Estudi bioinformàtic de la variabilitat genètica de la tonyina vermella al Mediterrani

Abstract

With the aim of studying genetic variability of Bluefin Tuna (Thunnus thynnus) 689 sequences of the mitochondrial DNA control region of this species have been analyzed using bioinformatics tools. Four analysis have been performed based on the study of the number of haplotypes and using a different data treatment in each case. In order to detect which haplotype belongs to each sequence a phylogenetic tree has been created and it has been established that two or more sequences belong to the same haplotype when there isn’t genetic distance between them. Analyzing the phylogenetic tree the huge variability of T. thynnus populations has been detected, where a large number of haplotypes are made up of only one sequence. In the four analysis it has been studied how haplotypes appear while the volume of analyzed sequences increases in order to see at what point new haplotypes don’t appear anymore, which means that complete genetic variability of the population has already been represented. The analysis that best represent the objectives suggested have been selected between the four analysis, principally due to data treatment, and it has been concluded that more than 657 sequences have to be analyzed in order to achieve the total representation of T. thynnus population. Haplotype diversity (h) has also been studied. It has been observed that these statistic values are generally high, despite the fact that they decrease while the volume of analyzed sequences is increasing. High haplotype diversity values indicate that T. thynnus populations present a huge genetic diversity and this implies that an extremely large number of individuals has to be analyzed to represent all this variability. This is essential when population, phylogenetic and phylogeography studies are performed. Moreover, it is crucial to perform population studies correctly when they center around species such as T. thynnus, because it is a highly valued and threatened species. For this reason it is necessary to know when one of these studies do or do not represent the entire Thunnus thynnus population