Netherlands Institute of Ecology (NIOO-KNAW) ROXINA SOLER PLANT-MEDIATED INTERACTIONS BETWEEN INSECTS ACROSS ABOVE- BELOWGROUND DOMAINS: ecology, mechanisms and utilization

Ehrlich and Raven 1964 Evolution, Pimentel and Andow 1984 Insect Science and its Application, May 1988, Science PLANT-INSECT INTERACTIONS PLANTS: Leaders in biomass, base of terrestrial ecosystems INSECTS: Largest group in numbers and species diversity Terrestrial food webs key components Numerous species economic importance human health and agriculture Excellent model organisms: small size, fast development, easy rearings > PAPERS / YEAR ON DIVERSE ASPECTS OF PLANT-INSECT INTERACTIONS… Biomas (Kg/Ha) Number and % of species Modified from Schoonhoven, van Loon and Dicke 2005 Organism group

Plant-Herbivore Herbivore-Carnivore or Plant-Herbivore-Carnivore ’s: Muliti-trophic approach (Plant Defenses) ‘PLANT-INSECT INTERACTIONS’ ‘MULTI-TROPHIC INTERACTIONS’ Increasing taxonomic, trophic & species complexity, Across domains, time, space & climates, Linkages beyond secondary plant compounds -‘metabolic links’- Merging ecological and molecular knowledge and tools: from ecological processes to underlying mechanisms at the gene level 2000’s - present: Multi-species multi-disciplinary approach: understanding how nature works ‘MODERN PLANT-INSECT INTERACTIONS’ ? ‘PLANT-MEDIATED TERRESTRIAL NETWORKS’ ?

From: PhD Project ( ) ‘Plant-mediated muliti-trophic interactions between above-belowground insects’ (I) Case study: Root Herbivores – Aboveground Hyperparasitoids Linkages Netherlands Institute of Ecology, Terrestrial Ecology (Multi-trophic interactions Department) Jeff Harvey, Martijn Bezemer Louise Vet, Wim van der Putten OUTLINE (II) How do we move forward?

Whether, and how, can effects extend to higher trophic levels? ‘ABOVE-BELOWGROUND INTERACTIONS’ IN THE EARLY 2000’s… Research question PhD work Plant biomass, nutrients and phytotoxins First trophic level: plants Second trophic level: root-associated organisms Second trophic level: shoot-associated organisms

Delia radicum (Diptera:Anthomyiidae) Cotesia glomerata (Hymenoptera:Braconidae) Lysibia nana (Hymenoptera:Ichneumonidae) Brassica nigra (Brassicaceae) Netherlands Institute of Ecology (NIOO-KNAW) Pieris brassicae (Lepidoptera:Pieridae) ‘PLANT-MEDIATED MULITI-TROPHIC INTERACTIONS BETWEEN ABOVE-BELOWGROUND INSECTS’

PARASITOIDS AND HYPERPARASITOIDS PERFORMANCE Increased foliar sinigrin slower & smaller smaller slower Sub-optimal performance on root-infested plants Insect parasitoids of foliar herbivores were particularly affected by root-feeding insects: suboptimal performance on root-damaged plants… Soler, et al. (2005) Journal of Animal Ecology

? 10 pairs of plants 10 ♀ / plant pair 100 ♀ tested PARASITOID HOST-SEARCHING TWO-CHOICE FLIGTH CAGE EXPERIMENTS % of Choices P=0.01 ** Entire larval dev. time L1L2L3 Female parasitoids prefer to search for hosts on root-uninfested plants over root-infested plants

10 female wasps foraging freely 2h PARASITOID HOST-PREFERENCE SEMI-FIELD EXPERIMENT a b a Control plants Root-infested plants % Plants with parasitized caterpillars Treatment ? Female parasitoids prefer to parasitize hosts feeding on root-uninfested plants over hosts on root-infested plants Soler, et al. (2007) Oikos

AVOIDANCE FOR HOSTS SHARING THE PLANT WITH ROOT HERBIVORES: INNATE OR LEARNED ? Training % of Choices Naïve 100 ♀ Kruidhof et al. 2013, Oikos 55 ♀ P< 0.01 * 55 ♀ Root herbivores can also influence parasitoid associative learning

PLANT VOLATILES Beta-farnesene Dimethyl-nonatriene Attractants : Low levels Dimethyl-disulfide Dimethyl-trisulfide Toxic : High levels Canonical Discriminate Analysis Enemy-free space? Soler, et al. (2007) Oikos, Soler et al Journal of Chemical Ecology

0% Plants with root herbivores in the surrounding habitat 20% Plants with root herbivores in the surrounding habitat 60% Plants with root herbivores in the surrounding habitat 100% Plants with root herbivores in the surrounding habitat Measured time parasitoid spent to find each of the 5 host-infested plants in the different habitats INFLUENCE OF ROOT HERBIVORY VIA THE ENVIRONMENT Soler, et al. (2007) Functionall Ecology

Environments with 20 and 60 % plants with RH showed intermediate bars 0% 100% 1 st 2 nd 3 rd 4 th 5 st Time (minutes) a Host infested plants a Foraging efficiency of the female parasitoids enhanced by the presence of root herbivores in the surroundings INFLUENCE OF ROOT HERBIVORY VIA THE ENVIRONMENT

Soler et al. In Preparation A FINAL CASE STUDY ON THE 4 th TROPHIC LEVEL: ROOT HERBIVORES – HYPERPARASITOIDS LINKAGES

Observation untill 3 parasitisations observed (or maximum 4 hours) 50 Petry-dishes, 1 female/dish, 10 cocoons/dish Proportion coccons selected Hyperparasitoid / Primary Parasitoid emergence Hyperparasitoid survival, weight and development time A PETRY DISH TEST WITH HOSTS OF SIMILAR SIZE FROM ROOT-INFESTED AND UNIFESTED PLANTS Selection of cocoons of similar size: small, medium and large cocoons 2 (pupae) hyperparasitoid speceis

0 0,5 1 EMERGENCES FROM THE COCCONS SELECETD BY THE FEMALE HYPERPARASITOIDS L. nana A. nens Proportion of emergence Hypers Primary Parasitoids No emergence 2/3 of what it ‘looked like’ parasitized coccons were not!

Apparently Selected Selected (Hyperparasitized) Apparently Selected Selected (Hyperparasitized) 0 0,5 * HYPERPARASITOID HOST SELECTION (host quality assessment)

* 0 0,25 0,50 Adult dry weight (mg) Juvenile development time (days) 0 0,5 1 Survival * HYPERPARASITOIDS PERFORMANCE Preference-performance linkages in hyperparasitoids, triggered by qualitative changes induced in the plant by root herbivores

HYPERPARASITOID PLANT-HOST COMPLEX PREFERENCES L 1 unparasitized L 5 parasitized Host cocoons L 5 unparasitized L 1 parasitized Combined treatment P=0,05 Most tested hyperparasitoids did not respond /100 43/100 46/100 64/100 23/100 % of Choices *

‘MODERN PLANT-INSECT INTERACTIONS’ ? ‘PLANT-MEDIATED TERRESTRIAL NETWORKS’ ? HOW TO MOVE FORWARD?

ACKNOWLEDGEMENTS Terrestrial Ecology Department, NIOO-KNAW Jeff Harvey, Martijn Bezemer Louise Vet, Wim van der Putten

EFFECTS OF ROOT-FEEDING INSECTS ON THE PERFORMANCE OF A FOLIAR HERBIVORE, ITS PARASITOIDS AND ITS HYPERPARASITOID Performance

METHODOLOGY Low density High density Control (Without root herbivores)

Root herbivory, at low density, negatively affected the development of the foliar herbivore Negative effect EFFECT OF ROOT HERBIVORY ON THE FOLIAR HERBIVORE a b a Root herbivore density

Negative effect Root herbivore density a a b Root herbivory, at low density, increased development time of the parasitoid EFFECT OF ROOT HERBIVORY ON THE PARASITOID Root herbivory reduced size of the parasitoid aa b Root herbivore density

Root herbivory negatively affected the growth of the hyperparasitoid aa b Root herbivore density Negative effect EFFECT OF ROOT HERBIVORY ON THE HYPERPARASIOTID

Root herbivory increased shoot-sinigrin levels High levels sinigrin: toxic for insects Increased sinigrin levels, reduced performance of the aboveground trophic chain Difference between low-high density? Root herbivore density SHOOT SECONDARY PLANT COMPOUNDS: GLUCOSINOLATES (sinigrin)

% of Choices P=0.92 The parasitoid recognise plants with root herbivores after certain level of root-damage L1-L2 (9 days) L3 (5 days) High damage intensity ROOT-FEEDING DAMAGE BY YOUNG VS. LATE INSTAR LARVAE P=0.004 ** % of Choices

Control clean plants Plants + Root Herbivores Plants+ Leaf Herbivores Plants + Leaf Herbivores + Root Herbivores Canonical Discriminate Analysis Beta-farnesene Dimethyl-nonatriene Attractants : Dimethyl-disulfide Dimethyl-trisulfide Toxics : PLANT VOLATILES

Beta-farnesene Dimethyl-nonatriene Attractants : Dimethyl-disulfide Dimethyl-trisulfide Toxics : Causing repellence/lowering the atraction of the parasitoid High levels Low levels VOLATILE BLEND OF ROOT-INFESTED PLANTS

Soler, et al. (2007) Functional Ecology INFLUENCE VIA THE ENVIRONMENT Do root herbivores influence parasitoids behaviour when the root herbivores and the parasitoid-host do not share the same host-plant but feed on neighbouring plants ?

Environment 1: 0% Plants with root herbivores No root herbivores in the environment Environment 2: 20% Plants with root herbivores Environment 3: 60% Plants with root herbivores Environment 4: 100% Plants with root herbivores All plants with root herbivores in the environment 5 plants carrying Parasitoid-host: Host-infested plants 25 plants with out Parasitoid-host: Surrounding-environment Tents with 30 B. nigra plants The environments differ in root herbivore pressure (% of plants exposed to root herbivores): METHODOLOGY Parasitoid behaviour

0% Plants with root herbivores in the surrounding habitat 20% Plants with root herbivores in the surrounding habitat 60% Plants with root herbivores in the surrounding habitat 100% Plants with root herbivores in the surrounding habitat Measured time parasitoid spent to find each of the 5 host-infested plants in the different habitats

Environments with 20 and 60 % plants with RH showed intermediate bars 0% 100% 1 st 2 nd 3 rd 4 th 5 st Time (minutes) a Host infested plants a

Foraging efficiency of the ♀ was higher when the surrounding plants were exposed to root herbivores Mechanisms?

Parasitoid avoiding root-infested plants: enemy free space for the herbivore? ? Grow ‘optimal’, but with higher chance of parasitism Grow ‘suboptimal’, but with lower chance of being found by parasitoids Enemy free-space Optimal growth R. Soler, JA Harvey, TM Bezemer & JF Stuefer (2008) Plant Signaling & Behavior

If we give the foliar herbivore the chance to choose…. would the females exploit the enemy-free space offered by root-infested plants ? Soler, et al. 2009, Soler et al. 2010

A SEMI-FIELD EXPERIMENT

a a b a a a a a bb

OVIPOSITION PREFERENCE OF Pieris brassicae Pieris brassicae 5 ♀ / tent replicate plants with and without root-herbivores

Proportion of plants with egg-clutches * * Low egg loadHigh egg load