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dc.contributor.advisorMooney, Emily
dc.contributor.authorMullins, Maria L.
dc.date.accessioned2019-05-15T21:45:34Z
dc.date.available2019-05-15T21:45:34Z
dc.date.submitted2019-05
dc.identifierMullins_uccs_0892N_10462.pdf
dc.identifier.urihttps://hdl.handle.net/10976/167101
dc.descriptionIncludes bibliographical references.
dc.description.abstractThe abundance of insect herbivores, such as aphids, is mediated by interactions with higher and lower trophic levels. Bottom-up processes can affect the phloem sap quality that aphids depend on for food, while natural enemies exert top-down control to directly and indirectly impact the success of aphids. This research asks (1) how phenological change across trophic levels affects host plant quality and selection for aphids, and (2) what mechanisms drive the ability of aphids to distinguish between potential hosts. We used a tri-trophic system to investigate these questions. Ligusticum porteri is a robust, perennial herb that hosts the sap-feeding aphid Aphis asclepiadis, and intraguild predators (Lygus spp.—lygus bugs) in a subalpine system near Gothic, Colorado. We used long term observational data to discover that species in this tri-trophic system respond differently to phenological cues, and when phenology of Lygus hesperus is advanced on early snowmelt years, aphid colonies do not reach high densities. These unique phenological responses to climatic cues can impact aphid abundance through changes to host plant quality and the host plant selection process. We used behavioral choice assays to assess how advanced L. hesperus phenology influences aphid host plant selection using plants experimentally colonized by L. hesperus compared to controls. More alate aphids chose to land and reproduce on lygus bug free control plants, indicating overall avoidance of plants with prior herbivory by L. hesperus. However, this preference did not correlate with aphid performance when we compared aphid relative growth rates between treatments. This suggests that advanced phenology of L. hesperus may impact aphid populations more through direct predation rather than reductions in host quality. These predation effects could be mediated if aphids can detect natural enemy presence during host selection. We measured plant cues involved in host selection and found differences in volatile composition from plants with prior L. besperus feeding compared to L. hesperus free control plants. Such differential host selection could demonstrate that aphids may be able to detect enemy free space using volatile cues. Our results indicate that higher trophic interactions both directly and indirectly influence aphid abundance. This work highlights the importance of including multi-trophic interactions in studies examining insect herbivore abundance.
dc.languageEnglish
dc.language.isoeng
dc.publisherUniversity of Colorado Colorado Springs. Kraemer Family Library
dc.rightsCopyright of the original work is retained by the author.
dc.subjecthost selection
dc.subjectnatural enemies
dc.subjectaphids
dc.subjectphenology
dc.subjectintraguild predator
dc.titleAdvanced phenology of higher trophic levels shifts aphid host plant preferences and performance
dc.typeThesis
dc.contributor.committeememberGibbes, Cerian
dc.contributor.committeememberHeschel, Shane
thesis.degree.levelMasters
thesis.degree.disciplineCollege of Letters, Arts, and Sciences-Biology
thesis.degree.grantorUniversity of Colorado Colorado Springs


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