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The evolutionary ecology of floral scent in Hesperis matronalis: assessing the potential for pollinator-mediated natural selection.

Majetic, Cassie Jane (2008) The evolutionary ecology of floral scent in Hesperis matronalis: assessing the potential for pollinator-mediated natural selection. Doctoral Dissertation, University of Pittsburgh. (Unpublished)

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Heritable trait variation and differential fitness among trait variants are conditions required for pollinator-mediated natural selection on attractive traits like floral scent. However, previous studies of floral scent have focused on assessing evolution through stereotypical pollination syndromes and often fail to evaluate the conditions of natural selection. I assess the potential for pollinator-mediated natural selection on the floral scent of color polymorphic Hesperis matronalis (Brassicaceae). A study that assessed the importance of shared biochemistry between floral scent and color found significant diurnal variation in scent emission and a population-specific effect of floral color on floral scent composition. Specifically, purple morphs tended to be similar, while white morphs tended to differ significantly. A survey of five wild populations across part of H. matronalis's introduced range supported this trend, particularly for aromatic composition; both scent composition and overall emission rates varied among populations. An experiment comparing scent profiles of plants grown in a common garden environment suggested both environmental and genetic causes of among-population variation. A three-part study assessed the relationship between scent and fitness. Experimental augmentation of floral targets with color-specific floral scent revealed increased syrphid fly visitation in response to increased scent emission rate, predicting a positive linear relationship between plant fitness and emission rate. An experiment limiting pollinator access to plants showed this expected relationship for plants exposed to diurnal pollinators, but no relationship for plants exposed to night pollinators. In contrast, I found a negative quadratic relationship between daytime emission rate and fitness across plants in four large wild populations, suggesting possible costs of scent production under wild conditions, i.e., attraction of herbivores or energetic expenditures.Overall, this dissertation suggests strong potential for pollinator-mediated natural selection on H. matronalis floral scent. Additionally, the results illustrate the importance of assessing all conditions necessary for natural selection of floral scent rather than relying on the observational pollination syndrome framework to describe the evolutionary trajectory of a species.


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Item Type: University of Pittsburgh ETD
Status: Unpublished
CreatorsEmailPitt UsernameORCID
Majetic, Cassie Janecam21@pitt.eduCAM21
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Committee ChairAshman, Tia-Lynntia1@pitt.eduTIA1
Committee MemberRelyea, Rickrelyea@pitt.eduRELYEA
Committee MemberRaguso,
Committee MemberTonsor, Stephentonsor@pitt.eduTONSOR
Committee MemberKalisz, Susankalisz@pitt.eduKALISZ
Date: 13 June 2008
Date Type: Completion
Defense Date: 17 March 2008
Approval Date: 13 June 2008
Submission Date: 15 April 2008
Access Restriction: 5 year -- Restrict access to University of Pittsburgh for a period of 5 years.
Institution: University of Pittsburgh
Schools and Programs: Dietrich School of Arts and Sciences > Biological Sciences
Degree: PhD - Doctor of Philosophy
Thesis Type: Doctoral Dissertation
Refereed: Yes
Uncontrolled Keywords: floral color polymorphism; floral scent; phenotypic variation; plant fitness; pollinators; volatiles
Other ID:, etd-04152008-121601
Date Deposited: 10 Nov 2011 19:37
Last Modified: 15 Nov 2016 13:40


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