title: Diagnostic SNPs reveal widespread introgressive hybridization between introduced bighead and silver carp in the Mississippi River Basin.
abstract: Hybridization among conspecifics in native and introduced habitats has important implications for biological invasions in new ecosystems. Bighead (Hypophthalmichthys nobilis) and silver carp (H. molitrix) are genetically isolated and occur in sympatry within their native range. Following their introduction to North America, however, introgressant hybrids have been reported throughout their expanded range within the Mississippi River Basin (MRB). The extent of introgression, both spatially and generationally, is largely unknown. Therefore, we examined mixed-species populations from across the MRB to characterize the extent of interspecific gene flow. We assayed 2798 individuals from nine locations with a suite of species-diagnostic SNPs (57 nuclear and one mitochondrial). Forty-four per cent (n = 1244) of individuals displayed hybrid genotypes. Moreover, the composition of hybrid genotypes varied among locations and represented complex hybrid swarms with multiple generations of gene flow. Introgressive hybrids were identified from all locations, were bidirectional and followed a bimodal distribution consisting primarily of parental or parental-like genotypes and phenotypes. All described hybrid categories were present among individuals from 1999 to 2008, with parents and later-generation backcrosses representing the largest proportion of individuals among years. Our mitochondrial SNP (COII), tested on a subset of 730 individuals, revealed a silver carp maternal bias in 13 of 21 (62%) F1 hybrids, in all silver carp backcrosses, and maintained throughout many of the bighead carp backcrosses. The application of this suite of diagnostic markers and the spatial coverage permits a deeper examination of the complexity in hybrid swarms between two invasive, introduced species.
authors.affiliation: Department of Natural Resources and Environmental Sciences, University of Illinois, 1102 South Goodwin Ave., Urbana, IL, 61801, USA.|Department of Biological Sciences, Western Illinois University, 1 University Circle, Macomb, IL, 61455, USA.
authors.forename: James T
authors.initials: JT
authors.lastname: Lamer
authors.affiliation: Illinois Department of Natural Resources, One Natural Resources Way, Springfield, IL, 62702, USA.
authors.forename: Blake C
authors.initials: BC
authors.lastname: Ruebush
authors.affiliation: Core Genomics Facility, University of Illinois at Chicago, 835 S. Wolcott Avenue, Chicago, IL, 60612, USA.
authors.forename: Zarema H
authors.initials: ZH
authors.lastname: Arbieva
authors.affiliation: Illinois Department of Natural Resources, 700 S. 10th St., Havana, IL, 62644, USA.
authors.forename: Michael A
authors.initials: MA
authors.lastname: McClelland
authors.affiliation: Illinois Natural History Survey, 1816 S. Oak Street, Champaign, IL, 61820, USA.
authors.forename: John M
authors.initials: JM
authors.lastname: Epifanio
authors.affiliation: Escanaba Lake Research Station, Wisconsin Department of Natural Resources, 10810 County Hwy N, Boulder Junction, WI, 54512, USA.
authors.forename: Greg G
authors.initials: GG
authors.lastname: Sass
mesh_terms: D000818:Animals; D002347:Carps / Q000235:genetics*; D003530:Cyprinidae / Q000235:genetics*; D004272:DNA, Mitochondrial / Q000235:genetics; D017753:Ecosystem; D051456:Gene Flow; D005838:Genotype; D006824:Hybridization, Genetic; D058865:Introduced Species; D020641:Polymorphism, Single Nucleotide; D045483:Rivers; D017422:Sequence Analysis, DNA; D014481:United States
chemical_list: D004272:DNA, Mitochondrial
keywords: SNP; bighead carp; hybridization; introgression; invasive species; silver carp