Unraveling the Mugil curema complex of American coasts integrating genetic variations and otolith shapes

Abstract

The white mullet, Mugil curema, is a commercially important species in coastal areas, with a large phenotypic variability and genetic dissimilarity among populations throughout its distribution. For management purposes it is important to determine whether the morphological variability reflects the genetic differences among groups. This study evaluates whether the genetic differentiation in Mugil curema is reflected in the otolith shape on a large geographic scale in the Neotropical Atlantic and the Mexican Pacific. We analyzed the COI (Cytochrome Oxidase I) gene polymorphism as a marker and followed the otolith contour-based Fourier analysis as a morphometric method. Seven locations were studied, four in coastal lagoons of the Gulf of Mexico, one in the Mexican Pacific, one in the Caribbean Sea at Nueva Esparta, Venezuela and one in San Antonio Lagoon, Brazil. The genetic divergence accounted by the COI and the morphological differentiation in M. curema otoliths did not, in general, present cross-scale patterns, and the variability of otolith shapes was not reflected in the mitochondrial genetic variability. Other molecular methods could potentially reveal genetic differences. In particular, the variability in otolith shape among the Gulf of Mexico individuals may indicate that local divergences are accumulated in the otoliths, reflecting a possible interaction effect between local and regional drivers that is not evidenced at the genetic level.