Evolutionary history of the polymorphic Coatzacoalcos River endemic Thorichthys panchovillai (Cichliformes: Cichlidae)

Cichlids of the genus Thorichthys are a morphologically diverse clade of nine species occurring from Mexico south to the Motagua River in Guatemala and Honduras. Our understanding of species relationships within Thorichthys and other genera of Northern Neotropical cichlids has improved in recent years; however, phylogenetic placement of some species, as well as population-level variation, remains understudied. Thorichthys panchovillai is a polymorphic species endemic to the Coatzacoalcos River in the Atlantic slope of Mexico.

The species was described from the upper reaches of this river, and since that time phenotypic variation in coloration and body shape has been observed. However, the species has never been included in a molecular phylogenetic study to understand its evolutionary relationships within the genus and better relate the observed morphological polymorphism to genetic patterns within this species. In this study we use mitochondrial data to study the phylogenetic placement of T. panchovillai in the context of all other species of Thorichthys.

Results show that spatially segregated haplotypes correspond to two main morphotypes of T. panchovillai and allow for the proposal of hypotheses regarding maintenance of this polymorphism in the Coatzacoalcos River.