Identifying genetic lineages through shape: An example in a cosmopolitan marine turtle species using geometric morphometrics

PLoS One. 2019 Oct 7;14(10):e0223587. doi: 10.1371/journal.pone.0223587. eCollection 2019.

Abstract

The green turtle (Chelonia mydas) is a globally distributed marine species whose evolutionary history has been molded by geological events and oceanographic and climate changes. Divergence between Atlantic and Pacific clades has been associated with the uplift of the Panama Isthmus, and inside the Pacific region, a biogeographic barrier located west of Hawaii has restricted the gene flow between Central/Eastern and Western Pacific populations. We investigated the carapace shape of C. mydas from individuals of Atlantic, Eastern Pacific, and Western Pacific genetic lineages using geometric morphometrics to evaluate congruence between external morphology and species' phylogeography. Furthermore, we assessed the variation of carapace shape according to foraging grounds. Three morphologically distinctive groups were observed which aligned with predictions based on the species' lineages, suggesting a substantial genetic influence on carapace shape. Based on the relationship between this trait and genetic lineages, we propose the existence of at least three distinct morphotypes of C. mydas. Well-defined groups in some foraging grounds (Galapagos, Costa Rica and New Zealand) may suggest that ecological or environmental conditions in these sites could also be influencing carapace shape in C. mydas. Geometric morphometrics is a suitable tool to differentiate genetic lineages in this cosmopolitan marine species. Consequently, this study opens new possibilities to explore and test ecological and evolutionary hypotheses in species with wide morphological variation and broad geographic distribution range.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animals
  • Phenotype*
  • Phylogeny*
  • Phylogeography
  • Turtles / anatomy & histology
  • Turtles / classification
  • Turtles / genetics*

Grants and funding

Financial support for this study was provided by the Vice-Rectory of Research of the University of Costa Rica through the Integral Network of Marine Turtles in the Eastern Pacific (RITMA), The Leatherback Trust, Veritas University, Surfari del Mar, Centro de Rescate de Especies Marinas Amenazadas (CREMA), National Marine Fisheries Service and the Turner Foundation, the National Oceanic and Atmospheric Administration (NOAA), Rufford Small Grant, Idea Wild, Chilean Government Environmental Protection Fund (FPA), and the Institute of Natural and Mathematical Sciences, Massey University, Auckland. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Genetic analyses were performed at the Centro de Investigación en Biología Celular y Molecular (CIBCM) of the University of Costa Rica (San José, Costa Rica); at the Molecular Genetics Laboratory from the South West Fisheries Science Center (NOAA-NMFS; La Jolla, San Diego, California, US) by Dr. Peter Dutton and his team; Laboratorio de Biodiversidad Molecular, Pontificia Universidad Católica de Chile (Santiago, Chile); and the Griffith School of Environment, Griffith University with assistance from N. FitzSimmons (Brisbane, Australia).