Due to the basal position of the tribe Cedreleae in the phylogeny of Meliaceae, functionally either male or female pentamerous flowers and the presence of (at least partially) free stamens may be considered plesiomorphic traits within the family. In contrast, sympetaly and the absence of nectaries in Cedrela species are synapomorphies.

A Egeria najas é uma espécie aquática submersa nativa da bacia hidrográfica do rio Paraná. Com o represamento das águas do rio para geração de energia elétrica a espécie tem mudado seu comportamento de colonização dos leitos dos rios e ocorrido em grandes maciços dentro da represa de Jupiá e rios afluentes. Essa planta tem causado problemas por obstruir a passagem de água para as turbinas de geração de energia elétrica. ABSTRACT Genetic characterization of Egeria najas presented in the Jupia Lake and its tributariesThe submerged aquatic species Egeria najas occurs naturally in the Parana River BasinBrazil. Several lakes have been constructed by CESP -Centrais Elétricas do Estado de São Paulo S.A. in the river basin, changing the ecology of the region. The species have altered their establishment strategy, and now grows in large, dense populations on the floor of Jupia Lake and its tributaries. This has had a negative impact on electricity generation as the branches of these species routinely block the hydroelectric turbines. We used genetic markers to study the pattern of genetic diversity in the species using plant material collected along Jupia Lake and the Paraná River Tributaries. Isoenzymes have shown four different biotypes, however, the RAPD technique has demonstrated greater genetic variability among individuals. The creation of Jupia Lake has resulted in an increase in genetic variability probably by migration of large amount of seeds and vegetative branches. These materials are increasing the genetic diversity in populations in the lake by favoring outcrossing among different genotypes. Results also present a possible understanding of Egeria najas genotype migrations in populations in the Jupia Lake and its tributaries.

The selection of candidate plus trees of desirable phenotypes from tropical forest trees and the rapid devastation of the natural environments in which these trees are found have created the need for a more detailed knowledge of the floral and reproductive biology of tropical tree species. In this article, the organogenic processes related to unisexual flower development in tropical mahogany, Swietenia macrophylla, are described. Mahogany inflorescences at different developmental stages were evaluated using scanning electron microscopy or optical microscopy of histological sections. The unisexual flowers of S. macrophylla are usually formed in a thyrse, in which the positions of the female and male flowers are not random. Differences between male and female flowers arise late during development. Both female and male flowers can only be structurally distinguished after stage 9, where ovule primordia development is arrested in male flowers and microspore development is aborted in female flower anthers. After this stage, male and female flowers can be distinguished by the naked eye as a result of differences in the dimensions of the gynoecium. The floral characteristics of S. macrophylla (distribution of male and female flowers within the inflorescence, and the relative number of male to female flowers) have practical implications for conservation strategies of this endangered species.

Guries. 2012. Genetic diversity in Egeria densa and E. najas in JupiáReservoir, Brazil. Cien. Inv. Agr. 39(2):321-330. The aquatic plant species Egeria densa (Planch.) Casp and E. najas Planchon occur naturally in the Paraná River Basin of southeastern Brazil. Hydroelectric dam construction in the river basin has created several lakes, changing the ecology of the river and altering the population ecology of Egeria. Large, dense populations of Egeria now grow in Jupiá Lake and its tributaries, occasionally blocking hydroelectric turbines. This study is part of a larger project examining environmental changes associated with large dam projects; the research objective of this study was to assess patterns of genetic diversity in Egeria populations growing in Jupiá and Três Irmãos Lakes and their Paraná River tributaries using genetic markers. Forty-two plants of E. najas and 46 of E. densa (for a total of 88 samples) were collected from 13 sites. Genotypes were identified by isoenzymes and Random Amplification of Polymorphic DNA RAPD markers. Using a genetic distance dendrogram we grouped all E. densa plants into one set and all E. najas plants into another set. The plant sample 8a, which presented intermediary morphological characteristics of both species, also presented intermediary genetic characteristics, indicating the possibility that gene introgression between these Egeria species may occur. The creation of Três Irmãos Lake appears to have increased some measures of genetic diversity in Egeria populations by facilitating outcrossing among previously semiisolated genotypes. Increased migration of large numbers of seeds and vegetative branches of E. densa and E. najas into Jupiá Lake and its tributaries can account for most of the changes in patterning of genetic diversity observed in these populations of Egeria.

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