Parallel evolution of a new sympatric species pair of Crenicichla (Teleostei: Cichlidae) from Misiones, Argentina with a review of biogeography and mitonuclear discordance in the C. mandelburgeri species complex

The Crenicichla mandelburgeri species complex from the Middle Paraná shows parallel evolution of ecomorphs to the unrelated Crenicichla missioneira species complex from the Uruguay River. In this article, we describe a new species pair (C. sp. Piray Guazú and C. sp. Piray Guazú Line) from the C. mandelburgeri species complex that has evolved a parallel morphological and ecological dichotomy to another species pair from the same species complex (Crenicichla ypo, Crenicichla yjhui) and also to species in the unrelated C. missioneira species complex (C. missioneira, Crenicichla celidochilus). The new species pair is endemic to a single tributary (the Piray Guazú) of the Middle Paraná River where it is sympatric and partly syntopic. Mitochondrial DNA phylogeny shows the two new species as distantly related within the C. mandelburgeri species complex, each with a sister species in the Iguazú rather than in the neighbouring Paraná river tributaries. Reduced genome representation ddRAD analyses of the nuclear genome demonstrate their close relationship, which is however complicated by the hybrid origin of one of the new species (C. sp. Piray Guazú Line). The hybrid origin of this species is demonstrated by sharing the ancestral genetic stock with its sympatric sister species (C. sp. Piray Guazú) while having an admixture from the widespread species C. mandelburgeri from the main Middle Paraná channel. In this study we also review the role of biogeography and mitonuclear discordance during evolution of the whole C. mandelburgeri species complex.