Host Plant Species Research Articles

Divergent Assembly Processes of Phyllosphere and Rhizosphere Microbial Communities Along Environmental Gradient.

The underlying assembly processes of surface microbial communities are crucial for host plants and ecosystem functions. However, the relative importance of stochastic and deterministic processes in shaping epiphytic microbes remains poorly understood in both the phyllosphere and rhizosphere. Here, we compared the spatial variations in epiphytic microbial communities of two dominant grasses along a 1400 km transect on the Tibetan Plateau and assessed the assembly processes between the phyllosphere and rhizosphere. We found significant variations in epiphytic microbial community compositions between plant compartments and host species. Stochastic processes (drift and homogenizing dispersal) predominantly shaped microbial communities in both the phyllosphere and rhizosphere, with a greater contribution of stochastic processes in the phyllosphere. As environmental heterogeneity intensified, we found a transition from stochasticity to determinism in affecting the microbial assembly. This transition to homogeneous or variable selection depended on plant compartments and host species. Our study is among the first to compare the contribution of stochastic versus deterministic processes to epiphytic community assembly between the phyllosphere and rhizosphere on the Tibetan Plateau. These findings advance our knowledge of epiphytic microbial assembly and disentangle how host plants exploit the microbiome for improved performance and functioning in stressful alpine ecosystems.

Early-Stage Infection-Specific Heterobasidion annosum (Fr.) Bref. Transcripts in H. annosum–Pinus sylvestris L. Pathosystem

Transcriptomes from stem-inoculated Scots pine saplings were analyzed to identify unique and enriched H. annosum transcripts in the early stages of infection. Comparing different time points since inoculation identified 131 differentially expressed H. annosum genes with p-values of ≤0.01. Our research supports the results of previous studies on the Norway spruce–Heterobasidion annosum s.l. pathosystem, indicating the role of carbohydrate and lignin degradation genes in pathogenesis at different time points post-inoculation and the role of lipid metabolism genes (including but not limited to the delta-12 fatty acid desaturase gene previously reported to be an important factor). The results of this study indicate that the malic enzyme could be a potential gene of interest in the context of H. annosum virulence. During this study, difficulties related to incomplete reference material of the host plant species and a low proportion of H. annosum transcripts in the RNA pool were encountered. In addition, H. annosum transcripts are currently not well annotated. Improvements in sequencing technologies (including sequencing depth) or bioinformatics focusing on small subpopulations of RNA would be welcome.

Specificity determinants of pathogens in forest

Abstract Host‐specific pathogens have long been suggested to act as a major driver of species diversity in tropical forests. However, determining the degree of host specificity of potential pathogens coupled to key cellular characteristics of infection is difficult and time‐consuming. These challenges have delayed progress in relating the functional specificity of pathogenic fungi to ecological consequences. We tested the pathogenicity of 27 (of 215) fungi that were isolated from surface sterilized roots of seedlings from four common tree species in a diverse subtropical forest. Inoculation experiments showed that six fungi exhibited strong pathogenicity on the host seedlings. Five of these only infected their specific hosts (i.e. host‐specific pathogen species). Green fluorescent protein labelling revealed that in three host‐specific pathogens fungal hyphae were able to grow into the vascular tissues only in their specific host plant, in contrast to other fungal‐host combinations that exhibit non‐pathogenic interactions. This fluorescent labelling technique allows direct tracking of the progress of fungal infection in different host tissues. Synthesis. By coupling the green fluorescent protein technique with standard host inoculation experiments, we determined the developmental differences between infections by pathogenic and non‐pathogenic fungi in a relatively simple and straightforward way. Our work provides a useful tool for rapidly screening and categorizing host–fungal interactions, reflecting the functional basis of host specificity of pathogenic fungi. More broadly, this technique can contribute to understanding the roles of pathogens in species coexistence and biodiversity maintenance in forest communities.

Larval growth rate is not a major determinant of adult wing shape and eyespot size in the seasonally polyphenic butterfly Melanitis leda.

Insects often show adaptive phenotypic plasticity where environmental cues during early stages are used to produce a phenotype that matches the environment experienced by adults. Many tropical satyrine butterflies (Nymphalidae: Satyrinae) are seasonally polyphenic and produce distinct wet- and dry-season form adults, providing tight environment-phenotype matching in seasonal environments. In studied Mycalesina butterflies, dry-season forms can be induced in the laboratory by growing larvae at low temperatures or on poor food quality. Since both these factors also tend to reduce larval growth rate, larval growth rate may be an internal cue that translates the environmental cues into the expression of phenotypes. If this is the case, we predict that slower-growing larvae would be more likely to develop a dry-season phenotype. We performed the first experimental study on seasonal polyphenism of a butterfly in the tribe Melanitini. We measured both larval growth rate and adult phenotype (eyespot size and wing shape) of common evening brown butterflies (Melanitis leda), reared at various temperatures and on various host-plant species. We constructed provisional reaction norms, and tested the hypothesis that growth rate mediates between external cues and adult phenotype. Reaction norms were similar to those found in Mycalesina butterflies. We found that both among and within treatments, larvae with lower growth rates (low temperature, particular host plants) were more likely to develop dry-season phenotypes (small eyespots, falcate wing tips). However, among temperature treatments, similar growth rates could lead to very different wing phenotypes, and within treatments the relationships were weak. Moreover, males and females responded differently, and eyespot size and wing shape were not strongly correlated with each other. Overall, larval growth rate seems to be weakly related to eyespot size and wing shape, indicating that seasonal plasticity in M. leda is primarily mediated by other mechanisms.

Influence of Temperature and Host Plant on the Digestion of Frankliniella intonsa (Trybom) Revealed by Molecular Detection.

Frankliniella intonsa (Trybom) (Thysanoptera: Thripidae) is an important type of thrip and a polyphagous pest, which poses a serious threat to many crops, especially those in tropical regions of China. Its feeding behavior and the damage caused vary among different host plant species and are affected by ambient temperature and plant nutrients as well. The digestion rate is an important index for directly observing the digestion process, but there have been no studies directly measuring the digestion in thrips under the influence of different temperatures and host plants. Here, the digestion rate of F. intonsa was assessed by using a molecular diagnostic tool. We also determined the nutrient content in three host plant (mango, cowpea, and pepper), including soluble proteins, free fatty acids, soluble sugars, and water. The results showed that the high and low temperatures (16 °C and 32 °C) both seemed to accelerate the digestion of F. intonsa compared to the optimal temperature (26 °C) and the protein content of plants played an important role in the digestive response of F. intonsa to temperature changes. The findings can help reveal the feeding damage caused by F. intonsa to different plants and help to better understand its feeding ecology, according to its interaction with the host plant.

ARTHROPOD-VECTORS OF PHYTOVIRUSES IN THE RUSSIAN FAR EAST: A REVIEW

This review presents the species diversity of arthropods-phytophages identified in the Russian Far East and capable of acting as vectors of phytoviruses. The most important taxon of these vectors is the order Hemiptera, especially the family Aphididae, whose representatives are able to transmit most of the identified phytoviruses. Viruses and their vectors are associated with host plant species cultivated in the Russian Far East: potatoes, soybeans, vegetables, and cereals.

An Aphid Pest Superclone Benefits From a Facultative Bacterial Endosymbiont in a Host-Dependent Manner, Leading to Reproductive and Proteomic Changes.

The English grain aphid, Sitobion avenae, is a significant agricultural pest affecting wheat, barley, and oats. In Chile, the most prevalent and persistent clone (superclone) of S. avenae harbors the facultative endosymbiont bacterium Regiella insecticola. To determine the role of this bacterium in the reproductive success of this superclone, the presence of R. insecticola was manipulated to assess its impact on (1) the reproductive performance of this clone on two host plant species (wheat and barley), (2) the production of winged morphs, (3) changes in the insects' proteomic profiles, and (4) the root/shoot ratio of plant. It was found that the reproductive performance of this S. avenae superclone varied across host plants, depending on the presence of the facultative bacterial endosymbiont. Aphids infected with R. insecticola showed higher reproductive success on wheat, while the opposite effect was observed on barley. Aphid biomass was greater when infected with R. insecticola, particularly on barley. Additionally, aphids harboring R. insecticola exhibited a higher proportion of winged individuals on both host plants. Protein regulation in aphids on wheat was lower compared to those on barley. A higher root/shoot biomass ratio was observed in wheat plants compared to barley when infested by R. insecticola-infected aphid. Thus, R. insecticola significantly influences the reproductive performance and proteomic profile of a S. avenae superclone, with these effects shaped by the host plant. This suggests that the interaction between the host plant and the facultative endosymbiont contributes to the ecological success of this superclone.

Arbuscular mycorrhizal fungal spore communities and co-occurrence networks demonstrate host-specific variation throughout the growing season.

Microbial community assembly involves a series of ecological filtering mechanisms that determine the composition of microbial communities. While the importance of both broad and local level factors on microbial communities has been reasonably well studied, this work often is limited to single observations and neglects to consider how communities change over time (i.e., seasonal variation). Because seasonal variation is an important determinant of community assembly and determines the relative importance of community assembly filters, this represents a key knowledge gap. Due to their close associations with seasonal variation in plant growth and fitness, arbuscular mycorrhizal (AM) fungi are useful groups for assessing the importance of seasonal dynamics in microbial community assembly. We tested how seasonal variation (spring vs. summer), plant life history stage (vegetative vs. flowering), and host plant species (Baptisia bracteata var. leucophaea & Andropogon gerardii) influenced AM fungal spore community assembly. AM fungal spore community temporal dynamics were closely linked to plant host species and life history stage. While AM fungal spore communities demonstrated strong turnover between the spring (e.g., higher sporulation) and late summer (e.g., higher diversity), the strength and direction of these changes was modified by host plant species. Here we demonstrate the importance of considering temporal variation in microbial community assembly, and also show how plant-microbe interactions can modify seasonal trends in microbial community dynamics.

Shifts in Structure and Assembly Processes of Root Endophytic Community Caused by Climate Warming and Precipitation Increase in Alpine Grassland.

Climate change poses great challenges to the survival of plants. Plant endophytes play important roles in improving plant adaptability. However, our knowledge of the effects of climate change on endophytic community structures is limited. Relying on a field experimental platform simulating climate warming, precipitation increases, and their combination in an alpine grassland, the root endophytic bacterial community structures and assembly processes of three coexisting plant species (Elymus nutans, Kobresia humilis, and Melissilus ruthenicus) were measured. The results indicated that Proteobacteria was the dominant phylum, with a relative abundance ranging from 50% to 80%, followed by Actinobacteria and Bacteroidetes. Bacterial diversity decreased significantly under the combined treatment for all three plant species, with the largest reduction observed in E. nutans. The climate manipulation treatments had a minimal effect on the endophytic bacterial community structures. The relative abundance of Burkholderiaceae increased significantly under the combined treatment for the three plant species. Moreover, the endophytic community assembly processes changed from stochastic dominated under control plots to deterministic dominated under the combined plots for E. nutans, while this shift was reversed for M. ruthenicus. The root endophytic bacterial community was affected by the soil's available nitrogen and stoichiometric ratio. These results revealed that the sensitivity of endophyte community structures to climate change varies with host plant species, which has implications for plant fitness differences.

Parasitism by Cuscuta gronovii mediated soil legacy effects and the competitive ability of invasive and native plant species by changing soil abiotic and biotic properties

Parasitic plants can mediate soil conditioning by invasive and native host plant species, but how this may affect the competitive ability of these plants when they later grow in the conditioned soil has never been tested. This study tested whether soil conditioned by three invasive and three native plant species, either parasitized by a holoparasitic plant Cuscuta gronovii or non-parasitized, would differentially affect the competitive ability of those species. In the first phase, field soil was conditioned using individuals of the six host plant species, either parasitized or non-parasitized. The second phase tested the competitive ability of individuals of those invasive and native plants by growing them alone or in competition with Trifolium repens in either live or sterilized conditioned soil. In the soil conditioning phase, parasitism significantly increased soil NH4+-N concentration by 17 %, decreased soil organic carbon by 18 %, and marginally decreased microbial biomass carbon concentration by 21 %. In the soil feedback phase, native plant species generally had higher competitive ability in soil that was conditioned by parasitized plants than in soil that was conditioned by non-parasitized plants. In contrast, soil conditioned by parasitized plants had only a marginal effect on the competitve ability of invasive plants, compared to growth in soil conditioned by non-parasitized plants. Native plants had greater competitive ability in soil with lower soil organic carbon, while invasive plants had greater competitive ability in soil with higher microbial biomass carbon and lower NH4+-N. These findings demonstrate that parasitism by C. gronovii mediated different soil legacy effects of invasive and native plant species through changes in soil organic carbon, soil NH4+-N, and microbial biomass carbon levels. Broadly, these results suggest that parasitic plants may limit invasions by alien plant species and promote the co-existence of the invaders with native plant species through soil-mediated legacy effects.

Morphological type and taxonomic diversity of arbuscular mycorrhizal fungi along an altitudinal gradient at Mount Ibuki, Japan

ABSTRACT Arbuscular mycorrhiza (AM) associations are among the most widespread interactions between plants and fungi. However, little is known about the AM distribution along altitudinal gradients in forest ecosystems, where the gradients are accompanied by shifts in climatic conditions and soil properties as well as the identity of host plant species. This study aimed to clarify AM fungal associations along an altitudinal gradient. Therefore, we determined the colonization rate and community composition of AM fungi at different elevations on Mount Ibuki, Japan. Root and soil samples were collected from Cryptomeria japonica at altitudes of 200, 500, and 800 m, Acer shirasawanum at an altitude of 1100 m, and Chrysanthemum japonicum at the summit of 1350 m. To evaluate AM fungal colonization, 15 root samples from each altitude were examined microscopically. These samples were identified by targeting V4 and V5 regions of a partial small subunit rRNA gene using Sanger sequencing. AM fungal colonization rates were significantly and positively correlated with altitude. The Arum and Paris types were observed in all plant species examined at each altitude. In total, 101 molecular operational taxonomic units belonging to two genera were identified: Glomus and Diversispora. No significant clustering among elevations was observed in the AM fungal community composition. Among environmental variables, soil temperature, and pH significantly affected AM fungal structure patterns. These results suggest that as altitude increases, plants require more tight mycorrhizal associations, which are selectively filtered by the surrounding environment.

Unveiled species diversity of moss-feeding mites (Stigmaeidae: Eustigmaeus): a research on their distribution, habitat, and host plant use in Japan.

The genus Eustigmaeus Berlese, 1910 represents the unique phytophagous group within the superfamily Raphignathoidea. Four species within this genus have been known to inhabit mosses and feed on them as larvae, nymphs, and adults. However, the interactions with mosses have remained poorly understood. In order to reveal the diversity and host-plant use of the moss-feeding species, we conducted an extensive field study in Japan. This study revealed an array of moss-feeding species inhabiting various moss species, with 10 morphologically distinctive species newly documented in Japan. Through DNA barcoding based on cytochrome c oxidase subunit I (COI) sequences, these morphospecies were recovered as distinct entities. Notably, the host-plant use of four species was elucidated. Among these, Eustigmaeus sp. 9 exhibited polyphagy, while three species (Eustigmaeus spp. 1-3) demonstrated varying degrees of host specificity, each using moss species from the Hypnales, Philonotis, and Dicranidae, respectively. While a few moss-feeding species were frequently found in the same geographic area, more than one species rarely co-occurred within the same moss colonies. Eustigmaeus offers a unique study system, with its diverse moss-feeding species and indications of specific host plant use. Consequently, the moss-feeding Eustigmaeus serves as a valuable model for exploring the macroevolutionary patterns underlying diversification in moss-feeding arthropods.

Philaenus tesselatus (Hemiptera: Aphrophoridae), the main potential vector of Xylella fastidiosa in Morocco: seasonal abundance, phenology and host-plant colonization by nymphs

Summary The bacterium Xylella fastidiosa presents a potential risk to the Moroccan flora, particularly for the citrus, olive, almond and grapevine industries. Philaenus tesselatus, the meadow spittlebug, is the most important Moroccan spittlebug, though recorded with uneven occurrence and considered to be the main potential insect vector of X. fastidiosa. A three-year field survey (2019 to 2021) was conducted at three sites in the provinces of Larache and Kenitra in northwestern Morocco, to study seasonal abundance, phenology and host-plant colonization by nymphs. Philaenus tesselatus is a univoltine species. Nymphs occurred in groundcover from end of mid-March to mid-May, with abundance peaking between end of March and mid-May. Emergence of teneral adults occurred between April and May, depending on the year. Adults were present on ground vegetation from March until early August, with the highest abundances surveyed by sweep net in April, and occurred in canopy in low abundance between the end of May and mid-September, depending on site. Both nymphal and adult abundances were significantly higher in Larache than at the other two sites. Philaenus tesselatus, the meadow spittlebug, is a polyphagous species, recorded on nine botanical families of host plant species including Asteraceae, Poaceae, Fabaceae, Polygonaceae, Apiaceae, Primulaceae, Urticaceae, Papaveraceae and Malvaceae, and 37 host plant species, of which 29 were identified. The Asteraceae were best represented. Carduus pycnocephalus, Vulpia geniculata, Anthoxanthum odoratum and Cistus salviifolius were the most suitable for this spittlebug. Avena barbata, L. foemina, Scolymus hispanicus and S. oleraceus were dominant in the herbaceous layer. Philaenus tesselatus preferred to feed on the mid-section of the host plants. A single foam can host zero to five individuals, but foams with one or two nymphs were most frequent. Implications of our findings for the setting up of a survey program to control X. fastidiosa and its vectors in case the bacterium is introduced to Morocco are discussed.

Utilizing Indigenous Knowledge Systems on Climate Change for Forestry Conservation in Kenya

A study on the toothing of edible caterpillar plants planted with FAS in Ibi- a village on the Batékéen Plateau the Democratic Republic of Congo. The main objective of this study was to identify and characterize the species of edible caterpillar plants planted in Ibi-village on the Batéké plateau. To do so, we used observation as a research method. In this study, 35 species of edible caterpillar host plants were identified, divided into 16 families and 7 orders. Regarding the ecological spectra of florule, Mesopotamians and sarcochores are predominant. On the phytogeographical level, the strong representativeness of the Guineo-Congolese element. Morphologically, the majority of species are trees. In this study, Pentaclethra eetveldeanaes the most dominant species. The most represented families are those of Fabaceae et Euphorbiaceae.

Nutrient content, osmolytes accumulation and antioxidative enzyme activities of sandalwood under drought and salt stresses

Sandalwood (Santalum album L.) has potential to grow into various types of soil under arid as well as semi-arid regions. To find out the sustainable host plant species for sandalwood grown under stress, an RBD experiment was conducted on sandalwood grown without a host and with five selected hosts (Alternanthera sp., Azadirachata indica, Dalbergia sissoo, Melia dubia, and Aquilaria malaccensis) based on prior studies. After 6 weeks of establishment, individual and combine water and salinity stresses were applied and maintained for up to 180 days to investigate their impact on the nutrient content, concentration of osmolytes, and activities of antioxidative enzymes in sandalwood. Haustoria formation showed significant reduction under individual and combined water deficit and salinity stress. Sandalwood grown with Dalbergia sissoo and Melia dubia showed relatively higher nutrients content such as N, P, Ca, Mg, Zn, Fe, and S, which were dramatically reduced under individual and combined water deficit and salinity stress. Osmolytes concentration (proline, soluble sugars, and soluble proteins) increased with intensified stress and sandalwood accumulated higher osmolytes when grown with Dalbergia sissoo and Melia dubia. The activities of antioxidant enzymes showed a significant increase under water deficit, salinity, and combined stress compared to the control, but sandalwood grown with Dalbergia sissoo and Melia dubia exhibited higher activities. Results signify the importance of hosts i.e. Dalbergia sissoo and Melia dubia which provide suitable growth and nutrition to growing sandalwood by maintaining ion homeostasis, ROS balance, and nutrient content under water deficit, salinity, and interactive stress. Results highlighted the significance of D. sissoo and M. dubia, which may be good long-lasting host species for sandalwood production in sub-tropical climates to adapt to changing environmental conditions.

Effects of host plants on aphid feeding behavior, fitness, and Buchnera aphidicola titer.

Aphids are sap-feeding plant pests that depend on their symbiotic relationships with the primary endosymbiont Buchnera aphidicola to adapt to impoverished diets. However, how the host plant affects the aphid primary symbiont and aphid adaptation to host plant transfer are poorly known. In this study, aphid symbiont screening and genotype identification were used to establish 2 aphid strains (Rhopalosiphum maidis [Rm] and Rhopalosiphum padi [Rp] strains) containing only Buchnera without any secondary symbionts for both wheat aphid species (R. maidis and R. padi). Aphid fitness and Buchnera titers were unstable on some of these host plants after transferring to novel host plants (G1-G5), which were influenced by host plant species and generations; however, they stabilized after prolonged feeding on the same plants for 10 generations. The electropenetrography (EPG) records showed that the allocation of aphid feeding time was significantly distinct in the 6 host plants; aphids had more intracellular punctures and spent more nonprobing time on green bristlegrass which was not conducive to its growth compared with other plants. The content of soluble sugar, soluble protein, and amino acid in the leaves of the 6 host plants were also clearly separated. The correlation coefficient analysis showed that the nutrient contents of host plants had significant correlations with aphid feeding behaviors, fitness, and Buchnera titers. In the meantime, aphid fitness, and Buchnera titers were also affected by aphid feeding behaviors. Also, Buchnera titers of aphid natural populations on 6 host plants showed a visible difference. Our study deepened our understanding of the interaction among aphids, endosymbionts, and host plants, indicating that the host plant nutrient content is a predominant factor affecting aphid adaptation to their diet, initially affecting aphid feeding behaviors, and further affecting aphid fitness and Buchnera titers, which would further contribute to exploiting new available strategies for aphid control.

Evaluation of Sheath Blight Resistance in Diverse Rice Varieties Under Artificial Inoculation and Field Conditions

Rice (Oryza sativa L.) a vital food crop for nearly half of the global population, facing significant threats from various biotic and abiotic stresses. Among biotic stresses, diseases pose the most common challenge. Sheath blight, caused by soil-borne fungal pathogen Rhizoctonia Solani Kühn (R. solani), is a major concern, leading to substantial damage to rice and cereal crops worldwide. This study evaluated sheath blight resistance across diverse rice varieties, including short grain, long grain, aromatic, hybrid, and wild types, under both artificial inoculation and field conditions. Ten host plant species were assessed for resistance to sheath blight caused by Rhizoctonia Solani, using physiological screening one-week post-inoculation. The highly virulent R. solani isolate (AG-1 IA anastomosis group) was cultured on PDA media, covering the entire plate 3 to 5 days. Screening of cultivated rice varieties, was conducted using field conditions and humidified chamber methods, with results confirmed through molecular characterization. Among the ten cultivated rice varieties, Arize 6444 and Dhanya 748 exhibited the lowest disease index, classifying them as moderately resistant. In contrast, Kalanamak and Pusa Basmati were highly susceptible, displaying high disease indices. Among wild rice accessions, Oryza rufipogon showed a disease index of five or less. Visual ratings indicated the highest susceptibility in Kalanamak, followed by Pusa Basmati and Swarna sub-1, while the lowest visual ratings were observed in wild rice accessions Oryza australiensis and Oryza rufipogon across all tested hosts. The findings underscore the importance of identifying resistant rice varieties to manage sheath blight effectively. The moderately resistant cultivars and wild rice accessions identified in this study offer valuable genetic resources for breeding programs aimed at enhancing sheath blight resistance in rice.

Evaluation of host plant species for a trap cropping strategy in integrated pest management of pineapple mealybug (Dysmicoccus brevipes)

Pineapple mealybugs are responsible for the emergence of pineapple wilt disease and the subsequent transmission of the pineapple disease virus. This study aimed to evaluate the alternate host plants as potential trap crops for pineapple mealybug. A total of nine host plant species, banana, pumpkin, roselle, hibiscus, ground fig, okra, java grass, goose grass and rhodes grass were selected for the study. Thirty adult females of pineapple mealybug were reared on a pumpkin for two months. Three replicates of a plot (area covered with black netting measuring 3 m × 3 m) were set up. Nine host plant species, approximately 2–3 feet in a 16 inch × 16 inch polybag were arranged in a circle around the pumpkin. The effectiveness of the host plant species was determined by calculating the infestation of each plant species for six months (with two-week observations). Our findings revealed that the pineapple mealybug prefers banana with the greatest mean and SD value (621.7±172.7), followed by pumpkin (237.0±45.6) and the lowest one is rhodes grass (2.00±26.5). ANOVA results show that there is a significant difference between host plant species (F-value of 26.87 and a P-value < 0.00). The observations suggest that banana has the potential to be utilized as trap crops for pineapple mealybug, and can be considered in IPM strategy to control pineapple mealybug.

Risk assessment of the laboratory host range and a molecular characterisation determining the field host range of Lixus aemulus, for the biological control of Chromolaena odorata in South Africa

Chromolaena odorata (Asteraceae: Eupatorieae) is a sprawling shrub native to the Americas, and a destructive invader of much of the humid tropics and subtropics of the Old World. Opportunistic native-range exploration in 1995 identified a stem-boring weevil, Lixus aemulus, as a promising biological control candidate agent. Host-specificity testing was conducted on L. aemulus in South Africa using laboratory no-choice and paired-choice tests. Three invasive alien plants closely related to C. odorata may be utilized by L. aemulus but no indigenous, ornamental or crop species in South Africa was or is expected to be attacked by the weevil. A native-range field survey was conducted in Brazil to determine the exact identity of the host plant L. aemulus had been collected in 1995, and to identify additional host-plant species. Genetic assessments of the Lixus sp.(p.). adults collected on the three host plants (C. odorata, Chromolaena laevigata and Heterocondylus vitalbae) reveal these individuals are L. aemulus and the weevil can be classed as an oligophage in its native range. Over 5,500 adults were released in South Africa, but overall establishment has been poor. The most likely explanation appears to be a climate mismatch between the region of South Africa invaded by C. odorata and the collection locality in Rio Branco, Acre state, Brazil. Additionally, because the full extent of the native range of L. aemulus is unknown, it is uncertain whether individuals can be sourced from an area whose climate resembles that of South Africa. Furthermore, despite being oligophagous, L. aemulus may perform sub-optimally on the southern African C. odorata biotype.

Variation in immune response in the generalist herbivore fall webworm across four common host plants

AbstractDietary generalist herbivorous insects are widespread and often occur in a variety of environments. Across their geographic range, herbivorous insects may encounter variable plant traits as they feed on high‐quality or low‐quality plants. Herbivorous insect larvae experience both bottom‐up (host plant) and top‐down (parasitoid) factors that affect survival. Host plant quality may affect larval growth and survival in that larvae feeding on low‐quality plants often suffer reduced fitness. However, herbivores on different host plants are also subject to different levels of parasitism. High‐quality plants confer stronger larval performance (higher survival, more offspring), but larvae may also face higher parasitism. In some herbivore species, diet mediates larval immune response. The generalist insect herbivore fall webworm (FW), Hyphantria cunea Drury (Lepidoptera: Erebidae), is a moth native to North America, and its larvae have considerable variance in their performance when reared on different host plants. We investigated whether diet affects the immune response in FW larvae when they are reared on different host plant species known to vary in food quality. We measured immune response by melanization of a nylon filament. We found significant differences in immune response across host plants, indicating that diet mediates immune response in FW larvae. Our study helps elucidate the factors that cause variation in immune response in a generalist herbivore.