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3D Genital Shape Complexity in Female Marine Mammals
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  • Dara Orbach,
  • Charlotte Brassey,
  • James Gardiner,
  • Patricia Brennan
Dara Orbach
Texas A&M University Corpus Christi
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Charlotte Brassey
Manchester Metropolitan University
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James Gardiner
University of Liverpool
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Patricia Brennan
Mount Holyoke College
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Abstract

Comparisons of 3D shapes have recently been applied to diverse anatomical structures using landmarking techniques. However discerning evolutionary patterns can be challenging for structures lacking homologous landmarks. We used alpha shape analyses to quantify vaginal shape complexity in 40 marine mammal specimens including cetaceans, pinnipeds, and sirenians. We explored phylogenetic signal and the potential roles of natural and sexual selection on vaginal shape evolution. Complexity scores were consistent with qualitative observations. Cetaceans had a broad range of alpha complexities, while pinnipeds were comparatively simple and sirenians were complex. Intraspecific variation was found. Three-dimensional surface heat maps revealed that shape complexity was driven by invaginations and protrusions of the vaginal wall. Phylogenetic signal was weak and metrics of natural selection (relative neonate size) and sexual selection (relative testes size, sexual size dimorphism, and penis morphology) did not explain vaginal complexity patterns. Additional metrics, such as penile shape complexity, may yield interesting insights into marine mammal genital coevolution. We advocate for the use of alpha shapes to discern patterns of evolution that would otherwise not be possible in 3D anatomical structures lacking homologous landmarks.

Peer review status:ACCEPTED

22 Oct 2020Submitted to Ecology and Evolution
23 Oct 2020Submission Checks Completed
23 Oct 2020Assigned to Editor
05 Nov 2020Reviewer(s) Assigned
30 Nov 2020Review(s) Completed, Editorial Evaluation Pending
02 Dec 2020Editorial Decision: Revise Minor
17 Dec 20201st Revision Received
18 Dec 2020Submission Checks Completed
18 Dec 2020Assigned to Editor
18 Dec 2020Review(s) Completed, Editorial Evaluation Pending
12 Jan 2021Editorial Decision: Accept