Genetic Differentiation of Japanese Sardinella(Sardinella zunasi) Populations in the Northwest Pacific Revealed by ISSR Analysis

Knowledge of population genetic structure plays an important role in fisheries management.In this research,In-ter-Simple-Sequence-Repeat(ISSR)markers were employed to evaluate the genetic structure of Japanese sardinella(Sardinella zun-asi)populations in the Northwest Pacific.Eighty seven individuals from 5 locations were screened using 4 highly polymorphic prim-ers.A total of 173 polymorphic loci were detected out of 191 loci amplified.Small but significant genetic differentiation was de-tected between the Chinese and Japanese populations by both AMOVA and pairwise FST analyses,which was further supported by cluster analysis.We consider that climate change during glaciations should be responsible for the genetic differentiation.Isolation by geographic distance among populations was observed,indicating that the distance might also lead to the genetic differentiation.However,no genetic structure was found within the populations off both the Chinese and Japanese coasts,indicating a high-level along-coast gene flow,which might result from ocean current transport and common ground for over-wintering.

Influence of Host Shift on Genetic Differentiation of the Oriental Fruit Fly,Bactrocera dorsalis

Invasion of the oriental fruit lfy, Bactrocera dorsalis, into new niches containing different food sources （a process referred to as host shift）, may cause population genetic differentiation and sympatric speciation. To attempt to infer that experimentally, test populations were established by transferring a subset of the original populations, which had been grown on banana for many generations, onto navel orange, and then subculturing the navel orange population and banana population for at least 20 generations. Four pairs of SSR primers with high polymorphism on laboratory strains were used to detect population genetic differentiation. All six tested populations （the 5th, 10th and 15th generations of B. dorsalis fed on banana and navel orange, respectively） were found to have low genetic diversity. Furthermore, the genetic diversity of the navel orange populations was found to decline after being crossed for several generations. Populations initially were deviated from Hardy-Weinberg equilibrium, however, equilibrium was achieved with increasing numbers of generations in both of the host populations. Limited gene lfows were found among the six populations. The Nei’s standard genetic distances between the two host populations of the same generation were initially low, but increased with generation number. Genetic distances between banana and navel orange populations of the same generation were lower than genetic distances between different generations grown on the same host plant. Analysis of molecular distance （AMOVA） results based on generation groups and host groups demonstrated that genetic variation among generations was greater than that between the two host populations. The results indicated that population genetic differentiation occurred after the host shift, albeit at low level. Biogeography and taxonomy of the B. dorsalis complex revealed that speciation of B. dorsalis might be tightly associated with host shift or host specialization of B. dorsalis following dispersal.

Molecular phylogeography and population genetic structure of the planktonic copepod Calanus sinicus Brodsky in the coastal waters of China

Planktonic copepod Calanus sinicus is the dominant meso-zooplankton in the Northwest Pacific Ocean. To better understand its population dynamics and phylogeographic patterns, 243 C. sinicus individuals were collected from seven locations across the shelf waters of China and its population genetics was studied by mitochondrial DNA cytochrome oxidase I（mtCOI） sequences analyses. Thirty-nine different sequences, or haplotypes, were detected with moderate haplotype diversity（h=0.749） and low nucleotide diversity（π=0.003） for all populations. The evolutionary divergence between geographic populations varied from 0.24% to 0.37%, indicative of very limited genetic differentiation. Visualized minimum spanning network（MSN） and phylogenetic analysis of all the detected haplotypes did not reveal any clear phylogeographic pattern. Furthermore, AMOVA data showed no significant spatial population differentiation existed among the individuals collected across China shelf waters. Pairwise FST values showed that population collected from northwest of the East China Sea（ECS） displayed a low difference to other populations. Mismatch distribution analyses and neutrality tests indicated that C. sinicus might undergo a demographic/population expansion. No significant population genetic structuring was detected, indicating an extensive gene flow among the C. sinicus populations. Our results provide molecular evidence for the hypothesis that C. sinicus in the northwestern South China Sea in winter is transported from the East China Sea and the Yellow Sea by the China Coastal Current during the northeast monsoon period.

Genetic variation and population structure of the mushroom Pleurotus ferulae in China inferred from nuclear DNA analysis

To investigate the genetic diversity of an edible fungus Pleurotus ferulae, a total of 89 wild samples collected from six geographical locations in the Xinjiang Uygur Autonomous Region of China and two geographical locations in Italy, were analyzed using three DNA fragments including the translation elongation factor（EF1α）, the second largest subunit of t he RNA polymerase II（RPB2） and the largest subunit of the RNA polymerase II（RPB1）. The results indicated relatively abundant genetic variability in the wild resources of P. ferulae. The analysis of molecular variance（AMOVA） showed that the vast majority of the genetic variation was found within geographical populations. Both the Chinese populations and the Italian populations of P. ferulae displayed a limited genetic differentiation. The degree of differentiation between the Chinese populations and the Italian populations was obviously higher than that between the populations from the same region, and moreover the genetic differentiation among all the tested populations was correlated to the geographical distance. T he phylogeny analyses confirmed that samples from China and Italy belonged to another genetic group separated from Pleurotus eryngii. They were closely related to each other but were clustered according to their geographical origins, which implied the Chinese populations were highly differentiated from the Italian populations because of distance isolation, and the two populations from different regions might be still in the process of allopatric divergence.