Mating system parameters at hierarchical levels of fruits, individuals and populations in the Brazilian insect-pollinated tropical tree, Tabebuia roseo-alba (Bignoniaceae)

For many tree species, mating system analyses have indicated potential variations in the selfing rate and paternity correlation among fruits within individuals, among individuals within populations, among populations, and from one flowering event to another. In this study, we used eight microsatellite markers to investigate mating systems at two hierarchical levels (fruits within individuals and individuals within populations) for the insect pollinated Neotropical tree Tabebuia roseo-alba. We found that T. roseo-alba has a mixed mating system with predominantly outcrossed mating. The outcrossing rates at the population level were similar across two T. roseo-alba populations; however, the rates varied considerably among individuals within populations. The correlated paternity results at different hierarchical levels showed that there is a high probability of shared paternal parentage when comparing seeds within fruits and among fruits within plants and full-sibs occur in much higher proportion within fruits than among fruits. Significant levels of fixation index were found in both populations and biparental inbreeding is believed to be the main cause of the observed inbreeding. The number of pollen donors contributing to mating was low. Furthermore, open-pollinated seeds varied according to relatedness, including half-sibs, full-sibs, self-sibs and self- half-sibs. In both populations, the effective population size within a family (seed-tree and its offspring) was lower than expected for panmictic populations. Thus, seeds for ex situ conservation genetics, progeny tests and reforestation must be collected from a large number of seed-trees to guarantee an adequate effective population in the sample.

Parasites in the neighbourhood: Interactions of the mistletoe Phoradendron affine (Viscaceae) with its dispersers and hosts in urban areas of Brazil

Mistletoes constitute an important food resource for animals in many ecosystems. However, these plants are considered pests in urban areas because of deleterious effects they have on the host trees. Studies in urban areas were mostly focused on listing host species or procedures to control the "pest". In this sense, broader studies including several aspects of mistletoes ecology in urban ecosystems are still missing. We studied the interaction of the mistletoe, Phoradendron affine, with its dispersers and hosts in two urban sites in Uberlandia, Brazil. Phoradendron affine fruits were consumed almost exclusively by Euphonia chlorotica, which was crucial for seed germination. Parasitism was recorded in five hosts, two native (Handroanthus chrysotrichus and Tabebuia roseoalba) and three exotic species (Spathodea campanulata, Ligustrum lucidum and Melia azedarach). Mistletoes were found parasitizing larger host trees, a trend commonly reported for mistletoe-host interaction. Mistletoe seed germination was not affected by the trees species, whether host or non-host, but the radicle of germinated seeds could not penetrate the bark and seedlings invariably died in non-host species. We found a high prevalence of parasitism in our study, in comparison to what previous studies reported for natural areas. The spatial distribution of the hosts and high light incidence on isolated host trees may lead to this high prevalence in urban areas. Rather than eradicated, mistletoes in urban areas should be ecologically managed and their importance for bird species conservation must be considered. More studies to determine which bird species are favoured by mistletoe presence in urban areas will be essential for, this purpose. (C) 2012 Elsevier GmbH. All rights reserved.

Conservação de sementes de ipê-roxo

O objetivo desta pesquisa foi estudar o comportamento fisiológico de sementes de ipê-roxo (Tabebuia heptaphylla (Vell.) Toledo) durante o amazenamento. Frutos colhidos manualmente de 15 plantas-matrizes foram colocados em ambiente sombreado para secagem complementar e posterior extração manual das sementes; primeiro, determinou-se o grau de umidade inicial das sementes (15,6%) e, em seguida, as sementes remanescentes foram submetidas a secagem para obtenção dos demais graus de umidade desejados (11,5, 8,0 e 4,3%). As amostras correspondentes aos diferentes graus de umidade foram armazenadas em câmaras, na temperaturas de 10, 20 e -196 °C. No início e após 120, 240 e 360 dias de armazenamento, as sementes foram submetidas a diversas avaliações fisiológicas. O delineamento experimental foi o inteiramente casualizado, em esquema fatorial, com 4 tratamentos (grau de umidade) no início do armazenamento e 12 tratamentos (4 grau de umidade x 3 condições térmicas), em cada época de avaliação, durante o armazenamento. A comparação das médias foi realizada pelo Teste de Tukey a 5%. A conservação das sementes de ipê-roxo com teores de água de 15,6, 11,5, 8,1 e 4,3% é favorecida no armazenamento a 10 e -196 °C.