| Bosmina is a cladoceran which is widely distributed throughout the world.It is fed by bacterial,phytoplankton,organic rot and is the aquatic animal opening bait.In eutrophic waterbodies,bosmina can become the dominant species of crustaceans which plays an important role in freshwater ecosystems.In this study,we investigated the relationship between the distribution of Bosmina and environmental factors.And then,we investigated population genetic structure of Bosmina from 11 waterbodies in East China using the mtDNA 16S rRNA and COI genes as molecular makers.The main results are as follows:(1)According to the investigation on the 11 water bodies in east China,the abundance of Bosmina in these water bodies and its relationship with environmental factors were analyzed.The results showed that there was no significant difference of DO,pH,NH4+ and NO3-,but transparency(SD),TN,TP and Chla presented significant differences among waterbodies.The results revealed that the abundance of Bosmina was different among seasons.Abundance of Bosmina in summer and autumn were higher than in winter and spring.Abundance of Bosmina in water bodies with higher trophic state such as lake Taihu,Luoma,Hongze,Gehu and Chaohu was higher than in water bodies with lower trophic state such as lake Baoying,reservoir of Hewangba and Zaolin.Pearson correlation analysis showed that abundance of Bosmina presented positive correlation with water temperature,chlorophyll a(P<0.05)and presented negative correlation with SD(P<0.05).These suggest that water temperature and the trophic state were related closely to the abundance of Bosmina.This must be useful for the collection of Bosmina.(2)Mitochondrial 16S rRNA was tested to investigate the genetic structure of Bosmina from 11 waterbodies from east China.The results showed that the A+T make up about 69.0%in the 467 bp fragement.9 variable sites were detected,and 10 haplotypes were defined based on the 16S rRNA sequences of 112 individuals.It indicated a lower haplotype diversity(Hd = 0.296)and nucleotide diversity(Pi = 0.00078)in these populations.Molecular variance analysis(AMOVA)demonstrated that most variation was explained by "within populations"(92.57%),and there is no significant variation among populations(7.43%).The Fst revealed no significant difference among all waterbodies.Total fixation index(Fst)was 0.07432,and the gene flow(Nm)was 3.1138.The result showed that the gene exchange was frequent in Bosmina of 16S rRNA gene.Phylogenetic tree showed that all haplotypes were separate from other sequences of Bosmina,indicating that the study was similar to that of B.fatalis.Haplotypes of Bosmina showed no obvious geographical structure in Haplotype network.Neutrality(Tajima's D =-2.03248,P<0.10;Fu's Fs =-10.922,P<0.10),together with mismatch distribution test indicated that there was recent population expansion of Bosmina in spatial scales.(3)The mitochondrial COI gene sequence of Bosmina was sequenced in order to further understand the genetic structure of eleven waterbodies populations in East China.The results showed that the A+T make up about 63.7%in the 658bp fragement.94 variable sites were detected,and 61 haplotypes were defined based on the COI sequences of 86 individuals.It indicated a higer haplotype diversity(Hd=0.981)and lower nucleotide diversity(Pi=0.00801)in these populations.Molecular variance analysis(AMOVA)demonstrated that most variation was explained by "within populations"(96.73%),and there is no significant variation among populations(3.27%).The Fst revealed no significant difference among all waterbodies.Total fixation index(Fst)was 0.03273,and the gene flow(Nm)was 7.3883.The result showed that the gene exchange was very frequent in Bosmina of COI gene.Haplotypes dispersed in different populations were clustered together in the phylogenetic tree of ML and MP,indicating that there was no obvious difference between the haplotypes of Bosmina.Neutrality and Mismatch distribution test indicated that there was recent population expansion of Bosmina in spatial scales. |
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