MicroRNA gene regulation in extremely young and parallel adaptive radiations of crater lake cichlid fish

Cichlid fishes provide textbook examples of explosive phenotypic diversification and sympatric speciation, thereby making them ideal systems for studying the molecular mechanisms underlying rapid lineage divergence. Despite the fact that gene regulation provides a critical link between diversification in gene function and speciation, many genomic regulatory mechanisms such as miRNAs have received little attention in these rapidly diversifying groups. Therefore, we investigated the post-transcriptional regulatory role of miRNAs in the repeated sympatric divergence of Midas cichlids (Amphilophus spp.) from Nicaraguan crater lakes. Using miRNA and mRNA sequencing of embryos from five Midas species, we first identified miRNA binding sites in mRNAs and highlighted the presences of a surprising number of novel miRNAs in these adaptively radiating species. Then, through analyses of expression levels, we identified putative miRNA/gene target pairs with negatively correlated expression level tha...