Do plant volatiles shape species interactions in agroecological fields? (PANOPLY)
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Plants use volatile organic compounds (VOCs) to continuously communicate with antagonistic organisms such as herbivore pests; and mutualistic organisms such as natural enemies of the pests, and pollinators. But we only know the basics of this communication and most of the studies come from laboratory experiments involving only pairwise or at most three-species interactions. How VOCs mediate multitrophic plant-insect interactions in field conditions remain massively unknown.
In PANOPLY, I will be the first one to study how VOCs shape plant-insect interactions in an unpresented long-term scale from the lab to the field. I will use the scientifically and economically important perennial system of grapevine (Vitis vinifera), and the leafhopper pest Scaphoideus titanus, which is the main insect vector of Flavescence dorée (FD); a lethal quarantine disease of threat to European grapevines. I will test VOC from aromatic plants that is a major group of plants containing VOCs that are distinct from other plant species. I will use single and mixtures of species of aromatic plants to:
(1) Identify VOCs that can affect life history traits of development, host choices and reproduction of grapevine leafhopper;
(2) Validate in the greenhouse and on common garden experiments, how VOCs affect insect’s behaviour and survival;
(3) Test aromatic plants in analytical field experiments over the long term to understand the role of VOCs on mediating multitrophic plant-insect interactions.
PANOPLY will be the first demonstration of how VOCs shape multitrophic plant-insect interactions in perennial plants answering this significant knowledge gap. PANOPLY will (i) reveal the mechanisms of plant-mediated cues and their long-term effects on plant-insect interactions, (ii) open new avenues for research in chemical ecology and agroecology, and (iii) enhance crop health and insect’s biodiversity by preventing plant disease outbreaks through biological pest control and zero-pesticides use. [ PANOPLY ]
Experiments in an open environment then made it possible to prove that the intensity of the bumble bee behavior is directly related to the local availability of flowers around the colony. We also observed two other species of wild bees with the same behavior. These results show an unprecedented behavior of bees by allowing them to affect the local availability of plant resources, a possible mechanism for the resilience of pollinators to plant coexistence. [Science paper]
Bumble bees damage plant leaves and accelerate flower production when pollen is scarce
Mutualistic interactions between flowering plants and pollinators can be affected by current environmental changes that may affect the appearance of the first flowers or the weakening of bumblebees after diapause. Such phenological mismatches can be particularly difficult for bumble bees, the main pollinators of many plants and which establish their colonies at the end of winter, when flower resources are still limited. Our study describes an unknown behavior of bumble bees, which, when they are hungry for pollen, pierce the leaves of plants that lead to faster flowering for 2 to 4 weeks.
A first series of laboratory experiments made it possible to point out that the availability of pollen is a major cause of bumble bee behavior and that plants that have been pierced have flowered much earlier than plants that have been mechanically pierced or not at all.
Priming of plant defences by oviposition induced plant volatiles
Priming of plant responses allows plants to eavesdrop on early warning cues related to herbivory such as eggs, and prepare themselves for insects attack. However, our understanding of diverse plant induced cues that prime defenses remains incomplete. I tested the response of a wild and a commercial Brassicae species to oviposition induced plant volatiles (OIPVs)
For one species I identified a key volatile compound involved in OIPV-mediated defense priming. We additionally tested the fitness consequences induced by eavesdropping OIPVs. [Ecology Letters paper]
How agricultural techniques mediating bottom-up and top-down regulation foster crop protection against pests. A review
In this paper, we review the last 10 years of published literature on the use in annual cash crops of three agricultural techniques: (i) crop spatial diversification, (ii) crop temporal diversification, and (iii) soil management influencing crop pests either through bottom-up effects or by supporting the top-down regulation of four categories of bioprotection agents: (i) macro- and (ii) micro-organisms, (iii) semiochemicals, and (iv) natural substances. We found that each agricultural technique is adopted to support a specific bioprotection category and to control a specific pest taxon. Crop spatial diversification was generally found to target herbivorous insects and to support macro-organism bioprotection agents. Crop temporal diversification and soil management mainly targeted pathogenic fungi and supported microorganism bioprotection agents. Despite the widespread idea that semiochemicals and natural substances are promising agents for pest regulation, their adoption remains largely unexplored. We also found that agricultural techniques are mostly adopted to support bioprotection in a conservation biological control approach while ignoring augmented bioprotection. In addition, the top-down regulation by means of bioprotection supported by agricultural techniques is just as effective against crop pests as the bottom-up effect produced by the agricultural techniques alone. We argue that a concerted effort to integrate bioprotection with agricultural techniques would open new research opportunities to reduce synthetic pesticide inputs fostering the transition from a conventional agriculture towards sustainable agroecosystems.
Priming of plant defences by herbivore egg deposition
To overcome herbivore attacks, plants have evolved highly sophisticated defences allowing invader recognition and an appropriate induced response. I investigated whether egg deposition by a butterfly can change the defensive phenotype of a wild Brassicaceae plant and prime its defences against subsequent attacks. I also studied the consequences and implications of plant-mediated responses against oviposition in a community context, under laboratory and field conditions. [phd thesis]
Variation in plant defenses along elevation gradients, and its effects on herbivory
Variation in local herbivore pressure along elevation gradients is predicted to drive variation in plant defense traits. Therefore, we used diverse populations of Arabidopsis halleri (Brassicaceae) occurring at different elevations in the Alps, Switzerland. We identified associations between elevation gradients, herbivore damage in the field, and constitutive chemical defense traits. Furthermore, we tested the feeding preferences and performance of a specialist butterfly Pieris brassicae, on plants from different elevations in the Alps. [paper]
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