Innate and Learned Responses of the Tephritid Parasitoid Psyttalia concolor (Hymenoptera: Braconidae) to Olive Volatiles Induced by Bactrocera oleae (Diptera: Tephritidae) Infestation.
Parasitic wasps can learn cues that alter their behavioral responses and increase their fitness, such as those that improve host location efficiency. Psyttalia concolor (Szépligeti) (Hymenoptera: Braconidae) is a koinobiont endoparasitoid of 14 economically important tephritid species, including the olive fruit fly, Bactrocera oleae (Rossi) (Diptera: Tephritidae). In this research, we investigated the nature of olfactory cues mediating this tritrophic interaction. First, we identified the chemical stimuli emanating from uninfested and B. oleae-infested olive fruits via solid phase microextraction and gas chromatography-mass spectrometry analyses and identified >70 volatile organic compounds (VOCs). Two of these were increased by B. oleae infestation, (E)-β-ocimene and 2-methyl-6-methylene-1,7-octadien-3-one, and four were decreased, α-pinene, β-pine ne, limonene, and β-elemene. Innate positive chemotaxis of mated P. concolor females toward these VOCs was then tested in olfactometer assays. Females were attracted only by (E)-β-ocimene, at both tested dosages, indicating an intrinsic response to this compound as a short-range attractant. Next, we tested whether mated P. concolor females could learn to respond to innately unattractive VOCs if they were first presented with a food reward. Two nonassociative controls were conducted, i.e., "odor only" and "reward only." Following training, females showed positive chemotaxis toward these VOCs in all tested combinations, with the exception of limonene, a VOC commonly produced by flowers. Control females showed no significant preferences, indicating that positive associative learning had occurred. These results clarify how learned cues can fine-tune innate responses to B. oleae-induced VOCs in this generalist parasitoid of tephritid flies.
Insect Behavior Group, Department of Agriculture, Food and Environment, University of Pisa, via del Borghetto 80, 56124 Pisa, Italy (giunti.giulia@gmail.com; benelli.giovanni@gmail.com; angelo.canale@unipi.it).
Giulia
G
Giunti
Insect Behavior Group, Department of Agriculture, Food and Environment, University of Pisa, via del Borghetto 80, 56124 Pisa, Italy (giunti.giulia@gmail.com; benelli.giovanni@gmail.com; angelo.canale@unipi.it).
Giovanni
G
Benelli
Department of Pharmacy, University of Pisa, Via Bonanno 6, 56126 Pisa, Italy (guido.flamini@farm.unipi.it).
Guido
G
Flamini
Department of Entomology, Agricultural Research Center-Hays, Kansas State University, 1232 240th Ave., Hays, KS 67601 (jpmi@ksu.edu).
J P
JP
Michaud
Insect Behavior Group, Department of Agriculture, Food and Environment, University of Pisa, via del Borghetto 80, 56124 Pisa, Italy (giunti.giulia@gmail.com; benelli.giovanni@gmail.com; angelo.canale@unipi.it).
Angelo
A
Canale
D000818:Animals; D002633:Chemotaxis; D005260:Female; D020387:Food Chain; D005638:Fruit / Q000254:growth & development / Q000469:parasitology / Q000502:physiology; D008401:Gas Chromatography-Mass Spectrometry; D007814:Larva / Q000254:growth & development / Q000469:parasitology / Q000502:physiology; D007858:Learning; D031658:Olea / Q000378:metabolism*; D052617:Solid Phase Microextraction; D033621:Tephritidae / Q000254:growth & development / Q000469:parasitology / Q000502:physiology*; D055549:Volatile Organic Compounds / Q000378:metabolism*; D014863:Wasps / Q000254:growth & development / Q000502:physiology*
D055549:Volatile Organic Compounds
Tephritidae; associative learning; herbivore-induced plant volatile; olive fruit fly; positive chemotaxis