Name: Thais Lemos Quintão
Type: MSc dissertation
Publication date: 13/02/2019
Advisor:

Namesort descending Role
Jean-Christophe Joyeux Advisor *

Examining board:

Namesort descending Role
Anderson Antônio Batista External Examiner *
Hudson Tercio Pinheiro External Examiner *
Jean-Christophe Joyeux Advisor *

Summary: Priolepis (Valenciennes, 1837) is a genus of small benthic fish of the Gobiidae family, associated mainly with reef environments and distributed in different depth gradients. Much of its biodiversity is concentrated in the Indo Pacific (32 species), with the exception of the species Priolepis hipoliti, P. dawsoni, P. ascensionis and P. robinsi, present in the Atlantic. These species, except P. robinsi, have their distribution limited by biogeographic barriers indicating, therefore, origin by allopatric speciation. In this study, we looked for the first time to understand the evolutionary history of the genus Priolepis in the Atlantic using molecular markers and Sanger sequencing. We tested the hypotheses of i) divergence between the Caribbean and Brazilian lineages by vicariance and ii) formation of the Ascension line by peripatric speciation. Phylogeny analyzes using the COI, Citb, 12s, ND2, and S7 genes were integrated with those of phylogeography with COI and Citb genes (in P. dawsoni), in order to generate a better understanding of the evolution of the studied group. Phylogenetic analyzes of p-distance, Bayesian Inference and Molecular Clock were performed to determine the evolutionary proximity between the species of the Priolepis Group as well as to infer if the time of divergence between them is associated with historical evolutionary processes. To understand population demographics, we used genetic diversity indexes (haplotype and nucleotide), neutrality tests, and the Bayesian Skyline Plot method to assess population fluctuations over time. Finally, we verified the hierarchical relationship between the haplotypes of each species and tested the structuring evidence found in Priolepis dawsoni using the Fst index and analyzes of molecular variance (SAMOVA and AMOVA) for Citb. Our results showed a great correlation between the divergences found in Priolepis and geological and climatic events. Its evolutionary history begins with the closure of the Tethys passage resulting in the isolation and origin of the Atlantic Clado (~ 13 Ma). Only two million years later (~ 10.5 Ma), the formation of the Amazon barrier divided the lines of the North and South Atlantic, corroborating our initial hypothesis of allopatric speciation by vicariance. The hypothesis of peripacic allopatric speciation for Ascension was also corroborated and the best scenario to explain the origin of P. ascensionis is the dispersion from Brazil. The phylogeographic and demographic analyzes point to great genetic diversity in all species and also suggest that the evolutionary history of the studied populations was influenced by the climatic variations of the Pleistocene and that the general habit of these can facilitate the dispersion between distant regions and different environments. Finally, the molecular evidence of P. dawsoni specimens in the Caribbean indicates that their status as endemic to Brazil should be reassessed.

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