Microbiome responses during virulence adaptation by a phloem‐feeding insect to resistant near‐isogenic rice lines

The microbiomes of phloem‐feeding insects include functional bacteria and yeasts essential for herbivore survival and development. Changes in microbiome composition are implicated in virulence adaptation by herbivores to host plant species or host populations (including crop varieties). We examined patterns in adaptation by the green leafhopper, Nephotettix virescens, to near‐isogenic rice lines (NILs) with one or two resistance genes and the recurrent parent T65, without resistance genes. Only the line with two resistance genes was effective in reducing leafhopper fitness. After 20 generations on the resistant line, selected leafhoppers attained similar survival, weight gain, and egg laying to leafhoppers that were continually reared on the susceptible recurrent parent, indicating that they had adapted to the resistant host. By sequencing the 16s rRNA gene, we described the microbiome of leafhoppers from colonies associated with five collection sites, and continually reared or switched between NILs. The microbiomes included 69–119 OTUs of which 44 occurred in ≥90% of samples. Of these, 14 OTUs were assigned to the obligate symbiont Candidatus sulcia clade. After 20 generations of selection, collection site had a greater effect than host plant on microbiome composition. Six bacteria genera, including C. sulcia, were associated with leafhopper virulence. However, there was significant within‐treatment, site‐related variability in the prevalence of these taxa such that the mechanisms underlying their association with virulence remain to be determined. Our results imply that these taxa are associated with leafhopper nutrition. Ours is the first study to describe microbiome diversity and composition in rice leafhoppers. We discuss our results in light of the multiple functions of herbivore microbiomes during virulence adaptation in insect herbivores.     

Consequences of stress induced by heat on fitness of Delphacodes kuscheli and its yeast‐like endosymbionts

The planthopper Delphacodes kuscheli is the main vector of Mal de Río Cuarto virus in Argentina, disease that severely affects maize production. In this study, we investigated the effects of heat stress on fitness traits and on the number of its obligate yeast‐like symbionts (YLS). The exposition of newly‐hatched nymphs to 35°C for 3 days, a well‐known procedure used to reduce the number of YLS in planthoppers, was applied. To compare different fitness components between control and heat‐treated insects, we estimated nymphal instars development time, nymphal survival, adult body length, longevity, fecundity and fertility. Also, correlates of fitness, as proportion of sexes and wing forms of the emerging adults, were evaluated. In heat‐treated group, the nymphal developmental time increased due to an increase in the fifth instar duration, and the nymphal survival, body length of adults and fecundity were reduced when compared to control. There was a significant association between treatments (control and heat‐treated insects) and wing morphs. The heat treatment successfully reduced the number of YLS in third instar nymphs of D. kuscheli. Our results revealed the negative effect of heat stress on development, survival and reproduction of D. kuscheli and on the load of its YLS endosymbionts suggesting that YLS could play a crucial role in the development and reproduction of these planthoppers.     

Associative learning of host presence in non‐host environments influences parasitoid foraging

1. Parasitoids are known to utilise learning of herbivore‐induced plant volatiles (HIPVs) when foraging for their herbivorous host. In natural situations these hosts share food plants with other, non‐suitable herbivores (non‐hosts). Simultaneous infestation of plants by hosts and non‐hosts has been found to result in induction of HIPVs that differ from host‐infested plants. Each non‐host herbivore may have different effects on HIPVs when sharing the food plant with hosts, and thus parasitoids may learn that plants with a specific non‐host herbivore also contain the host. 2. This study investigated the adaptive nature of learning by a foraging parasitoid that had acquired oviposition experience on a plant infested with both hosts and different non‐hosts in the laboratory and in semi‐field experiments. 3. In two‐choice preference tests, the parasitoid Cotesia glomerata shifted its preference towards HIPVs of a plant–host–non‐host complex previously associated with an oviposition experience. It could, indeed, learn that the presence of its host is associated with HIPVs induced by simultaneous feeding of its host Pieris brassicae and either the non‐host caterpillar Mamestra brassicae or the non‐host aphid Myzus persicae. However, the learned preference found in the laboratory did not translate into parasitisation preferences for hosts accompanying non‐host caterpillars or aphids in a semi‐field situation. 4. This paper discusses the importance of learning in parasitoid foraging, and debates why observed learned preferences for HIPVs in the laboratory may cancel out under some field experimental conditions.     

The role of herbivore‐ and plant‐related experiences in intraspecific host preference of a relatively specialized parasitoid

Parasitoids use odor cues from infested plants and herbivore hosts to locate their hosts. Specialist parasitoids of generalist herbivores are predicted to rely more on herbivorederived cues than plant-derived cues. Microplitis croceipes (Cresson)(Hymenoptera: Braconidae) is a relatively specialized larval endoparasitoid of Heliothis virescens (F.)(Lepidoptera: Noctuidae), which is a generalist herbivore on several crops including cotton and soybean. Using M. croceipes/H. virescens as a model system, we tested the following predictions about specialist parasitoids of generalist herbivores:(i) naive parasitoids will show innate responses to herbivore-emitted kairomones, regardless of host plant identity and (ii) herbivore-related experience will have a greater influence on intraspecific oviposition preference than plant-related experience. Inexperienced (naive) female M. croceipes did not discriminate between cotton-fed and soybean-fed H. virescens in oviposition choice tests, supporting our first prediction. Oviposition experience alone with either host group influenced subsequent oviposition preference while experience with infested plants alone did not elicit preference in M. croceipes, supporting our second prediction. Furthermore, associative learning of oviposition with host-damaged plants facilitated host location. I terestingly, naive parasitoids attacked more soybeathan cotton-fed host larvae in two-choice tests when a background of host-infested cotton odor was supplied, and vice versa. This suggests that plant volatiles may have created an olfactory contrast effect. We discussed ecological significance of the results and concluded that both plant- and herbivore-related experiences play important role in parasitoid host foraging.     

Predicting novel trophic interactions in a non‐native world

Humans are altering the global distributional ranges of plants, while their co‐evolved herbivores are frequently left behind. Native herbivores often colonise non‐native plants, potentially reducing invasion success or causing economic loss to introduced agricultural crops. We developed a predictive model to forecast novel interactions and verified it with a data set containing hundreds of observed novel plant–insect interactions. Using a food network of 900 native European butterfly and moth species and 1944 native plants, we built an herbivore host‐use model. By extrapolating host use from the native herbivore–plant food network, we accurately forecasted the observed novel use of 459 non‐native plant species by native herbivores. Patterns that governed herbivore host breadth on co‐evolved native plants were equally important in determining non‐native hosts. Our results make the forecasting of novel herbivore communities feasible in order to better understand the fate and impact of introduced plants.     

Planthopper‐rice interactions: unequal stresses on pure‐line and hybrid rice under similar experimental conditions

Hybrid and pure‐line (inbred) rice [Oryza sativa L. (Poaceae)] varieties have distinct physiologies, particularly as related to their nutrient requirements. These differences could confound the results and interpretation of experiments that compare rice varieties grown in pots for their resistance and responses to herbivores. In this study, a series of experiments was conducted to identify potentially confounding interactions between pot size (soil volume), fertilizer regime, and the use of acetate insect cages with rice line type (hybrid, fertile parental inbred, and male sterile inbred) during bioassays with the brown planthopper, Nilaparvata lugens (Stål) (Hemiptera: Delphacidae). The growth of hybrid rice was often limited (relatively low biomass and low grain production) compared to fertile inbred lines even in large pots (7 200 ml) and when grown without added fertilizer. Several interactions between the effects of growth conditions and line type were detected. Acetate cages caused a significant reduction in grain yield in hybrids, but not in inbreds, mainly resulting from a cage‐induced decrease in grain weight (smaller grains). Hybrids and male sterile lines often had higher root or above‐ground biomass in the largest caged pots compared with fertile inbred lines, but biomass was similar in smaller pots, indicating that the large pots allowed longer unimpeded growth of fertile inbreds, but not other line types. There were no interactions between the presence or absence of planthoppers with line type or experimental conditions. All line types were equally susceptible to planthoppers. Often the effects of planthopper feeding on plant fitness (i.e., tolerance) were apparent when plants were grown in large pots but not in small pots, particularly for hybrid lines and under high nitrogen regimes. On the basis of these results we recommend that researchers ensure that plants are not unequally stressed by inadequate growth conditions during comparative studies with herbivores on physiologically distinct rice varieties or rice species. We recommend the use of large pots (soil volume) and lower fertilizer levels with young, non‐reproductive plants during comparative bioassays with planthoppers. Field cages are recommended for hybrid‐inbred comparisons during older plant stages but these are subject to a range of other confounding variables.     

Herbivore species identity rather than diversity of the non‐host community determines foraging behaviour of the parasitoid wasp Cotesia glomerata

Extensive research has been conducted to reveal how species diversity affects ecosystem functions and services. Yet, consequences of diversity loss for ecosystems as a whole as well as for single community members are still difficult to predict. Arthropod communities typically are species‐rich, and their species interactions, such as those between herbivores and their predators or parasitoids, may be particularly sensitive to changes in community composition. Parasitoids forage for herbivorous hosts by using herbivore‐induced plant volatiles (indirect cues) and cues produced by their host (direct cues). However, in addition to hosts, non‐suitable herbivores are present in a parasitoid's environment which may complicate the foraging process for the parasitoid. Therefore, ecosystem changes in the diversity of herbivores may affect the foraging efficiency of parasitoids. The effect of herbivore diversity may be mediated by either species numbers per se, by specific species traits, or by both. To investigate how diversity and identity of non‐host herbivores influence the behaviour of parasitoids, we created environments with different levels of non‐host diversity. On individual plants in these environments, we complemented host herbivores with 1–4 non‐host herbivore species. We subsequently studied the behaviour of the gregarious endoparasitoid Cotesia glomerata L. (Hymenoptera: Braconidae) while foraging for its gregarious host Pieris brassicae L. (Lepidoptera: Pieridae). Neither non‐host species diversity nor non‐host identity influenced the preference of the parasitoid for herbivore‐infested plants. However, after landing on the plant, non‐host species identity did affect parasitoid behaviour, whereas non‐host diversity did not. One of the non‐host species, Trichoplusia ni Hübner (Lepidoptera: Noctuidae), reduced the time the parasitoid spent on the plant as well as the number of hosts it parasitized. We conclude that non‐host herbivore species identity has a larger influence on C. glomerata foraging behaviour than non‐host species diversity. Our study shows the importance of species identity over species diversity in a multitrophic interaction of plants, herbivores, and parasitoids.     

Differential induction of plant chemical defenses by parasitized and unparasitized herbivores: consequences for reciprocal,multitrophic interactions

Insect parasitoids can play ecologically important roles in virtually all terrestrial plant–insect herbivore interactions, yet whether parasitoids alter the defensive traits that underlie interactions between plants and their herbivores remains a largely unexplored question. Here, we examined the reciprocal trophic interactions among populations of the wild cabbage Brassica oleracea that vary greatly in their production of defensive secondary compounds – glucosinolates (GSs), a generalist herbivore, Trichoplusia ni, and its polyembryonic parasitoid Copidosoma floridanum. In a greenhouse environment, plants were exposed to either healthy (unparasitized), parasitized, or no herbivores. Feeding damage by herbivores induced higher levels of the indole GSs, glucobrassicin and neoglucobrassicin, but not any of the other measured GSs. Herbivores parasitized by C. floridanum induced cabbage plants to produce 1.5 times more indole GSs than levels induced by healthy T. ni and five times more than uninduced plants. As a gregarious endoparasitoid, C. floridanum causes its host T. ni to feed more than unparasitized herbivores resulting in increased induction of indole GSs. In turn, herbivore fitness parameters (including differential effects on male and female contributions to lifetime fecundity in the herbivore) were negatively correlated with the aliphatic GSs, sinigrin and gluconapin, whereas parasitoid fitness parameters were negatively correlated with the indole GSs, glucobrassicin and neoglucobrassicin. That herbivores and their parasitoids appear to be affected by different sets of GSs was unexpected given the intimate developmental associations between host and parasitoid. This study is the first to demonstrate that parasitoids, through increasing feeding by their herbivorous hosts, can induce higher levels of non‐volatile plant chemical defenses. While parasitoids are widely recognized to be ubiquitous in most terrestrial insect herbivore communities, their role in influencing plant–insect herbivore relationships is still vastly underappreciated.     

Development and preliminary application of a triplex real‐time polymerase chain reaction assay for evaluating predation on three planthoppers in a rice ecosystem

A multiplex real‐time quantitative polymerase chain reaction (PCR) assay was developed to simultaneously detect the DNA of three rice planthoppers, that is, Sogatella furcifera (Horváth) (white‐backed planthopper), Nilaparvata lugens (Stål) (brown planthopper) and Laodelphax striatellus (Fallén) (small brown planthopper), in the gut of their predators. The sets of primers and ALLGlo probes were targeted to the regions of internal transcribed spacer 2 (ITS2) genes in nuclear ribosomal DNA (rDNA). The sensitivity, specificity and interference test for the multiplex real‐time quantitative PCR assay were analysed. The assay's detection limits were 100, 1000 and 100 copies for the white‐backed planthopper, the brown planthopper and the small brown planthopper, respectively. The specificity tests showed no cross‐reactivity with genomic DNA from 30 other dominant herbivores, saprophagous insects and predators from rice ecosystem for each planthopper species. The assay was used in a preliminary study of predation events on the three planthoppers by three major spiders viz., Pardosa pseudoannulata (Bösenberg et Strand), Ummeliata insecticeps (Bösenberg et Strand) and Tetragnatha maxillosa Thorell which each differ in their preferred microhabitat as well as their predatory habits in rice field, and the results showed their predation on each planthopper species could be well evaluated using this method. Therefore, the multiplex real‐time quantitative PCR assay provides a new tool to study the mechanisms of prey shifting and natural regulation of the three rice planthoppers by generalist predators in rice ecosystem.     

Parasitic wasp‐associated symbiont affects plant‐mediated species interactions between herbivores

Microbial mutualistic symbiosis is increasingly recognised as a hidden driving force in the ecology of plant–insect interactions. Although plant‐associated and herbivore‐associated symbionts clearly affect interactions between plants and herbivores, the effects of symbionts associated with higher trophic levels has been largely overlooked. At the third‐trophic level, parasitic wasps are a common group of insects that can inject symbiotic viruses (polydnaviruses) and venom into their herbivorous hosts to support parasitoid offspring development. Here, we show that such third‐trophic level symbionts act in combination with venom to affect plant‐mediated interactions by reducing colonisation of subsequent herbivore species. This ecological effect correlated with changes induced by polydnaviruses and venom in caterpillar salivary glands and in plant defence responses to herbivory. Because thousands of parasitoid species are associated with mutualistic symbiotic viruses in an intimate, specific relationship, our findings may represent a novel and widespread ecological phenomenon in plant–insect interactions.     

Differential attraction of parasitoids in relation to specificity of kairomones from herbivores and their by‐products

Infochemicals are used by foraging parasitoids in the host selection process from habitat preference until host recognition. Kairomones from the herbivore host plays a vital role in the attraction of parasitoids, particularly in the micro‐habitat. Parasitoids are specifically attracted to their respective herbivore species even when different herbivores are present on the same plant. Chemicals emitted from different stages of host (eggs, larvae, pupae, adult), host by‐products (e.g., frass, exuviae, mandibular gland secretions, defense secretions etc.), or intra‐specific infochemicals (pheromones) can be main signals for the parasitoids. Parasitoids can differentiate between host and non‐host, between different hosts and host stages by perceiving specific volatile and contact kairomones from the host itself, host along with its by‐product, by‐products alone or intra‐specific infochemicals; of which frass (by‐product) and intra‐specific infochemicals are the most reported ones. Adult and larval parasitoids have been reported to be attracted to kairomones of their target stage or byproduct of their host. Pupal parasitoids have been found to utilize kairomones from the preceding host stage while egg parasitoids are known to exploit a variety of host infochemicals, for example, either from eggs themselves or other non‐target host stages, especially adults and adult‐related by‐products. The kairomonal chemicals identified so far include various groups, but mainly hydrocarbons. A high degree of host specificity and host acceptance is important for the parasitoids as any mistake may result in the loss of fitness.     

稻飞虱酵母类胞内共生菌的组织学研究进展

褐飞虱Nilaparvata lugens体内酵母类共生菌在褐飞虱生长发育和繁殖中起着重要作用,并影响着褐飞虱对寄主植物的致害性变异。该文系统总结了国内外已有的研究成果,讨论了褐飞虱共生菌的分类地位、形态特征、在寄主发育中的功能、侵染途径等,提出了开展褐飞虱生物型形成过程中体内共生菌变异的研究建议,以便利用共生菌来监测田间不同生物型褐飞虱的发生情况,最终实现控菌防虫和对不同生物型的准确预测。     

Planthopper "adaptation" to resistant rice varieties: changes in amino acid composition over time

The brown planthopper, Nilaparvata lugens, shows considerable geographic and temporal variability in its response to varieties of cultivated rice. N. lugens has repeatedly “adapted” to resistant rice varieties; however, the physiological changes underlying planthopper adaptation are poorly understood. Endosymbionts within planthoppers, such as yeast-like endosymbionts (YLS) could play a role as they produce essential amino acids for planthoppers. We used a full factorial study to determine how natal rice variety, exposed rice variety, YLS presence, and the number of reared generations affected nymphal development, planthopper total nitrogen content, and planthopper hydrolyzed amino acid profiles. Nymphal development was strongly influenced by a four-way interaction between the exposed rice variety, natal rice variety, number of reared generations, and YLS presence. While symbiosis improved nymphal performance in the 8th generation, it appeared to be a drain on nymphs in the 11th generation, when the aposymbiotic nymphs actually showed higher performance than the symbiotic nymphs. This suggests that the symbiotic relationship may be acting beneficially in one generation while acting as a drain during another generation. Aposymbiotic planthoppers reared for 11 generations had a higher proportional concentration of rare amino acids than those reared for 8 generations, indicating that the planthopper itself appears to improve its ability to acquire rare amino acids. Therefore, the change in amino acid composition of planthoppers suggests an underlying change in protein expression or amino acid metabolism over time.     

The plant hormone salicylic acid interacts with the mechanism of anti‐herbivory conferred by fungal endophytes in grasses

The plant hormone salicylic acid (SA) is recognized as an effective defence against biotrophic pathogens, but its role as regulator of beneficial plant symbionts has received little attention. We studied the relationship between the SA hormone and leaf fungal endophytes on herbivore defences in symbiotic grasses. We hypothesize that the SA exposure suppresses the endophyte reducing the fungal‐produced alkaloids. Because of the role that alkaloids play in anti‐herbivore defences, any reduction in their production should make host plants more susceptible to herbivores. Lolium multiflorum plants symbiotic and nonsymbiotic with the endophyte Epichloë occultans were exposed to SA followed by a challenge with the aphid Rhopalosiphum padi. We measured the level of plant resistance to aphids, and the defences conferred by endophytes and host plants. Symbiotic plants had lower concentrations of SA than did the nonsymbiotic counterparts. Consistent with our prediction, the hormonal treatment reduced the concentration of loline alkaloids (i.e., N‐formyllolines and N‐acetylnorlolines) and consequently decreased the endophyte‐conferred resistance against aphids. Our study highlights the importance of the interaction between the plant immune system and endophytes for the stability of the defensive mutualism. Our results indicate that the SA plays a critical role in regulating the endophyte‐conferred resistance against herbivores.     

Plant‐mediated indirect effects and the persistence of parasitoid–herbivore communities

We have examined the effects of herbivore diversity on parasitoid community persistence and stability, mediated by nonspecific information from herbivore‐infested plants. First, we investigated host location and patch time allocation in the parasitoid Cotesia glomerata in environments where host and/or nonhost herbivores were present on Brassica oleracea leaves. Parasitoids were attracted by infochemicals from leaves containing nonhost herbivores. They spent considerable amounts of time on such leaves. Thus, when information from the plant is indistinct, herbivore diversity is likely to weaken interaction strengths between parasitoids and hosts. In four B. oleracea fields, all plants contained herbivores, often two or more species. We modelled parasitoid–herbivore communities increasing in complexity, based on our experiments and field data. Increasing herbivore diversity promoted the persistence of parasitoid communities. However, at a higher threshold of herbivore diversity, parasitoids became extinct due to insufficient parasitism rates. Thus, diversity can potentially drive both persistence and extinctions.     

灰飞虱类酵母型共生菌18S rDNA序列变异及系统发生

分离纯化了云南楚雄、宁夏银川、北京通县、上海七宝镇、四川西昌５个地区的灰飞虱体内类酵母型共生菌（Ｙｅａｓｔ－ｌｉｋｅ Ｓｙｍｂｉｏｎｔｓ,ＹＬＳ）,并对其１８ＳｒＤＡＮ的约６００ｂｐ的序列进行了测定。结合已有的序列,构建了不同宿主的ＹＬＳ的分子系统树。结果表明,灰飞虱的ＹＬＳ属于子囊菌亚门Ｐｙｒｅｎｏｍｙｃｅｔｅｓ纲,与此纲的Ｈ．ｃｈｒｙｓｏｓｐｅｒｍｕｓ亲缘关系最近。我国各地区及日本的灰飞虱体内     

褐飞虱不同致害性种群体内共生菌18S rDNA部分序列比较

分离纯化了褐飞虱3种不同致害性种群体内类酵母共生菌 (yeast-like symbionts, YLS),并对其18S rDNA基因序列进行了比较。结果表明,褐飞虱3种不同致害性种群体内类酵母共生菌18S rDNA均扩增出600 bp左右的片断。依据获得的18S rDNA特异性序列,结合已知真菌的18S rDNA部分序列,构建了不同宿主的YLS分子系统树。结果显示, 褐飞虱3种不同致害性种群体内的YLS同属子囊菌亚门（Ascomycotina）的核菌纲（Pyrenomycetes）,并与此纲中的Hypomyces chrysospermus亲缘关系相对最近。     

Genetic structure and host–parasite co‐divergence: evidence for trait‐specific local adaptation

Host–parasite co‐evolution can lead to genetic differentiation among isolated host–parasite populations and local adaptation between parasites and their hosts. However, tests of local adaptation rarely consider multiple fitness‐related traits although focus on a single component of fitness can be misleading. Here, we concomitantly examined genetic structure and co‐divergence patterns of the trematode Coitocaecum parvum and its crustacean host Paracalliope fluviatilis among isolated populations using the mitochondrial cytochrome oxidase I gene (COI). We then performed experimental cross‐infections between two genetically divergent host–parasite populations. Both hosts and parasites displayed genetic differentiation among populations, although genetic structure was less pronounced in the parasite. Data also supported a co‐divergence scenario between C. parvum and P. fluviatilis potentially related to local co‐adaptation. Results from cross‐infections indicated that some parasite lineages seemed to be locally adapted to their sympatric (home) hosts in which they achieved higher infection and survival rates than in allopatric (away) amphipods. However, local, intrinsic host and parasite characteristics (host behavioural or immunological resistance to infections, parasite infectivity or growth rate) also influenced patterns of host–parasite interactions. For example, overall host vulnerability to C. parvum varied between populations, regardless of parasite origin (local vs. foreign), potentially swamping apparent local co‐adaptation effects. Furthermore, local adaptation effects seemed trait specific; different components of parasite fitness (infection and survival rates, growth) responded differently to cross‐infections. Overall, data show that genetic differentiation is not inevitably coupled with local adaptation, and that the latter must be interpreted with caution in a multi‐trait context.     

Cover Caption

The endosymbiont Wolbachia is widely distributed among insects. It can manipulate the reproduction of its hosts and affect hosts' other fitness‐related traits as well. Revealing infection status and variation of Wolbachia within the natural populations of rice planthoppers will help understand the diversification, horizontal transmission and host‐associated specialization of the endosymbiont. The research may have implications for the biological control of planthoppers (see pages 329‐344). Here, the result of specific fluorescence in situ hybridization (FISH) detection of Wolbachia in nymph abdomen of the brown planthopper, Nilaparvata lugens (Stål) is showed. The Wolbachia‐specific probes are red and cell nuclei are shown in blue. (Photo provided by Xiao‐Yue Hong of Nanjing Agricultural University, China).     

Role of olfaction in host plant selection and local adaptation of a polyphagous herbivore,Eucolaspis Sharp

Host plant cues are known to shape insect–host plant association in many insect groups. More pronounced associations are generally manifested in specialist herbivores, but little is known in generalist herbivores. We used a polyphagous native beetle from New Zealand, bronze beetle, Eucolaspis sp. ‘Hawkes Bay’ (Chrysomelidae: Eumolpinae) to explore the role of olfaction in locating host plants and local adaptation. We also tested the role of other cues in the degree of acceptance or rejection of hosts. Adult Eucolaspis beetles were attracted to fresh leaf volatiles from apple and blackberry (Rosaceae). Male and female beetles responded similarly to olfactory cues of host plants. An indication of evolutionary affiliation was observed in olfactory preferences of geographically isolated conspecific populations. We found that geographically isolated populations of the beetles differ in their olfactory responses and exhibit some degree of local adaptation. However, irrespective of geographical and ecological associations, blackberry was preferred over apple as a feeding plant, and another novel plant, bush lawyer (Rubus australis), was readily accepted by 53.25% of the tested beetles. We show that plant volatiles play an important role in host location by Eucolaspis, but the acceptance or rejection of a particular host could also involve visual and contact cues.