Abstract
The genetic differentiation of many marine fish species is low. Yet local adaptation may be common in marine fish species as the vast and changing marine environment provides more chances for natural selection. Here, we used anonymous as well as known protein gene linked microsatellites and mitochondrial DNA to detect the population structure of the small yellow croaker (Larimichthys polyactis) in the Northwest Pacific marginal seas. Among these loci, we detected at least two microsatellites, anonymous H16 and HSP27 to be clearly under diversifying selection in outlier tests. Sequence cloning and analysis revealed that H16 was located in the intron of BAHCC1 gene. Landscape genetic analysis showed that H16 mutations were significantly associated with temperature, which further supported the diversifying selection at this locus. These marker types presented different patterns of population structure: (i) mitochondrial DNA phylogeny showed no evidence of genetic divergence and demonstrated only one glacial linage; (ii) population differentiation using putatively neutral microsatellites presented a pattern of high gene flow in the L. polyactis. In addition, several genetic barriers were identified; (iii) the population differentiation pattern revealed by loci under diversifying selection was rather different from that revealed by putatively neutral loci. The results above suggest local adaptation in the small yellow croaker. In summary, population genetic studies based on different marker types disentangle the effects of demographic history, migration, genetic drift and local adaptation on population structure and also provide valuable new insights for the design of management strategies in L. polyactis.
Highlights
In many marine fish species, especially migratory species, the signal of population differentiation is weak and hard to detect due to high levels of gene flow
We didn’t observe a clear population differentiation pattern at hot shock protein 27 (HSP27), we found several samples significantly differentiated from the other samples, which was different from the neutral loci (Figure 4c & Table S4c)
Our work demonstrates that joint application of different genetic marker types to study population dynamics provides a comprehensive understanding of the interplay among different evolutionary forces
Summary
In many marine fish species, especially migratory species, the signal of population differentiation is weak and hard to detect due to high levels of gene flow. It is traditionally difficult to delineate the population structure or detect the population subdivision lacking clear barriers to gene flow within ocean basins [1]. In fishes of recent speciation, this problem has become more complicated because of little accumulation of genetic differentiation in such a short period of time [2]. Advancement in population genetic studies has greatly improved our methods in elucidating the population genetic structure of marine fishes of high mobility and high dispersal potential during egg and larval stages [3]. Electronic and microchemical tagging techniques provide direct information in analyzing population dynamics of some marine fishes. The genetic approaches can suggest unique strategies for stock management and evolutionary unit conservation [4,5], proving to be important for the economically important marine fish species facing high fishing pressure or already being threatened
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