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Cucurbitaceae plants produce cucurbitacins, bitter triterpenoids, to protect themselves against various insects and pathogens. Adult banded cucumber beetles (Diabrotica balteata), a common pest of maize and cucurbits, sequester cucurbitacins, presumably as a defensive mechanism against their natural enemies, which might reduce the efficacy of biological control agents. Whether the larvae also sequester and are protected by cucurbitacins is unclear. We profiled cucurbitacin levels in four varieties of cucumber, Cucumis sativus, and in larvae fed on these varieties. Then, we evaluated larval growth and resistance against common biocontrol organisms including insect predators, entomopathogenic nematodes, fungi and bacteria. We found considerable qualitative and quantitative differences in the cucurbitacin levels of the four cucumber varieties. While two varieties were fully impaired in their production, the other two accumulated high levels of cucurbitacins. We also observed that D. balteata larvae sequester and metabolize cucurbitacins, and although the larvae fed extensively on both belowground and aboveground tissues, the sequestered cucurbitacins were mainly derived from belowground tissues. Cucurbitacins had no detrimental effects on larval performance and, surprisingly, did not provide protection against any of the natural enemies evaluated. Our results show that D. balteata larvae can indeed sequester and transform cucurbitacins, but sequestered cucurbitacins do not impact the biocontrol potential of common natural enemies used in biocontrol. Hence, this plant trait should be conserved in plant breeding programs, as it has been demonstrated in previous studies that it can provide protection against plant pathogens and generalist insects., Journal of Pest Science, 96 (3), ISSN:1612-4758, ISSN:1612-4766

Cotton has been used as a model plant to study direct and indirect plant defence against herbivorous insects. However, the plant growing conditions could have an important effect on the outcome of such plant defence studies. We examined how common experimental growth conditions influence constitutive and inducible defences in two species of cotton, Gossypium hirsutum and G. herbaceum. We induced plants by applying caterpillar regurgitant to mechanical wounds to compare the induction levels between plants of both species grown in greenhouse or phytotron conditions. For this we measured defence metabolites (gossypol and heliocides) and performance of Spodoptera frugiperda caterpillars on different leaves, the emission of plant volatiles, and their attractiveness to parasitic wasps. Induction increased the levels of defence metabolites, which in turn decreased the performance of S. frugiperda larvae. Constitutive and induced defence levels were the highest in plants grown in the phytotron (compared to greenhouse plants), G. hirsutum and young leaves. Defence induction was more pronounced in plants grown in the phytotron and in young leaves. Also, the differences between growing conditions were more evident for metabolites in the youngest leaves, indicating an interaction with plant ontogeny. The composition of emitted volatiles was different between plants from the two growth conditions, with greenhouse-grown plants showing more variation than phytotron-grown plants. Also, G. hirsutum released higher amounts of volatiles and attracted more parasitic wasps than G. herbaceum. Overall, these results highlight the importance of experimental abiotic factors in plant defence induction and ontogeny of defences. We therefore suggest careful consideration in selecting the appropriate experimental growing conditions for studies on plant defences.

Main conclusion Cucurbita argyrosperma domestication affected plant defence by downregulating the cucurbitacin synthesis-associated genes. However, tissue-specific suppression of defences made the cultivars less attractive to co-evolved herbivores Diabrotica balteata and Acalymma spp. Abstract Plant domestication reduces the levels of defensive compounds, increasing susceptibility to insects. In squash, the reduction of cucurbitacins has independently occurred several times during domestication. The mechanisms underlying these changes and their consequences for insect herbivores remain unknown. We investigated how Cucurbita argyrosperma domestication has affected plant chemical defence and the interactions with two herbivores, the generalist Diabrotica balteata and the specialist Acalymma spp. Cucurbitacin levels and associated genes in roots and cotyledons in three wild and four domesticated varieties were analysed. Domesticated varieties contained virtually no cucurbitacins in roots and very low amounts in cotyledons. Contrastingly, cucurbitacin synthesis-associated genes were highly expressed in the roots of wild populations. Larvae of both insects strongly preferred to feed on the roots of wild squash, negatively affecting the generalist’s performance but not that of the specialist. Our findings illustrate that domestication results in tissue-specific suppression of chemical defence, making cultivars less attractive to co-evolved herbivores. In the case of squash, this may be driven by the unique role of cucurbitacins in stimulating feeding in chrysomelid beetles.

Plant domestication has commonly reduced levels of secondary metabolites known to confer resistance against insects. Chili pepper is a special case because the fruits of different varieties have been selected for lower and higher levels of capsaicin, the main compound associated with defense. This may have important consequences for insect herbivores and their natural enemies. Despite the widespread consumption of chili peppers worldwide, the effects of capsaicin on insects are poorly understood. Here, we investigated the effect of capsaicin on a generalist herbivore, Spodoptora latifascia (Lepidoptera: Noctuidae) and its ectoparasitoid, Euplectrus platyhypenae (Hymenoptera: Eulophidae). Using chili varieties with three pungency levels: non-pungent (Padron), mild (Cayenne) and highly pungent (Habanero), as well as artificial diets spiked with three different levels of synthetic capsaicin, we determined if higher capsaicin levels negatively affect the performance of these insects.Overall, capsaicin had a negative effect on both herbivore and parasitoid performance, particularly at high concentrations. Caterpillars reared on highly pungent fruits and high-capsaicin diet had longer development time, reduced pupation success, lower adult emergence, but also lower parasitism rates than caterpillars reared on mild or non-capsaicin treatments. In addition, we found that the caterpillars were capable of sequestering capsaicinoids in their haemolymph when fed on the high pungent variety with consequences for parasitoids’ performance and oviposition decisions. These results increase our understanding of the role of capsaicin as a chemical defense against insects and its potential implications for pest management.

Native to southeast Asia, the spotted-wing drosophila (Drosophila suzukii (Matsumura); Diptera: Drosophilidae) has become a major pest of small fruits in the Americas and Europe. Field studies were conducted over a two-year period (2015–2016) in cultivated highbush blueberry (Vaccinium corymbosum Linnaeus; Ericaceae) fields and adjacent non-crop habitats containing wild blueberries in New Jersey (United States of America). We tracked seasonal changes in D. suzukii adult abundance and fruit infestation throughout the ripening period (June–August). In both years, D. suzukii adult counts post-harvest were generally higher in traps located in non-crop habitats compared with those located in highbush blueberry fields. Wild and cultivated fruits synchronised in maturation, and the numbers of eggs laid and of emerged adults in both fruit types were comparable for most of the season, although sometimes these numbers were higher in wild fruits post-harvest. Overall, immature success (measured as the per cent egg-to-adult survival) was also mostly higher in wild than in cultivated fruits. Altogether, these studies document that non-crop habitats, and wild hosts therein, are used by D. suzukii during fruit ripening and may serve as potential sources of infestation to nearby highbush blueberry fields. Hence, methods that reduce D. suzukii populations in non-crop habitats may help manage this pest in neighbouring highbush blueberries.

PREMISE Plant responses to herbivores and their elicitors include changes in traits associated with phenology, defense, and reproduction. Induced responses by chewing herbivores are known to be hormonally mediated by the jasmonate pathway and can cascade and affect late-season seed predators and pollinators. Moreover, herbivore-induced plant responses can be transmitted to the next generation. Whether herbivore-induced transgenerational effects also apply to phenological traits is less well understood. METHODS Here, we explored responses of wild lima bean plants (Phaseolus lunatus) to herbivory and jasmonate treatment and possible transgenerational effects of herbivore-induced early flowering. In a controlled field experiment, we exposed lima bean plants to herbivory by leaf beetles or methyl jasmonate sprays (MJ). We then compared plant development, phenology, reproductive fitness and seed traits among these treatments and undamaged, untreated control plants. RESULTS We found that MJ and leaf herbivory induced similar responses, with treated plants growing less, flowering earlier, and producing fewer seeds than undamaged plants. However, seed size, phenolics and cyanogenic glycosides concentrations did not differ among treatments. Seed germination rates and flowering time of the offspring were similar among maternal treatments. CONCLUSIONS Overall, the results confirm that responses of lima bean to herbivory by leaf beetles are mediated by jasmonate; however, effects on phenological traits are not transmitted to the next generation. We discuss why transgenerational effects of herbivory might be restricted to traits that directly target herbivores.

Organisms of the third trophic level can indirectly interact with plants. However, whether parasitoids of herbivores have a positive effect on plant fitness has been controversial. In addition to possible effects on plant fitness, parasitoid‐mitigated herbivory can modify plant physiological responses and thereby alter the plant‐mediated indirect interactions between different herbivore species. These types of indirect multitrophic interactions remain largely unexplored. Thus, to understand the full effect of the third trophic level on plants, it is necessary to consider the context of the community of interacting species, both herbivores and their enemies. Here, we investigated whether parasitoids of leaf‐feeding caterpillars affect plant fitness (seed quantity and quality) and the consequences for seed‐dwelling insects at the second and third trophic levels through plant‐mediated effects. To test this, we exposed lima bean plants (Phaseolus lunatus), under controlled field conditions, to caterpillars (Spodoptera latifascia) that were unparasitized or parasitized by the parasitoid species Cotesia marginiventris. Later in the season, we measured seed production and infestation by seed beetles and their parasitoids. We found that parasitoids significantly reduced the leaf damage inflicted by the caterpillars, such that the plants suffered no loss in seed production. Yet, parasitoids had no effect on the emergence of seed beetles (Zabrotes subfasciatus and Acanthoscelides obtectus), which was equally reduced in plants attacked by unparasitized and by parasitized caterpillars. Seeds from undamaged plants were significantly more attacked by Z. subfasciatus beetles. Parasitism rates of seed beetle larvae were similar for all treatments. Although parasitized caterpillars did not damage the plants enough to reduce seed production (unlike unparasitized caterpillars), the damage they inflicted induced resistance against other herbivores. Taken together, these results show how parasitoids can indirectly enhance plant fitness in the context of the local multitrophic ecological networks. These findings have significant implications for natural and agricultural systems since they reveal that the indirect interaction between plants and parasitoids can be beneficial in communities with multiple herbivore species.

Highbush blueberry is a crop native to the northeast USA that has been domesticated for about 100 years. This study compared the susceptibility of wild and domesticated/cultivated highbush blueberries to an invasive frugivorous pest, the spotted wing drosophila (Drosophila suzukii). We hypothesized that: 1) cultivated fruits are preferred by D. suzukii for oviposition and better hosts for its offspring than wild fruits; and, 2) wild and cultivated fruits differ in physico-chemical traits. Fruits from wild and cultivated blueberries were collected from June through August of 2015 and 2016 from 10 to 12 sites in New Jersey (USA); with each site having wild and cultivated blueberries growing in close proximity. The preference and performance of D. suzukii on wild and cultivated blueberries were studied in choice and no-choice bioassays. In addition, we compared size, firmness, acidity (pH), total soluble solids (°Brix), and nutrient, phenolic, and anthocyanin content between wild and cultivated berries. In choice and no-choice bioassays, more eggs were oviposited in, and more flies emerged from, cultivated than wild blueberries. Cultivated fruits were 2x bigger, 47% firmer, 14% less acidic, and had lower °Brix, phenolic, and anthocyanin amounts per mass than wild fruits. Levels of potassium and boron were higher in cultivated fruits, while calcium, magnesium, and copper were higher in wild fruits. These results show that domestication and/or agronomic practices have made blueberries more susceptible to D. suzukii, which was associated with several physico-chemical changes in fruits. Our study documents the positive effects of crop domestication/cultivation on an invasive insect pest.

Plant domestication is assumed to result in reduced levels of defensive compounds in crops, because this makes the plants more suitable for consumption by humans and livestock. We argue that this should mainly be reflected in the concentrations of defense compounds in the plant parts that are used for consumption and not necessarily for other parts of crop plants. We tested this hypothesis for domesticated lima bean (Phaseolus lunatus), by comparing its chemical defenses against a leaf herbivore, the beet armyworm (Spodoptera exigua), and a seed predator, the beetle Zabrotes subfasciatus. For seeds and leaves we determined the concentrations of cyanogenic glycosides (CNGs) in cultivated varieties and wild populations and evaluated the preference and performance of the herbivores when exposed to leaves and seeds from wild and cultivated plants. Concentrations of CNGs were significantly different between wild and cultivated plants. In the leaves the concentration of CNGs in the cultivated varieties were more than double that of the wild leaves. In contrast, seeds from cultivated plants had up to 20 times lower CNG concentration compared to seeds from the wild populations. Insect preference and performance do not parallel the chemical data. Larvae of S. exigua preferred wild leaves but had higher survival on cultivated leaves. The beetles, however, strongly preferred seeds from cultivated plants and females developed more quickly on these seeds. We conclude that domestication of P. lunatus has altered the concentration of CNGs in both the seeds and the leaves in opposite directions. This results in differential effects on the herbivores that attack these two plant structures. The contrasting effect of domestication on different plant tissues can be explained by the fact that bean plants have been specifically selected for human consumption of the seeds. Tissue-specific effects of plant domestication on plant defenses can be expected for other crops as well.

Lima bean plants (Phaseolus lunatus) exhibit compensatory growth responses to herbivory. Among the various factors that have been identified to affect plant compensatory growth are the extent and type of tissue damage, the herbivore's feeding mode and the time of damage. Another factor that can greatly impact plant responses to herbivory, but has been largely ignored in previous studies, is the action of parasitoids. In most cases, parasitoids halt or slow down the development of herbivorous hosts, which, can result in decreased leaf damage, thereby affecting plant responses and ultimately plant fitness. Here, we investigated the effects of two koinobiont parasitoids on the amount of leaf damage inflicted by the Southern armyworm Spodoptera latifascia to wild lima bean, and the consequences of this for plant growth and seed production in the field. We specifically tested the hypothesis that the action of parasitoids will reduce plant damage and that this reduction will alter plant growth responses and seed production. Indeed, we found that in the presence of parasitoids plants suffered less damage than plants with only herbivores. As a consequence, compensatory growth was reduced and more and heavier seeds were produced earlier in the season, compared to plants exposed to only herbivores.

Simple Summary The pepper weevil is an economically important pest that causes major damage to fruits of chili pepper varieties selected for consumption. However, the impact of this pest on wild and ornamental peppers remains unknown. Therefore, we studied the effect of chili domestication on the feeding and oviposition behavior of pepper weevil when exposed to wild chili, ornamental varieties, and varieties used for consumption. More specifically, we examined how changes in fruit and flower size, fruit thickness, spiciness level, and fruit position as a result of the domestication of chili peppers affected their susceptibility to this specialist pepper pest. In addition, we recorded that fruits and flowers from wild and ornamental plants were less susceptible to pepper weevil attacks than those from chili varieties selected for consumption. Our results have important implications for chili pepper breeders and could guide the selection of new resistant varieties against this pest. Abstract The pepper weevil, Anthonomus eugenii, Cano (Coleoptera: Curculionidae), is one of the most destructive pests of chili pepper. It causes extensive damage on varieties selected for consumption. However, the occurrence of this pest on wild and ornamental peppers remains unknown. We investigated the consequences of chili domestication on the feeding and oviposition of A. eugenii on fruits and flowers. We used plants of one wild accession, Bird Eye Pepper, five ornamental varieties (Pops Yellow, Black Pearl, Sedona Sun, Chilli Chilli, and Salsa Deep), and two domesticated varieties selected for consumption (Scotch Bonnet and Jalapeño). First, we characterized the plants according to their fruit and flower sizes, pericarp thickness, capsaicin level, fruit position, and flower color. Then, we evaluated the susceptibility of fruits and flowers to A. eugenii. Overall, domestication increased fruit and flower sizes and pericarp thickness, altered capsaicin levels, and altered fruit position and flower color. Weevils laid more eggs and caused more feeding damage on varieties selected for consumption than on wild and ornamental plants. Our results add to the growing literature on the consequences of crop domestication on herbivores. This knowledge could be integrated into breeding programs to select varieties resistant against the pepper weevil.

The viburnum leaf beetle (VLB), Pyrrhalta viburni (Paykull), is an invasive chrysomelid in North America where it infests native Viburnum shrubs in woody areas and managed landscapes. Despite its invasive and destructive nature, little is known about the chemical ecology of this beetle, and efficient chemical lures for monitoring and trapping this insect have yet to be developed. Using two of the main host plants of VLB in its native range, Viburnum opulus L. (Caprifoliaceae) and V. lantana L., we examined the olfactory preferences of adult females of VLB under laboratory conditions and measured volatile emissions of Viburnum twigs with and without VLB damage. VLB females had a clear preference for V. opulus and V. lantana twigs compared to blank odor sources. In addition, twigs with foliar damage and fresh egg masses were found to be more attractive than noninfested twigs in V. opulus when VLB infestation was recent, but not when twigs had been infested for several weeks. Chemical analyses revealed consistent treatment-specific blends of compounds, which may be used for the elaboration of attractive lures. Future research should focus on the identification of these compounds and on exploring the olfactory preferences of VLB with Viburnum species present in North America.

[Premise] The occurrence and amount of herbivory are shaped by bottom‐up forces, primarily plant traits (e.g., defenses), and by abiotic factors. Addressing these concurrent effects in a spatial context has been useful in efforts to understand the mechanisms governing variation in plant–herbivore interactions. Still, few studies have evaluated the simultaneous influence of multiple sources of bottom‐up variation on spatial variation in herbivory., [Methods] We tested to what extent chemical (phenolics, production of terpenoid glands) and physical (pubescence) defensive plant traits and climatic factors are associated with variation in herbivory by leaf‐chewing insects across populations of wild cotton (Gossypium hirsutum)., [Results] We found substantial population variation in cotton leaf defenses and insect leaf herbivory. Leaf pubescence, but not gossypol gland density or phenolic content, was significantly negatively associated with herbivory by leaf‐chewing insects. In addition, there were direct effects of climate on defenses and herbivory, with leaf pubescence increasing toward drier conditions and leaf damage increasing toward wetter and cooler conditions. There was no evidence, however, of indirect effects (via plant defenses) of climate on herbivory., [Conclusions] These results suggest that spatial variation in insect herbivory on wild G. hirsutum is predominantly driven by concurrent and independent influences of population variation in leaf pubescence and climatic factors., This research was financially supported by a Swiss seed money grant (for collaborations with Latin America) to T.C.J.T. and V.P.T. and by a Spanish National Research Grant (AGL2015‐70748‐R) to X.M.

Species of Horismenus Walker associated with bruchid beetles are investigated and five new species are described. Some of the new species are very similar to already described species and have previously been misidentified. The new species include H. depressoides sp. nov. similar to H. depressus Gahan , H. stator sp. nov. similar to H. missouriensis (Ashmead), and H. dennoi & H. multistriatus spp. nov., both similar to H. butcheri Hansson & Aebi and one species, H. gabrielae sp. nov., that is morphologically distinct from the other species but also associated with this host group. All 14 Horismenus species associated with bruchid beetles are included in a key. New host and distributional records are included for H. depressus.

Cyanogenic glycosides present in the seeds of wild lima bean plants are associated with seedling defense but do not affect seed germination and seedling growth. Wild lima bean plants contain cyanogenic glycosides (CNGs) that are known to defend the plant against leaf herbivores. However, seed feeders appear to be unaffected despite the high levels of CNGs in the seeds. We investigated a possible role of CNGs in seeds as nitrogen storage compounds that influence plant growth, as well as seedling resistance to herbivores. Using seeds from four different wild lima bean natural populations that are known to vary in CNG levels, we tested two non-mutually exclusive hypotheses: (1) seeds with higher levels of CNGs produce seedlings that are more resistant against generalist herbivores and, (2) seeds with higher levels of CNGs germinate faster and produce plants that exhibit better growth. Levels of CNGs in the seeds were negatively correlated with germination rates and not correlated with seedling growth. However, levels of CNGs increased significantly soon after germination and seeds with the highest CNG levels produced seedlings with higher CNG levels in cotyledons. Moreover, the growth rate of the generalist herbivore Spodoptera littoralis was lower in cotyledons with high-CNG levels. We conclude that CNGs in lima bean seeds do not play a role in seed germination and seedling growth, but are associated with seedling defense. Our results provide insight into the potential dual function of plant secondary metabolites as defense compounds and storage molecules for growth and development.

Thousands of plant species throughout tropical and temperate zones secrete extrafloral nectar to attract ants, whose presence provides an indirect defense against herbivores. Extrafloral nectaries are located close to flowers and may modify competition between ants and pollinators. Here, we used Lima bean (Phaseolus lunatus L.) to study the plants interaction between ants and flower visitors and its consequences for plant fitness. To test these objectives, we carried out two field experiments in which we manipulated the presence of ants and nectar production via induction with jasmonic acid (JA). We then measured floral and extrafloral nectar production, the number of patrolling ants and flower visitors as well as specific plant fitness traits. Lima bean plants under JA induction produced more nectar in both extrafloral nectaries and flowers, attracted more ants and produced more flowers and seeds than non-induced plants. Despite an increase in floral nectar in JA plants, application of this hormone had no significant effects on flower visitor attraction. Finally, ant presence did not result in a decrease in the number of visits, but our results suggest that ants could negatively affect pollination efficiency. In particular, JA-induced plants without ants produced a greater number of seeds compared with the JA-treated plants with ants. Resumen Miles de especies de plantas en zonas tropicales y templadas producen nectar extra floral con el fin de atraer hormigas, cuya presencia representa una defensa indirecta contra los herbivoros. Los nectarios extra florales se encuentran cerca de las flores y pueden generar conflictos entre hormigas y polinizadores. En el presente estudio utilizamos plantas de frijol Lima (Phaseolus lunatus L.) para investigar la interaccion entre hormigas y los visitantes de flores y sus consecuencias para la adecuacion de las plantas. Se llevaron a cabo dos experimentos en los cuales manipulamos la presencia de hormigas y la produccion de nectar a traves de la induccion con acido jasmonico. Se midio la produccion de nectar floral y extra floral, el numero de hormigas que patrullaban las plantas y el numero de visitantes florales, asi como algunos caracteres de las plantas. Las plantas inducidas con acido jasmonico produjeron mas nectar en ambas estructuras, atrajeron mas hormigas y produjeron mas flores y semillas que las plantas control, no inducidas. A pesar del aumento en el nectar floral en plantas inducidas con acido jasmonico, la aplicacion de esta hormona no tuvo efectos significativos sobre la atraccion de los polinizadores. Por ultimo, la presencia de hormigas no tuvo un efecto significativo sobre la abundancia de polinizadores. Sin embargo, nuestros resultados sugieren que la presencia de hormigas puede afectar negativamente la eficiencia de los polinizadores. Especificamente, las plantas inducidas con acido jasmonico en las que se excluyeron las hormigas, produjeron mas semillas que las plantas inducidas pero con presencia hormigas.

1. An increasing number of studies have addressed the mechanisms by which plant inter-specific variation influence interactions at higher trophic levels, but little is known about the underlying plant traits driving these dynamics. 2. Here we investigated the effects of host plant species on herbivore-parasitoid interactions and the underlying traits driving such effects. For this, we measured the abundance of seed-eating bruchids and their parasitoids across seven sympatric populations of the bean species Phaseolus coccineus and Phaseolus vulgaris in Central Mexico. To investigate the mechanisms underlying differences between bean species in bruchid-parasitoid interactions, we carried out two laboratory experiments to test whether bruchid and parasitoid performance differed between plant species. We also measured seed size and phenolic compounds to investigate if seed traits mediate bruchid-parasitoid interactions by influencing herbivore susceptibility or resistance to parasitoids. 3. Field surveys revealed that the rate of parasitoid recruitment to bruchids was significantly higher on P. vulgaris than on P. coccineus. Subsequent laboratory bioassays indicated that bruchids developed more slowly and exhibited lower fitness on P. vulgaris seeds than on P. coccineus seeds. Accordingly, we found that bean species differed in seed size, with P. vulgaris having smaller (less nutritious) seeds, which explains why bruchid development was slower on this plant species. 4. These results provide a mechanism for why bruchids exhibited higher parasitism rates on seeds of P. vulgaris in the field which could be due to Slow-Growth/High-Mortality effects, a smaller physical refuge provided by the seed, or both factors. The roles of these mechanisms remain inconclusive without further study.

In this study, the role of native plant growth-promoting rhizobacteria (PGPR) as bio-inoculants was assessed as an alternative to ameliorate Ilex paraguariensis St. Hill. growth in nursery comparing poorer (soil) versus richer (compost) substrates. Twelve rhizospheric strains isolated from yerba mate plantations were evaluated in vitro for their potential as PGPRs. Three isolates, identified as Kosakonia radicincitans YD4, Rhizobium pusense YP3, and Pseudomonas putida YP2, were selected on the basis of their N2 fixation activity, IAA-like compound and siderophore production, and phosphate solubilization. A highly significant positive effect of bio-inoculation with the native isolates was observed in 5-month-old seedlings cultivated in soil. The highest increase was observed in seedlings inoculated with K. radicincitans YD4 with an increase of 183 % in the dry shoot weight and a 30 % increase in shoot N content. In contrast, in compost, no increment in the dry weight was observed; however, an increase in content in some macronutrients in shoots was observed. Remarkably, when plant biomass was compared between soil and compost, seedlings inoculated with K. radicincitans YD4 in soil produced the highest yields, even though higher yields could be expected in compost due to the richness of this substrate. In conclusion, bio-inoculation of yerba mate seedlings with native PGPR increases the yield of this crop in nursery and could represent a promising sustainable strategy to improve yerba mate growth in low-fertility soils.

Crop domestication is the process of artificially selecting plants to increase their suitability to human tastes and cultivated growing conditions. There is increasing evidence that crop domestication can profoundly alter interactions among plants, herbivores, and their natural enemies. However, there are few generalizable predictions on how insect herbivores and natural enemies should respond to artificial selection of specific plant traits. We reviewed the literature to determine how different insect herbivore feeding guilds and natural enemy groups (parasitoids and predators) respond to existing variation in wild and cultivated plant populations for plant traits typically targeted by domestication. Our goal was to look for broad patterns in tritrophic interactions to generate support for a range of potential outcomes from human-mediated selection. Overall, we found that herbivores benefit from directional selection on traits that have been targeted by domestication, but the effects on natural enemies were less studied and less consistent. In general, herbivores appear to mirror human preferences for higher nutritional content and larger plant structures. In contrast, the general effect of lowered plant secondary metabolites did not always influence herbivores consistently. Given that crop domestication appears to be a transformative process that fundamentally alters insect–plant interactions, we believe that a more detailed understanding of the community-wide effects of crop domestication is needed to simultaneously stimulate both biological control and plant breeding efforts to enhance sustainable pest control.

Crop domestication is the process of artificially selecting plants to increase their suitability to human requirements: taste, yield, storage, and cultivation practices. There is increasing evidence that crop domestication can profoundly alter interactions among plants, herbivores, and their natural enemies. Overall, little is known about how these interactions are affected by domestication in the geographical ranges where these crops originate, where they are sympatric with the ancestral plant and share the associated arthropod community. In general, domestication consistently has reduced chemical resistance against herbivorous insects, improving herbivore and natural enemy performance on crop plants. More studies are needed to understand how changes in morphology and resistance-related traits arising from domestication may interact with environmental variation to affect species interactions across multiple scales in agroecosystems and natural ecosystems.

The domestication of beans has selected for larger seeds in cultivated plants compared to their wild relatives. This has not only resulted in an enhanced resource for humans, but also for the insects that feed on these seeds. Seed beetles that attack wild and cultivated seeds often lay several eggs on a single seed. We hypothesized that the larger seed size of domesticated beans will mitigate the competition among the larvae that hatch from these eggs, with important implications for their growth and survival. To test this we examined how seed size of wild and cultivated Phaseolus lunatus (lima bean) affect the performance of the Mexican bean weevil Zabrotes subfasciatus, an important pest of beans in Mexico. A negative correlation was found between the initial number of eggs on a seed and the weight of female beetles that emerged, but only for the much smaller wild seeds. Similarly, beetle survival was found to be negatively correlated with competition intensity only on wild seeds. Our results imply that by selecting for larger seeds, domestication of Phaseolus lunatus has reduced the intensity of intraspecific larval competition of Z. subfasciatus.

Crop domestication has been embraced as a model system to study the genetics of plant evolution. Yet, the role of the environment, including biotic forces such as microbial and insect communities, in contributing to crop phenotypes under domestication and diversification has been poorly explored. In particular, there has been limited progress in understanding how human selection, agricultural cultivation (soil disturbance, fertilization, and irrigation), and biotic forces act as selective pressures on crop phenotypes. For example, geographically-structured pathogenic, pestiferous, and mutualistic interactions with crop plants have likely given rise to landraces that interact differently with local microbial and insect communities. In order to understand the adaptive role of crop traits, we argue that more studies should be conducted in the geographic centers of origin to test hypotheses on how abiotic, biotic, and human selective forces have shaped the phenotypes of domesticated plants during crop domestication and subsequent diversification into landraces. In these centers of origin, locally endemic species associated with wild ancestors have likely contributed to the selection on plant phenotypes. We address a range of questions that can only be studied in the geographic center of crop origin, placing emphasis on Mesoamerican polyculture systems, and highlight the significance of in situ studies for increasing the sustainability of modern agricultural systems.

Cyanogenic glycosides (CNGs) act as feeding or oviposition deterrents and are toxic after enzymatic hydrolysis, thus negatively affecting herbivore performance. While most studies on CNGs focus on leaf herbivores, here we examined seeds from natural populations of Phaseolus lunatus in Mexico. The predominant CNGs, linamarin and lotaustralin, were quantified for each population by using ultra-high pressure liquid chromatography-mass spectrometry. We also examined whether there was a correlation between the concentration of CNGs and the performance of the Mexican bean beetle, Zabrotes subfasciatus, on seeds from each population(.) The concentrations of CNGs in the seeds were relatively high compared to the leaves and were significantly variable among populations. Surprisingly, this had little effect on the performance of the bruchid beetles. Zabrotes subfasciatus can tolerate high concentrations of CNGs, most likely because of the limited β-glucosidase activity in the seeds. Seed herbivory does not appear to liberate hydrogen cyanide due to the low water content in the seed. This study illustrates the importance of quantifying the natural variation and activity of toxic compounds in order to make relevant biological inferences about their role in defense against herbivores.

There is an increasing awareness that herbivory by one insect species induces changes in a plant that affect the performance of other herbivore species that feed on the same plant. However, previous studies of interspecies interactions mediated by plant defense responses have rarely taken into account different insect guilds or the third trophic level. Using a combination of field and laboratory experiments, we examined how early-season herbivory in lima bean plants (Phaseolus lunatus) by the leaf-chewing herbivore Cerotoma ruficornis and the bean pod weevil Apion godmani affects the abundance and performance of the seed beetle Zabrotes subfasciatus and that of its parasitoid Stenocorse bruchivora, which occurs on the plants at the end of the growing season. In addition, we determined the consequences of early-season herbivore-induced defenses on plant performance. We hypothesized that early-season induction would affect plant reproduction and, hence, would alter the suitability of seeds for late-season seed-eating beetles, and that this would in turn alter the vulnerability of these seed beetles to parasitoids. We found strong support for these hypotheses. In the field, early-season herbivory negatively affected plant reproduction and seeds of these plants suffered lower levels of infestation by seed-eating beetles, which in turn suffered less parasitism. Laboratory assays with field-collected seeds confirmed that the performance of beetles and parasitoids was lower on seeds from plants that had been subjected to early-season herbivory. Further analyses revealed that seeds produced by control plants were larger, heavier, and had a higher concentration of cyanogenic glycosides and total protein content than seeds from plants subjected to herbivory. Our results provide insight into how direct and indirect interactions between and within different trophic levels affect the dynamics and structure of complex communities.

PREMISE OF STUDY Although there is increasing recognition of the effects of plant intraspecific diversity on consumers, the mechanisms by which such effects cascade-up to higher trophic levels remain elusive. METHODS We evaluated the effects of plant (lima bean, Phaseolus lunatus) intraspecific diversity on a suite of insect herbivores (leaf-chewers, aphids, and seed-eating beetles) and their third trophic-level associates (parasitoids and aphid-tending ants). We established plots of three plants, classified as monocultures of one population source or polycultures with mixtures of three of the four population sources (N = 16 plots per level of diversity). Within each plot, plants were individually placed in pots and canopy contact was prevented, therefore eliminating diversity effects on consumers arising from changes in plant traits due to plant physical interactions. KEY RESULTS Plant diversity reduced damage by leaf-chewers as well as aphid abundance, and the latter effect in turn reduced ant abundance. In contrast, plant diversity increased the abundance of seed-eating beetles, but did not influence their associated parasitoids. There were no effects of diversity on seed traits potentially associated with seed predation, suggesting that differences in early season herbivory between monocultures and polycultures (a likely mechanism of diversity effects on plants since plant interactions were prevented) did not drive concomitant changes in plant traits. CONCLUSIONS This study emphasizes that effects of plant intraspecific diversity on consumers are contingent upon differences in associate responses within and among higher trophic levels and suggests possible mechanisms by which such effects propagate up this food web.

Plant chemistry can strongly influence interactions between herbivores and their natural enemies, either by providing volatile compounds that serve as foraging cues for parasitoids or predators, or by affecting the quality of herbivores as hosts or prey. Through these effects plants may influence parasitoid population genetic structure. We tested for a possible specialization on specific crop plants in Chelonus insularis and Campoletis sonorensis, two primary parasitoids of the fall armyworm, Spodoptera frugiperda. Throughout Mexico, S. frugiperda larvae were collected from their main host plants, maize and sorghum and parasitoids that emerged from the larvae were used for subsequent comparison by molecular analysis. Genetic variation at eight and 11 microsatellites were respectively assayed for C. insularis and C. sonorensis to examine isolation by distance, host plant and regional effects. Kinship analyses were also performed to assess female migration among host-plants. The analyses showed considerable within population variation and revealed a significant regional effect. No effect of host plant on population structure of either of the two parasitoid species was found. Isolation by distance was observed at the individual level, but not at the population level. Kinship analyses revealed significantly more genetically related—or kin—individuals on the same plant species than on different plant species, suggesting that locally, mothers preferentially stay on the same plant species. Although the standard population genetics parameters showed no effect of plant species on population structure, the kinship analyses revealed that mothers exhibit plant species fidelity, which may speed up divergence if adaptation were to occur.

PREMISE OF THE STUDY: Following herbivore attack, plants can either reduce damage by inducing defenses or mitigate herbivory effects through compensatory growth and reproduction. It is increasingly recognized that such induced defenses in plants are herbivore-specific, but less is known about the specificity of compensatory responses. Damage by multiple herbivores may also lead to synergistic effects on induction and plant fitness that differ from those caused by a single herbivore species. Although largely unstudied, the order of arrival and damage by different herbivore species might also play an important role in the impacts of herbivory on plants., METHODS: We investigated the specificity of defense induction (phenolics) and effects on growth (number of stems and leaves) and reproduction (number of seeds, seed mass, and germination rate) from feeding by two generalist leaf-chewing herbivores (Spodoptera eridania and Diabrotica balteata) on Phaseolus lunatus plants and evaluated whether simultaneous attack by both herbivores and their order of arrival influenced such dynamics., KEY RESULTS: Herbivory increased levels of leaf phenolics, but such effects were not herbivore-specific. In contrast, herbivory enhanced seed germination in an herbivore-specific manner. For all variables measured, the combined effects of both herbivore species did not differ from their individual effects. Finally, the order of herbivore arrival did not influence defense induction, plant growth, or seed number but did influence seed mass and germination., CONCLUSIONS: Overall, this study highlights novel aspects of the specificity of plant responses induced by damage from multiple species of herbivores and uniquely associates such effects with plant lifetime fitness., Swiss National Science Foundation (Project No. 3100AO-10923), Ramon y Cajal Research Programme (RYC-2013-13230)

Bruchid beetles in the genus Zabrotes are important pests of field and stored beans all around the world and cause enormous economical losses in Mexico and Central America. Native parasitoids have been successfully used to suppress infestations by bruchid beetles in Africa, but few studies have assessed their potential to reduce seed damage in the New World and no successful biological control programs have been implemented, mainly due to the poor knowledge on their biology, systematics and ecology in this region. In this study, we used molecular tools to describe a new complex of three parasitoid species of bruchid beetles in the genus Horismenus, and investigated the level of gene flow and presence of ecotypes in this complex. We also examined the specific association between species of Horismenus and two sibling species of Zabrotes beetles, in order to evaluate their potential as biological control agents. Microsatellite data support the previous morphological description of three species, H. butcheri, H. missouriensis and H. depressus, but suggest some gene flow between H. missouriensis and H. depressus. Host-plant is shown to be the most important factor determining the ecological distribution of the two Zabrotes species, whereas altitude explains most of the distribution of the three Horismenus species. These results complement our understanding of this tritrophic system, providing a solid base for a potential biological control program using native parasitoids.

Horismenus parasitoids are an abundant and understudied group of eulophid wasps found mainly in the New World. Recent surveys based on morphological analyses in Costa Rica have quadrupled the number of named taxa, with more than 400 species described so far. This recent revision suggests that there is still a vast number of unknown species to be identified. As Horismenus wasps have been widely described as parasitoids of insect pests associated with crop plants, it is of high importance to properly establish the extant diversity of the genus, in order to provide biological control practitioners with an exhaustive catalog of putative control agents. In this study, we first collected Horismenus wasps from wild Phaseolus bean seeds in Central Mexico and Arizona to assess the genetic relatedness of three morphologically distinct species with overlapping host and geographical ranges. Sequence data from two nuclear and two mitochondrial gene regions uncovered three cryptic species within each of the three focal species (i.e., H. missouriensis, H. depressus and H. butcheri). The monophyly of each cryptic group is statistically supported (except in two of them represented by one single tip in which monophyly cannot be tested). The phylogenetic reconstruction is discussed with respect to differences between gene regions as well as likely reasons for the differences in variability between species.

Herbivore-induced volatiles are widespread in plants. They can serve as alert signals that enable neighbouring leaves and plants to pre-emptively increase defences and avoid herbivory damage. However, our understanding about the factors mediating volatile organic compound (VOC) signal interpretation by receiver plants and the degree to which multiple herbivores affect VOC signals is still limited. Here we investigated whether plant responses to damage-induced VOC signals were population specific. As a secondary goal, we tested for interference in signal production or reception when plants were subjected to multiple types of herbivore damage. We factorially crossed the population sources of paired Phaseolus lunatus plants (same vs. different population sources) with a mechanical damage treatment to one member of the pair (i.e. the VOC emitter, damaged vs. control), and we measured herbivore damage to the other plant (the VOC receiver) in the field. Prior to the experiment, both emitter and receiver plants were naturally colonized by aphids, enabling us to test the hypothesis that damage from sap-feeding herbivores interferes with VOC communication by including emitter and receiver aphid abundances as covariates in our analyses. One week after mechanical leaf damage, we removed all the emitter plants from the field and conducted fortnightly surveys of leaf herbivory. We found evidence that receiver plants responded using population-specific “dialects” where only receivers from the same source population as the damaged emitters suffered less leaf damage upon exposure to the volatile signals. We also found that the abundance of aphids on both emitter and receiver plants did not alter this volatile signalling during both production and reception despite well-documented defence crosstalk within individual plants that are simultaneously attacked by multiple herbivores. Overall, these results show that plant communication is highly sensitive to genetic relatedness between emitter and receiver plants and that communication is resilient to herbivore co-infestation., This research was financially supported by a grant from the Swiss National Science Foundation (Project No. 3100AO-10923) to BB and by the Ramon y Cajal Research Programme (RYC-2013-13230) to XM.

The effect of different bean varieties on the performance of the bruchid beetle Zabrotes subfasciatus Boheman (Coleoptera: Bruchidae), was determined by using wild and cultivated seeds of the genus Phaseolus. Results showed that the quality of the host plant affected the performance and the oviposition behavior of female beetles. Overall, bruchid performance was higher on cultivated seeds than on wild seeds. It was also found that the oviposition behavior and the performance of their offspring differed between females that originated from wild versus cultivated seeds. We also demonstrated the importance of a genetic component in bruchid performance: longevity, fecundity, larval development, adult size, and the sex ratio of the progeny varied according to their maternal lineage (‘familyrsquo;). For example, on the same host type, some females laid twice as many eggs as females from other ‘familiesrsquo;, and the sex ratio among the offspring correlated with that of their mother. Thus, the performance and behavior of Z. subfasciatus are not only affected by environmen tal factors such as the quality of the seeds on which they develop, but also have a genetic basis which can counterbalance a less suitable quality of the host plant. For a crop pest such as Z. subfasciatus, its ability to survive and adapt on host plants of differing quality may be an important attribute to consider for pest management.

Adaptation to host-plant defences through key innovations is a driving force of evolution in phytophagous insects. Species of the neotropical bruchid genus Acanthoscelides Schilsky are known to be associated with specific host plants. The speciation processes involved in such specialization pattern that have produced these specific associations may reflect radiations linked to particular kinds of host plants. By studying host-plant associations in closely related bruchid species, we have shown that adaptation to a particular host-plant (e.g. with a certain type of secondary compounds) could generally lead to a radiation of bruchid species at the level of terminal branches. However, in some cases of recent host shifts, there is no congruence between genetic proximity of bruchid species, and taxonomic similarity of host plants. At deeper branches in the phylogeny, vicariance or long-distance colonization events seem to be responsible for genetic divergence between well-marked clades rather than adaptation to host plants. Our study also suggests that the few species of Acanthoscelides described from the Old World, as well as Neotropical species feeding on Mimosoideae, are misclassified, and are more closely related to the sister genus Bruchidius.

For parasitoids of herbivores, the two most important biotic factors that will influence their fitness are the host species that they attack and the plant species that the host feeds on. Variation in these two trophic levels because of different habitat characteristics may largely drive the evolution of the interaction between parasitoids and their hosts. Through transplant experiments with three plant–insect populations in Mexico, we examined the consequences of plant variation for the interaction between a bruchid beetle, Zabrotes subfasciatus (Boheman) (Coleoptera: Bruchidae), that feeds on bean seeds of the genus Phaseolus L. (Leguminosae: Phaseolinae) and one of its main parasitoids, Stenocorse bruchivora (Crawford) (Hymenoptera: Braconidae). Results revealed great variation in performance among parasitoid populations. Both the population of origin of the parasitoid and of the host plant influenced the performance of developing parasitoids as well as adult oviposition behavior. Wasps from the Atila population were more likely to parasitize the herbivore and developed faster than wasps from the other two populations, Malinalco and Tepoztlan. The results can be explained in part by the spatial distribution of the host plant, host availability, and seed quality in this population. Variation in performance among parasitoid populations decreased when wasps were exposed to their host in cultivated seeds. This could be caused by the better and less variable quality of this novel resource, and consequently, of the bruchid host. The results from this study indicate that both host plant quality and genetic variation among populations are crucial factors in determining the nature and evolution of the interaction between parasitoids and their herbivorous hosts.

Acanthoscelides obtectus Say is a bruchid species of Neotropical origin, and is specialized on beans of the Phaseolus vulgaris L. group. Since the domestication and diffusion of beans, A. obtectus has become cosmopolitan through human-mediated migrations and is now a major pest in bean granaries. Using phylogeographic methods applied to mitochondrial DNA (mtDNA) and nuclear microsatellite molecular markers, we show that the origin of this species is probably further south than Mesoamerica, as commonly thought. Our results also indicate that A. obtectus and its Mesoamerican sister species Acanthoscelides obvelatus, two morphologically close species differing principally in voltinism, speciated in allopatry: A. obtectus (multivoltine) arising in Andean America and A. obvelatus (univoltine) in Mesoamerica. In contrast to Mesoamerica where beans fruit once yearly, wild beans in Andean America fruit year-round, especially in regions showing little or no seasonality. In such habitats where resources are continuously present, multivoltinism is adaptive. According to existing hypotheses, multivoltinism in A. obtectus is a new adaptation that evolved after bean domestication. Our data suggest the alternative hypothesis that multivoltinism is an older trait, adapted to exploit the year-round fruiting of wild beans in relatively aseasonal habitats, and allowed A. obtectus to become a pest in bean granaries. This trait also permitted this species to disperse through human-mediated migrations associated with diffusion of domesticated beans. We also show that diversity of Old World A. obtectus populations can be quite well explained by a single colonization event about 500 bp. Human-mediated migrations appear not to be rare, as our results indicate a second more recent migration event from Andean America to Mexico.

Acanthoscelides Schilsky is a large genus of neotropical bruchid beetles, in which most species show host plant specialization. Acanthoscelidesobtectus and Acanthoscelides obvelatus are two sibling species specialized on Phaseolus beans, and are therefore considered pests. Up to now, thestatus of these two taxa has remained unclear, the few studies conducted having failed to elucidate whether these are two differentiated species ora single morphologically variable species. In addition, A. obvelatus has not been taken into account in the great majority of studies of beanbruchids. In this morphological and genetic study, we show that A. obtectus and A. obvelatus are two true non-hybridizing species, whichdiverged about 22 Mya. Although the two species demonstrate only few morphological differences, we point out some diagnostic characters thatenable their identification in the field. We also address a genetic method of differentiation of the two species, based on species-specificmicrosatellite loci. The strong morphological resemblance of these two species, despite their ancient divergence, may be the result of evolutionarystasis, which could be the consequence of stabilizing selection. Niche differentiation could enable the two species to coexist indefinitely.Key words: Sibling species – bruchids – coleoptera – phylogenetic studies – evolutionary stasis