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The ecological niche of aphids is largely defined by the phloem sap of plants, which they consume. Previous studies revealed that aphids may change the phloem sap metabolome and that a previous aphid infestation may benefit them. As aphids reproduce parthenogenetically, the performance and preference of aphids of the same monoclonal aphid lineage can be compared between previously uninfested and previously aphid‐infested plants.Wheat (Triticum aestivum) leaves were infested by clonal lineages of Sitobion avenae aphids for 9–10 days. Leaf phloem exudates were analysed using amino acid profiling and metabolic fingerprinting, capturing mainly specialised metabolites. It was investigated whether aphid colony sizes differ between leaves that were previously uninfested or infested by aphids of a different clonal lineage or by aphids of the same clonal lineage and whether aphids show a preference for any of these leaves.The relative concentrations of metabolites in the phloem exudates were not affected by aphid infestation. Aphid colonies were partly larger on previously aphid‐infested leaves than on control leaves. However, this effect was transient and finally colonies had similar sizes. Given a choice between previously aphid‐infested and uninfested leaves, S. avenae nymphs showed no preferences.The findings that positive effects of previous aphid infestation on aphid performance are transient and that the performance but not the preference of the aphids was affected by previous aphid infestation highlight the temporal dynamics and complexity of aphid–plant interactions. Niche alteration processes may be partly involved in these interactions. [ABSTRACT FROM AUTHOR]

Microbes associated with flowers and leaves affect plant health and fitness and modify the chemical phenotypes of plants with consequences for interactions of plants with their environment. However, the drivers of bacterial communities colonizing above‐ground parts of grassland plants in the field remain largely unknown. We therefore examined the relationships between phytochemistry and the epiphytic bacterial community composition of flowers and leaves of Ranunculus acris and Trifolium pratense. On 252 plant individuals, we characterized primary and specialized metabolites, that is, surface sugars, volatile organic compounds (VOCs), and metabolic fingerprints, as well as epiphytic flower and leaf bacterial communities. The genomic potential of bacterial colonizers concerning metabolic capacities was assessed using bacterial reference genomes. Phytochemical composition displayed pronounced variation within and between plant species and organs, which explained part of the variation in bacterial community composition. Correlation network analysis suggests strain‐specific correlations with metabolites. Analysis of bacterial reference genomes revealed taxon‐specific metabolic capabilities that corresponded with genes involved in glycolysis and adaptation to osmotic stress. Our results show relationships between phytochemistry and the flower and leaf bacterial microbiomes suggesting that plants provide chemical niches for distinct bacterial communities. In turn, bacteria may induce alterations in the plants' chemical phenotype. Thus, our study may stimulate further research on the mechanisms of trait‐based community assembly in epiphytic bacteria. [ABSTRACT FROM AUTHOR]

Inbreeding and herbivory can interactively reduce the performance of flowering plants. Here, we investigated whether the magnitude of plant inbreeding depression increases under herbivory as a result of diminished leaf metabolic responses to herbivory in inbreds, which entails increased herbivore growth and feeding damage. We additionally explored whether genetic differentiation among native and invasive plant populations impacts the magnitude and direction of these inbreeding × herbivory interactions.Inbred and outbred plants from eight European (native) and eight North American (invasive) populations of Silene latifolia were exposed to two consecutive control or herbivory treatments (infestation with larvae of Mamestra brassicae). After the first treatment, leaf metabolic responses to herbivory were assessed with untargeted metabolic fingerprinting using UHPLC‐ESI+‐QTOF‐MS/MS. After the second herbivory treatment, herbivore growth and plant feeding damage were assessed. Moreover, plant performance traits were recorded 4 weeks after the second herbivory treatment.Metabolic fingerprinting revealed that changes in the pool sizes of various metabolic features in response to herbivory were less intense in inbred than outbred plants from native and invasive populations. While herbivore growth and feeding damage were largely unaffected by plant breeding status in invasive populations, herbivores consumed more biomass from, but showed reduced growth on, inbred than outbred native plants. The magnitude of inbreeding depression in plant performance traits was not affected by herbivory.Synthesis. Our findings suggest that inbreeding compromises herbivory‐induced metabolic defences in S. latifolia, and simultaneously reduces the nutritional quality of plants. The magnitude and direction of these inbreeding effects were shaped by genetic differentiation among native and invasive plants. These range‐specific responses provide novel insights into the role of inbreeding x herbivory interactions in invasion success. Inbreeding and herbivory can interactively reduce plant performance. Using native and invasive Silene latifolia populations, we found support that inbreeding compromises herbivory‐induced metabolic plant defences as well as plant nutritional values, which shapes herbivore growth and feeding damage. The magnitude and direction of these inbreeding effects were modified by genetic differentiation among native and invasive plants. These range‐specific responses highlight the need to investigate multiple populations with different evolutionary histories to gain a deeper understanding of inbreeding × herbivory interactions and provide novel insights into the role of these interactions in invasion success. [ABSTRACT FROM AUTHOR]

Summary: Phloem sap quality can differ between and within plants, and affect the performance of aphids. In turn, aphid infestation may change the chemical composition and nutritional value of phloem sap. However, the effects of different aphid species on the overall phloem sap composition of distinct parts within plant individuals in relation to aphid performance remain unclear.To test the specificity of plant responses to aphids, we used two chemotypes of Tanacetum vulgare plants and placed the monophagous aphids Macrosiphoniella tanacetaria and Uroleucon tanaceti on different plant parts (stems close to the inflorescence, young and old leaves). Aphid population growth was determined and sugars, organic acids, amino acids and metabolic fingerprints of phloem exudates were analysed.Macrosiphoniella tanacetaria performed best on stems, whereas U. tanaceti performed best on old leaves, indicating differences in niche conformance. Aphid infestation led to distinct changes in the phloem exudate composition of distinct metabolite classes, differing particularly between plant parts but less between chemotypes.In summary, plant responses to aphids are highly specific for the chemotype, plant part, metabolite class and aphid species. These changes may indicate that aphids construct their own niche, optimizing the food quality on the plant parts they prefer. [ABSTRACT FROM AUTHOR]