tritroph

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Predators- Role in ecosystem: 

Predators- Role in ecosystem Energy Flow Regulation of Populations Maintain Prey Fitness Selective agents Alter populations

Predator/Parasitoid: 

Predator/Parasitoid Predator- kills and consumes many prey during lifetime Parasitoid- receives all nutrients from a single prey item

Predator-Nutrition: 

Predator-Nutrition Prey composition often similar to predator High ECD Prey may produce anti-nutritive or defensive substances Predators may supplement prey items with other nutrients

Finding Prey: 

Finding Prey Active prey Let prey come to predator Mantids Odonate larvae Spiders Active Pursuit Odonate Adults Passive prey Requires active pursuit

Let prey come to predator: 

Let prey come to predator Advantages: Energy not lost in movement Predator not exposed to other predators Disadvantages Location, timing critical to success

Active Pursuit / Active Prey: 

Active Pursuit / Active Prey Advantages Large amount of nutrients can be collected in a short time Disadvantages Energy lost in movement Exposure to predators Must be faster, nimbler than prey

Passive prey : 

Passive prey Niche Passive prey requires both host and plant eaten by the host

Sources of chemical information:: 

Sources of chemical information: the herbivore its food organisms associated with the herbivore combination of the three

Potentially important products: 

Potentially important products Feces Cuticle Exuvia Feeding secretions Pheromones Honeydew Body scales Flowers and leaves Microorganisms

Infochemicals: 

Infochemicals Interspecies chemical communications Kairomones Deleterious to sender Host Kairomones beneficial to parasitoid Allomones Beneficial to sender Host plant allomones beneficial to parasitoid

Infochemical usefulness: 

Infochemical usefulness Detectability How easily can it be detected? Reliability How reliable is information in finding host?

Information from host: 

Information from host High Reliability Low Detectability Host a small part of complex environment Selection favors low detection

Reducing host detectability: 

Reducing host detectability Bark beetles pheromones attract predators and parasitoids Other insects Release controlled Emitted when predators inactive

Reducing host detectability: 

Reducing host detectability Defecation Releases odors Move to new feeding location away from defecation Insects in galls, mines concealed

Information from plants: 

Information from plants Plants damaged by insects Increased volatiles emitted Plants release “synomones” Cotesia marginiventris Attracted to terpenoids Spodoptera feeding on corn Releases copious terpenoids Cotesia CMave UFl

Dietary Specialization & Infochemicals: 

Dietary Specialization & Infochemicals Predators Less picky, less info One prey does not necessarily = one offspring Ants attack a multiple prey insects from multiple taxa identity of the prey? Don’t know Don’t care

Dietary Specialization & Infochemicals: 

Dietary Specialization & Infochemicals Parasitoids choice of single prey offspring life or death Specialists spend proportionally more time searching than generalists Infochemicals are of more use

Specialization & Infochemicals: 

Specialization & Infochemicals Microplitis croceipes Specialized on Heliothis Uses host specific frass cues Aphaaereta minuta Uses many fly species Orients decaying flesh odor Finds hosts with vibrational cues

Specialization & Infochemicals: 

Specialization & Infochemicals Generalist Formicine ants Attack most insects Don't use chemical host cues Specialist Megaponera foetens ants Use termite odors

Parasitoid host range?: 

Parasitoid host range? Easy to find all the parasitoids of a host Less easy to find all the hosts of a parasitoid Hosts on one plant may be attacked Hosts on another may not Do parasitoids have host races?

Predicted infochemical use: 

Predicted infochemical use 1 host plant + 1 host Strong response to Kairomone Synomone Herbivore induced synomone Many host plants 1host Strong response to Kairomone May learn S and HIS 1 host plant many hosts Response to Kairomone, general Strong synomone HIS Many host plants/ hosts no response