Diversity of gall-inducing insects in the high altitude wetland forests in Pernambuco, Northeastern Brazil.

We report on the richness of galling insects in the altitudinal wetland forests of Pernambuco State, Northeastern Brazil. We found 80 distinct types of insect galls on 49 species of host plants belonging to 28 families and 35 genera. Most of the galled plant species belong to Nyctaginaceae, Fabaceae, Meliaceae, Sapindaceae and Myrtaceae. The most common gall were spheroid and globoid; most galls were glabrous, predominantly green and with one chamber, and on the leaves. Most galls were induced by Cecidomyiidae (Diptera). The results of this study contribute to existing knowledge richness of galling insects and host-plant diversity in the altitudinal wetland forests of Northeastern Brazil.

Plant Vigor Hypothesis refuted: preference-performance linkage of a gall-inducing weevil on small-sized host plant resources.

The Plant Vigor Hypothesis (PVH) predicts an oviposition preference of females and higher offspring performance for insect herbivores on longer and fast-growing plant modules. We tested the PVH predictions by investigating the effects of leaf size of Miconia prasina (Sw.) DC. (Melastomataceae) on the oviposition preference and on the offspring survival of the gall-inducing weevil Prospoliata bicolorata (Coleoptera: Curculionidae). Additionally, we analysed the effects of top-down mortality force on this system. Approximately 83% of the developed galls resulted in adults of P. bicolorata, whereas 17% of the galls successfully induced were killed by natural enemies (top-down effect). Leaves of intermediate size were more abundant while smaller and longer leaves were rare. Nevertheless, the percentage of P. bicolorata galls was higher on the smallest leaves of M. prasina, refuting the preference prediction of the PVH. Our results also refuted the performance prediction: the ratio of survival per leaf was negatively related to the leaf length. Thus, we found a link between female preference and larval performance of P. bicolorata on small-sized leaves of M. prasina. The next goal is to understand the mechanisms involved in the selection of gall-inducing weevil on short leaves of its host plant.

Fate of native and introduced seeds consumed by captive white-lipped and collared peccaries (Tayassu pecari, Link 1795 and Pecari tajacu, Linnaeus 1758) in the Atlantic rainforest, Brazil.

We studied the role of white-lipped and collared peccaries (Tayassu pecari and Pecari tajacu) as seed predators and dispersers in the Atlantic rainforest of Brazil. The Atlantic rainforest ecosystem is highly threatened and has experienced dramatic declines in its populations of large mammals. Local extinctions can disrupt essential plant-animal interactions such as seed dispersion and seed predation. We tracked seeds from time of consumption to germination to assess the direct impact peccaries have on seed survival. We offered fruits of 20 species found in the Atlantic rainforest to the peccaries. Seeds were categorised as intact, scarified, ingested or defecated, and germination tests were performed. The overall impact by both peccary species was similar. Seeds were sometime scarified by mastication, always with fatal consequences. Most seeds that were consumed were destroyed during ingestion and digestion. Only small seeds (<10 mm) were found in the feces and germination tests suggest a positive effect from the passage through the guts. Peccaries clearly have a double role as both seed predators and as small seeds dispersers, which is a specialised role within the granivore/frugivore community of the Atlantic rainforest.

Morphology and anatomy of a leaf mine in Vismia guianensis (Aubl.) Choisy (Clusiaceae) in a fragment of Brazilian Atlantic forest.

Mines or hyponomes are channels caused by larva miners consuming internal plant tissues. These miners live on the leaf and feed from these tissues. Leaf mines are usually visible on the exterior of the leaf as serpentine paths, blotches, or other characteristic shapes of discolored tissues. Morphological and structural modifications undergone by mined leaves of Vismia guianensis (Aubl.) Choisy are presented here with the purpose of elucidating their structure and to contribute to studies about insect-plant interactions. Healthy and mined leaves were harvested from thirty plants and taken to the laboratory. For each branch, the total number of young and mature leaves, the number of leaves with mines and the number of mine per leaf were counted. Transverse sections of healthy and mined leaves were obtained to observe the morpho-anatomic aspects. From the 1,438 mature leaves and 379 young leaves analyzed, 214 (14.9%) and 70 (18.5%) were mined, where most of the leaves (67%) presented one mine per leaf. Transverse sections of the mine revealed that the larva consumed only mesophyll parenchyma tissue and the epidermis remains intact. There is not a pattern of leaf mining, but the larvae did not consume the druses observed on mesophyll and the vascular tissues of the mid-vein and lateral vein.

Morphology and anatomy of a leaf mine in Vismia guianensis (Aubl) Choisy (Clusiaceae) in a fragment of Brazilian Atlantic forest

Minas ou hiponomas são canais causados pelo consumo de tecidos internos da planta por larvas minadoras que habitam na folha e se alimentam desses tecidos. Minas em folhas são freqüentemente visíveis na folha em forma de serpentina, manchas ou outras formas características de tecido descolorido. Modificações morfológicas e anatômicas causadas por minadores em folhas de Vismia guianensis (Aubl.) Choisy são apresentadas neste trabalho, com o objetivo de elucidar a sua estrutura e contribuir com os estudos sobre interação inseto-planta. Folhas sadias e minadas de trinta indivíduos foram coletadas e levadas ao laboratório. Para cada ramo coletado foram mensurados o número total de folhas jovens e maduras, o número de folhas minadas e o número de minas por folha. Secções transversais de folhas sadias e minadas foram obtidas para observar aspectos morfo-anatômicos. Das 1.438 folhas maduras e 379 folhas jovens analisadas, 214 (14,9%) e 70 (18,5%) estavam minadas e muitas dessas folhas (67%) apresentavam uma única mina. Secções transversais das folhas minadas revelaram que a larva consome apenas tecido parenquimático do mesofilo e a epiderme permanece intacta. Não foi observado um padrão das minas foliares, mas a larva não consome as drusas observadas no mesofilo e os tecidos vasculares das nervuras central e laterais.

Growth and chemical defense in relation to resource availability: tradeoffs or common responses to environmental stress?

One aspect of plant defense is the production of constitutive secondary compounds that confer toxicity on herbivores and pathogens. The purpose of this study was to compare patterns of plant tissue toxicity across gradients of irradiance and nutrient content. We measured the potential toxicity (1/LC50) of extracts of six species of herbaceous Asteraceae grown under controlled conditions of temperature (25 degrees C), humidity (80%), photoperiod (16 h/day), in a range of concentrations of a modified Hoagland hydroponic solution (full-strength, 1/5 dilute, 1/10 dilute, and 1/50 dilute) and under two different light intensities (250 and 125 micromol/m2/s). The plants grew from seed for 42 days post-germination, and randomly chosen plants were harvested each 7 days. We did a general measure of potential phytochemical toxicity using an alcohol extraction of secondary compounds followed by brine shrimp (Artemia sp.) bioassay. Contrary to the carbon/nutrient balance hypothesis, tissue toxicity generally increased with decreasing irradiance and nutrient levels, so that plants whose growth was most restricted had tissues that were most toxic, although there were species-specific differences in this trend.

Growth and chemical defense in relation to resource availability: tradeoffs or common responses to environmental stress?

Um dos aspectos da defesa das plantas é a produção de compostos secundários constitutivos que são tóxicos para herbívoros e patógenos. O objetivo deste estudo foi comparar padräes de toxidez nas folhas em diferentes gradientes de nutrientes e intensidade luminosa. Foi medida a potencial toxidez (1/CL50) em extratos de seis espécies herbáceas de Asteraceae, desenvolvidas sob condiçäes controladas de temperatura (25§C), umidade (80%) e fotoperíodo (16 h/dias), com diferentes concentraçäes de solução hidropônica de Hoagland modificada (completa, 1/5, 1/10 e 1/50 diluídas) e sob três intensidades de luminosidade (250 e 125 mmol/m2/s). As plantas germinadas foram acompanhadas por 42 dias e, então, 15 indivíduos de cada espécie foram coletados ao acaso a cada 7 dias. Foi realizada uma medida geral da toxidez fitoquímica potencial usando extração alcoólica de compostos secundários das plantas estudadas, seguida do teste biológico com Artemia sp. Contrariando a hipótese de carbono/nutriente, a toxidez do tecido geralmente aumenta com a redução dos níveis de nutrientes e luminosidade. Isto é, plantas que tiveram crescimento restringido apresentaram-se mais tóxicas, embora as espécies tivessem tendências diferentes.