Abstract

The genetic and morphological structure and phylogenetic relationships of three Caranx species (Caranx crysos, Caranx hippos, and Caranx rhoncus) inhabiting Turkish marine waters were investigated for the first time using an integrative approach. Molecular phylogenetic analyses were performed based on nucleotide sequence variation of the mitochondrial DNA control region (D-loop) using the Tamura three-parameter substitution model. The nucleotide composition exhibited a clear AT bias, with GC content ranging from 35.7% to 38.1% (mean=37.2%) and AT content ranging from 62.0% to 63.8% (mean=62.8%). Genetic distance analysis revealed the highest nucleotide divergence between C. crysos and C. hippos (0.461), whereas C. hippos and C. rhoncus showed the closest genetic relationship (0.148). Maximum Likelihood phylogenetic reconstruction based on D-loop sequences resolved two main lineages: one comprising C. rhoncus and C. hippos, and the other consisting solely of C. crysos. The Minimum Spanning Tree haplotype network provided strong evidence for genetic differentiation among Caranx species and supports their recognition as distinct evolutionary lineages and suggests limited or no recent maternal gene flow between species, despite their potential geographic overlap. Morphological differentiation among species was assessed using 36 truss network morphometric characters and 12 meristic traits. Discriminant function analysis indicated that second dorsal fin length, interorbital distance, and the number of soft rays in the second dorsal fin were the most informative variables in the first discriminant function, whereas body depth measurements and lateral line scale counts contributed most strongly to species separation in the second discriminant function. Neighbor-Joining analysis of morphological data grouped C. rhoncus and C. crysos together, while C. hippos formed a distinct cluster. The contrasting clustering patterns obtained from molecular and morphological datasets reveal a notable discordance between genetic and phenotypic relationships among Mediterranean Caranx species. These results demonstrate that reliance on morphology alone may obscure true evolutionary relationships and highlight the importance of integrating molecular and morphological approaches for accurate systematics. This study provides the first molecular phylogenetic framework for Caranx species in Turkish marine waters and contributes to a better understanding of their evolutionary history and taxonomic relationships in the Mediterranean Sea.