Study On Population Morphological Differences And Population Genetics Of Hemiculter(Cyprinidae:Culterinae)

Hemiculter leucisculus and Hemiculter bleekeri are small,widespread and native fish in China.They both belong to Cyprinidae,Culterinae,Hemiculter.They have prominent habitat suitability and high invasive potential and are the dominant species in many freshwater ecosystems of our country.But how the 2 species acclimate to extremely heterogeneous environments remains unclear.The morphological difference of 18 different H.leucisculus populations was obtained by geometric morphology.The relationship of morphological and climatic change was then analysized.With mitochondrial gene Cytb,nuclear gene RAG2 and Rho as molecular markers,the genetic structure,genetic diversity and phylogeography of 18 H.leucisculus populations from different drainages were explored.The relationship of morphological difference and genetic differentiation was also discussed preliminarily.In addition,the relationship between the brain volume difference of 8 populations and climatic change was also studied.At the same time the analysis of morphological vatiation from six H.bleekeri populations along Yangtze River basin was conducted.The relationship of their morphological difference and climate change was analysized.Cytb,Rag2 and Rho were emploied as molecular markers to analyze the genetic structure and genetic diversity of the six populations.The relationship between morphological difference and genetic distance of these populations was also explored.The main results are shown as follows:1.The size and shape of H.leucisculus are related to climate,which vary significantly along the latitude and longitude gradient of climate.As to the body size,along the latitude gradient,in high-latitude that is in the northern,the fish is big;along the longitude gradient,fish is bigger from inland and high altitude area than the coastal and low altitude area.But the interactive effect of the climate is more complicated,there is a critical point,on both sides of the point the trend of change is oppositive.The shape of H.leucisculus is also related to climatic gradients.The effect of climatic longitude gradient makes the H.leucisculus body inland narrower than in the coastal area,accompanied by anal fin forward and longer,dorsal fin deepen,backwards and curved,caudal peduncle shorter and volume decreased.Along the longitude gradient,the trend of climatic interaction in the south was different from or on some traits even opposive to the north.Latitude gradient effect makes the H.leucisculus body shorter in the north than in the south,along with the anal fin shorter,caudal peduncle longer and volume larger.The interaction effect along the latitude is stronger inland than in coastal areas.2.The brain or brain components' volume of H.leucisculus from different populations is significantly associated with climatic change.The result showed that along the latitudinal gradient,just from north to south,the volume of telencephalic lobes,hypothalamus,total brain,cerebellum,and optic tectum decreases.Along the longitude gradient,from coastal to inland,the volume of olfactory bulbs,hypothalamus,cerebellum,and telencephalic lobes increases;there is a critical point on the interaction term along latitude or longitude gradient.On both sides of the point,the trends of climatic effect on the brain and some regions of the brain volume are oppositive.3.Mitochondrial gene Cytb and two nuclear gene RAG2,Rho were used as molecular markers for population genetic diversity,genetic structure and phylogeography analysis of H.leucisculus.According to parameters,H.leucisculus is on a higher level of genetic diversity compared with other fish.The range of genetic differentiation index(F_ST)between populations is wide,which shows that H.leucisculus populations are highly differentiated.The BI phylogenetic tree,haplotype network,STRUCTURE diagram and AMOVA results,although there are some differences between Cytb,RAG2 and Rho,all support the Beihai and Hainan populations differentiating from the others,Beihai and Hainan populations forming the independent evolving lineage.Moreover,the analysis of the genetic structure based on Cytb shows the populations from Yellow River or the Yangtze River drainage gather together resepectively,and supports the two drainage groups have some differentiation too.4.The Mantel test and partial Mantel test were performed between morphological,genetic and climatic distances,results show that the morphological distances between populations are associated with the distances of climate whatever before or after controlling for the genetic factor,which in accord with the previous conclusion of 18 different H.leucisculus populations showing significant morphological variations along the climate latitude and longitude gradient.However,morphological variations have no correlation with genetic differentiations after controlling for climatic factor.Therefore,based on the current sampling range and experimental results,we cannot think that morphological variations have genetic basis.It is speculated that the plasticity caused by climatic change plays important roles in morphological variation.5.The study on the shape and size of 6 populations of H.bleekeri from Yangtze River basin shows changes of shape and size being associated with the climatic longitude gradient.By covariance analysis it is identified that along longitude gradient,the farther inland,the bigger the fish body,and at the same time H.bleekeri developed bigger volume caudal peduncle,shorter anal fin,much streamlined body contour.By the partial least squares analysis,we also make sure the distance to the sea,altitude and annual precipitation contributing greatly to the morphological changes.6.With mitochondrial gene Cytb,two nuclear genes RAG2 and Rho as molecular markers,population genetic diversity,genetic structure and phylogeography of H.bleekeri were studied.Genetic diversity parameters show that H.bleekeri own high diversity.The BI phylogenetic tree and haplotype network indicate no distinct populations gathered geographically,and no obvious branches.The range of genetic differentiation indexes between populations is small which means small population differentiation.STRUCTURE analysis indicates that genetic clusters contributing to each population are similar.AMOVA result suggests the main source of genetic variation comes from within populations.The Mantel test on pairwise F_STs and geographic distances shows that geographical isolation does not exist,and genetic exchange frequently.7.The Mantel test and partial Mantel test were performed on the pairwise distances of morphology,climatic and the genetic variation,the results showe that controlling for the genetic factor or not,morphological variations both associate with climatic changes significantly,which is consistent with the conclusions of covariance analysis and partial least squares.But there is no correlation between morphological differences and genetic variations.A wide span of H.leucisculus sampling was done and the subsequent study on ecological morphology and genetic structure was conducted.Additionally a morphology and phylogenetic study of H.bleekeri of 6 populations from the Yangtze River basin was also carried out.The correlation between morphological variations and climate changes,and correlation between morphological variations and genetic differentiations were analyzed.The important role of plasticity mechanism due to climate gradient in the morphological change was clear out in the research.