for conservation of Cedrela odorata, which is heavily harvested throughout its range in the American tropics.

The mahogany family "out-of-Africa": divergence time estimation, global biogeographic patterns inferred from plastid rbcL DNA sequences, extant, and fossil distribution of diversity.

With information on fossils and extant distribution of diversity/endemism in the mahogany family, we perform a global biogeographic study of Meliaceae using plastid rbcL data for all subfamilies, tribes and nearly all genera. Our study indicates that: (1) Meliaceae are of western Gondwanan origin; (2) dispersal played an important role for the current distribution of mahogany biota; and (3) the direction of dispersal was most likely an "out-of-Africa" scenario with important dispersal routes across Eurasia and between Eurasia and North America provided by Beringia and the North Atlantic land bridge and North America and South America via island chains and/or direct land connections. Populations in North America, Europe, and East Asia were presumably eliminated as tropical climates disappeared from these areas during the Miocene. Extensive Meliaceae fossil findings confirm that the entry of megathermal (frost-intolerant) angiosperms into southern continents from Oligocene to Pliocene must be considered as an important means of establishing pantropical distribution patterns.

Aglaia (Meliaceae): an evaluation of taxonomic concepts based on DNA data and secondary metabolites.

We performed maximum parsimony and Bayesian analyses (nuclear ITS rDNA, plastid rps16 intron) to estimate phylogenetic relationships within Aglaia (over 100 species in Southeast Asia, the Pacific, and Australia) and its relations among Aglaieae (Meliaceae). Based on 67 accessions of Aglaieae, three taxa of Guareae, and two taxa of Melieae (outgroup), this study provides the first assessment of the current circumscription of Aglaieae, Aglaia, and its sections and to a more limited extent of species concepts in Aglaia. DNA data are compared to recently collected data on chemical profiles. Our analyses indicate (1) the monophyly of Aglaieae; (2) the polyphyly of Aphanamixis; (3) the paraphyly of Aglaia; (4) the existence of at least three entities with respect to Aglaia: (a) the core group of Aglaia section Amoora (dehiscent fruits) with close relationships to Lansium and Reinwardtiodendron, (b) a group comprising morphological intermediates between the two sections, and (c) the core group of Aglaia section Aglaia (indehiscent fruits). Macro- and micromolecular data indicate that complex species are more heterogeneous, i.e., probably containing more than one taxon each, than taxonomically isolated species. A third section in Aglaia is recognized to accommodate A. lawii, A. teysmanniana, and A. beccarii.

Molecular phylogenetics of Meliaceae (Sapindales) based on nuclear and plastid DNA sequences.

Phylogenetic analyses of Meliaceae, including representatives of all four currently recognized subfamilies and all but two tribes (32 genera and 35 species, respectively), were carried out using DNA sequence data from three regions: plastid genes rbcL, matK (partial), and nuclear 26S rDNA (partial). Individual and combined phylogenetic analyses were performed for the rbcL, matK, and 26S rDNA data sets. Although the percentage of informative characters is highest in the segment of matK sequenced, rbcL provides the greatest number of informative characters of the three regions, resulting in the best resolved trees. Results of parsimony analyses support the recognition of only two subfamilies (Melioideae and Swietenioideae), which are sister groups. Melieae are the only tribe recognized previously that are strongly supported as monophyletic. The members of the two small monogeneric subfamilies, Quivisianthe and Capuronianthus, fall within Melioideae and Swietenioideae, respectively, supporting their taxonomic inclusion in these groups. Furthermore, the data indicate a close relationship between Aglaieae and Guareeae and a possible monophyletic origin of Cedreleae of Swietenioideae. For Trichilieae (Melioideae) and Swietenieae (Swietenioideae) lack of monophyly is indicated.