Leaf Chewers Research Articles

Oral pathology patterns in late farmers of the Central Andes: A comparative perspective between coastal and highland populations

Aiming at future comparisons with earlier hunter-gatherers or transitional populations, this paper intends to characterize and describe the oral pathology pattern of late agriculturalists from Central Andes dating to the Late Intermediate Period (LIP) and Inca periods (1000–1532 CE), and identify differences and/or similarities between coastal and highland populations. Although the botanical inventories of the LIP suggest carbohydrate-rich diets and similar components, it has been hypothesized that coastal and highland populations had, nevertheless, substantially different oral pathology patterns. We evaluated 14 indicators of oral pathology from Los Pinos (n=200) and Armatambo (n=25) sites in the Central Coast and two chronological phases from Laguna de los Cóndores site (LC-Inca, n=23; and LC-LIP, n=55), in the Peruvian northern highlands. The results showed a recurrent pattern of oral pathologies characterized by cervical caries (above 30%), extra-occlusal caries (above 60%), high rates of gross-gross caries, high frequency of ante mortem tooth loss, and signals of periodontal disease among these four populations. The diets of the coast were slightly more abrasive than those of the highlands. Oral pathology patterns were compatible with a slightly more cariogenic diet in the coast than in the highlands. In all four populations, those patterns were modulated by other common factors such as consumption of fermented drinks (maize beer – chicha) and the coca leaf chewing habit.

Tree species richness attenuates the positive relationship between mutualistic ant-hemipteran interactions and leaf chewer herbivory.

Interactions across trophic levels influence plant diversity effects on ecosystem functions, but the complexity of these interactions remains poorly explored. For example, the interplay between different interactions (e.g. mutualism, predation) might be an important moderator of biodiversity-ecosystem function relationships. We tested for relationships between trophobioses (facultative ant-hemipteran mutualism) and leaf chewer herbivory in a subtropical forest biodiversity experiment. We analysed trophobiosis and herbivory data of more than 10 000 trees along a tree species richness gradient. Against expectations, chewing damage was higher on trees with trophobioses. However, the net positive relationship between trophobioses and overall herbivory depended on tree species richness, being most pronounced at low richness. Our results point to indirect, positive effects of ant-tended sap suckers on leaf chewers, potentially by altering plant defences. Direct antagonistic relationships of trophobiotic ants and leaf-chewing herbivores-frequently reported to drive community-wide effects of trophobioses in other ecosystems-seemed less relevant. However, antagonistic interactions likely contributed to the attenuating effect of tree species richness, because trophobiotic ant and herbivore communities changed from monocultures to species-rich mixtures. Our findings, therefore, suggest that biodiversity loss might lead to complex changes in higher trophic level effects on ecosystem functions, mediated by both trophic and non-trophic interactions.

Seasonal and diel variations in the activity of canopy insect herbivores differ between deciduous and evergreen plant species in a tropical dry forest

This study evaluated whether herbivorous insects can be expected to have particular adaptations to withstand the harsh dry season in tropical dry forests (TDFs). We specifically investigated a possible escape in space, with herbivorous insects moving to the few evergreen trees that occur in this ecosystem; and escape in time, with herbivores presenting an increased nocturnal rather than diurnal activity during the dry season. We determined the variation in the free-feeding herbivorous insects (sap-sucking and leaf chewing) between seasons (beginning and middle of both rainy and dry seasons), plant phenological groups (deciduous and evergreen trees) and diel period (diurnal and nocturnal) in a Brazilian TDF. We sampled a total of 5827 insect herbivores in 72 flight-interception traps. Contrary to our expectations, we found a greater herbivore diversity during the dry season, with low species overlap among seasons. In the dry season, evergreen trees supported greater richness and abundance of herbivores as compared to deciduous trees. Insects were also more active at night during the dry season, but no diel differences in insect abundance were detected during the rainy season. These results indicate that the strategies used by insect herbivores to withstand the severe climatic conditions of TDFs during the dry season include both small-scale escape in space and time, with evergreen trees playing a key role in maintaining resident insect herbivore populations in TDFs. Relatively more nocturnal activity during the dry season may be related to the avoidance of harsh climatic conditions during the day. We suggest that the few evergreen tree species occurring in the TDF landscape should be especially targeted for protection in this threatened ecosystem, given their importance for insect conservation.

Plant‐mediated species networks: the modulating role of herbivore density

1. When herbivores of distinct feeding guilds, such as phloem feeders and leaf chewers, interact, the outcome of these interactions often shows facilitation. However, whether this facilitation turns into competition at stronger herbivory pressure remains unknown.2. Using an integrative approach that links ecological processes (behavioural choices of insects) with physiological plant mechanisms (nutrient and phytohormone levels) for the wild crucifer Brassica nigra (L.) Koch., this study evaluates preferences of leaf chewers for plants previously infested with several densities of the specialist aphid Brevicoryne brassicae L. (Hemiptera, Aphididae). As leaf chewers, four species of caterpillars (Lepidoptera) were selected that differ in their degree of specialisation in crucifers.3. These results show that, whereas at low and medium aphid densities caterpillars displayed a preference for aphid‐infested plants or no preference, at high aphid infestation density, all four species of caterpillar preferred uninfested plants, with a significant difference for Pieris rapae and Mamestra brassicae.4. In contrast to our expectation, the consistent preference for uninfested plants at a high aphid density could not be associated with a decrease in plant nutrition. However, while jasmonate concentrations [i.e. 12‐oxo‐phytodienoic acid and jasmonic acid (JA)] at medium aphid‐density infestation decreased compared with low levels of infestation, at high infestation level, the jasmonates JA as well as JA conjugated with the amino acid isoleucine were present at higher levels compared with low‐infestation treatments.5. This work provides evidence that positive interactions observed in herbivore communities can be transient, leading to negative interactions mediated by changes in plant defences rather than in plant nutrition.

Phylogenetic composition of host plant communities drives plant-herbivore food web structure.

Insects tend to feed on related hosts. The phylogenetic composition of host plant communities thus plays a prominent role in determining insect specialization, food web structure, and diversity. Previous studies showed a high preference of insect herbivores for congeneric and confamilial hosts suggesting that some levels of host plant relationships may play more prominent role that others. We aim to quantify the effects of host phylogeny on the structure of quantitative plant-herbivore food webs. Further, we identify specific patterns in three insect guilds with different life histories and discuss the role of host plant phylogeny in maintaining their diversity. We studied herbivore assemblages in three temperate forests in Japan and the Czech Republic. Sampling from a canopy crane, a cherry picker and felled trees allowed a complete census of plant-herbivore interactions within three 0·1ha plots for leaf chewing larvae, miners, and gallers. We analyzed the effects of host phylogeny by comparing the observed food webs with randomized models of host selection. Larval leaf chewers exhibited high generality at all three sites, whereas gallers and miners were almost exclusively monophagous. Leaf chewer generality dropped rapidly when older host lineages (5-80myr) were collated into a single lineage but only decreased slightly when the most closely related congeneric hosts were collated. This shows that leaf chewer generality has been maintained by feeding on confamilial hosts while only a few herbivores were shared between more distant plant lineages and, surprisingly, between some congeneric hosts. In contrast, miner and galler generality was maintained mainly by the terminal nodes of the host phylogeny and dropped immediately after collating congeneric hosts into single lineages. We show that not all levels of host plant phylogeny are equal in their effect on structuring plant-herbivore food webs. In the case of generalist guilds, it is the phylogeny of deeper plant lineages that drives the food web structure whereas the terminal relationships play minor roles. In contrast, the specialization and abundance of monophagous guilds are affected mainly by the terminal parts of the plant phylogeny and do not generally reflect deeper host phylogeny.

Tree diversity increases levels of herbivore damage in a subtropical forest canopy: evidence for dietary mixing by arthropods?

Aims Plant diversity has been linked to both increasing and decreasing levels of arthropod herbivore damage in different plant communities. So far, these links have mainly been studied in grasslands or in artificial tree plantations with low species richness. Furthermore, most studies provide results from newly established experimental plant communities where trophic links are not fully established or from stands of tree saplings that have not yet developed a canopy. Here, we test how tree diversity in a species-rich subtropical forest in China with fully developed tree canopy affects levels of herbivore damage caused by different arthropod feeding guilds. Methods We established 27 plots of 30×30 m area. The plots were selected randomly but with the constraint that they had to span a large range of tree diversity as required for comparative studies in contrast to sample surveys. We recorded herbivore damage caused by arthropod feeding guilds (leaf chewers, leaf skeletonizers and sap feeders) on canopy leaves of all major tree species. Important Findings Levels of herbivore damage increased with tree species richness and tree phylogenetic diversity. These effects were most pronounced for damage caused by leaf chewers. Although the two diversity measures were highly correlated, we additionally found a significant interaction between them, whereby species richness increased herbivory mostly at low levels of phylogenetic diversity. Tree species with the lowest proportion of canopy leaf biomass in a plot tended to suffer the highest levels of herbivore damage, which is in contrast to expectations based on the resource concentration hypothesis. Our results are in agreement with expectations of the dietary mixing hypothesis where generalist herbivores with a broad spectrum of food plants benefit from increased resource diversity in tree species-rich forest patches.

Opposing intraspecific vs. interspecific diversity effects on herbivory and growth in subtropical experimental tree assemblages

Aims Positive plant diversity–ecosystem function relations are ultimately driven by variation in functional traits among individuals that form a community. To date, research has largely focused on the role of species diversity for ecosystem functioning. However, substantial intraspecific trait variation is common and a significant part of this variation caused by genetic differences among individuals. Here, we studied the relative importance of species diversity and seed family (SF) diversity within species for growth and herbivory in experimental subtropical tree assemblages. Methods In 2010, we set up a field experiment in subtropical China, using four species from the local species pool. Trees were raised from seeds, with seeds from the same mother tree forming an SF. We established 23 plots containing one or four species (species diversity treatment) and one or four SFs per species (SF diversity treatment). Tree growth (stem diameter, plant height and crown expansion) and herbivory (percentage leaf loss due to leaf chewers) were monitored annually from 2011 to 2013. Important findings Tree species richness promoted growth but had no effect on herbivory. In contrast, SF diversity reduced growth and increased herbivory but only so in species mixtures. Most of the observed effects were time dependent, with the largest effect found in 2013. Our results suggest that biodiversity can affect plant performance directly via tree species–species interactions, or context dependent, via potential effects on inter-trophic interactions. Two important conclusions should be drawn from our findings. Firstly, in future studies regarding biodiversity and ecosystem functioning (BEF) relationships, intraspecific genetic diversity should be given similar weight as species diversity as it has often been neglected and its effects are not well understood. Secondly, we demonstrate opposite effects of biodiversity among and within species, stressing the importance to consider the effects of multiple levels of biodiversity simultaneously.

Reading the Leaves' Palm: Leaf Traits and Herbivory along the Microclimatic Gradient of Forest Layers.

Microclimate in different positions on a host plant has strong direct effects on herbivores. But little is known about indirect effects due to changes of leaf traits. We hypothesized that herbivory increases from upper canopy to lower canopy and understory due to a combination of direct and indirect pathways. Furthermore, we hypothesized that herbivory in the understory differs between tree species in accordance with their leaf traits. We investigated herbivory by leaf chewing insects along the vertical gradient of mixed deciduous forest stands on the broad-leaved tree species Fagus sylvatica L. (European beech) with study sites located along a 140 km long transect. Additionally, we studied juvenile Acer pseudoplatanus L. (sycamore maple) and Carpinus betulus L. (hornbeam) individuals within the understory as a reference of leaf traits in the same microclimate. Lowest levels of herbivory were observed in upper canopies, where temperatures were highest. Temperature was the best predictor for insect herbivory across forest layers in our study. However, the direction was opposite to the generally known positive relationship. Herbivory also varied between the three tree species with lowest levels for F. sylvatica. Leaf carbon content was highest for F. sylvatica and probably indicates higher amounts of phenolic defense compounds. We conclude that the effect of temperature must have been indirect, whereby the expected higher herbivory was suppressed due to unfavorable leaf traits (lower nitrogen content, higher toughness and carbon content) of upper canopy leaves compared to the understory.

New Communities on Eucalypts Grown Outside Australia

The expansion of eucalypt forestry worldwide has been accompanied by accidental and deliberate introductions of Australian insects associated with eucalypts. Local insect species have also colonized introduced eucalypts in many regions. This situation provides a unique opportunity to observe the development of new insect communities across trophic levels. Here the history of Australian invaders and native colonizers on eucalypts outside Australia is reviewed from the perspective of herbivore guilds: leaf chewers, sap suckers, wood borers, gall formers, termites. Historical patterns of invasion are identified across these guilds. Very few species of Australian leaf chewers, wood borers or termites have become widespread but these guilds are proportionately high in native colonizers. In contrast, sap suckers have multiple invasive species globally with relatively fewer native colonizers. The gall former guild also has several invasive species but so far includes no native colonizers, perhaps due to their tendency to have highly specific host plant associations. Natural enemies of Australian invaders are also members of new eucalypt insect communities, partly through planned biological control programs, but the rate of accidental introductions at higher trophic levels is increasing steadily. At the same time, local natural enemies enter eucalypt communities either to form new associations with Australian invaders or to follow native colonizers into this new habitat. Australian sap suckers have attracted far more new associations than other guilds so far. Native leaf chewers have often been followed by their local natural enemies into eucalypt communities, particularly in Brazil. Generally there are fewer records relating to local natural enemies and their role in new eucalypt communities. The complexity of new eucalypt communities outside Australia is expected to increase in future.

Tree diversity promotes generalist herbivore community patterns in a young subtropical forest experiment.

Stand diversification is considered a promising management approach to increasing the multifunctionality and ecological stability of forests. However, how tree diversity affects higher trophic levels and their role in regulating forest functioning is not well explored particularly for (sub)tropical regions. We analyzed the effects of tree species richness, community composition, and functional diversity on the abundance, species richness, and beta diversity of important functional groups of herbivores and predators in a large-scale forest biodiversity experiment in south-east China. Tree species richness promoted the abundance, but not the species richness, of the dominant, generalist herbivores (especially, adult leaf chewers), probably through diet mixing effects. In contrast, tree richness did not affect the abundance of more specialized herbivores (larval leaf chewers, sap suckers) or predators (web and hunting spiders), and only increased the species richness of larval chewers. Leaf chemical diversity was unrelated to the arthropod data, and leaf morphological diversity only positively affected oligophagous herbivore and hunting spider abundance. However, richness and abundance of all arthropods showed relationships with community-weighted leaf trait means (CWM). The effects of trait diversity and CWMs probably reflect specific nutritional or habitat requirements. This is supported by the strong effects of tree species composition and CWMs on herbivore and spider beta diversity. Although specialized herbivores are generally assumed to determine herbivore effects in species-rich forests, our study suggests that generalist herbivores can be crucial for trophic interactions. Our results indicate that promoting pest control through stand diversification might require a stronger focus on identifying the best-performing tree species mixtures.

Feeding guild of non-host community members affects host-foraging efficiency of a parasitic wasp.

Interactions between predator and prey, or parasitoid and host, are shaped by trait- and density-mediated processes involving other community members. Parasitoids that lay their eggs in herbivorous insects locate their hosts through infochemicals such as herbivore-induced plant volatiles (HIPVs) and host-produced kairomones. Hosts are frequently accompanied by non-host herbivores that are unsuitable for the parasitoid. These non-hosts may interfere with host location primarily through trait-mediated processes, by their own infochemicals, and their induction of the emission of plant volatiles. Although it is known that single non-hosts can interfere with parasitoid host location, it is still unknown whether the observed effects are due to species specific characteristics or to the feeding habits of the non-host herbivores. Here we addressed whether the feeding guild of non-host herbivores differentially affects foraging of the parasitoid Cotesia glomerata for its common host, caterpillars of Pieris brassicae feeding on Brassica oleracea plants. We used different phloem-feeding and leaf-chewing non-hosts to study their effects on host location by the parasitoid when searching for host-infested plants based on HIPVs and when searching for hosts on the plant using infochemicals. To evaluate the ultimate effect of these two phases in host location, we studied parasitism efficiency of parasitoids in small plant communities under field-tent conditions. We show that leaf-chewing non-hosts primarily affected host location through trait-mediated effects via plant volatiles, whereas phloem-feeding non-hosts exerted trait-mediated effects by affecting foraging efficiency of the parasitoid on the plant. These trait-mediated effects resulted in associational susceptibility of hosts in environments with phloem feeders and associational resistance in environments with non-host leaf chewers.

Using a botanical garden to assess factors influencing the colonization of exotic woody plants by phyllophagous insects.

The adoption of exotic plants by indigenous herbivores in the region of introduction can be influenced by numerous factors. A botanical garden in Western Siberia was used to test various hypotheses on the adaptation of indigenous phyllophagous insects to exotic plants invasions, focusing on two feeding guilds, external leaf chewers and leaf miners. A total of 150 indigenous and exotic woody plant species were surveyed for insect damage, abundance and species richness. First, exotic woody plants were much less damaged by chewers and leaf miners than native plants, and the leaf miners' species richness was much lower on exotic than native plants. Second, exotic woody plants having a congeneric species in the region of introduction were more damaged by chewers and hosted a more abundant and species-rich community of leaf miners than plants without native congeneric species. Third, damage by chewers significantly increased with the frequency of planting of exotic host plants outside the botanical garden, and leaf miners' abundance and species richness significantly increased with residence time in the garden. Finally, no significant relationship was found between insect damage or abundance and the origin of the exotic plants. Besides the ecological implications of the results, this study also illustrates the potential of botanical gardens to test ecological hypotheses on biological invasions and insect-plant interactions on a large set of plant species.

Negative impact of drought stress on a generalist leaf chewer and a phloem feeder is associated with, but not explained by an increase in herbivore-induced indole glucosinolates

Plants are constantly exposed to multiple biotic and abiotic stresses, such as drought and herbivory. However, plant responses to these stresses have usually been studied in isolation. Here, we take a multidisciplinary approach addressing ecological and chemical aspects of plant responses to generalist herbivores and several intensities of drought. We hypothesize that in brassicaceous plants, the effects of drought stress on herbivores can be explained by an increase in indole glucosinolates. Four-week-old Arabidopsis thaliana plants were drought stressed for one week or watered as normal. Three types of drought stress were compared: (1) no watering for 1 week and then rewatered to saturation (low drought); (2) no watering for 1 week and then rewatered to 60% of soil water content (high drought); (3) watering every other day to 60% of soil water content (continuous drought). All three types of drought stress negatively affected both the larval mass of the leaf chewer Mamestra brassicae and the population growth of the phloem feeder Myzus persicae. This was associated with increased levels of herbivore-induced indole glucosinolates compared to infested control plants. Interestingly, the levels of total indole glucosinolates did not change in uninfested plants, except for the indole 4-methoxy-glucobrassicin that was induced by continuous drought. Two-choice experiments also showed that caterpillars of M. brassicae, but not aphids, avoided drought-stressed plants only after feeding on them, but not by visual/olfactory cues. However, on a knockout mutant blocked in the production of indole glucosinolates (cyp79B2 cyp79B3), the effect of drought on herbivore performance was similar to that on wild-type plants. The results of this study show that drought stress induced higher levels of indole glucosinolates; however, these levels were not responsible for higher resistance to generalist herbivores in drought-stressed plants.

Tree Species Composition and Harvest Intensity Affect Herbivore Density and Leaf Damage on Beech, Fagus sylvatica, in Different Landscape Contexts.

Most forests are exposed to anthropogenic management activities that affect tree species composition and natural ecosystem processes. Changes in ecosystem processes such as herbivory depend on management intensity, and on regional environmental conditions and species pools. Whereas influences of specific forest management measures have already been addressed for different herbivore taxa on a local scale, studies considering effects of different aspects of forest management across different regions are rare. We assessed the influence of tree species composition and intensity of harvesting activities on arthropod herbivores and herbivore-related damage to beech trees, Fagus sylvatica, in 48 forest plots in three regions of Germany. We found that herbivore abundance and damage to beech trees differed between regions and that – despite the regional differences - density of tree-associated arthropod taxa and herbivore damage were consistently affected by tree species composition and harvest intensity. Specifically, overall herbivore damage to beech trees increased with increasing dominance of beech trees – suggesting the action of associational resistance processes – and decreased with harvest intensity. The density of leaf chewers and mines was positively related to leaf damage, and several arthropod groups responded to beech dominance and harvest intensity. The distribution of damage patterns was consistent with a vertical shift of herbivores to higher crown layers during the season and with higher beech dominance. By linking quantitative data on arthropod herbivore abundance and herbivory with tree species composition and harvesting activity in a wide variety of beech forests, our study helps to better understand the influence of forest management on interactions between a naturally dominant deciduous forest tree and arthropod herbivores.

Latitudinal variation in herbivory: influences of climatic drivers, herbivore identity and natural enemies

Although a number of investigations have concluded that lower latitudes are associated with increases in herbivore abundance and plant damage, the generality of this pattern is still under debate. Multiple factors may explain the lack of consistency in latitude–herbivory relationships. For instance, latitudinal variation in herbivore pressure may be shaped entirely or not by climatic variables, or vary among herbivore guilds with differing life‐history traits. Additionally, the strength of top–down effects from natural enemies on herbivores might also vary geographically and influence latitude–herbivory patterns. We carried out a field study where we investigated the effects of latitude and climate on herbivory by a seed‐eating caterpillar and leaf chewers, as well as parasitism associated to the former across 30 populations of the perennial herb Ruellia nudiflora (Acanthaceae). These populations were distributed along a 5° latitudinal gradient from northern Yucatan (Mexico) to southern Belize, representing one‐third of the species' latitudinal distribution and the entirety and one‐third of the precipitation and temperature gradient of this species' distribution (respectively). We found opposing latitudinal gradients of seed herbivory and leaf herbivory, and this difference appeared to be mediated by contrasting effects of climate on each guild. Specifically, univariate regressions showed that seed herbivory increased at higher latitudes and with colder temperatures, while leaf herbivory increased toward the equator and with wetter conditions. Multiple regressions including temperature, precipitation and latitude only found significant effects of temperature for seed herbivory and latitude for leaf herbivory. Accordingly, that latitudinal variation in seed herbivory appears to be driven predominantly by variation in temperature whereas latitudinal variation in leaf herbivory was apparently driven by other unexplored correlates of latitude. Parasitism did not exhibit variation with latitude or climatic factors. Overall, these findings underscore that the factors driving latitudinal clines in herbivory might vary even among herbivore species coexisting on the same host plant.

Association Between Serum C- Reactive Protein With Migraine: A Case Control Study

Objective: The present case-control study was undertaken to find the association between serum level of CRP and attack of migraine.
 Methods: The study was carried out at the Headache Clinic and Outpatient Department of Neurology, Bangabandhu Sheikh Mujib Medical University (BSMMU), Dhaka over a period of 2 years from January 2010 to December 2011. Migraine patients attending at the above mentioned places were enrolled as cases, while apparently healthy attendants of cases and other healthy persons, who did not have any history of migraine, were included as control. Based on predefined enrollment criteria, a total of 163 subjects were included in the study. Of them 87 were cases and 76 were controls. The serum levels of CRP of both cases and controls were measured and a serum level of > 6 mg/L was considered as raised/ elevated CRP. Levels of CRP were compared between groups (case and control) using appropriate statistical tests.
 Result: The findings of the study showed that the age and sex distribution of case and control groups were almost comparable. The behavioral factors like food or smoking habit and tobacco leaf chewing had no difference between the groups. Over 20% of migraine patients had abnormally high CRP as compared to 7.9% in the control group (p = 0.021). The migraine patients were 3(95% CI = 1.1 - 8.1) times more likely to be associated with raised CRP (> 6 mg/L) than their healthy counterparts. There were 7 migraine patients with aura and 80 without aura. The level of CRP was not found to be associated with type of migraine (with or without aura) (p = 0.960).
 Conclusion: Every one in five patients exhibits abnormally high CRP. The level of CRP does not vary whether the migraine is being associated with or without aura. The migraineurs carry higher risk of developing elevated CRP than their normal counterparts.
 Bangladesh Journal of Neuroscience 2015; Vol. 31 (1): 1-8

Comparison of invertebrate herbivores on native and non‐native Senecio species: Implications for the enemy release hypothesis

AbstractThe enemy release hypothesis posits that non‐native plant species may gain a competitive advantage over their native counterparts because they are liberated from co‐evolved natural enemies from their native area. The phylogenetic relationship between a non‐native plant and the native community may be important for understanding the success of some non‐native plants, because host switching by insect herbivores is more likely to occur between closely related species. We tested the enemy release hypothesis by comparing leaf damage and herbivorous insect assemblages on the invasive species Senecio madagascariensis Poir. to that on nine congeneric species, of which five are native to the study area, and four are non‐native but considered non‐invasive. Non‐native species had less leaf damage than natives overall, but we found no significant differences in the abundance, richness and Shannon diversity of herbivores between native and non‐native Senecio L. species. The herbivore assemblage and percentage abundance of herbivore guilds differed among all Senecio species, but patterns were not related to whether the species was native or not. Species‐level differences indicate that S. madagascariensis may have a greater proportion of generalist insect damage (represented by phytophagous leaf chewers) than the other Senecio species. Within a plant genus, escape from natural enemies may not be a sufficient explanation for why some non‐native species become more invasive than others.

Relationships among plant genetics, phytochemistry and herbivory patterns in Quercus castanea across a fragmented landscape

AbstractHerbivorous insects respond to the chemical variation of their host plants which, in turn, usually has a genetic component. Therefore, it is expected that individual host plants with similar genotypes will have similar secondary chemistries and herbivore communities. However, natural or anthropogenic environmental variation can also influence secondary chemistry and herbivore abundance and composition. Here, we determined the relationships among plant genetics, phytochemistry, and herbivory levels by leaf chewers and miners in the red oak Quercus castanea, across a fragmented landscape. Ten oak individuals were sampled at each of four sites in the Cuitzeo basin, central Mexico. Two sites were small and fragmented forest patches and two were large and continuous patches. Individuals were genotyped with six nuclear microsatellites, and analyzed chemically to determine foliar concentrations of water, total nonstructural carbohydrates, and secondary compounds. Damage by leaf chewers was higher in the small fragments than in the large fragments. Mantel tests indicated significant correlations of the genetic distance among individuals with their chemical similitude, and also of chemical similitude with damage levels by leaf miners, but not with damage by folivores. There was no direct relationship between genetic distance and herbivory levels by any of the two insect guilds. Our results suggest that variation in concentration of secondary metabolites in Q. castanea has a genetic component and that plant chemistry acts as an intermediate link between plant genes and the community of associated herbivores. However, this effect was only apparent for herbivory by leaf miners, probably because these insects interact more intimately with the host, while free‐living leaf chewers may be more responsive to environmental variation.

Taxonomic and Functional Structure of Phytophagous Insect Communities Associated with Grain Amaranth.

Amaranthus are worldwide attacked mainly by leaf chewers and sucker insects. Stem borers and leaf miners follow in importance, while minor herbivores are leaf rollers, folders, and rasping-sucking insects. The herbivorous community observed on Amaranthus spp. in Argentina was consistent with the information reported worldwide both in guild composition and order proportion. Amaranth plants had a higher number of phytophagous species in their native rather than in its introduced range. Occurrence of insect guilds differed in space and time. The highest density of leaf chewers was observed shortly after the emergence of plants, while higher density of borer and sucker insects coincided with reproductive stages of the crop. The sucking guild was observed mainly at panicles, while the insects within the leaf chewer group were registered in both leaves (92.6%, n = 746 adults) and inflorescences (7.4%). The borer guild was also recorded in stems and inflorescences; however, the density of larvae in stems was about four times as high as the density observed in panicles (n = 137 larvae).

Importance of Secondary Metabolites for Leaf Beetles (Coleoptera: Chrysomelidae)

Leaf beetles (Chrysomelidae) are one of the most diverse families of herbivorous insects. Many of them are important agricultural pests and cause remarkable loss of crop and money as well. Plant leaves and roots are primary food source of both larva and adults of leaf beetles. Plants produce many secondary metabolites in reaction to herbivore insects. It is a well-known phenomenon that quantity and variety of secondary metabolites in plant leaves may change in response to insect attacks. Herbivore insects have to deal with such defensive secondary chemicals and overcome either by detoxifying or storing them. Accordingly, many specialist herbivores coevolved with their host plant. Certain phenolic glycosides may reduce leaf beetle feeding. Condensed tannins are anti-herbivore defenses against leaf chewing beetles, including leaf beetles. Flavonoid compounds are feeding deterrents for many flea leaf beetles. Cinnamic acid derivatives are other known feeding deterrents for leaf beetles. Secondary metabolites quantity and nutritional quality of host plants are not only important for feeding but also for providing enemy-free space and suitable oviposition sites.