Root‐feeding larvae increase their performance by inducing leaf volatiles that attract above‐ground conspecific adults

Liu

et al. 2020

Sci Rep

Herbivorous insects use plant volatile compounds to find their host plants for feeding and egg deposition. The monophagous beetle Agasicles hygrophila uses a volatile (E)-4,8-dimethyl-1,3,7-nonanetriene (DMNT) to recognize its host plant Alternanthera philoxeroides. Alternanthera philoxeroides releases DMNT in response to A. hygrophila attack and nerolidol synthase (NES) is a key enzyme in DMNT biosynthesis; however, the effect of A. hygrophila on NES expression remains unclear. In this study, the A. philoxeroides transcriptome was sequenced and six putative NES genes belonging to the terpene synthase-g family were characterized. The expression of these NES genes was assayed at different times following A. hygrophila contact, feeding or mechanical wounding. Results showed that A. hygrophila contact and feeding induced NES expression more rapidly and more intensely than mechanical wounding alone. This may account for a large release of DMNT following A. hygrophila feeding in a previous study and subsequently facilitate A. hygrophila to find host plants. Our research provides a powerful genetic platform for studying invasive plants and lays the foundation for further elucidating the molecular mechanisms of the interaction between A. philoxeroides and its specialist A. hygrophila.

Section: Discussionmentioning

confidence: 99%

Agasicles hygrophila attack increases nerolidol synthase gene expression in Alternanthera philoxeroides, facilitating host finding

Liu

et al. 2020

Sci Rep

“…Leaf damage by the red milkweed beetle Tetraopes tetraophthalmus, for instance, increases larval survival on the roots of the same plans (Erwin et al, 2014). Similarly, aboveground feeding by adult Bikasha collaris beetles on Triadica sebifera enhances the survival of conspecific larvae on the roots while reducing the performance of heterospecific herbivores (Huang et al, 2013;Huang et al, 2014;Sun et al, 2019). Whether insect herbivores can also modify plant metabolism to directly boost pupation -a critical step in their development-has not been investigated so far.…”

Section: Discussionmentioning

confidence: 99%

Leafminer attack induces plant-mediated facilitation of conspecific pupae in the soil

Escobar‐Bravo

Schimmel

Klinkhamer

et al. 2020

Preprint

Plants and herbivores are engaged in intimate antagonistic interactions, with plants trying to mount effective defense responses and herbivores attempting to manipulate plants for their own benefit. Here we report on a new mechanism by which herbivores can facilitate their own development. We show that tomato (Solanum lycopersicum) leaf attack by the American serpentine leafminer Lyriomiza trifolii accelerates the development of conspecific pupae in the soil adjacent to the plant. This pattern was reversed in the jasmonate-signaling deficient tomato mutant def-1. Chemical analyses revealed that L. trifolii leaf attack changes the production of root volatiles in a def-1 dependent manner. Thus, leaf-feeding herbivores can interact with their soil-dwelling pupae, and jasmonates and root volatiles likely play relevant roles in this phenomenon. This study expands the repertoire of plant-herbivore interactions to herbivory-induced modulation of metamorphosis.

“…Then, 400 ng of n‐nonyl acetate (Sigma) was added to each sample as the internal standard (IS) and they were stored at −80°C until analysis. Volatile extracts were analysed by GC‐MS (GCMS‐QP2010 Ultra) equipped with a Rxi‐5MS capillary column (30 m × 0.32 mm × 0.25 µm) following previously established protocols (Sun et al., 2019). Briefly, 1 μl sample was injected in splitless mode with the EI detector source at 250°C and helium as the carrier at 1 ml/min, maintained the oven temperature at 40°C for 2 min and then increased to 250°C at a rate of 6°C/min, followed by a final stage at 250°C for 2 min.…”

Section: Methodsmentioning

confidence: 99%

Herbivory of a biocontrol agent on a native plant causes an indirect trait‐mediated non‐target effect on a native insect

Zhang

Siemann

et al. 2021

Journal of Ecology

Self Cite

Identifying food web linkages between biocontrol agents of invasive plants and native species is crucial for predicting indirect non‐target effects. Biocontrol insects can integrate into food webs within recipient habitats and influence native insects through apparent competition (altering shared natural enemies) or density‐mediated exploitation competition (changing density of native plants). However, whether and how trait‐mediated exploitation competition (modifying native plant chemicals and volatiles profiles) can produce indirect non‐target effects remains largely overlooked, despite plant phenotypic responses to insect herbivory being common and widely documented. The flea beetle Agasicles hygrophila was introduced into China for management of alligator weed Alternanthera philoxeroides, but it also attacks the native congener sessile joyweed Alternanthera sessilis, which may cause indirect non‐target effects on the native tortoise beetle Cassida piperata that also feeds on sessile joyweed. Here, we examined the relationships among abundances of the flea beetle and tortoise beetle, and coverage of sessile joyweed in the field. Then, we investigated the impact of flea beetle herbivory on tortoise beetle development and oviposition, as well as on sessile joyweed primary metabolites and leaf volatiles. Tortoise beetle abundance was not related to sessile joyweed coverage, but they were less abundant on plants with more flea beetles in the field survey, and produced fewer offspring on plants with more prior flea beetle damage in the field cage experiment. Tortoise beetle development was inhibited by prior flea beetle herbivory in bioassays in enemy‐free conditions and they preferred to oviposit on sessile joyweed that had experienced little or no flea beetle damage. Flea beetle herbivory decreased sessile joyweed foliar glucose and protein, and substantially changed its leaf volatile blend. Synthesis. Our results show that the flea beetle has major indirect non‐target effects on the tortoise beetle through trait‐mediated exploitation competition, rather than apparent competition or density‐mediated exploitation competition. Our results demonstrate a new example for indirect non‐target effects of biocontrol agents. Furthermore, our results indicate that minor brief negative impacts of biocontrol agents on non‐target plants might propagate to higher trophic levels and such negative impacts can strengthen with increasing intensity of the direct non‐target effect.