Host plant preferences of Hyalesthes obsoletus,the vector of the grapevine yellows disease ‘bois noir’, in Switzerland

Bois noir is an important grapevine yellows disease in Europe that can cause serious economic losses in grapevine production. It is caused by stolbur phytoplasma strains of the taxonomic group 16Sr‐XII‐A. Hyalesthes obsoletus Signoret (Hemiptera: Cixiidae) is the most important vector of bois noir in Europe. This polyphagous planthopper is assumed to mainly use stinging nettle [Urtica dioica L. (Urticaceae)] and field bindweed [Convolvulus arvensis L. (Convolvulaceae)] as its host plants. For a better understanding of the epidemiology of bois noir in Switzerland, host plant preferences of H. obsoletus were studied in the field and in the laboratory. In vineyards of Western Switzerland, adults of H. obsoletus were primarily captured on U. dioica, but a few specimens were also caught on C. arvensis, hedge bindweed [Calystegia sepium (L.) R. Brown (Convolvulaceae)], and five other dicotyledons [i.e., Clematis vitalba L. (Ranunculaceae), Lepidium draba L. (Brassicaceae), Plantago lanceolata L. (Plantaginaceae), Polygonum aviculare L. (Polygonaceae), and Taraxacum officinale Weber (Asteraceae)]. The preference of the vector for U. dioica compared to C. arvensis was confirmed by a second, more targeted field study and by the positioning of emergence traps above the two plant species. Two‐choice experiments in the laboratory showed that H. obsoletus adults originating from U. dioica preferred to feed and to oviposit on U. dioica compared to C. arvensis. However, H. obsoletus nymphs showed no host plant preference, even though they developed much better on U. dioica than on C. arvensis. Similarly, adults survived significantly longer on U. dioica than on C. arvensis or any other plant species tested [i.e., L. draba and Lavandula angustifolia Mill. (Lamiaceae)]. In conclusion, although nymphs of H. obsoletus had no inherent host plant preference, adults tested preferred to feed and oviposit on U. dioica, which is in agreement with the observed superior performance of both nymphal and adult stages on this plant species. Urtica dioica appears to be the principal host plant of H. obsoletus in Switzerland and plays therefore an important role in the epidemiology of the bois noir disease in Swiss vineyards.     

Origin of a sudden mass occurrence of the stolbur phytoplasma vector Hyalesthes obsoletus (Cixiidae) in Austria

The grapevine disease ‘bois noir’ is widespread in European viticulture, but in many regions there is a lack of correspondence between disease spread and abundance of the main insect vector, the planthopper Hyalesthes obsoletus. This was the situation in Austria until 2012, when a mass occurrence of the vector was observed on Urtica dioica, a new host plant for the vector and reservoir plant for the pathogen, stolbur phytoplasma, in this area. Here we analyse the origin of the Austrian vector populations using genetic markers. The origin was unambiguously assigned to two regional populations, and two causes for the population expansion: immigration of East Central European populations and local demographic expansion. The observed population increase was thus independent of phylogenetic ancestry, but linked to the host plant and the exchange of a specific stolbur phytoplasma strain between the two vector populations. These circumstances are identical to but independent of the emergence of bois noir west of the European Alps, where an exchange between other vector populations associated with U. dioica of another stolbur phytoplasma genotype has led to disease outbreaks. Combined, the independent outbreaks in Austria and Europe west of the Alps are suggestive of an active role for stolbur phytoplasma in the vector–plant interaction and thus the host distribution of the vector.     

Sympatric diversification vs. immigration: deciphering host‐plant specialization in a polyphagous insect,the stolbur phytoplasma vector Hyalesthes obsoletus (Cixiidae)

The epidemiology of vector transmitted plant diseases is highly influenced by dispersal and the host‐plant range of the vector. Widening the vector's host range may increase transmission potential, whereas specialization may induce specific disease cycles. The process leading to a vector's host shift and its epidemiological outcome is therefore embedded in the frameworks of sympatric evolution vs. immigration of preadapted populations. In this study, we analyse whether a host shift of the stolbur phytoplasma vector, Hyalesthes obsoletus from field bindweed to stinging nettle in its northern distribution range evolved sympatrically or by immigration. The exploitation of stinging nettle has led to outbreaks of the grapevine disease bois noir caused by a stinging nettle‐specific phytoplasma strain. Microsatellite data from populations from northern and ancestral ranges provide strong evidence for sympatric host‐race evolution in the northern range: Host‐plant associated populations were significantly differentiated among syntopic sites (0.054 < F_HT < 0.098) and constant over 5 years. While gene flow was asymmetric from the old into the predicted new host race, which had significantly reduced genetic diversity, the genetic identity between syntopic host‐race populations in the northern range was higher than between these populations and syntopic populations in ancestral ranges, where there was no evidence for genetic host races. Although immigration was detected in the northern field bindweed population, it cannot explain host‐race diversification but suggests the introduction of a stinging nettle‐specific phytoplasma strain by plant‐unspecific vectors. The evolution of host races in the northern range has led to specific vector‐based bois noir disease cycles.     

Invasion biology and host specificity of the grapevine yellows disease vector Hyalesthes obsoletus in Europe

Within the past 10 years, the yellows disease ‘bois noir’ (BN) has become one of the commercially most important diseases of grapevine [Vitis vinifera L. (Vitaceae)] in Europe. Infection pressure is caused by phytoplasmas of the stolbur 16SrXII‐A group that are transmitted by a planthopper vector, Hyalesthes obsoletus Signoret (Homoptera: Auchenorrhyncha). Infestation happens as an accidental side‐effect of the feeding behaviour of the vector, as vector and pathogen proliferation is dependent on other plants. In Germany, the increase of BN is correlated with the use of a new host plant by the vector, increase in abundance of the vector on the new host plant, and dissemination of host plant‐specific pathogen strains. In this article, we investigate geographic and host‐associated range expansion of the vector. We test whether host‐plant utilization in Germany, hence the increase in BN, is related to genetic host races of the vector and, if so, whether these have evolved locally or have immigrated from southern populations that traditionally use the new host plant. The genetic population analysis demonstrates a recent expansion and circum‐alpine invasion of H. obsoletus into German and northern French wine‐growing regions, which coincides with the emergence of BN. No H. obsoletus mitochondrial DNA haplotype host‐plant affiliation was found, implying that the ability to use alternative host plants is genetically intrinsic to H. obsoletus. However, subtle yet significant random amplified polymorphic DNA (RAPD) genetic differentiation was found among host plant populations. When combined, these results suggest that a geographic range expansion of H. obsoletus only partly explains the increase of BN, and that interactions with host plants also occur. Further possible beneficial factors to H. obsoletus, such as temperature increase and phytoplasma interactions, are discussed.     

Infection of Bois‐Noir tuf‐type‐I stolbur phytoplasma in Hyalesthes obsoletus (Hemiptera: Cixiidae) larvae and influence on larval size

Recent dramatic spread of the grapevine yellows disease Bois Noir (BN) in Germany is above all explained by highly increased abundances of the vector Hyalesthes obsoletus (Hemiptera: Cixiidae) associated to the plant Urtica dioica, the reservoir of the BN pathogen stolbur tuf‐type‐I. The vector acquires BN‐phytoplasma as larvae whilst feeding on the roots of infected U. dioica. To understand the dynamics of the Urtica‐cycle, we tested at what instar larvae become infected and whether infection affects larvae size (i.e. growth) at two sites in the Mosel Valley, Germany. Larvae were tested from infected plants and collected at instar‐stages 3, 4 and 5. Larvae at stage 3 were already infected but infection rates increased significantly between stage 3 and 5, mean infection rates: 0.12–0.62. There was no effect of infection on larval size at any instar stage.     

Survival relative to new and ancestral host plants,phytoplasma infection,and genetic constitution in host races of a polyphagous insect disease vector

Dissemination of vectorborne diseases depends strongly on the vector's host range and the pathogen's reservoir range. Because vectors interact with pathogens, the direction and strength of a vector's host shift is vital for understanding epidemiology and is embedded in the framework of ecological specialization. This study investigates survival in host‐race evolution of a polyphagous insect disease vector, Hyalesthes obsoletus, whether survival is related to the direction of the host shift (from field bindweed to stinging nettle), the interaction with plant‐specific strains of obligate vectored pathogens/symbionts (stolbur phytoplasma), and whether survival is related to genetic differentiation between the host races. We used a twice repeated, identical nested experimental design to study survival of the vector on alternative hosts and relative to infection status. Survival was tested with Kaplan–Meier analyses, while genetic differentiation between vector populations was quantified with microsatellite allele frequencies. We found significant direct effects of host plant (reduced survival on wrong hosts) and sex (males survive longer than females) in both host races and relative effects of host (nettle animals more affected than bindweed animals) and sex (males more affected than females). Survival of bindweed animals was significantly higher on symptomatic than nonsymptomatic field bindweed, but in the second experiment only. Infection potentially had a positive effect on survival in nettle animals but due to low infection rates the results remain suggestive. Genetic differentiation was not related to survival. Greater negative plant‐transfer effect but no negative effect of stolbur in the derived host race suggests preadaptation to the new pathogen/symbiont strain before strong diversifying selection during the specialization process. Physiological maladaptation or failure to accept the ancestral plant will have similar consequences, namely positive assortative mating within host races and a reduction in the likelihood of oviposition on the alternative plant and thus the acquisition of alternative stolbur strains.     

Identifying local drivers of a vector-pathogen-disease system using Bayesian modeling

‘Bois noir’ is a phytoplasma-mediated grapevine yellows disease that causes great economic damage in European vineyards. Previous studies have examined habitat relationships on a regional scale, which help to better understand the large-scale epidemiology. Local drivers, such as micro-habitat preferences of the vector (Hyalesthes obsoletus, a cixiid planthopper), or local interactions with reservoir host plants, however, are still poorly understood, although this knowledge is crucial for developing site-specific management strategies.Here, we examined the local environment-species relationships of a phytoplasma-mediated grapevine disease on a scale of 15 m in a 2.9 ha vineyard using: (i) data on elevation and habitat types; (ii) cover of host plants Urtica dioica and Convolvulus arvensis over three seasons, (iii) vector monitoring over four seasons; (iv) genetic tests for phytoplasma presence in the vector; and (v) inspection of 6056 grapevine plants for visual symptoms of the ‘bois noir’ disease. The data were analyzed in a joint causal model that describes the interplay between vector, pathogen, disease and environment, estimated with Bayesian inference.Our results indicate that surrounding natural and semi-natural vegetation (fallow land, forest and managed agricultural land) and high density of the major host plant U. dioica are associated with an increase in vector population densities. Higher vector population densities at low availability of U. dioica were associated with higher phytoplasma infection rates in the vector. The prevalence of disease symptoms in grapevine plants was nonetheless more affected by grapevine cultivar and higher elevation than by the estimated availability of infected vectors.The results of our local analysis support current bois noir management recommendations stating that (1) removal of the host plant U. dioica should be best carried out in either spring or autumn; and (2) grapevine cultivars are unequally susceptible. Moreover, we provide evidence that U. dioica control before the flight period may result in low U. dioica densities and high H. obsoletus population densities, causing an increase in vector infection rates and disease pressure.     

Vector activity of Hyalesthes obsoletus living on nettles and transmitting a stolbur phytoplasma to grapevines: a case study

We report a case study on the vector activity of a Hyalesthes obsoletus (Hemiptera: Cixiidae) population living on nettle plants (Urtica dioica) and transmitting a stolbur phytoplasma (Sp) to grapevines (Vitis vinifera). The research was conducted in a site that included a vineyard bordered with a large fallow area where nettles were the predominant plant species together with sparse old grapevines. Nettles hosted a high population of H. obsoletus. By using transparent sticky traps to sample adults, we observed that the daily flight activity of males and females to grapevines in the fallow was unimodal peaking between 15 and 21 h in the day. Adults were unable of great dispersion into the vineyard and the pattern of insect captures inside the planting reflected the pattern of Sp‐infected grapevines in the late autumn. When insects were forced to feed on grapevine cuttings for transmission assays, survival of H. obsoletus decreased after 24–48 h. The scarce propensity of the vector to move into the vineyard and feed on grapevines was counterbalanced by the rapidity of H. obsoletus to inoculate Sp to grapevines (estimated minimum inoculation access period ranged from 3 to 6 h) and a relative high incidence of Sp in the population of H. obsoletus that ranged between 20% and 30% of sampled insects as shown by a polymerase chain reaction–based procedure. Characterisation of Sp by restriction fragment length polymorphism analysis of nonribosomal phytoplasma DNA showed the occurrence of an Sp strain known to infect H. obsoletus associated to nettles and grapevines in Germany.     

Vitex agnus‐castus cannot be used as trap plant for the vector Hyalesthes obsoletus to prevent infections by ‘Candidatus Phytoplasma solani’ in northern Italian vineyards: Experimental evidence

Bois noir (BN), the most prevalent disease of the grapevine yellows complex, causes considerable yield loss in vineyards. BN is associated with phytoplasma strains of the species ‘Candidatus Phytoplasma solani’ (taxonomic subgroup 16SrXII‐A). In Europe, the BN phytoplasma is transmitted to grapevine mainly by Hyalesthes obsoletus, a polyphagous cixiid completing its life cycle on stinging nettle and field bindweed. As a result of the complexity of BN epidemiology, no effective control strategies have been developed. In previous studies conducted in the eastern Mediterranean coast of Israel, chaste tree (Vitex agnus‐castus) was found to be the preferred host plant of H. obsoletus but did not harbour BN phytoplasma. Thus, a ‘push and pull’ strategy was suggested based on the fact that chaste tree plants located at vineyard borders was an effective trap plant for H. obsoletus adults. However, in other studies carried out in the eastern Adriatic coast of Montenegro, chaste tree was found to be a key source plant for BN phytoplasma transmission to grapevine. This study aimed to investigate (i) the interaction between chaste tree and H. obsoletus through survival, attractiveness and oviposition experiments conducted comparing the behaviour of H. obsoletus in chaste tree versus stinging nettle and grapevine and (ii) the capability of chaste tree to harbor ‘Ca. P. solani’ in northern Italy through transmission trials. H. obsoletus adults were found to survive on chaste tree and grapevine over a 1 week period and prefer chaste tree to grapevine. Moreover, H. obsoletus produced eggs and overwintered as nymphs on chaste tree, even if at a lesser extent than on stinging nettle. H. obsoletus originating from nettle was found able to transmit ‘Ca. P. solani’ to chaste tree (2 plants of 16 were found infected by the BN phytoplasma strain St5 identified in H. obsoletus specimens). These results increased our knowledge about the role of Vitex agnus‐castus as host plant of H. obsoletus and BN phytoplasma in northern Italy and do not recommend considering chaste tree as trap plant at vineyard borders.     

Geographical variation in host plant utilization in the comma butterfly: the roles of time constraints and plant phenology

What is the role of time-constraints in determining geographical variation in the resource use of organisms? One hypothesis concerning phytophagous insects predicts a local narrowing of host plant range at localities where a short development time is important (because an additional generation per season is only just possible), with increased specialization on host plants permitting fast development. To test this hypothesis, populations of the polyphagous comma butterfly (Nymphalidae: Polygonia c-album) from five European areas (localities in Norway, Sweden, England, Belgium and Spain) were sampled and the preferences of laboratory-reared female butterflies were investigated, by a choice test between Salix caprea and the fastest host Urtica dioica. The results suggest that females of both of two northern univoltine populations (time-stressed from Norway and time-relaxed from Sweden) accept the slow host S. caprea to a higher degree than females of more southern populations with partial additional generations (time-stressed). We thus found partial support for the tested hypothesis, but also conflicting results that cast doubt on its broad generality. Moreover, a split-brood investigation on Swedish stock demonstrated that larval performance is similar on S. caprea and U. dioica early in the summer, but that later in the season S. caprea is a much inferior host. This is reflected by a seasonal trend towards specialization on U. dioica and also provides a simpler explanation than the time-constraints theory for avoidance of S. caprea (and other woody hosts) in areas with two or more generations of insects per year, illustrating the importance of plant phenology as a constraint on resource use in phytophagous insects. Absolute and relative larval performance on the two hosts varied little among populations across Europe, but lower survival on S. caprea in the populations most specialized on U. dioica and related plants may be indicative of performance trade-offs.     

Controlling ‘bois noir’ disease on grapevine: does the timing of herbicide application affect vector emergence?

Bois noir is an important grapevine yellows disease that can cause serious economical losses in European grapevine production. Hyalesthes obsoletus Signoret (Hemiptera, Cixiidae) is the principal vector of bois noir in Switzerland and stinging nettle (Urtica dioica) is its favourite host plant species in vineyards. As bois noir disease can hardly be cured and direct control measures against H. obsoletus are ineffective, viticultural control practices target stinging nettle, the actual reservoir and source of both the pathogen and its vector. Currently, it is recommended to apply herbicides against stinging nettle at the end of the season to kill developing H. obsoletus nymphs. To verify if this late period of herbicide application is justified, stinging nettle patches were treated with glyphosate in the autumn, in the spring or were left untreated as a control. Herbicide applications at both dates controlled the growth of stinging nettle very well in the subsequent summer, although the autumnal treatment was slightly more efficient. To study glyphosate’s direct impact on the development of H. obsoletus nymphs, emergence traps were placed directly in the centre of treated and untreated stinging nettle patches. There was no significant difference among the three treatments in the total number of adults emerging. Thus, an aerial application of glyphosate in either spring or autumn did not inhibit the nymphs’ development on the roots of stinging nettle in the soil. Our results challenge current recommendations of applying herbicides against stinging nettle at the end of the season and suggest that stinging nettle could also be controlled in spring, alike other viticultural weeds.     

Phytoplasma Transmission by Heterologous Grafting Influences Viability of the Scion and Results in Early Symptom Development in Periwinkle Rootstock

The stolbur phytoplasma ‘Candidatus Phytoplasma solani’ is responsible for the grapevine disease ‘bois noir’ affecting a number of wine‐growing areas in Europe. Transmission of stolbur phytoplasma to different laboratory hosts can be difficult due to the requirement of transmitting insect vectors or parasite plants. Here, heterologous grafting was used as an alternative technique for transmission of common and strongly symptomatic stolbur genotypes CPsM4_At1 and CPsM4_At6 of ‘Ca. P. solani’ to experimental host plants such as Catharanthus roseus and tomato making phytoplasma strains more accessible for molecular and experimental investigations in different plant species. Transmission was confirmed by quantitative PCR, microscopy and nested PCR followed by marker gene sequencing. In our study, the transmission of different genotypes of ‘Ca. P. solani’ resulted in distinguishable symptom development in the laboratory host C. roseus. Symptom development in grafted rootstock was observed three to 7 weeks after heterologous grafting. Survival of the graft unit was influenced by the presence of ‘Ca. P. solani’ in the scions and was clearly reduced in phytoplasma free scion – rootstock combinations.     

Impact of Vector Dispersal and Host-Plant Fidelity on the Dissemination of an Emerging Plant Pathogen

Dissemination of vector-transmitted pathogens depend on the survival and dispersal of the vector and the vector''s ability to transmit the pathogen, while the host range of vector and pathogen determine the breath of transmission possibilities. In this study, we address how the interaction between dispersal and plant fidelities of a pathogen (stolbur phytoplasma tuf-a) and its vector (Hyalesthes obsoletus: Cixiidae) affect the emergence of the pathogen. Using genetic markers, we analysed the geographic origin and range expansion of both organisms in Western Europe and, specifically, whether the pathogen''s dissemination in the northern range is caused by resident vectors widening their host-plant use from field bindweed to stinging nettle, and subsequent host specialisation. We found evidence for common origins of pathogen and vector south of the European Alps. Genetic patterns in vector populations show signals of secondary range expansion in Western Europe leading to dissemination of tuf-a pathogens, which might be newly acquired and of hybrid origin. Hence, the emergence of stolbur tuf-a in the northern range was explained by secondary immigration of vectors carrying stinging nettle-specialised tuf-a, not by widening the host-plant spectrum of resident vectors with pathogen transmission from field bindweed to stinging nettle nor by primary co-migration from the resident vector''s historical area of origin. The introduction of tuf-a to stinging nettle in the northern range was therefore independent of vector''s host-plant specialisation but the rapid pathogen dissemination depended on the vector''s host shift, whereas the general dissemination elsewhere was linked to plant specialisation of the pathogen but not of the vector.     

Evaluating the role of ecological isolation in maintaining the species boundary between <Emphasis Type="Italic">Silene dioica</Emphasis> and <Emphasis Type="Italic">S. latifolia</Emphasis>

The relative importance of floral versus ecological isolation in preventing introgression remains unclear. This study examines whether ecological isolation can explain the continuing integrity of Silene dioica and S. latifolia where floral isolation is weak and hybrids are fully viable. Eighteen small replicate founder populations of 6 individuals (3 males and 3 females) of either S. latifolia, S. dioica or hybrids were created in woodland and in open sites in southern UK. Survival, reproduction and introgression of these populations were examined over 9 years. S. latifolia and hybrid plants suffered higher mortality than S. dioica in woodland. In open sites, there was extensive introgression, with few or no pure S. latifolia or S. dioica surviving by the end of the experiment. The experiment suggests that the integrity of S. dioica is maintained by its ability to survive in shaded habitats where S. latifolia and hybrids cannot persist. However, how S. latifolia survives as a distinct species in the study area remains a puzzle. Immigration from regions where S. latifolia occurs in isolation (i.e. large-scale ecological isolation) may balance introgression in the study area.     

Mitochondrial DNA haplotypes indicate two postglacial re‐colonization routes of the spruce bark beetle Ips typographus through northern Europe to Scandinavia

Species in northern Europe re‐colonized the region after the last glacial maximum via several routes, which could have lingering signatures in current intraspecific trait variation. The spruce bark beetle, Ips typographus, occurs across Europe, and biological differences have been found between southern and northern Scandinavian populations. However, the postglacial history of I. typographus in Scandinavia has not been previously studied at a fine geographical scale. Therefore, we collected specimens across northern Europe and analysed the genetic variation in a quite large mitochondrial fragment (698 bp). A high genetic diversity was found in some of the most northern populations, in the Baltic States, Gotland and central Europe. Detected genetic and phylogeographic structures suggest that I. typographus re‐colonized Scandinavia via two pathways, one from the northeast and one from the south. These findings are consistent with the re‐colonization history of its host plant, Picea abies. However, we observed low haplotype and nucleotide diversity in southern Scandinavian populations of I. typographus, indicating that (unlike P. abies) it did not disperse across the Baltic Sea in multiple events. Further, the divergence among Scandinavian populations was shallow, conflicting with a scenario where I. typographus expanded concurrently with its host plant from a ‘cryptic refugium’ in the northwest.     

Pathways of introduction of the invasive aquatic plant Cabomba caroliniana

The pathway and frequency of species' introductions can affect the extent, impact, and management of biological invasions. Here, we examine the pathway of introduction of the aquatic plant Cabomba caroliniana (fanwort) into Canada and the northern United States using plastid DNA sequence (intergenic spacers atpF‐atpH, trnH‐psbA, and trnL‐trnF) and DNA content analyses. We test the hypothesis that the spread of fanwort is a result of commercial trade by comparing a Canadian population (Kasshabog Lake, ON) to native populations from southern U.S., introduced populations in northern U.S., and plants from commercial retailers. Thirteen plastid haplotypes were identified throughout North America, including one dominant haplotype, which was present in all C. caroliniana populations. Several rare haplotypes were used to infer shared colonization history. In particular, the Canadian population shared two rare alleles with a population from Massachusetts, suggesting range expansion of C. caroliniana from the northern U.S. However, the possibility of a commercial introduction cannot be excluded, as common alleles were shared between the Canadian population and both commercial and southern U.S. sources. Variation in C. caroliniana genome size was bimodal and populations were classified into “high” and “low” categories. The Canadian population had DNA contents similar to several northern U.S. populations (low DNA content). This may provide additional support for range expansion from these introduced populations rather than from commercial sources or populations in the southern U.S., which had high DNA content.     

Vestiges of an ancestral host plant: preference and performance in the butterfly Polygonia faunus and its sister species P. c‐album

1. In the study of the evolution of insect–host plant interactions, important information is provided by host ranking correspondences among female preference, offspring preference, and offspring performance. Here, we contrast such patterns in two polyphagous sister species in the butterfly family Nymphalidae, the Nearctic Polygonia faunus, and the Palearctic P. c‐album. 2. These two species have similar host ranges, but according to the literature P. faunus does not use the ancestral host plant clade – the ‘urticalean rosids’. Comparisons of the species can thus test the effects of a change in insect–plant associations over a long time scale. Cage experiments confirmed that P. faunus females avoid laying eggs on Urtica dioica (the preferred host of P. c‐album), instead preferring Salix, Betula, and Ribes. 3. However, newly hatched larvae of both species readily accept and grow well on U. dioica, supporting the general theory that evolutionary changes in host range are initiated through shifts in female host preferences, whereas larvae are more conservative and also can retain the capacity to perform well on ancestral hosts over long time spans. 4. Similar rankings of host plants among female preference, offspring preference, and offspring performance were observed in P. c‐album but not in P. faunus. This is probably a result of vestiges of larval adaptations to the lost ancestral host taxon in the latter species. 5. Female and larval preferences seem to be largely free to evolve independently, and consequently larval preferences warrant more attention.