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| Author(s): |
Adriana Marcela Morales Guerrero
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | São Paulo. |
| Institution: | Universidade de São Paulo (USP). Instituto de Biociências (IBIOC/SB) |
| Defense date: | 2021-10-13 |
| Examining board members: |
Antonio Carlos Marques;
Maria de Los Angeles Mendoza Becerril;
Cristina Yumi Miyaki;
Edgar Gamero Mora
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| Advisor: | Antonio Carlos Marques; Lucília Souza Miranda |
| Abstract | |
Establishing an accurate evolutionary timescale for the phylum Cnidaria is essential to place diverse adaptations, such as biomineralization origin or the multi-phase life cycle evolution into a correct geological timeframe. Molecular clock dating studies have suggested a Precambrian divergence for Cnidaria. However, most of these studies have addressed only some subclades within Cnidaria and all have failed to include the uncertainties associated with various components of Bayesian molecular dating. Here we test the sensitivity of the divergence time estimates for the deeper cnidarian lineages regarding (1) uncertainty in the phylogenetic relationships, (2) different interpretations of the fossil record, and (3) alternative birth-death parameters setting of the branching process. Our results indicate that topology has little impact on age estimates, and greater differences derive from alternative fossil strategies and birth-death parameters setting. We corroborated a Precambrian origin of Cnidaria in all analyses, although this origin may vary from as much as ~804 Ma (Tonian Period), or as little as ~606 Ma (Ediacaran Period). The estimated ages for the crown Anthozoa and Medusozoa range from the middle Neoproterozoic to the late Cambrian interval. This timescale also suggested a discordance between molecular clock and purely fossil-based interpretations of cnidarian diversification. The origin of the crown group of Cnidaria and its major lineages may have occurred in a Precambrian atmosphere with low oxygen concentration, and the origin of relevant innovations to the phylum, such as the metagenetic life-cycle or the skeleton, may have occurred in the early Edicaranlate Cambrian period, which coincides with the progressive oxygenation of the oceans. (AU) | |
| FAPESP's process: | 17/00312-3 - Time and space in the evolution of Staurozoa (Cnidaria) |
| Grantee: | Adriana Marcela Morales Guerrero |
| Support Opportunities: | Scholarships in Brazil - Doctorate |