Geometric morphometric comparison of the oral and lower pharyngeal jaws of the closely related cichlids Vieja bifasciata, V. breidohri, and V. hartwegi (Cichliformes: Cichlidae)

The systematics of the genus Vieja is complex because it contains many morphologically similar species that have little genetic differentiation. Examination of morphological traits can be useful for clarifying their taxonomic status. We analyzed the morphological variation of bones in the oral and lower pharyngeal jaws to determine whether these structures permit the differentiation of species and to study possible functional implications. Morphological differences were quantified using canonical variates analysis, MANOVA, and paired comparisons. Differences in the number of pharyngeal teeth in the lower pharyngeal jaw were determined using an ANCOVA. The shape of the premaxilla and lower pharyngeal jaw proved useful for the delimitation of these species. Although the morphological variation between V. breidohri and V. hartwegi is minimal, the shapes of their lower pharyngeal jaws differ in morphospace. Vieja bifasciata possesses more teeth in the lower pharyngeal jaw when compared to the other species. Variation in these bones may affect jaw biomechanics and influence feeding behavior. However, these morphological differences contradict the weak genetic differentiation observed. The geographic isolation of V. bifasciata is likely related to its morphological differentiation. The close phylogenetic relationship between V. breidohri and V. hartwegi likely explains their low morphological divergence.