Trait measurements
The plant genotypes used in this study were previously shown to harbour
high genetic variation in direct and indirect defence against the
strawberry leaf beetle (Weber et al. 2020a; Weber et al.2020b), as evidenced by the differential performance and preference of
both the herbivore and its specialist endoparasitoid, Asecodes
parviclava Thompson (Hymenoptera: Eulophidae), on diets of varying
genotypic composition. Several primary and secondary compounds were
ultimately identified as markers associated with either direct or
indirect defence (Weber et al. 2020a). We included here the five
compounds most strongly associated with defence: two carbohydrates
(dehydroascorbic acid and myo-inositol), and three phenolics (catechin,
dihydroxybenzoic acid, and shikimic acid). Details of leaf sampling and
GC/TOF-MS metabolomic profiling are presented in Weber et al.(2020a), which was conducted concurrently for the same plants used in
this study. Owing to capacity limitations experienced with metabolomic
profiling, defence-related traits could only be quantified for 27 of the
81 genotypes. However, selection of these 27 genotypes was made such
that the full spectrum of genetic variation in direct and indirect
defence was still represented (following Weber et al. 2020a and
Weber et al. 2020b). The four attractive traits examined were
plant size, total flower number, flower frost tolerance, and
inflorescence density. Frost damaged flowers show a complete blackening
of the receptacle at the centre of the flower, and in this way could be
expected to impact floral attractiveness to pollinators and florivores.
Details of how each trait was quantification are provided in Eganet al. (2018).