title: Species-specific markers provide molecular genetic evidence for natural introgression of bullhead catfishes in Hungary.
abstract: Since three bullhead catfish species were introduced to Europe in the late 19th century, they have spread to most European countries. In Hungary, the brown bullhead (Ameiurus nebulosus) was more widespread in the 1970s-1980s, but the black bullhead (Ameiurus melas) has gradually supplanted since their second introduction in 1980. The introgressive hybridization of the two species has been presumed based on morphological examinations, but it has not previously been supported by genetic evidence. In this study, 11 different Hungarian habitats were screened with a new species-specific nuclear genetic, duplex PCR based, marker system to distinguish the introduced catfish species,Ameiurus nebulosus, Ameiurus melas, andAmeiurus natalis, as well as the hybrids of the first two. More than 460 specimens were analyzed using the above markers and additional mitochondrial sequence analyses were also conducted on >25% of the individuals from each habitat sampled. The results showed that only 7.9% of the specimens from two habitats belonged toAmeiurus nebulosus, and 92.1% were classified asAmeiurus melasof all habitats, whereas the presence ofAmeiurus nataliswas not detected. Two specimens (>0.4%) showed the presence of both nuclear genomes and they were identified as hybrids ofAmeiurus melas and Ameiurus nebulosus. An additional two individuals showed contradicting results from the nuclear and mitochondrial assays as a sign of a possible footprint of introgressive hybridization that might have happened two or more generations before. Surprisingly, the level of hybridization was much smaller than expected based on the analyses of the North American continent's indigenous stock from the hybrid zones. This phenomenon has been observed in several invasive fish species and it is regarded as an added level of complexity in the management of their rapid adaptation.
authors.affiliation: Department of Aquaculture, Szent István University , Gödöllő , Hungary.
authors.forename: Beatrix
authors.initials: B
authors.lastname: Béres
authors.affiliation: Department of Aquaculture, Szent István University, Gödöllő, Hungary; Regional University Center of Excellence in Environmental Industry, Szent István University, Gödöllő, Hungary.
authors.forename: Dóra
authors.initials: D
authors.lastname: Kánainé Sipos
authors.affiliation: Department of Aquaculture, Szent István University , Gödöllő , Hungary.
authors.forename: Tamás
authors.initials: T
authors.lastname: Müller
authors.affiliation: Department of Aquaculture, Szent István University , Gödöllő , Hungary.
authors.forename: Ádám
authors.initials: Á
authors.lastname: Staszny
authors.affiliation: Regional University Center of Excellence in Environmental Industry, Szent István University, Gödöllő, Hungary; Department of Environmental Safety and Ecotoxicology, Szent István University, Gödöllő, Hungary.
authors.forename: Milán
authors.initials: M
authors.lastname: Farkas
authors.affiliation: Department of Aquaculture, Szent István University, Gödöllő, Hungary; Regional University Center of Excellence in Environmental Industry, Szent István University, Gödöllő, Hungary.
authors.forename: Katalin
authors.initials: K
authors.lastname: Bakos
authors.affiliation: Department of Aquaculture, Szent István University, Gödöllő, Hungary; Reproductive Genomics Group, Temasek Life Sciences Laboratory, Singapore; Centre for Comparative Genomics, Murdoch University, Murdoch, Australia.
authors.forename: László
authors.identifier: 0000-0001-5435-5948
authors.initials: L
authors.lastname: Orbán
authors.affiliation: Department of Aquaculture, Szent István University , Gödöllő , Hungary.
authors.forename: Béla
authors.initials: B
authors.lastname: Urbányi
authors.affiliation: Department of Aquaculture, Szent István University, Gödöllő, Hungary; Regional University Center of Excellence in Environmental Industry, Szent István University, Gödöllő, Hungary.
authors.forename: Balázs
authors.identifier: 0000-0003-1753-5098
authors.initials: B
authors.lastname: Kovács
keywords: Ameiurus; Bullhead catfishes; Hybridization; Introgression; Multiplex PCR; Species-specific marker