Abstract
BackgroundSturgeon cultivation is important for both industry and aquaculture in China. To date, more than 17 species or strains have been farmed for fillets and caviar production. Crossbreeding among different sturgeon species is frequent and the F2 hybrids are fertile. However, large-scale farming can have negative impacts on wild populations i.e. escape of exotic sturgeons and must be taken into consideration. Escape of exotic sturgeons can cause severe ecological problems, including threatening native sturgeon species once the exotic varieties become established or hybridize with native individuals. However, little is known about their genetic resources and variation.MethodsGenetic diversity and introgression of seven sturgeon species were analyzed using mitochondrial DNA cytochrome oxidase subunit I (COI) and nine microsatellite markers. This study included 189 individuals from seven sturgeon species and 277 individuals from ten lineages of F2 hybrid strains.ResultsMtDNA COI sequences (632 bp long) were generated from 91 individuals across the 17 sturgeon strains and produced 23 different haplotypes. Haplotype diversity was high (h = 0.915 ± 0.015) and nucleotide diversity was low (π = 0.03680 ± 0.00153) in the seven sturgeon species and ten interspecific hybrids. Phylogenetic analyses resulted in almost identical tree topologies, and different haplotype structures were mainly related with sturgeons of different female parents. Analysis of molecular variance revealed that 81.73% of the genetic variance was due to matrilineal differences, while 9.40% resulted from strain variation. Pairwise Fst values obtained with POLYSAT software, were high among strains and ranged from 0.031 to 0.164. Admixture analysis assigned seven distinct groups and ten genotypes of admixed clusters composed of hybrid strains using STRUCTURE when assuming K = 7.ConclusionsThe interspecific mtDNA gene tree corresponded to the expected taxonomic divisions. These relationships were also supported by the results from the microsatellite analysis and contributed to unambiguously identify seven sturgeon species and ten F2 hybrid strains from sturgeon farms in China. Moreover, we found that introgressive hybridization is pervasive, exists in both purebred and hybrid sturgeons, and may reflect widespread mismanagement in sturgeon breeding in China.
Highlights
Sturgeon cultivation is important for both industry and aquaculture in China
The most recent survey has recorded more than 17 sturgeon strains aquacultured in China, with two species i.e. Acipenser baerii and A. schrenckii, and three hybrid sturgeon strains i.e. A. baerii × A. schrenckii, A. schrenckii × Huso dauricus, and A. baerii × A. gueldenstaedti dominating sturgeon farming [17]
Mitochondrial DNA MtDNA cytochrome oxidase subunit I (COI) sequences (632 bp) were generated from 17 strains represented by 91 individuals
Summary
Sturgeon cultivation is important for both industry and aquaculture in China. To date, more than 17 species or strains have been farmed for fillets and caviar production. Hybridization is probably an inevitable process during speciation [1], in which offspring inherit restructured parental genes obtained by mating individuals of different genotypes Hybridization is common both in plants and animals [2,3,4], and is largely exploited to improve various species [5,6,7], especially plants [8,9]. When selective breeding is performed, the genetic relationships between candidate parents are unknown, resulting in random hybridization of different sturgeons. We used nine microsatellites and the mitochondrial DNA (mtDNA) gene cytochrome oxidase subunit I (COI) to examine the genetic diversity, introgression, and differences in genetic background of 17 farmed sturgeon strains, including seven species and ten hybrids
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