Population genetics and phenotypic adaptive variation of seaweed pipefish Syngnathus schlegeli at different latitudes

Uncover the differentiation among natural marine populations is of great importance for understanding the molecular mechanisms of adaptive evolution in the background of high level gene flow. The seaweed pipefish (Syngnathus schlegeli) is well known for exclusive paternal care of eggs which are widely distributed along the coast of western Pacific Ocean and generally inhabit in shallow waters of coral reefs or seagrass beds. S. schlegeli is one kind of the ideal species for the study of differentiation and environmental adaptation of marine animals, because their populations live in divergent ecological environments and rapid evolution of local adaptive traits may occurs. Here, we performed morphological analysis and RADseq of S. schlegeli individuals from different geographical populations. Our results revealed the existence of phenotypic variation in eye size among S. schlegeli populations, and the genetic divergence of S. schlegeli populations were detected using genome-wide SNP markers. Several differentiated loci were identified by genome-wide scan that was associated with the formation of visual system, which can provide hard evidence for the local adaptation in seaweed pipefish.