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Post-mating, pre-zygotic interactions and their potential to drive speciation in the Cabbage White butterfly, Pieris rapae

Plakke, Melissa (2019) Post-mating, pre-zygotic interactions and their potential to drive speciation in the Cabbage White butterfly, Pieris rapae. Doctoral Dissertation, University of Pittsburgh. (Unpublished)

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Research on the evolution of reproductive barriers during incipient speciation has typically focused on either pre-copulatory or post-zygotic processes. However post-mating, pre-zygotic (PMPZ) interactions between males and females may play an important role in the early stages of speciation. PMPZ interactions are shaped by both sexual conflict and selection for reproductive cooperation, and preliminary observations suggest they evolve rapidly. I use butterflies to explore the PMPZ interactions between the female reproductive tract and the male ejaculate. Female butterflies have a specialized reproductive organ, the bursa copulatrix, which receives and digests the male ejaculate, or spermatophore. Spermatophore proteins aid in the cooperative venture of egg production, but also function to manipulate female remating rate, resulting in conflict between the sexes over remating frequency. However, it was unknown how the bursa digests the spermatophore, what spermatophore proteins are targeted for digestion by the bursa, or how these proteins interact and evolve over time. In the Cabbage White butterfly, Pieris rapae, I discovered that females of the European subspecies, Pieris rapae rapae, experience difficulty degrading spermatophores from males of the Japanese subspecies, Pieris rapae crucivora. I hypothesized that this mismatch is due to rapid evolution at the interface between the proteases of the bursa and the proteins of the spermatophore. I first identified spermatophore proteins and bursal enzymes responsible for spermatophore digestion using bioinformatic and biochemical techniques. I classified spermatophore and bursal protein functions and how the proteins from both sexes interact with each other within the context of the female reproductive tract. I then investigated divergence of spermatophore and bursal proteins using RNA-seq and Pool-seq in both subspecies. I found a total of 40 bursal proteases and 66 spermatophore proteins that likely contribute to the interaction and digestion of the spermatophore. The proteases directly digest the spermatophore at a rapid rate and without prejudice. I also uncovered that female proteases exhibit higher expression and genomic differentiation than the corresponding male proteins involved at the interface between the spermatophore and female reproductive tract. I discuss these results in the context of rapid evolution of PMPZ interactions and their potential to lead to speciation.


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Item Type: University of Pittsburgh ETD
Status: Unpublished
CreatorsEmailPitt UsernameORCID
Plakke, Melissamep115@pitt.edumep1150000-0002-2775-8394
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Committee CoChairClark, Nathan
Committee CoChairMorehouse, Nathan
Committee MemberRebeiz, Mark
Committee MemberRichards-Zawacki, Corinne
Committee MemberCarlson, Anne
Date: 25 September 2019
Date Type: Publication
Defense Date: 9 July 2019
Approval Date: 25 September 2019
Submission Date: 28 June 2019
Access Restriction: 1 year -- Restrict access to University of Pittsburgh for a period of 1 year.
Number of Pages: 131
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: speciation, reproductive co-evolution, lepidoptera, sexual conflict, post-mating prezygotic
Date Deposited: 25 Sep 2019 16:35
Last Modified: 25 Sep 2020 05:15


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