「Habitat-related divergence of body shape and its genetic architecture in Gnathopogon (Cyprinidae) fishes」

Ryo Kakioka

Advances in genomics technologies, especially the improving performance and accessibility of next-generation sequencers, have facilitated the genomic studies of non-model organisms. Despite the enormous diversity of Cyprinidae, few studies have been conducted to elucidate the genetic background of the phenotypic diversification of cyprinid fishes. I conducted a evolutionary genomic study in Gnathopogon to determine the genetic architecture of the lake–stream divergence of body shape – streamlined fish in lakes and robust fish in streams – a phenomenon common among various taxa of fishes. First, I constructed a linkage map of Gnathopogon for quantitative trait locus (QTL) analysis of body shape and for comparative genomic analysis with model fish species. The genetic map was constructed using 198 F2 interspecific cross between two closely related Gnathopogon species of Japan: the riverine species Gnathopogon elongatus and the limnetic species Gnathopogon caerulescens. Using restriction-site associated DNA sequencing (RAD-seq), a linkage map containing 1,622 markers with 25 linkage groups was constructed. Synteny and collinearity were extensively conserved between Gnathopogon and zebrafish. Next, I studied the genetic architecture of the differentiated body shape of Gnathopogon between the riverine and limnetic species. Vertebral counts and geometric morphometrics were used to quantify body shape. QTL analysis of body shape-related traits was carried out for the above F2 interspecific cross. I identified QTLs that exert moderate effect on the traits that have ecological significance in the variation of body shape. Most of the QTLs affected only one trait; however, I found several QTLs that affected multiple traits.  These findings will contribute to understanding the genetic background of the diversification of cyprinid fishes.