Evolution and genetics of bighead and silver carps: Native population conservation versus invasive species control

Abstract

Bighead carp (Hypophthalmichthys nobilis) and silver carp (H. molitrix), collectively called bigheaded carps, are cyprinids native mainly to China and have been introduced to over 70 countries. Paleontological and molecular phylogenetic analyses demonstrate bighead and silver carps originated from the Yangtze‐Huanghe River basins and modern populations may have derived from the secondary contact of geographically isolated fish during the last glacial events. Significant genetic differences are found among populations of native rivers (Yangtze, Pearl, and Amur) as well as introduced/invasive environments (Mississippi R., USA and Danube R., Hungary), suggesting genetic backgrounds and ecological selection may play a role in population differentiation. Population divergence of bighead carp or silver carp has occurred within their native rivers, whereas, within the Mississippi River Basin (MRB)—an introduced region, such genetic differentiation is likely taking place at least in silver carp. Interspecific hybridization between silver and bighead carps is rare within their native regions; however, extensive hybridization is observed in the MRB, which could be contributed by a shift to a more homogenous environment that lacks reproductive isolation barriers for the restriction of gene flow between species. The wild populations of native bighead and silver carps have experienced dramatic declines; in contrast, the introduced bigheaded carps overpopulate the MRB and are considered two invasive species, which strongly suggests fishing capacity (overfishing and underfishing) be a decisive factor for fishery resource exploitation and management. This review provides not only a global perspective of evolutionary history and population divergence of bigheaded carps but also a forum that calls for international research collaborations to deal with critical issues related to native population conservation and invasive species control.

Comparison of the Genetic Structure of Invasive Bigheaded Carp (Hypophthalmichthys spp.) Populations in Central-European Lacustrine and Riverine Habitats

“…Bigheaded carps show different genetic and stock/population characteristics in their native range and in their introduced habitats. The loss of genetic diversity results in population decline in the native habitat (due to the degradation of growth, adaptability, and fecundity), but in the Mississippi River Basin, the two introduced species became invasive parallel with the ability of hybridization in natural waters [20]. The genetic diversity of the species based on microsatellite data in this study (AR ranging between 4.6 and 6.4) was similar to the literature data.…”

“…The Balaton stock presented the same value as the Danube stock for haplotype diversity (HD: 0.85 vs. 0.84) but reported higher values for the nucleotide diversity (ND: 0.005 vs. 0.018). In the case of the Tisza population, these values proved to be lower and show similarities with the values of the North American stock (Mississippi River Basin) (HD: 0.73 vs.0.73 and ND: 0.002 vs. 0.003) [20].…”

“…The average heterozygosity in the USA (0.66- [21] or 0.60- [41]) was also similar to the heterozygosity in our "natural" populations/stocks (0.61-0.78). Lu et al [20] provided a detailed review of previous mitochondrial DNA diversity patterns in native and introduced habitats. In contrast to microsatellite studies, previous data on the Danube River area are available for mitochondrial DNA (where sample collection was partially in the Tisza River (Szeged location) [22]).…”

“…High genetic diversity often implies better adaptability, and multiple introductions from different sources also influence the control of the invasive species. The difference in the genetic structure of the native and introduced populations (reviewed by [20]) suggests that the interaction of the genetic background and the ecological environment has a significant role in the adaptation of the species and influence the choice of the proper management techniques on the individual habitats. In North America, a study on the genetic structure of bigheaded carps [21] showed that they could expand rapidly, even with lower diversity, compared with Asian stocks, as indicated by the lack of structure.…”

Patterns in spatial use and movement of Silver Carp among tributaries and main-stem rivers: Insight from otolith microchemistry analysis

“…Silver Carp (Hypophthalmichthys molitrix) are an invasive species from eastern Asia that invaded U.S.A. waterways in the early 1980's (Freeze and Henderson 1982;Conover et al 2007;Lu et al 2020). Since their introduction, they have expanded their range to encompass the majority of the Mississippi River Basin (Conover et al 2007), including the lower Missouri River drainage where they have expanded as far north as North Dakota (Hayer et al 2014).…”