Study On Morphology And Genetics Of Pholis Fangi And P. Nebulosa

Pholis fangi and P. nebulosa, which belong to Perciformes, Blennoidei, Pholidae,Pholis, are both cold temperate demersal fish. P. fangi are mainly distributed in theBohai Sea and Yellow Sea; P. nebulosa are mainly distributed in the Bohai Sea,Yellow Sea and East China Sea. In this study, we used traditional morphologicalmarkers and mtDNA markers to analysis the genetic diversity, population geneticstructure and the demographic history of P. fangi and P. nebulosa and the relationshipbetween P. fangi and P. nebulosa.We compared the morphological difference among four P. fangi populationsbased on13morphological characteristics and10meristic counts. The meristic countswere consistent with the previous taxonomic information. The range of meristiccounts were approximate same in different populations, so it couldn’t be the factor tojudgment. The result of principal component analysis, discriminatory analysis, clusteranalysis and one-way ANOVA showed that there were some genetic differencesamong different populations.To study the genetic diversity, population genetic structure and the demographichistory of P. fangi, we amplified the control region, COI and Cyt b sequencefragments of nine populations. In control region analysis, a total of181samples werecollected and25haplotypes were obtained. Moderate haplotype diversity and lowlevels of nucleotide diversity were detected for all populations. Hierarchical molecularvariance analysis (AMOVA) and conventional population FSTcomparisons revealedno significant genetic structure throughout the examined range. The demographichistory of P. fangi was examined using neutrality tests and mismatch distributionanalysis which indicated a Pleistocene population expansion. Meanwhile, similarresults were found in COI and Cyt b analysis. The entire mitochondrial DNA control region sequence of P. fangi was also amplified. The complete sequence was853bp inlength. The TAS and conservative sequence blocks (CSB-F、CSB-E、CSB-D、CSB-C、CSB-B、CSB-A and CSB-1、CSB-2、CSB-3) in the D-loop were characterized andanalyzed.We compared the morphological difference among two P. nebulosa populationsbased on the principal component analysis, discriminatory analysis, cluster analysisand one-way ANOVA. The result showed that the range of meristic counts wereapproximate same in different populations, so it couldn’t be the factor to judgment.However, there existed genetic differences among different populations onmorphological characteristics.The demographic history and population genetic structure of P. nebulosa wereinvestigated based on control region sequences. Two distinct lineages were found,which might be isolated and diverged in different marginal seas of the NorthwesternPacific during Pleistocene low sea level stands. Moderate haplotype diversity andhigh levels of nucleotide diversity were detected for two populations. The populationstatistic FSTrevealed no significant genetic structure among populations. The resultsof neutrality tests and mismatch distribution analysis indicated a population expansion.The structure of control region of P. nebulosa was quite similar to P. fangi.We compared the difference between P. fangi and P. nebulosa based ontraditional morphological characteristic and mtDNA sequences. Using principalcomponent analysis, discriminatory analysis and cluster analysis to analyzemorphological difference between P. fangi and P. nebulosa, two species havesignificant difference. But the range of meristic counts crossed, so it couldn’t be thefactor to judgment the species. The result of mtDNA analysis showed moderatehaplotype diversity and low levels of nucleotide diversity of P. fangi and P. nebulosa.The population statistic FSTrevealed significant genetic differences between the twospecies. The estimated time of divergence between P. fangi and P. nebulosa was5.3million years ago according to the net genetic distance based on Cyt b analysis, which indicated an early Pliocene divergence for them.