BioOne Complete (complete.BioOne.org) is a full-text database of 200 subscribed and open-access titles in the biological, ecological, and environmental sciences published by nonprofit societies, associations, museums, institutions, and presses.
Phytophagous insects choose their feeding resources according to their own requirements in addition to properties of the host plants, such as biomechanical defences. The feeding preferences of the native folivorous insects of the Andean-Patagonian forest (Argentina) have rarely been studied. These environments present a wide diversity and abundance of insects associated with trees of the Nothofagus and Lophozonia (Nothofagaceae) genera, which represent the main tree species of the forests of the southern hemisphere. In particular, Lophozonia alpina and Lophozonia obliqua are of great interest because they have a wide distribution, a high capacity for hybridization and exhibit great phenotypic plasticity. This versatility causes substantial variation in the biomechanical properties of leaves, affecting the feeding preferences of insects. The purpose of this work was to study the food selection behaviour of three leaf-chewing insects (Polydrusus nothofagii, Polydrusus roseaus (Coleoptera: Curculionidae) and Perzelia arda (Lepidoptera: Oecophoridae)) associated with L. alpina and L. obliqua as host plants. Based on their choices, our aim was to determine a preference scale for each insect species and the variables on which these preferences were based. Therefore, we selected trees of L. alpina and L. obliqua, measured several properties such as cellulose content and recorded which leaves were eaten. As a result, we determined that the three species of insects feed on both host plants but prefer the leaves of L. obliqua, with cellulose content being the main determining factor for their decisions. However, in the case of P. arda, there was a positive relationship between cellulose and host plant preference, whereas there was an opposite relationship for the weevils. We conclude that during feeding selection, there are some properties of the leaves that have a more important role than others and that the same property does not exert the same behavioural response in all folivorous insects.
Vespula germanica is a social wasp and an opportunistic predator. While foraging, these wasps learn and integrate different kinds of cues. They have successfully invaded many parts of the world, including native Nothofagus and Lophozonia forests located in the Andean-Patagonian region, where they forage on native arthropods. Perzelia arda, a lepidopteron defoliator of Lophozonia obliqua, uses the foliage to hide in and feed on. The purpose of this work is to study whether V. germanica use olfactory cues when foraging on P. arda. To do this, we used a Y-tube olfactometer and established three treatments to compare pairs of all combinations of stimuli (larvae, leaves with larval traces, and leaves without larval traces) and controls. Data were analysed via two developed models that showed decisions made by V. germanica and allowed to establish a scale of preferences between the stimuli. The analysis demonstrates that V. germanica wasps choose P. arda as larval prey and are capable of discriminating between the offered stimuli (deviance information criterion (DIC) null model = 873.97; DIC simple model = 84.5, n = 152). According to the preference scale, V. germanica preferred leaves with traces of larvae, suggesting its ability to associate these traces with the presence of the prey. This may be because, under natural conditions, larvae are never exposed outside their shelters of leaves and therefore V. germanica uses indirect signals. The presence of V. germanica foraging on P. arda highlights the flexible foraging behaviour of this wasp which may also act as a positive biological control, reducing lepidopteran populations.
BioOne Complete (complete.BioOne.org) is a full-text database of 200 subscribed and open-access titles in the biological, ecological, and environmental sciences published by nonprofit societies, associations, museums, institutions, and presses.
The aim of this work was to evaluate the ash toxicity from the Puyehue-Cordón Caulle volcanic complex on the survival of two Orthopteran species: the grasshoper Dichroplus vittigerum and the green locust Brugilis sp. Two grain size were used to evaluate the effect of volcanic eruption on these insects. Chemical analyses from this eruption proved that the ashes were very abrasive and predominantly composed of silica shards (SiO 2 ) and aluminia (Al 2 O 3 ), two substances with insecticidal properties. In northern Patagonia, both orthopteran species are polyphagous chewers on grasses and dicots. The laboratory data showed that sustained exposure to volcanic ash induced mortality in adult grasshoppers. Survival of D. vittigerum significantly decreased once exposed to the two ash granulometries. In turn, Brugilis sp. survival was significantly reduced when exposed to fine grain ashes. These results suggest that the onset of the volcanic eruption with the consequent suspension of the pyroclastic material in the air might negatively impacted these orthopteran due to the mortality of adults. The ash from the Puyehue-Cordón Caulle volcanic complex could be compared to the application of non-persistent and broad spectrum insecticide, causing a temporary reduction in orthopteran populations.
Environmental temperature may cause changes in the physiology and feeding behaviour of herbivorous insects and, consequently, in the damage they can cause. In the Andean Patagonian forest, an eco-region dominated by trees of the Nothofagaceae family, it is common to find the leaf-tying larvae Perzelia arda consuming seeds and leaves of several species of Nothofagus genus. The pattern of damage caused by P. arda in these forests varies from year to year and even within seasons. We hypothesise that this phenomenon may be related to an increase in the ambient temperature of this region. The purpose of this work was to determine the host plant preferences of P. arda among four species of Nothofagus genus and to evaluate whether temperature influences the feeding behaviour of the larvae. We first evaluated the food preferences of P. arda by means of twochoice tests, using leaves of N. alpina, N. obliqua, N. antarctica and N. pumilio as stimuli. Secondly, we evaluated the effect of three levels of temperature on herbivory. Our results demonstrated that P. arda feed on and equally choose the four species of host plants studied. Temperature influenced the feeding behaviour of the larvae; high levels of consumption of N. obliqua occurred at 6°C and differed for the other host plant suggesting that consumption also depends on the type of food resource. In conclusion, the feeding behaviour of P. arda depends on a complex interaction between host plant and abiotic conditions. Further studies are required for a better understanding about the use of resources by this native insect, as well as the ecological consequences.
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