The Impacts Of Paleoenviromental Changes And Anthropogenic Selection On The Genetic Structure Of Carassius

Glacial cycling through the Quaternary is known to have caused dramatic climatic and (?) graphic changes. These oscillations are likely to have been imprinted in rapidly evolving and maternally inherited mitochondrial genes. It is useful to understand the impacts of paleoenviromental variation on the speciation by identifying the present biogeography. The Carassius (Cypriniformes, Cyprinidae) is widely distributed across Eurasia, including the Oriental islands, and have high genetic diversity and a late Pliocene origin. Futhermore, the goldfish, as a variation of native Carassius, have tremendous extent of phenotypic variation caused by the anthropogenic selection. Therefore, the genus Carassius is great material to reveal the impacts of paleoenviromental changes and anthropogenic selection on the speciation.We reconstructed the matrilineal history of Eurasian goldfish using1876sequences from the partial mitochondrial DNA control region (426bp) and191complete sequences of cytochrome b (1140bp) from67localities representing most of the range of the species, trying to test whether vicariance events or human-mediated translocations best explained lineage divergence and phylogeographical history. Three lineages had high levels of regional specificity. Lineages A and B from the main islands of Japan differed greatly from Lineage C, which occurred on the mainland, Taiwan and the Ryukyus. Lineages A and B had late Pliocene origins. Six geographically constrained sublineages within Lineage C had near-simultaneous mid-Pleistocene divergences. Genetic structure in the C. auratus complex appears to have been driven by palaeoenvironmental perturbations rather than human translocations. Disappearance of a land bridge in the Tsushima Strait around3.0Ma is responsible for the separation of Japanese and continental lineages; the estimated divergence time is2.75-2.32Ma. Fujian, China and Vietnam appear to have provided important refugia for the C. auratus complex during glaciation. After warm, moist summer monsoons intensified during the mid-Pleistocene, goldfish are likely to have dispersed north-eastwards to recolonize the Ryukyus via Taiwan and northwards to recolonize mainland China.We sequenced the mitochondria DNA ND2, ND4, ND5, Cyt b, COII and the partial control region (CR) of119specimens, trying to identify the phylogenetic relationships within Carassius. The C. carassius species formed the sister group to the remained members of genus Carassius, and originated in Eurasia around4.0Ma. Within the species C. auratus complex, the C. cuvieri formed the sister group to the remained C. auratus complex, and had high genetic differentiation from other lineages. The specific distributed ranges and chromosome numbers also suggested it was likely more reasonable to regard the C. cuvieri as an independent species. The C. a. langsdorfii formed a monophyletic lineage, and could be taken as a subspecies of Japanese C. auratus complex. The C. a. gibelio also formed a monophyletic lineage, and had closer relationship with sublineage C6. The divergence dates estimation revealed that the C. a. gibelio probably originated from an older mainland lineage (C1) from the Fujian, China and Vietnam. All Chinese regional lineages tested were morphological variants of the C. a. auratus (sublineage C5or C6) or the C. a. gibelio inferred from the mitochondria DNA.To locate the geographic origin of goldfish, we analyzed nucleotide sequences from part of the control region (CR) and the entire cytochrome b (Cytb) mitochondrial DNA genes for234goldfish and a large series of native specimens. Haplotypes of goldfish rooted in two sublineages (C5and C6), which contained the haplotypes of native C. a. auratus from southern China. The FST and Nm values revealed a close relationship between goldfish and native C. a. auratus from the lower Yangtze River. An extraordinary, stepwise loss of genetic diversity was detected from native fish to goldfish and from Grass-goldfish relative to other breeds. Significantly negative results for the tests of Tajima’s D and Fu and Li’s D*and F*were identified in goldfish, including the Grass breed. The results identified eye-shape as being the least informative character for grouping goldfish with respect to their evolutionary history. Fisher’s exact test identified matrilineal constraints on domestication. Chinese goldfish have a matrilineal origin from native southern Chinese C. a. auratus, especially the lineages from the lower Yangtze River. Anthropogenic selection of the native Carassius eliminated aesthetically unappealing goldfish and this action appeared to be responsible for the stepwise decrease in genetic diversity of domesticated goldfish, a process similar to that reported for the domestication of pigs, rice, and maize. The three-breed taxonomy—Grass-goldfish, Egg-goldfish, and Wen-goldfish—better reflected the history of domestication.Our analyses revealed that both the paleoenviromental Changes and anthropogenic selection had huge impacts on the genetic structure of the Carassius. Additional molecular markers and more extensive sampling, especially from Siberia and the Far East, may identify lineages involved in the early evolution of Carassius. The further examination of other genes closely related to the morphological characteristics of goldfish might better reveal the evolution of Chinese goldfish.