Rogério Fernandes de Souza

Genetic variability of pre and post-fragmentation cohorts of Aspidosperma polyneuron Muell. Arg. (Apocynaceae)

RAPD was used to access the genetic variability in Aspisdosperma polyneuron, a long-lived, late-reproducing tropical tree, and highly important for the Atlantic Forest. RAPD profiles from adults (pre-fragmentation, >300 years old) and seedlings (post-fragmentation, <<50 years old) were analyzed. Results showed a decrease of genetic polymorphism of post-fragmentation cohorts in small fragments and higher genetic diversity within population. The genetic diversity distribution suggested the establishment of fragments as protected reserves, and the transference of seedlings among fragments for conservation of A. polyneuron.

Population structure and genetic diversity of the orchid bee Eufriesea violacea (Hymenoptera, Apidae, Euglossini) from Atlantic Forest remnants in southern and southeastern Brazil

In this study, both the genetic diversity and population genetic structure of Eufriesea violacea from six Atlantic Forest fragments, located in four Brazilian states, were assessed using microsatellite markers. The results showed that genetic diversity was high in all populations and the genetic differentiation (ΦST), based on allelic frequency differences, for all population pairwise comparisons was found to be significantly different from zero, indicating from low to moderate genetic differentiation among populations. Considerably higher genetic differentiation values were revealed by the Dest estimator, indicating very high levels of differentiation for some pairs of populations. The present results on the population structure of E. violacea suggest a restriction in gene flow among populations from different Atlantic Forest remnants. Thus, considering the intense threats over the current Atlantic Forest remnants, more attention should be paid to populations of this euglossine species.

Terminal-Repeat Retrotransposons with GAG Domain in Plant Genomes: A New Testimony on the Complex World of Transposable Elements

A novel structure of nonautonomous long terminal repeat (LTR) retrotransposons called terminal repeat with GAG domain (TR-GAG) has been described in plants, both in monocotyledonous, dicotyledonous and basal angiosperm genomes. TR-GAGs are relatively short elements in length (<4 kb) showing the typical features of LTR-retrotransposons. However, they carry only one open reading frame coding for the GAG precursor protein involved for instance in transposition, the assembly, and the packaging of the element into the virus-like particle. GAG precursors show similarities with both Copia and Gypsy GAG proteins, suggesting evolutionary relationships of TR-GAG elements with both families. Despite the lack of the enzymatic machinery required for their mobility, strong evidences suggest that TR-GAGs are still active. TR-GAGs represent ubiquitous nonautonomous structures that could be involved in the molecular diversities of plant genomes.

Distribution of Divo in Coffea genomes, a poorly described family of angiosperm LTR-Retrotransposons

Coffea arabica (the Arabica coffee) is an allotetraploid species originating from a recent hybridization between two diploid species: C. canephora and C. eugenioides. Transposable elements can drive structural and functional variation during the process of hybridization and allopolyploid formation in plants. To learn more about the evolution of the C. arabica genome, we characterized and studied a new Copia LTR-Retrotransposon (LTR-RT) family in diploid and allotetraploid Coffea genomes called Divo. It is a complete and relatively compact LTR-RT element (~5 kb), carrying typical Gag and Pol Copia type domains. Reverse Trancriptase (RT) domain-based phylogeny demonstrated that Divo is a new and well-supported family in the Bianca lineage, but strictly restricted to dicotyledonous species. In C. canephora, Divo is expressed and showed a genomic distribution along gene rich and gene poor regions. The copy number, the molecular estimation of insertion time and the analysis at orthologous locations of insertions in diploid and allotetraploid coffee genomes suggest that Divo underwent a different and recent transposition activity in C. arabica and C. canephora when compared to C. eugenioides. The analysis of this novel LTR-RT family represents an important step toward uncovering the genome structure and evolution of C. arabica allotetraploid genome.

Morphological and genomic characterization of Rhynchospora tenuis complex (Cyperaceae) and its taxonomic implications

Species of Rhynchospora sect. Tenues are morphologically very similar. Rhynchospora tenuis complex is the most problematic species complex in this group and it concentrates entities of difficult delimitation, as is the case of R. tenuis, R. tenuis subsp. austro-brasiliensis and R. enmanuelis. Samples of these three taxonomic entities, besides R. junciformis and R. breviuscula (Dichromena), were analyzed in a comparative way using morphologic, cytogenetic and molecular tools. Despite of high morphological similarity between these taxa, R. tenuis was separated from R. tenuis subsp. austro-brasiliensis and R. enmanuelis according to chromosome numbers (2n = 4 and 2n = 18) and ISSR markers. The combined analysis of shape and size of achenes and stylopodium, number of spikelets, cytogenetic features and molecular markers suggest a clear proximity among Rhynchospora junciformis, R. tenuis subsp. austro-brasiliensis and R. enmanuelis, in relation to R. tenuis. These data indicate the need for a new taxonomic review of R. sect. Tenues, mainly to solve the status and nomenclatural situation of R. tenuis subsp. austro-brasiliensis and R. enmanuelis.

Genome differentiation, natural hybridisation and taxonomic relationships among Eleocharis viridans, E. niederleinii and E. ramboana (Cyperaceae)

Abstract. The role of natural hybridisation and genome changes in the differentiation and speciation of Eleocharis (Cyperaceae) was addressed through the study of the following three closely related species of the polyphyletic series Tenuissimae: Eleocharis viridans Kük. ex Osten, E. ramboana R.Trevis & Boldrini and E. niederleinii Boech., which often reproduce asexually. Molecular and cytogenetic data were used to understand the genomic and karyotypic relationships in the group. Genomes were compared using internal transcribed spacer–cleaved amplified polymorphic sequence (ITS-CAPS) marker and confirmed with random amplified polymorphic DNA, which allowed identification of different genetic groups, with clear evidence of natural hybrids. Karyotype analysis showed numerical variation from 2n = 20–42, with occurrence of chromosome heteromorphisms and polymorphisms, including variability in 35S rDNA site numbers. Meiotic studies demonstrated irregular pairing in some samples, which is associated with hybridisation and asexual reproduction. Genomic in situ hybridisation (GISH) reactions were conducted using two well defined genetic groups as probes, with 2n = 20 and normal meiosis. Probes were tested against each one of the genetic groups and showed positive, partial and negative GISH results, which supported the molecular analysis data. The results indicated that the three studied species are undergoing an intense process of genomic and karyotypic re-arrangement, which results in overlapping of morphological and genomic characteristics. The present study has exemplified the value of an integrative taxonomic approach to solve conflicts in species delimitation in groups undergoing hybridisation.