Vertebrate Herbivores Research Articles

Gut microbial diversity and stabilizing functions enhance the plateau adaptability of Tibetan wild ass (Equus kiang).

Interactions between gut microbiota not only regulate physical health, but also form a vital bridge between the environment and the host, thus helping the host to better adapt to the environment. The improvement of modern molecular sequencing techniques enables in‐depth investigations of the gut microbiota of vertebrate herbivores without harming them. By sequencing the 16S rRNA V4‐V5 region of the gut microbiota of both the captive and wild kiang in winter and summer, the diversity and function of the microbiota could be compared. The reasons for observed differences were discussed. The results showed that the dominant phyla of the kiang were Bacteroidetes and Firmicutes, and the structure and abundance of the gut microbiota differed significantly between seasons and environments. However, the relatively stable function of the gut microbiota supplies the host with increased adaptability to the environment. The diversity of the intestinal flora of the kiang is relatively low in captivity, which increases their risk to catch diseases to some extent. Therefore, importance should be attached to the impact of captivity on wildlife.

Invasive plant Arundo donax alters habitat use by carnivores

Invasive plants can have significant negative interactions with native flora and fauna, often decreasing the abundance and diversity of native plants and invertebrate and vertebrate herbivores. Less is known, however, about how invasive plants influence higher-order consumers, such as carnivores. Arundo donax is a globally distributed invasive grass that forms dense monotypic stands in the habitats where it successfully establishes. This study investigated the influence of Arundo invasion on mammal assemblages in California’s Santa Clara River Valley. Specifically, we aimed to determine whether Arundo alters habitat use for carnivores, and if so, assess the possible mechanisms driving these differences. We used remote cameras to evaluate carnivore habitat use and model occupancy, and live traps and remote cameras to assay abundance of small mammals, common prey of these larger predators. We found that detections of all carnivores were significantly lower in Arundo-dominated habitat patches, suggesting decreased preference for Arundo habitat. This was reflected in the occupancy model, which found the highest probability of coyote and bobcat habitat use in native patches and lowest in Arundo; however, habitat did not seem to be as important of a predictor as in the pooled species results. Small mammal abundance was similar if not higher in Arundo, suggesting the possibility of Arundo acting as a refuge for prey species and altered predator–prey dynamics in Arundo-dominated patches. This study improves our knowledge of the often-complex ways that invasive plants, like Arundo, influence the ecology and behavior of faunal communities in invaded ecosystems.

Multiple Dose Pharmacokinetic Models Predict Bioavailability of Toxins in Vertebrate Herbivores.

In this paper, compartmental pharmacokinetic models are built to predict the concentration of toxic phytochemical in the gastrointestinal tract and blood following oral intake by an individual vertebrate herbivore. The existing single and multiple dose pharmacokinetic models are extended by inclusion of impulsive differential equations which account for an excretion factor whereby unchanged toxins are excreted in the feces due to gastrointestinal mobility. An index α is defined to measure the fraction of bioavailability attributed to the excretion factor of gastrointestinal motility. Sensitivity analysis was conducted and suggests, for any toxin, the bioavailability index α depends mostly on absorption rate of toxin from gastrointestinal tract into the blood, frequency of elimination due to gastrointestinal motility, and the frequency of toxin intake, under the model assumptions.

Herbivory Effects on <i>Ephedra</i> spp. in the Chihuahuan Desert

Two species of Ephedra: E. trifurca and E. torreyana inhabit shrub and grassland habitats in the northern Chihuahuan Desert. E. torreyana is limited to black grama grasslands where grasses are taller than the shrub. E. torreyana is heavily browsed by vertebrates and E. trifurca is browsed during some years. We established an experiment with cylindrical exclosures that excluded rabbits and rodents, rabbits but accessible to rodents, for comparison with E. torreyana plants available to all herbivores. Plants accessible to all vertebrate herbivores were significantly smaller with shorter stem lengths than plants in exclosures. We concluded that E. torreyana in black grama grassland are largely hidden from vertebrate herbivores and that intense herbivory reflects the degraded state of the study site which makes the E. torreyana evergreen shrubs apparent to vertebrates.

Below‐ground responses to insect herbivory in ecosystems with woody plant canopies: A meta‐analysis

Abstract Insect herbivory can have important consequences for the functioning of terrestrial ecosystems. Despite a growing recognition of the role of herbivores in above‐ground–below‐ground interactions, our current understanding is mainly restricted to studies of vertebrates in grassland and tundra ecosystems, while ecosystems with tree‐like canopies (termed forests below) and invertebrates remain understudied. Here, we assess the current state of knowledge of one key aspect of plant–herbivore interactions by conducting a meta‐analysis of the peer‐reviewed literature on the below‐ground consequences of above‐ground insect herbivory in forest ecosystems. Main results are reported as aggregated relative effect sizes (Cohen's d). We find that above‐ground insect herbivory reduced below‐ground carbon (C) allocation by plants to roots (−0.56) and root exudation (−0.85), causing shifts in root–symbiont communities, for example, a decrease (−0.67) in the abundance of ectomycorrhizal fungi. Microbial decomposer abundances showed no significant responses, while soil faunal abundances increased (0.50). C and nitrogen (N) mineralization rates (C: 0.48, N: 0.48) along with nutrient leaching (C: 0.30, N: 0.77) increased, with a stronger response to outbreak relative to background insect densities. The negative responses increased in strength in colder and dryer biomes while positive responses were reinforced in warmer and wetter biomes, thus extending previously shown effects for vertebrate herbivores to also include insect herbivory. The positive response by soil fauna to insect herbivory was the notable exception. This may be associated with the limited physical soil disturbance caused by insects compared to ungulates. Furthermore, we identified an under‐representation in the literature of large areas of boreal and tropical biomes calling for research priorities to fill these knowledge gaps. We present three recommendations for future research: addressing (a) biological drivers of biogeochemistry and response pathways, (b) knowledge gap from boreal and tropical forests, and (c) heterogeneity of herbivore disturbances. Synthesis. Insect herbivores significantly accelerate soil C and N cycling during outbreaks in forest ecosystems, but we lack knowledge on the underlying biological drivers. Overall, below‐ground responses to insect herbivory are similar to vertebrate herbivory responses, which may simplify implementing herbivory effects into ecosystem models. Nonetheless, we identify a few important differences and general knowledge gaps on which we base recommendations for future research.

Moose effects on soil temperatures, tree canopies, and understory vegetation: a path analysis

AbstractLarge vertebrate herbivores are ubiquitous and increasingly numerous in boreal forests where they are known to influence ecosystems in many ways. However, separating the direct effects of herbivores from their indirect effects on plant communities via forest structural changes and microclimate remains unexplored, limiting the predictability of herbivore impacts. We used an exploratory path analysis approach to investigate potential mechanistic pathways between herbivore removal, forest canopy cover, soil temperature, and understory vegetation dynamics. Moose (Alces alces) were excluded from 15 recently clear‐cut boreal forest sites in Norway using 20 × 20 m fences with paired open un‐fenced plots. Soil temperatures and vegetation data were recorded after eight years (total n = 98). Moose exclusion reduced summer soil temperatures but not winter soil temperatures, leading to no net effect over 344 d. Path analysis showed a strong positive effect of moose exclusion on canopy cover and subsequently reduced summer soil temperatures. There was some support for an increase in the dominant grass species Avenella flexuosa with increasing summer soil temperatures, but neither temperature, canopy cover, nor A. flexuosa had clear links to plant species densities. Moose exclusion directly increased herb biomass and shifted understory species composition toward less shrub‐dominated communities, resulting in increased species densities of vascular plants and bryophytes. Our results indicate that in early‐successional boreal forests, direct effects of large herbivores on plant communities are clearly visible, and indirect effects are detectable but much weaker.

Food and habitat provisions jointly determine competitive and facilitative interactions among distantly related herbivores

Abstract Interactions between distantly related herbivores exert powerful influences on ecosystems, but most studies to date have only considered unidirectional effects. Few have simultaneously examined the mutual effects that vertebrate herbivores and insect herbivores have on one another. We conducted a set of manipulative experiments to evaluate the potential competition and facilitation between two pairs of distantly related herbivore taxa: an insect caterpillar (Gynaephora alpherakii) and two large vertebrate herbivores, yak (Bos grunniens) and Tibetan sheep (Ovis aries tibetica). We found that these large herbivores consistently increased the density of caterpillars likely by improving the habitat for caterpillars. The caterpillars, in turn, decreased yak but increased Tibetan sheep foraging time and intake bites by differently changing available food resources of the two large herbivores. Diet preferences of herbivores modified the habitat and food resources, thereby causing a diet‐mediated competition between yak and caterpillars, and facilitation between sheep and caterpillars. The vertebrate herbivores non‐feeding upon Lamiophlomis rotata and Gentiana straminea, the caterpillars preferred habitat, increased densities of the two plant species, thus favouring the caterpillars. In turn, the caterpillar preference for Kobresia pygmaea significantly reduced food resources for yak, while promoting food resources (multiple forbs) for sheep. Synthesis. Our study indicates that two different mechanisms (the changes in habitat and food availability) induced by herbivore foraging jointly determine competitive and facilitative interactions between distantly related herbivore species. We also suggest that examining the bi‐directional effects between herbivores offers a better understanding of competition and facilitation in terrestrial animal communities.

Multiple colonizations of the Pacific by Peperomia (Piperaceae): Complex patterns of long‐distance dispersal and parallel radiations on the Hawaiian Islands

AbstractAimOur understanding of the biogeographical history of the flora of the Pacific is hampered by limited geographical sampling, and the evolutionary history for many species‐rich lineages in the Pacific remain poorly known. Here, we examine the spatial and temporal context of the evolutionary history of Peperomia (Piperaceae) in the Pacific, where it is one of the largest angiosperm groups (c. 100 species) and a ubiquitous part of wet forests. We focus on the native taxa on the Hawaiian Islands (25 species) where they represent a hotspot of diversity for the genus in the Pacific.LocationIslands of the Pacific, with focus on the Hawaiian Islands.TaxonPeperomia (Piperaceae).MethodsPhylogenetic analyses of Pacific taxa were performed using full chloroplast genomes for 115 accessions of Peperomia, including 42 Pacific species (∼40% of the diversity in the Pacific). To examine the timing of colonization and diversification of Peperomia in the Pacific, we implemented a Bayesian relaxed‐clock model for the Piperales, using multiple fossils in a fossilized‐birth death framework.ResultsThe Hawaiian Islands (and the Pacific) have been colonized by four separate Peperomia lineages originating from the Neotropics. Endemic Hawaiian taxa are derived from independent radiations from two different ancestors, and represent the first documented case of multiple radiations among species‐rich plant groups on the Hawaiian Islands. While extant Peperomia originated in the Eocene (∼54.2 million years old, Ma), most lineages in the Pacific are young and originated in the Pliocene (5.33–2.58 Ma), consistent with the ages of the major islands in the Pacific.Main conclusionsThe multiple colonizations and radiations of Peperomia in the Pacific attest to the efficacy of their epizoochorous mode of dispersal. The diversification of two clades in parallel on the Hawaiian Islands suggests that the effect of niche‐preemption from the earlier‐arriving clade on the diversification of the later‐arriving lineage has been weak. Ecological release due to the paucity of large native vertebrate herbivores and the relatively open understoreys of Hawaiian wet forests may have allowed both lineages to flourish, and suggests a context‐dependent role of niche‐preemption in the assembly of oceanic island biotas.

Role of seed size and relative abundance in conspecific negative distance-dependent seedling mortality for eight tree species in a temperate forest

Conspecific negative distance dependent seedling mortality and negative density-dependent seedling survival (CNDD) are among the most important mechanisms of species diversity maintenance. Recent research has demonstrated that CNDD is greater for species with abundant seeds, due mainly to attack by density-dependent pathogens. If seed number were correlated negatively with seed size, species with smaller seeds would exhibit much greater negative CNDD. We explored whether CNDD is affected by seed size. We evaluated the strength of CNDD as a log response ratio of the probability of mortality among seedlings at conspecific and heterospecific sites and at high and low densities as functions of distance and density, respectively, in a seed-sowing experiment using eight hardwood species in a temperate forest in northern Japan. As a function of distance, CNDD attributable to pathogens was correlated positively with seed mass at low density, but not at high density, whereas seed mass was not correlated with CNDD attributable to invertebrate or vertebrate herbivores. As a function of density, seed mass was not correlated with CNDD attributable to pathogens or invertebrate or vertebrate herbivores. The ability of large-seeded species to better tolerate CNDD suggests a novel mechanism through which seed size may contribute to CNDD variation and promote species coexistence due to distance-dependent attack by pathogens, particularly those bearing leaf diseases.

Lack of fire and insect herbivory constrain recruitment in a rare legume from Western Australia

AbstractWe investigated factors influencing recruitment in the rare endemic shrub Acacia insolita subsp. recurva (Fabaceae) from the heavily cleared south‐west of Western Australia. We examined annual seed production over 4 years, including the impact of herbivory on reproductive output. Conversion of bud to fruit was low (overall 0.02%). The lack of significant difference in canopy dimensions between caged and uncaged plants suggested that vertebrate herbivore grazing was negligible, but invertebrate predation had a negative impact on seed production (loss of >80% of fruiting potential). Soil cores determined the presence of soil‐stored seeds and an experimental burn confirmed that plants are fire‐killed and can regenerate from the seed bank. This seed reserve was found to contain <5 seeds m−2, and both freshly collected seeds and seeds retrieved from the soil had high viability (99% vs. 91%) when subjected to a germination test. Seedling recruitment 29 months post‐fire resulted in a ratio of three seedlings for every adult killed by fire. We also compared reproductive success in this rare Acacia with its common conspecific and although the rare species produced more flowers, the success of flowering did not translate into better fruit set. We conclude that insect damage to reproductive branchlets and lack of appropriate disturbance are major factors constraining recruitment. Active site management may be required for the continued persistence of this fire‐dependent legume.

Trophic interactions and abiotic factors drive functional and phylogenetic structure of vertebrate herbivore communities across the Arctic tundra biome

Communities are assembled from species that evolve or colonise a given geographic region, and persist in the face of abiotic conditions and interactions with other species. The evolutionary and colonisation histories of communities are characterised by phylogenetic diversity, while functional diversity is indicative of abiotic and biotic conditions. The relationship between functional and phylogenetic diversity infers whether species functional traits are divergent (differing between related species) or convergent (similar among distantly related species). Biotic interactions and abiotic conditions are known to influence macroecological patterns in species richness, but how functional and phylogenetic diversity of guilds vary with biotic factors, and the relative importance of biotic drivers in relation to geographic and abiotic drivers is unknown. In this study, we test whether geographic, abiotic or biotic factors drive biome‐scale spatial patterns of functional and phylogenetic diversity and functional convergence in vertebrate herbivores across the Arctic tundra biome. We found that functional and phylogenetic diversity both peaked in the western North American Arctic, and that spatial patterns in both were best predicted by trophic interactions, namely vegetation productivity and predator diversity, as well as climatic severity. Our results show that both bottom–up and top–down trophic interactions, as well as winter temperatures, drive the functional and phylogenetic structure of Arctic vertebrate herbivore assemblages. This has implications for changing Arctic ecosystems; under future warming and northward movement of predators potential increases in phylogenetic and functional diversity in vertebrate herbivores may occur. Our study thus demonstrates that trophic interactions can determine large‐scale functional and phylogenetic diversity just as strongly as abiotic conditions.

Vertebrate herbivory on shrub seedlings in California sage scrub: important but understudied interactions

Herbivory is poorly characterized in the endangered California sage scrub ecosystem, because previous studies were conducted only in winter and spring. To better understand vertebrate herbivore impacts, we first examined if and when vertebrate herbivores influence Artemisia californica seedling survivorship by examining differences in mortality between caged and uncaged seedlings. Then, we examined: (1) vertebrate herbivore preference of common sage scrub shrub species, and (2) which vertebrate species constitute important herbivores in the ecosystem. We found that mortality for uncaged A. californica seedlings was twice that of caged seedlings, and occurred in the summer and early fall, when previous studies in the system were not conducted. Short leaved shrubs, Artemisia californica and Eriogonum fasciculatum, were more susceptible to herbivory than broader leaved Salvia apiana and Eriodictyon trichocalyx. However, susceptibility likely depends on the herbivore assemblage, as the three main herbivore species [Sylvilagus audubonii (desert cottontail), Zonotrichia leucophrys (white-crowned sparrow; a bird, not a mammal), and Otospermophilus beecheyi (California gray squirrel)] all had different shrub preferences. Our results contrast with previous studies that suggests that native vertebrate herbivores facilitate shrub seedling survivorship by highlighting that late-season vertebrate herbivory may negatively affect shrub seedling survivorship. We demonstrate the complex but understudied role herbivores play in the sage scrub ecosystem, and highlight that further study of these key ecological interactions is warranted.

Vertebrate florivory of vascular epiphytes: the case of a bromeliad

The avoidance of vertebrate herbivory is thought to be one of the possible drivers for the evolution of epiphytism. Scarce literature suggests that epiphyte herbivory is mainly related to insect attack on reproductive structures. In a pine-oak forest we observed almost all inflorescences of an epiphytic bromeliad (Tillandsia carlos-hankii) with signs of florivory; the degree of damage suggested that vertebrate herbivores could be involved. To assess the intensity of vertebrate florivory damage we recorded the percentage of damaged individuals in a 500 m2 plots during two flowering seasons. To identify possible vertebrate herbivores, we installed 20 mixed capture stations, 10 photo-traps focused on bromeliads and analyzed stomach contents of captured vertebrates. Florivory was observed on 62% of individuals during the first flowering season and 77% on the second; and average one individual lost 41% of reproductive structures. Vertebrates associated with florivory were a bird, Icterus bullockii (Aves, Passeriformes, Icteridae), a squirrel Sciurus aureogaster (Mammalia, Rodentia, Sciuridae), and mice, Peromyscus gratus, P. levipes and P. aztecus (Mammalia, Rodentia, Cricetidae). Our results suggest that vascular epiphytes are used as opportunistic resources for small vertebrates during seasons when preferred resources are scarce.

Egg-laying decisions based on olfactory cues enhance offspring fitness in Stomoxys calcitrans L. (Diptera: Muscidae)

Selection of oviposition substrate is critical in holometabolous insects. Female stable flies, Stomoxys calcitrans, locate and select vertebrate herbivore dung in which they lay their eggs. However, the preference for vertebrate herbivore dung by S. calcitrans females, its fitness consequences for offspring, and the semiochemicals used to locate and select oviposition substrates remain unclear. Using oviposition choice tests and life table bioassays we found that gravid female S. calcitrans prefer to oviposit on donkey and sheep dung, which also improves the performance of their offspring. GC-MS analysis followed by random forest classification identified β-citronellene and carvone as the most important predictive volatile organic compounds of donkey and sheep dung, respectively. In multiple choice oviposition bioassays, S. calcitrans laid more eggs in wet sand containing β-citronellene and carvone than in other treatments. The attractiveness of these compounds was confirmed in a field trial, with traps baited with β-citronellene and carvone catching more S. calcitrans. We conclude that gravid female S. calcitrans use semiochemical cues to choose oviposition substrates that maximise offspring fitness.

The bitter end: primate avoidance of caterpillar-infested trees in a central Amazon flooded forest

Animal–plant interactions are often mediated by chemical compounds. It has been widely reported that herbivore damage to plants induces chemical defenses which may then affect subsequent interactions with both invertebrate and vertebrate herbivores. Our study investigated the effects of the interaction between larvae of an unidentified nymphalid butterfly and the tanimbuca tree (Buchenavia ochroprumna Eichl.; Combretaceae) on subsequent folivory by a primate, the golden-backed uacari (Cacajao ouakary (Spix, 1823); Pitheciidae). Primate-feeding observations, records of the extent of nymphalid – B. ochroprumna interactions, and tree distribution occurred in Jaú National Park, Amazonas State, Brazil. The values of Ivlev’s electivity index showed that C. ouakary strongly rejected trees infested by caterpillars (−0.68), whereas non-infested trees were highly selected by them (+0.84). Given this behavior, we suggest that C. ouakary may be deterred by (i) caterpillars, (ii) change in leaf chemical composition induced by caterpillars, or (iii) a combination of both.

Overcompensation for insect herbivory: a review and meta-analysis of the evidence.

Not all herbivory is detrimental to plants. In some cases, plants can compensate for herbivory, maintain growth and fitness following damage, or even overcompensate for herbivory and perform better than if left undamaged. Examples of overcompensation to vertebrate herbivory are well known, but here we review the literature for examples of reproductive overcompensation (i.e., increased production of traits associated with fitness) and increased vegetative growth (i.e., vegetative overcompensation) following insect herbivory. We used a meta-analysis to explore the effects of plant growth form, evolutionary history, herbivore feeding guild, and other plant and insect traits on the expression of reproductive and vegetative overcompensation by plants. Our literature search revealed 86 studies documenting examples of overcompensation for insect herbivory by 67 plant species representing 26 families. These plants included monocots and dicots, annuals and perennials, and woody and herbaceous plants. We also found that varied insect herbivores induce overcompensation, including 75 insect species in six orders representing 27 families and myriad feeding guilds. In our meta-analysis, we calculated 53 effect sizes from 21 publications documenting reproductive overcompensation and 89 effect sizes from 40 publications documenting vegetative overcompensation. Variation in reproductive overcompensation was seen among plant growth forms, functional groups, cultivation, herbivore feeding sites, and plant and herbivore families. Variation in vegetative overcompensation was seen among plant families, herbivore families, and latitudinal gradients. We suggest overcompensation for insect herbivory may be far more prevalent than previously thought. Additional research focusing on the mechanisms, patterns, and ecological and evolutionary consequences of overcompensation for insect herbivory is likely to provide exciting new insights into this poorly understood and largely overlooked outcome of plant-insect interactions.

Transcriptional profiling of methyl jasmonate-induced defense responses in bilberry (Vaccinium myrtillus L.)

BackgroundBilberry (Vaccinium myrtillus L.) is one of the most abundant wild berries in the Northern European ecosystems. This species plays an important ecological role as a food source for many vertebrate and invertebrate herbivores. It is also well-recognized for its bioactive compounds, particularly substances involved in natural defenses against herbivory. These defenses are known to be initiated by leaf damage (e.g. chewing by insects) and mediated by activation of the jasmonic acid (JA) signaling pathway. This pathway can be activated by exogenous application of methyl jasmonate (MeJA), the volatile derivative of JA, which is often used to stimulate plant defense responses in studies of plant-herbivore interactions at ecological, biochemical, and molecular organismal levels. As a proxy for herbivore damage, wild V. myrtillus plants were treated in the field with MeJA and changes in gene expression were compared to untreated plants.ResultsThe de novo transcriptome assembly consisted of 231,887 unigenes. Nearly 71% of the unigenes were annotated in at least one of the databases interrogated. Differentially expressed genes (DEGs), between MeJA-treated and untreated control bilberry plants were identified using DESeq. A total of 3590 DEGs were identified between the treated and control plants, with 2013 DEGs upregulated and 1577 downregulated. The majority of the DEGs identified were associated with primary and secondary metabolism pathways in plants. DEGs associated with growth (e.g. those encoding photosynthesis-related components) and reproduction (e.g. flowering control genes) were frequently down-regulated while those associated with defense (e.g. encoding enzymes involved in biosynthesis of flavonoids, lignin compounds, and deterrent/repellent volatile organic compounds) were up-regulated in the MeJA treated plants.ConclusionsEcological studies are often limited by controlled conditions to reduce the impact of environmental effects. The results from this study support the hypothesis that bilberry plants, growing in natural conditions, shift resources from growth and reproduction to defenses while in a MeJA-induced state, as when under insect attack. This study highlights the occurrence of this trade-off at the transcriptional level in a realistic field scenario and supports published field observations wherein plant growth is retarded and defenses are upregulated.

Leaf nutrients, not specific leaf area, are consistent indicators of elevated nutrient inputs.

Leaf traits are frequently measured in ecology to provide a 'common currency' for predicting how anthropogenic pressures impact ecosystem function. Here, we test whether leaf traits consistently respond to experimental treatments across 27 globally distributed grassland sites across 4 continents. We find that specific leaf area (leaf area per unit mass)-a commonly measured morphological trait inferring shifts between plant growth strategies-did not respond to up to four years of soil nutrient additions. Leaf nitrogen, phosphorus and potassium concentrations increased in response to the addition of each respective soil nutrient. We found few significant changes in leaf traits when vertebrate herbivores were excluded in the short-term. Leaf nitrogen and potassium concentrations were positively correlated with species turnover, suggesting that interspecific trait variation was a significant predictor of leaf nitrogen and potassium, but not of leaf phosphorus concentration. Climatic conditions and pretreatment soil nutrient levels also accounted for significant amounts of variation in the leaf traits measured. Overall, we find that leaf morphological traits, such as specific leaf area, are not appropriate indicators of plant response to anthropogenic perturbations in grasslands.

The effect of sideroxylonal-A on feeding of steelblue sawfly, Perga affinis affinis Kirby (Hymenoptera : Pergidae), larvae

Plant secondary metabolites can affect insect feeding but responses are species-specific. Sideroxylonal-A (a formylated phloroglucinol) has been shown to inhibit feeding in several vertebrate and invertebrate herbivores. To investigate whether sideroxylonal-A affected feeding in sawfly larvae, Perga affinis affinis, we fed larvae eucalypt leaves containing various concentrations of sideroxylonal-A, and measured frass production as an indicator of consumption. We found that: (1) at least 80% of the sideroxylonal-A ingested by larvae was stored in the diverticulum; (2) less than 1% was excreted in frass; (3) feeding was unaffected by the concentration of sideroxylonal-A; and (4) larvae produced more frass on natal host leaves than on non-natal host leaves.

Total grazing pressure - a defining concept for extensive pastoral systems in the southern rangelands of Australia

In Australia, particularly in the southern rangelands, large populations of native and feral herbivores (including kangaroos, goats, rabbits, pigs, donkeys and camels, depending on the location) co-exist with domestic livestock. In recent decades the concept of ‘total grazing pressure’ has been developed, and widely accepted, to denote the total forage demand of all vertebrate herbivores relative to the forage supply. This concept provides a framework within which both domestic and non-domestic species can be managed to allow commercially viable livestock production, landscape maintenance or restoration and species conservation. The concept should have relevance wherever pest animal control programs, biodiversity conservation, or commercialisation of wildlife are conducted in conjunction with extensive livestock production. The rationale for the compilation of the Special Issue is outlined.