Do age and mating status affect olfactory response of the parasitoid, Microplitis croceipes (Hymenoptera: Braconidae) to host-related plant odors? [version 2; referees: 2 approved]

Background: Parasitic wasps (parasitoids) use volatile organic compounds released by herbivore-infested plants to locate their hosts. Response of parasitoids to plant odors may be plastic and dependent on their physiological state. Using Microplitis croceipes (Hymenoptera: Braconidae), a relatively specialized larval endoparasitoid of Heliothis virescens (Lepidoptera: Noctuidae), we asked whether age and mating status of parasitoids affect their olfactory response to host-related odors. Methods: Four odor stimuli of varying complexity were selected based on previous reports of parasitoid response to cotton volatiles: cis-3-hexenol (a green leaf volatile), α-pinene (a constitutive monoterpene), a 50/50 v/v binary mixture (cis-3-hexenol + α-pinene), and H. virescens-infested cotton odors. Female M. croceipes used in Y-tube olfactometer bioassays were either mated or unmated, and grouped 1–3, 4–6, and 7–9 d-old. Female parasitoids used in electroantennogram (EAG) recording were mated and grouped 1–3, 4–6, 7–9 and 10–12 d-old. Results: In Y-tube olfactometer bioassays, neither age nor mating status played a major role in the attraction of parasitoids to test odor stimuli, with two exceptions: 4–6 d-old mated parasitoids showed attraction to the binary mixture, and 1–3 d-old mated parasitoids showed attraction to H. virescens-infested cotton. Age did not affect EAG response of parasitoids to test stimuli. Conclusions: The present results suggest that age and mating status do not play a major role in modulating olfactory responses of M. croceipes to host-related plant odors. Instead, plasticity of olfactory response may be limited in M. croceipes due to strong innate sensitivity to host-related odor cues

Identifying invasive species threats, pathways, and impacts to improve biosecurity

Managing invasive species with prevention and early-detection strategies can avert severe ecological and economic impacts. Horizon scanning, an evidence-based process combining risk screening and consensus building to identify threats, has become a valuable tool for prioritizing invasive species management and prevention. We assembled a working group of experts from academic, government, and nonprofit agencies and organizations, and conducted a multi-taxa horizon scan for Florida, USA, the first of its kind in North America. Our primary objectives were to identify high-risk species and their introduction pathways, to detail the magnitude and mechanism of potential impacts, and, more broadly, to demonstrate the utility of horizon scanning. As a means to facilitate future horizon scans, we document the process used to generate the list of taxa for screening. We evaluated 460 taxa for their potential to arrive, establish, and cause negative ecological and socioeconomic impacts, and identified 40 potential invaders, including alewife, zebra mussel, crab-eating macaque, and red swamp crayfish. Vertebrates and aquatic invertebrates posed the greatest invasion threat, over half of the high-risk taxa were omnivores, and there was high confidence in the scoring of high-risk taxa. Common arrival pathways were ballast water, biofouling of vessels, and escape from the pet/aquarium/horticulture trade. Competition, predation, and damage to agriculture/forestry/aquaculture were common impact mechanisms. We recommend full risk analysis for the high-risk taxa; increased surveillance at Florida's ports, state borders, and high-risk pathways; and periodic review and revision of the list. Few horizon scans detail the comprehensive methodology (including list-building), certainty estimates for all scoring categories and the final score, detailed pathways, and the magnitude and mechanism of impact. Providing this information can further inform prevention efforts and can be efficiently replicated in other regions. Moreover, harmonizing methodology can facilitate data sharing and enhance interpretation of results for stakeholders and the general public.</p

Electroantennogram response of the parasitoid, Microplitis croceipes to host-related odors: The discrepancy between relative abundance and level of antennal responses to volatile compound [version 1; referees: 2 approved, 1 approved with reservations]

Herbivores emit volatile organic compounds (VOCs) after feeding on plants. Parasitoids exploit these VOCs as odor cues to locate their hosts. In nature, host-related odors are emitted as blends of various compounds occurring in different proportions, and minor blend components can sometimes have profound effects on parasitoid responses. In a previous related study, we identified and quantified VOCs emitted by cotton plant-fed Heliothis virescens (Lepidoptera: Noctuidae) larvae, an herbivore host of the parasitoid Microplitis croceipes (Hymenoptera: Braconidae). In the present study, the olfactory response of female M. croceipes to synthetic versions of 15 previously identified compounds was tested in electroantennogram (EAG) bioassays. Using M. croceipes as a model species, we further asked the question: does the relative abundance of a volatile compound match the level of antennal response in parasitoids? Female M. croceipes showed varying EAG responses to test compounds, indicating different levels of bioactivity in the insect antenna. Eight compounds, including decanal, 1-octen-3-ol, 3-octanone, 2-ethylhexanol, tridecane, tetradecane, α-farnesene and bisabolene, elicited EAG responses above or equal to the 50th percentile rank of all responses. Interestingly, decanal, which represented only 1% of the total amount of odors emitted by cotton-fed hosts, elicited the highest (0.82 mV) EAG response in parasitoids. On the other hand, (E)-β-caryophyllene, the most abundant (29%) blend component, elicited a relatively low (0.17 mV) EAG response. The results suggest that EAG response to host-related volatiles in parasitoids is probably more influenced by the ecological relevance or functional role of the compound in the blend, rather than its relative abundance

Electroantennogram response of the parasitoid, Microplitis croceipes to host-related odors: The discrepancy between relative abundance and level of antennal responses to volatile compound [version 2; referees: 3 approved, 1 approved with reservations]

Herbivores emit volatile organic compounds (VOCs) after feeding on plants. Parasitoids exploit these VOCs as odor cues to locate their hosts. In nature, host-related odors are emitted as blends of various compounds occurring in different proportions, and minor blend components can sometimes have profound effects on parasitoid responses. In a previous related study, we identified and quantified VOCs emitted by cotton plant-fed Heliothis virescens (Lepidoptera: Noctuidae) larvae, an herbivore host of the parasitoid Microplitis croceipes (Hymenoptera: Braconidae). In the present study, the olfactory response of female M. croceipes to synthetic versions of 15 previously identified compounds was tested in electroantennogram (EAG) bioassays. Using M. croceipes as a model species, we further asked the question: does the relative abundance of a volatile compound match the level of antennal response in parasitoids? Female M. croceipes showed varying EAG responses to test compounds, indicating different levels of bioactivity in the insect antenna. Eight compounds, including decanal, 1-octen-3-ol, 3-octanone, 2-ethylhexanol, tridecane, tetradecane, α-farnesene and bisabolene, elicited EAG responses above or equal to the 50th percentile rank of all responses. Interestingly, decanal, which represented only 1% of the total amount of odors emitted by cotton-fed hosts, elicited the highest (0.82 mV) EAG response in parasitoids. On the other hand, (E)-β-caryophyllene, the most abundant (29%) blend component, elicited a relatively low (0.17 mV) EAG response. The results suggest that EAG response to host-related volatiles in parasitoids is probably more influenced by the ecological relevance or functional role of the compound in the blend, rather than its relative abundance

Do age and mating status affect olfactory response of the parasitoid, Microplitis croceipes (Hymenoptera: Braconidae) to host-related plant odors? [version 1; referees: 2 approved]

Background: Parasitic wasps (parasitoids) use volatile organic compounds released by herbivore-infested plants to locate their hosts. Response of parasitoids to plant odors may be plastic and dependent on their physiological state. Using Microplitis croceipes (Hymenoptera: Braconidae), a relatively specialized larval endoparasitoid of Heliothis virescens (Lepidoptera: Noctuidae), we asked whether age and mating status of parasitoids affect their olfactory response to host-related odors. Methods: Four odor stimuli of varying complexity were selected based on previous reports of parasitoid response to cotton volatiles: cis-3-hexenol (a green leaf volatile), α-pinene (a constitutive monoterpene), a 50/50 v/v binary mixture (cis-3-hexenol + α-pinene), and H. virescens-infested cotton odors. Female M. croceipes used in Y-tube olfactometer bioassays were either mated or unmated, and grouped 1–3, 4–6, and 7–9 d-old. Female parasitoids used in electroantennogram (EAG) recording were mated and grouped 1–3, 4–6, 7–9 and 10–12 d-old. Results: In Y-tube olfactometer bioassays, neither age nor mating status played a major role in the attraction of parasitoids to test odor stimuli, with two exceptions: 4–6 d-old mated parasitoids showed attraction to the binary mixture, and 1–3 d-old mated parasitoids showed attraction to H. virescens-infested cotton. Age did not affect EAG response of parasitoids to test stimuli. Conclusions: The present results suggest that age and mating status do not play a major role in modulating olfactory responses of M. croceipes to host-related plant odors. Instead, plasticity of olfactory response may be limited in M. croceipes due to strong innate sensitivity to host-related odor cues