title: Finish line plant-insect interactions mediated by insect feeding mode and plant interference: a case study of Brassica interactions with diamondback moth and turnip aphid.
abstract: There are gaps in our understanding of plant responses under different insect phytophagy modes and their subsequent effects on the insect herbivores' performance at late season. Here we compared different types of insect feeding by an aphid, Lipaphis erysimi, and a lepidopteran, Plutella xylostella, and how this affected defensive metabolites in leaves of 2 Brassica species when plants gain maturity. Thiocyanate concentrations after P. xylostella and L. erysimi feeding activities were the same. Total phenolics was higher after the phloem feeder feeding than the folivore activity. The plants compensatory responses (i.e., tolerance) to L. erysimi feeding was significantly higher than the responses to P. xylostella. This study showed that L. erysimi had higher carbon than P. xylostella whereas nitrogen in P. xylostella was 1.42 times that in L. erysimi. Population size of the phloem feeder was not affected by plant species or insect coexistence. However, there was no correlation between plant defensive metabolites and both insects' population size and biomass. This suggests that plant root biomass and tolerance index after different insect herbivory modes are not necessarily unidirectional. Importantly, the interaction between the folivore and the phloem feeder insects is asymmetric and the phloem feeder might be a trickier problem for plants than the folivore. Moreover, as both plants' common and special defenses decreased under interspecific interference, we suggest that specialist insect herbivores can be more challenged in ecosystems in which plants are not involved in interspecific interference.
authors.affiliation: Department of Entomology, Faculty of Agriculture, Tarbiat Modares University, Tehran, Iran.
authors.forename: Mahmoud
authors.initials: M
authors.lastname: Soufbaf
authors.affiliation: Department of Entomology, Faculty of Agriculture, Tarbiat Modares University, Tehran, Iran.
authors.forename: Yaghoub
authors.identifier: http://orcid.org/0000-0002-7963-5409
authors.initials: Y
authors.lastname: Fathipour
authors.affiliation: Department of Terrestrial Ecology, Netherlands Institute of Ecology, Wageningen, the Netherlands.|Section Animal Ecology, Department of Ecological Sciences, VU University Amsterdam, Amsterdam, the Netherlands.
authors.forename: Jeffrey A
authors.initials: JA
authors.lastname: Harvey
authors.affiliation: Department of Mathematical Sciences, Centre for Invasion Biology, Stellenbosch University, Matieland, South Africa.|Mathematical and Physical Biosciences, African Institute for Mathematical Sciences, Cape Town, South Africa.
authors.forename: Cang
authors.initials: C
authors.lastname: Hui
mesh_terms: D000818:Animals; D001042:Aphids / Q000502:physiology*; D001937:Brassica / Q000737:chemistry / Q000502:physiology*; D005247:Feeding Behavior / Q000502:physiology*; D060434:Herbivory / Q000502:physiology; D006790:Host-Parasite Interactions; D007814:Larva / Q000502:physiology; D009036:Moths / Q000254:growth & development / Q000502:physiology*; D052585:Phloem; D018515:Plant Leaves / Q000737:chemistry
keywords: glucosinolates; herbivory mode; plant resistance; stoichiometric analysis; tolerance