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Herbivore population dynamics are strongly influenced by the interactions established through their shared host. Such plant-mediated interactions can occur between different herbivore species and different life developmental stages of the same herbivore. However, whether these interactions occur between leaf-feeding herbivores and their soil-dwelling pupae is unknown. We studied whether tomato (Solanum lycopersicum) leaf herbivory by the American serpentine leafminer Liriomyza trifolii affects the performance of conspecific pupae exposed to the soil headspace of the plant. To gain mechanistic insights, we performed insect bioassays with the jasmonate-deficient tomato mutant def-1 and its wild-type, along with phytohormones, gene expression and root volatiles analyses. Belowground volatiles accelerated leafminer metamorphosis when wild-type plants were attacked aboveground by conspecifics. The opposite pattern was observed for def-1 plants, in which aboveground herbivory slowed metamorphosis. Leafminer attack induced jasmonate and abscisic acid accumulation and modulated volatile production in tomato roots in a def-1-dependent manner. Our results demonstrate that aboveground herbivory triggers changes in root defence signalling and expression, which can directly or indirectly via changes in soil or microbial volatiles, alter pupal development time. This finding expands the repertoire of plant-herbivore interactions to herbivory-induced modulation of metamorphosis, with potential consequences for plant and herbivore community dynamics., (© 2022 The Authors. New Phytologist © 2022 New Phytologist Foundation.)

Hybridization can lead to novel qualitative or quantitative variation of secondary metabolite (SM) expression that can have ecological and evolutionary consequences. We measured pyrrolizidine alkaloid (PA) expression in the shoots and roots of a family including one Jacobaea vulgaris genotype and one Jacobaea aquatica genotype (parental genotypes), two F(1) hybrid genotypes, and 102 F(2) hybrid genotypes using liquid chromatography-tandem mass spectrometry (LC-MS/MS). We detected 37 PAs in the roots and shoots of J. vulgaris, J. aquatica and the hybrids. PA concentrations and compositions differed between genotypes, and between roots and shoots. Three otosenine-like PAs that only occurred in the shoots of parental genotypes were present in the roots of F(2) hybrids; PA compositions were sometimes novel in F(2) hybrids compared with parental genotypes, and in some cases transgressive PA expression occurred. We also found that PAs from within structural groups covaried both in the roots and in the shoots, and that PA expression was correlated between shoots and roots. Considerable and novel variation present among F(2) hybrids indicates that hybridization has a potential role in the evolution of PA diversity in the genus Jacobaea, and this hybrid system is useful for studying the genetic control of PA expression., (© 2011 Institute of Biology Leiden. New Phytologist © 2011 New Phytologist Trust.)

In a study of Cynoglossum officinale L. it was found that the number of seeds per flower increased with plant weight, and that flower production was inversely related to the number of seeds per flower. As a result, the number of seeds and total seed weight increased proportionally with plant weight. Seed size was not related to plant weight. Differences in seed size within the individual were, in part, related to the position of the seed on the cyme and not related to the number of seeds within a flower. The relationship, between plant size and female fitness found in this study is discussed in relation to life-history theory.