Ontogenetic origins of cranial convergence between the extinct marsupial thylacine and placental gray wolf

Axel H. Newton, Vera Weisbecker, Andrew J. Pask, Christy A. Hipsley

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Abstract

Phenotypic convergence, describing the independent evolution of similar characteristics, offers unique insights into how natural selection influences developmental and molecular processes to generate shared adaptations. The extinct marsupial thylacine and placental gray wolf represent one of the most extraordinary cases of convergent evolution in mammals, sharing striking cranial similarities despite 160 million years of independent evolution. We digitally reconstructed their cranial ontogeny from birth to adulthood to examine how and when convergence arises through patterns of allometry, mosaicism, modularity, and integration. We find the thylacine and wolf crania develop along nearly parallel growth trajectories, despite lineage-specific constraints and heterochrony in timing of ossification. These constraints were found to enforce distinct cranial modularity and integration patterns during development, which were unable to explain their adult convergence. Instead, we identify a developmental origin for their convergent cranial morphologies through patterns of mosaic evolution, occurring within bone groups sharing conserved embryonic tissue origins. Interestingly, these patterns are accompanied by homoplasy in gene regulatory networks associated with neural crest cells, critical for skull patterning. Together, our findings establish empirical links between adaptive phenotypic and genotypic convergence and provides a digital resource for further investigations into the developmental basis of mammalian evolution.

Original languageEnglish
Article number51
Number of pages9
JournalCommunications Biology
Volume4
DOIs
Publication statusPublished - 8 Jan 2021

Keywords

  • Thylacine
  • phenotypic convergence
  • Ontogenetic development
  • placental gray wolf
  • cranial development

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