Lázaro José Chaves

Caracterização de frutos e árvores de populações naturais de Hancornia speciosa Gomes do cerrado

O trabalho objetivou caracterizar arvores e frutos de populacoes naturais de Hancornia speciosa Gomes, bem como avaliar a distribuicao da variabilidade fenotipica existente. Populacoes de mangabeiras foram amostradas no Cerrado, incluindo os Estados de Goias, Tocantins, Mato Grosso, Mato Grosso do Sul e Bahia, abrangendo 109 matrizes de 35 populacoes das variedades botânicas pubescens, gardneri, speciosa e cuyabensis. Os resultados mostraram que, nas condicoes do Cerrado, as matrizes de H. speciosa apresentam elevados niveis de variacao fenotipica quanto a caracteres de frutos, sendo que a maioria dessas variacoes esta entre populacoes. Ha, tambem, uma grande variacao fenotipica dentro das variedades botânicas. H. speciosa var. gardneri e H. speciosa var. pubescens tem frutos maiores e mais pesados. A variedade botânica gardneri apresenta porte mais alto que as demais. Nas variedades gardneri e pubescens, predominam frutos redondos e verde-claros, enquanto em speciosa e cuyabensis predominam frutos de formato oblongo e coloracao amarelo-escura e verde-escura, respectivamente. As variedades gardneri e pubescens destacam-se como de maior potencial para a selecao baseada em caracteres de tamanho e massa dos frutos.

Patterns of genetic variability in central and peripheral populations of Dipteryx alata (Fabaceae) in the Brazilian Cerrado

This study tested whether genetic parameters in Dipteryx alata populations, estimated from genomic and chloroplastidial microsatellite markers, were distributed according to a central-peripheral model, inferring which factors drive this spatial distribution of genetic variability within populations. For each of the 23 populations sampled throughout the species’ range, the mean number of alleles per locus, expected heterozygosity and intrapopulation fixation indices were calculated using a rarefaction approach based on 54 alleles from 8 nuclear microsatellites. Explanatory variables were grouped into three subsets: the ecological suitability estimated by combining different techniques of ecological niche modeling, variables expressing human occupation, and a historical variable represented by the first eigenvector from the pairwise FST matrix based on cpDNA microsatellites. Each response variable was modeled using first (linear) and second (quadratic) order trend surface analysis (TSA). Multiple regressions were then used to evaluate the relative effects of the explanatory variables, based on AIC multi-model selection. In general, the genetic parameters did not follow a classical central-periphery model. Ecological suitability had a significance influence in all genetic parameters, so more suitable regions have higher genetic diversity and low endogamy. There was also a relationship between fixation indices and human impacts. The high genetic diversity in the southwestern region of Cerrado suggested that recent range expansion (after the Last Glacial Maximum) may also influenced the observed intrapopulation genetic patterns. Thus, complex combinations of both historical and ecological drivers, as well as contemporary human occupation, seem to drive current genetic composition within D. alata populations throughout its geographic range.