Morphological and functional consequences of the land-to-water transition in the salamander families Ambystomatidae and Plethodontidae

Darcy, Hannah Elizabeth

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https://hdl.handle.net/2142/120565 Copy

Description

Title

Morphological and functional consequences of the land-to-water transition in the salamander families Ambystomatidae and Plethodontidae

Author(s)

Darcy, Hannah Elizabeth

Issue Date

2023-04-26

Director of Research (if dissertation) or Advisor (if thesis)

Anderson, Philip SL

Doctoral Committee Chair(s)

Anderson, Philip SL

Committee Member(s)

• Kawano, Sandy
• Roseman, Charles
• Suarez, Andrew

Department of Study

Evolution Ecology Behavior

Discipline

Biology

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• morphology
• salamanders
• secondarily aquatic
• morphometrics
• nanoindentation
• finite element analysis

Abstract

Land-to-water transitions are major evolutionary events and introduce new constraints to tetrapod morphology. Two North American salamander groups have recolonized aquatic habitats: mole salamanders (Ambystomatidae) and lungless salamanders (Spelerpini; Plethodontidae). I examined the morphological and biomechanical consequences of this transition using a comparative approach. First, I tested the hypothesis that aquatic species have convergent skull morphologies, given the different developmental pathways followed by the two groups. Using 3D microCT scan data from online repositories and museum specimens, I performed a geometric morphometric analysis on skull shape and applied a phylomorphospace to the morphometric data to determine whether morphological variation was due to phylogeny or ecology. Second, I performed nanoindentation tests on cartilage and bone from dissected Ambystoma to determine if Young’s modulus differed significantly between aquatic and terrestrial taxa, and to determine the difference in magnitude between cartilage and bone. Finally, to focus more closely on a structure primarily involved in feeding, I examined the mandibular morphology and functional performance in the two families. I tested the importance of morphology and Young’s modulus values in the mandible in resisting forces that simulated prey-capture by holding shape volume and applied loads constant in a Finite Element Model. While there are statistically significant differences in the jaw proportions in aquatic and terrestrial salamanders in both families, the mechanical models did not support that terrestrial morphologies are better suited for applying bite forces. The results of these four studies will guide future work investigating the functional demands on salamander skulls and what structural changes occur when terrestrial species recolonize aquatic habitats.

Graduation Semester

2023-05

Type of Resource

Thesis

Copyright and License Information

Copyright 2023 Hannah Darcy

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