Kaltenegger, E. | bioRxiv Science

bioRxiv2025

Aphid infestation induces plant-sex-specific changes in floral chemistry and pollinator behaviour in Silene latifolia

Pollinators share the complex information and resource landscape of their host plants with herbivores. Yet, how sap feeders affect floral attractiveness to pollinators remains poorly understood, despite the critical role of this tripartite interaction in natural and agricultural ecosystems. In dioecious plant species, which display pronounced sexual dimorphism, these intricate interactions may vary in magnitude and direction between females and males, with significant implications for plant population dynamics and species co-evolution. In this study, we examined how infestation by the oligophagous aphid Brachycaudus lychnidis affects sex-specific interactions among the dioecious plant Silene latifolia and its specialist moth pollinator Hadena bicruris. We exposed male and female plants to aphid herbivory and evaluated its effects on floral traits (visual cues, floral scent, and nectar chemistry) and pollinator behaviour. While aphid infestation affected some floral traits equally in both sexes and others more strongly in males or in females, we observed stronger declines in female attractiveness to pollinators, which were mainly linked to nectar compounds potentially acting as feeding cues or behavioural modulators. We discuss our results in the light of sexual selection and plant defence theory while emphasizing the complementarity of female and male traits in stabilizing this specialized plant-pollinator-herbivore system. HighlightAphid infestation alters multiple visual and chemical floral traits in a plant sex-specific manner, leading to reduced attractiveness to moth pollinators in female plants, but not in males. Graphical AbstractPlant-sex specific effect of aphid infestation on floral traits (number, size, colour, scent composition, nectar quantity and composition) and pollinator behaviour. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=171 SRC="FIGDIR/small/666187v3_ufig1.gif" ALT="Figure 1"> View larger version (38K): org.highwire.dtl.DTLVardef@14256borg.highwire.dtl.DTLVardef@a49b05org.highwire.dtl.DTLVardef@bd8c92org.highwire.dtl.DTLVardef@57eb93_HPS_FORMAT_FIGEXP M_FIG C_FIG

plant biology↗

bioRxiv2023

In defense of Apocynaceae: inference on evolution of pyrrolizidine alkaloids from evolution of an enzyme in their biosynthetic pathway, homospermidine synthase

PremiseWhen enzymes encoded by paralogous genes produce identical specialized metabolites in distantly related plant lineages, it is strong evidence of parallel phenotypic evolution. Inference of phenotypic homology for metabolites produced by orthologous genes is not so straightforward, however, since orthologs may be recruited in parallel into novel pathways. Prior research on pyrrolizidine alkaloids (PAs), specialized metabolites of Apocynaceae, reconstructed evolution of homospermidine synthase (HSS), an enzyme of PA biosynthesis, and inferred a single origin of PAs because HSS enzymes of all known PA-producing Apocynaceae species are orthologous and descended from an ancestral enzyme with the predicted motif (VXXXD) of an optimized HSS. MethodsWe increased sampling, tested the effect of amino acid motif on HSS function, revisited motif evolution, and tested for selection to infer evolution of HSS function and its correlation with phenotype. Key resultsSome evidence supports a single origin of PAs: an IXXXD HSS, similar in function to VXXXD HSS, evolved in the shared ancestor of all PA-producing species; loss of optimized HSS occurred multiple times via pseudogenization and perhaps via evolution of an IXXXN motif. Other evidence indicates multiple origins: the VXXXD motif, highly correlated with the PA phenotype, evolved two or four times independently; the ancestral IXXXD gene was not under positive selection while some VXXXD genes were; substitutions at sites experiencing positive selection occurred on multiple branches in the HSS-like gene tree. ConclusionsComplexity of the genotype-function-phenotype map confounds inference of PA homology from HSS evolution in Apocynaceae.

evolutionary biology↗