Post Fire Resprouting of Banisteriopsis malifolia(Malpighiaceae) and the Role of Extrafloral Nectaries on the Associated Ant Fauna in a Brazilian Savanna

<p>According to the plant vigor hypothesis, herbivores are favored by the growth of rapid resprouting plants, however in plants with extrafloral nec-taries not the herbivores, but rather patrolling ants would be favored. This ant-plant interaction may have a negative impact on herbivore populations,<br>thus benefiting the plant. In this study I showed that the ant community as-sociated with the extrafloral nectary-bearing shrub Banisteriopsis malifolia<br>in Brazilian savanna is composed of six species in four subfamilies and these ants were more abundant in resprouting B. malifoliaindicating a relation of<br>ants with functional extrafloral nectaries. As a consequence the number of herbivores sampled was low, because of the ants’ aggressive behavior. This work provides evidence that the effects of plant vigor are buffered in extrafloral nectary-bearing plants because of the patrolling ants which feed on sugar-rich nectar and protect the plant against invaders.</p> <p> </p

Herbivory causes increases in leaf spinescence and fluctuating asymmetry as a mechanism of delayed induced resistance in a tropical savanna tree

Background and aims – Leaf spinescence is thought to be a defense against herbivory and may increase in years following high herbivory pressure (DIR – delayed induced resistance). Besides DIR, herbivory also causes plant stress, which can be assessed using fluctuating asymmetry analysis (FA – random departures from leaf bilateral symmetry). In this two-year field study we first investigated the relationships between herbivory, FA and spinescence in Solanum lycocarpum trees during an outbreak of moth caterpillars in 2010; then in 2011 we examined whether plants with intense herbivory the previous year presented changes in FA (herbivory induced stress) and spinescence.Key results – In 2010, leaves damaged by moths were significantly more asymmetrical than undamaged leaves. In addition, moths preferentially fed on leaves with fewer and shorter spines. In 2011, plants severely attacked by moths the year before showed significant increases in FA (28%), spine abundance (21%) and spine length (84%), compared to less damaged plants.Conclusions – Our data suggest a delayed response of S. lycocarpum to herbivory, in that plants subjected to high leaf damage the previous year maximized their display of anti-herbivore mechanisms, in this case, leaf spinescence. This is one of the few studies to show that FA increased as a response to herbivore attack. We conclude that FA can be used as an indicator of plant stress following leaf damage

Herbivory causes increases in leaf spinescence and fluctuating asymmetry as a mechanism of delayed induced resistance in a tropical savanna tree

Background and aims – Leaf spinescence is thought to be a defense against herbivory and may increase in years following high herbivory pressure (DIR – delayed induced resistance). Besides DIR, herbivory also causes plant stress, which can be assessed using fluctuating asymmetry analysis (FA – random departures from leaf bilateral symmetry). In this two-year field study we first investigated the relationships between herbivory, FA and spinescence in Solanum lycocarpum trees during an outbreak of moth caterpillars in 2010; then in 2011 we examined whether plants with intense herbivory the previous year presented changes in FA (herbivory induced stress) and spinescence.Key results – In 2010, leaves damaged by moths were significantly more asymmetrical than undamaged leaves. In addition, moths preferentially fed on leaves with fewer and shorter spines. In 2011, plants severely attacked by moths the year before showed significant increases in FA (28%), spine abundance (21%) and spine length (84%), compared to less damaged plants.Conclusions – Our data suggest a delayed response of S. lycocarpum to herbivory, in that plants subjected to high leaf damage the previous year maximized their display of anti-herbivore mechanisms, in this case, leaf spinescence. This is one of the few studies to show that FA increased as a response to herbivore attack. We conclude that FA can be used as an indicator of plant stress following leaf damage

Leaf phenotypic variation and developmental instability in relation to different light regimes

ABSTRACT For pioneer plants, shaded habitats represent a stressful condition, where sunlight exposure is below the optimum level and so leaves expand in order to intercept a greater amount of light. We investigated changes in both phenotypic variation and stress of Bauhinia brevipes in sunny and shaded microhabitats. Leaf area was used as a measure of phenotypic variation, whereas leaf asymmetry (difference between right and left sides of leaves), was used as a measure of stress. We hypothesized an increase in leaf area and stress in shaded locations, which might indicate that B. brevipes was compensating for low light absorption, and elevated levels of stress, respectively. Plants in the sun fitted a fluctuating asymmetry pattern (normal distribution of right minus left sides), while shaded plants were clearly antisymmetric (bimodal distribution of leaf side differences). Leaf asymmetry and area were 5% and 26.8% higher in plants in the shade compared to plants in the sun, respectively. These results were expected since B. brevipes is found predominantly in open areas; so sunlight exposure is important for its development. The presence of antisymmetry is rare in studies of developmental instability, and here it might indicate higher stress compared to plants with fluctuating asymmetry

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

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)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.20710768773Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)FAPEMIGCoordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

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.CNPqCNPqFAPEMIGFAPEMIGCAPESCAPE

Weed control strip influences the initial growth of Eucalyptus grandis

Reforestation in Brazil is conventionally carried out with a 50-cm weed control strip, using mechanical or manual hoeing or herbicides. The aim of this study was to determine effects of varying the width of the herbicide-treated strip on the establishment of Eucalyptus grandis. Eucalyptus plants were transplanted in Araraquara and Altinopolis counties, São Paulo State, Brazil. In Araraquara, the following treatments were evaluated: 0, 25, 50, 75, 100 and 150-cm wide strips, treated with herbicide, on either side of the eucalyptus row; in Altinopolis, the width of the strip on either side of the eucalyptus row was 0, 25, 50, 75, 100, 125 or 150 cm. Were evaluated dry matter of leaves, branches and stem and leaf area at 270 days after planting (270 DAP), chlorophyll content (400 DAP), stem diameter and eucalyptus plants height (410 DAP). In Araraquara, the main weed was Panicum maximum, and in Altinopolis, it was Rhynchelytrum repens. For both areas, a minimum of 75 cm of treated strip was required to minimise weed interference with eucalyptus plants' development.Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

To what extent is clearcutting vegetation detrimental to the interactions between ants and Bignoniaceae in a Brazilian savanna?

Anthropogenic disturbances decrease the resources available to ants and simplify the ant fauna. This could affect ant-plant interactions, especially if key-species disappear. In terms of conservation, disturbances can select for ants resilient to disturbances, and such species can be considered indicators of succession processes. Here, we investigated the extent to which a vegetation clearcutting event (by bulldozer) affected the communities of both plants (seven species of Bignoniaceae) and associated ants. We hypothesized that only generalist ants would remain after clearcutting. Clearcutting reduced plant abundance, with only 40% of individuals resprouting after disturbance. Plant species richness was not affected by clearcutting, but ant species richness was lower in disturbed than in undisturbed conditions (four instead of seven species). Camponotus ants were dominant and were found regularly on all plant species before and after clearcutting. These ants had high centrality values and were regarded as influential species in the structure of the ant-plant network. Camponotus are generalists and nest in the soil; thus, clearcutting did not affect them to the same degree as the ants that nest in plants. The ant-plant network showed no changes in the specialization index (H-2 '), indicating that even with losses of some ant species, the network properties were maintained: plants were still being visited by ants. Therefore, we show that clearcutting had a weak effect on ant-plant interactions, especially because Camponotus buffered the losses of other ants24103114CAPES - Coordenação de Aperfeiçoamento de Pessoal e Nível SuperiorCNPQ - Conselho Nacional de Desenvolvimento Científico e Tecnológicosem informaçãosem informaçãosem informaçãoFAPEMAT - Fundação de Amparo à Pesquisa do Estado de Mato Gross