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Phylogenomics of pike cichlids (Cichlidae: Crenicichla) of the C. mandelburgeri species complex: rapid ecological speciation in the Iguazú River and high endemism in the Middle Paraná basin

Piálek, Lubomír, Burress, Edward, Dragová, Klára, Almirón, Adriana, Casciotta, Jorge, Říčan, Oldřich
Hydrobiologia 2019 v.832 no.1 pp. 355-375
Crenicichla, basins, flocks, hybridization, indigenous species, monophyly, niches, periphyton, pike, rivers, sympatry
The Crenicichla mandelburgeri species complex from the Middle Paraná basin is a diverse group of cichlid species and contains all known ecomorphs found within the entire genus Crenicichla. Here, we study the phylogenetic relationships within the C. mandelburgeri species complex using ddRAD sequencing with focus on its two candidate species flocks endemic to the Iguazú and Urugua-í Rivers, and on two putative sympatric species in the Piray Guazú River. These species flocks include four and three syntopic species, respectively, which are strongly adapted to different trophic niches and include derived ecomorphs of Crenicichla (molluscivores, a periphyton grazer, and a crevice-feeding thick-lipped invertivore). Our phylogenomic analyses strongly support monophyly and rapid diversification of the Iguazú species flock, but reveal more complex evolutionary histories in the Urugua-í and Piray Guazú tributaries. Most species in the Middle Paraná, including one species in the Urugua-í and both species in the Piray Guazú show cytonuclear discordance, and in both of these tributaries, we also found hybridization in one of the resident species. Population-level analyses reveal complete isolation of the Iguazú species and coupled with their dramatic ecological diversity, this radiation exemplifies characteristics of a species flock that arose via ecological speciation.