Abstract
Background:
Study of five Carangid species to estimate the degree of genetic divergence and draw phylogenetic relationships by using cytochrome c oxidase subunit I (COI), and small (12S rRNA) mitochondrial rRNA genes.

Aim:
This investigation was designed to evaluate genetic relationships and association analyses in the taxonomy studies of Carangid fishes using mitochondrial sequences.

Methods:
The present study analyzed sequence data using two genes to estimate the relationships among five species of the family Carangidae (ray-finned fish), such as Carangoides bajad (gold-spotted trevally), Carangoides malabaricus (Malabar trevally), Caranx melampygus (Bluefin trevally), Caranx sexfasciatus (Bigeye trevally), and Scomberoides lysan (doublespotted queenfish) and to assess the phylogenetic utility of these markers.

Results:
The classification analysis of the family Carangidae is controversial. Our study was performed to examine the phylogenetic relationships among five Carangid species using 12S rRNA and COI genes, that illustrated certain Carangidae family genera are not monophyletic that does not include all the descendants of a common ancestor (Paraphyletic) refers to a taxonomic grouping that includes a common ancestor and some, but not all, of its descendants. This means that a paraphyletic group consists of the last common ancestor and excludes certain lineages that are part of the broader group, for example, in traditional taxonomy, the class of fish is considered paraphyletic because it does not include all descendants. The data reported here may be employed in study and analysis of the phylogenetic variety and relationships among species and genera of the family Carangidae.

Conclusion:
Our results confirmed the thermostability and environmental adaptation of the five species of the Carangidae family due to higher A+T content. Our results also confirmed the earlier conclusions of other authors that several genera of the Carangidae family are not monophyletic which does not include all the descendants of a common ancestor (Paraphyletic) and demonstrated the usefulness of the 12S rRNA gene and the COI gene in the phylogenetic analysis of the Carangid species.

Key words: Carangid species, Mitochondrial rRNA genes, Cytochrome c oxidase subunit I (COI), Small (12S rRNA) mitochondrial rRNA genes, Phylogenetic analysis, Environmental adaptation, Non-monophyletic