Andrea Raposo

Pollen and seed flow patterns of Carapa guianensis Aublet. (Meliaceae) in two types of Amazonian forest

Various factors affect spatial genetic structure in plant populations, including adult density and primary and secondary seed dispersal mechanisms. We evaluated pollen and seed dispersal distances and spatial genetic structure of Carapa guianensis Aublet. (Meliaceae) in occasionally inundated and terra firme forest environments that differed in tree densities and secondary seed dispersal agents. We used parentage analysis to obtain contemporary gene flow estimates and assessed the spatial genetic structure of adults and juveniles. Despite the higher density of adults (diameter at breast height ≥ 25 cm) and spatial aggregation in occasionally inundated forest, the average pollen dispersal distance was similar in both types of forest (195 ± 106 m in terra firme and 175 ± 87 m in occasionally inundated plots). Higher seed flow rates (36.7% of juveniles were from outside the plot) and distances (155 ± 84 m) were found in terra firme compared to the occasionally inundated plot (25.4% and 114 ± 69 m). There was a weak spatial genetic structure in juveniles and in terra firme adults. These results indicate that inundation may not have had a significant role in seed dispersal in the occasionally inundated plot, probably because of the higher levels of seedling mortality.

Parâmetros do sistema reprodutivo em uma população de alta densidade de andirobas na Floresta Amazônica

O objetivo deste trabalho foi estimar parâmetros do sistema reprodutivo de uma populacao de andirobas (Carapa guianensis), com uso de marcadores microssatelites e de modelos de cruzamentos mistos e correlacionados. Doze arranjos de progenies com 15 individuos oriundos de polinizacao aberta foram amostrados em area com densidade populacional de andirobas de 25,7 arvores por hectare. No geral, a especie tem um sistema misto de reproducao, com predominância de fecundacao cruzada. A taxa de reproducao multiloco (tm = 0,862) foi significativamente menor que a unidade, o que indica que houve autofecundacao. A taxa de cruzamento entre individuos aparentados foi substancial (tm ‑ ts = 0,134) e significativamente diferente de zero. A correlacao de autofecundacao nas progenies foi alta (rs = 0,635), o que indica taxa de fecundacao cruzada individual variavel. Em consonância com esse resultado, a estimativa da taxa de fecundacao cruzada individual variou de 0,598 a 0,978. A correlacao multiloco de paternidade foi baixa (rp(m) = 0,081), mas significativamente diferente de zero, o que sugere progenies com irmaos completos. A coancestria dentro das progenies (Θ = 0,185) foi maior e o tamanho efetivo de variância (Ne(v) = 2,7) foi menor que o esperado para verdadeiras progenies de meios‑irmaos (Θ = 0,125; Ne(v) = 4). Esses resultados sugerem que, para manter um tamanho efetivo minimo de 150 individuos, para melhoramento, conservacao genetica e programas de reflorestamento ambiental, sementes de pelo menos 56 arvores devem ser coletadas.

EFEITO DO SOMBREAMENTO NA ANATOMIA FOLIAR DE PLANTAS JOVENS DE ANDIROBA (Carapa guianensis Aubl.)

The ability to use light varies between species and the success of each individual depends on his morphoanatomical adaptations. The aim of this study was to evaluate the influence of different light intensities on leaf anatomy of seedlings of Carapa guianensis Aubl. Healthy leaves of the second and third nodes were collected from young plants grown in four levels of shading: 30%, 50%, 70% and 0% (full sun) during the eight months of the experiment. Anatomical analyzes were made under Optical Microscopy (OM), from temporary and permanent slides, and Scanning Electron Microscopy (SEM). The stomatal density showed no significant differences. The dimensions of stomata and thicknesses of the leaf tissue were greater with increasing light intensity. C. guianensis presents anatomical plasticity enabling survival in the forest under different lighting