Refer To Expts, How Might You Demonstrate Plants Use Natural Enemies Of Herbivores As Effective Defence Against Herbivory

Front 1

reduce herbivory by increasing likelihood that herbivores are attacked, removed or harassed by predators like ants, wasps and mites. They rely on what

Back 1

third trophic, or feeding, level within the web= tritrophic defences.

Front 2

plants increase predation of herbivores by doing what

Back 2

luring and keeping predators on a plant with food rewards, shelters, or chemicals signalling prey availability

Front 3

agrawal and karban 1997

Back 3

simulated presence of domatia on cotton plants- fewer herbivorous spider mites on plants w domatia. predatory arthropods found in simulated domatia. addition of leaf domatia increased yield. where spider mite densities high, domatia favour predatory arthropods and increase plant repro. such benefits weren't spp specific as leaf domatia benefit predatory mites, thrips and bugs. predation by thrips and bugs, mediated by domatia, reduces pop of herbivorous spider mites and increases plant production

Front 4

Heil et al 2001

Back 4

field experiments. neighbouring twigs selected and treated as matched pairs w one twig per pair randomly selected for removal- after 6 wks, leaves on M. triloba twigs on which ants still present lost 1.2% of area, leaf damage on ant free twigs 2.6%. highest efficacy on young leaves- 1.4% ant leaves, 4.2% w/o.

Front 5

ants

Back 5

used as indirect biotic defence mechanism. obligate ant plants (myrmecophytes) of genus macaranga house specific ant colonies in shoots, feed on food bodies which are cellular structure made by plants containing large amounts of lipids, proteins and carbohydrates. ants patrol surface, remove foreign material, defend host against biotic stress caused by herbivores and competing and parasitic plants and fungal pathogens

Front 6

M. triloba

Back 6

longer term study on m. triloba, experimentally deprived of ants, lost on average 80% of total leaf area, while total leaf area of inhabited trees increased by about 40%

Front 7

Wind tunnel dual choice experiments- Mattiacci et al 2001

Back 7

brussel sprouts attacked by Pieris brassicae larvae- release volatiles, attract natural antagonist of herbivores, the parasitoid Cotesia glomerata to damaged plant. placed wasps in wind tunnels, downwind from odour source- either excised leaves releasing volatiles or whole plants. recorded wasp choice. induced plants more easily located than non-induced ones. larvae preferred to feed and fed more on systematically induced than non-induced, consumed more area of induced leaves as well.