Widespread Hybridization between Invasive Bleak (<i>Alburnus alburnus</i>) and Iberian Chub (<i>Squalius</i> spp.): A Neglected Conservation Threat
Manuel Curto,
Miguel Morgado-Santos,
Carlos M. Alexandre,
Maria Judite Alves,
Hugo F. Gante,
Christos Gkenas,
João P. Medeiros,
Paulo J. Pinheiro,
Pedro R. Almeida,
Maria Filomena Magalhães,
Filipe Ribeiro
Affiliations
Manuel Curto
MARE—Marine and Environmental Sciences Centre/ARNET—Aquatic Research Network, Faculty of Sciences, University of Lisbon, 1749-016 Lisbon, Portugal
Miguel Morgado-Santos
MARE—Marine and Environmental Sciences Centre/ARNET—Aquatic Research Network, Faculty of Sciences, University of Lisbon, 1749-016 Lisbon, Portugal
Carlos M. Alexandre
MARE—Marine and Environmental Sciences Centre/ARNET—Aquatic Research Network, Institute for Research and Advanced Training (IIFA), University of Évora, 7002-554 Évora, Portugal
Maria Judite Alves
MUHNAC—National Museum of Natural History and Science, University of Lisbon, 1250-102 Lisbon, Portugal
Hugo F. Gante
cE3c—Centre for Ecology, Evolution and Environmental Change, Faculty of Sciences, University of Lisbon, 1749-016 Lisbon, Portugal
Christos Gkenas
MARE—Marine and Environmental Sciences Centre/ARNET—Aquatic Research Network, Faculty of Sciences, University of Lisbon, 1749-016 Lisbon, Portugal
João P. Medeiros
MARE—Marine and Environmental Sciences Centre/ARNET—Aquatic Research Network, Faculty of Sciences, University of Lisbon, 1749-016 Lisbon, Portugal
Paulo J. Pinheiro
AQUALOGUS, Engineering and Environment Lda, Rua do Mar da China 1, Office 2.4, Parque das Nações, 1990-137 Lisbon, Portugal
Pedro R. Almeida
MARE—Marine and Environmental Sciences Centre/ARNET—Aquatic Research Network, Institute for Research and Advanced Training (IIFA), University of Évora, 7002-554 Évora, Portugal
Maria Filomena Magalhães
cE3c—Centre for Ecology, Evolution and Environmental Change, Faculty of Sciences, University of Lisbon, 1749-016 Lisbon, Portugal
Filipe Ribeiro
MARE—Marine and Environmental Sciences Centre/ARNET—Aquatic Research Network, Faculty of Sciences, University of Lisbon, 1749-016 Lisbon, Portugal
Hybridization between native and nonnative fish species is a major conservation issue, especially in ecosystems with high levels of endemism, such as Iberian streams. To date, hybridization with the invasive bleak Alburnus alburnus has been reported for the Iberian chub Squalius alburnoides and S. pyrenaicus and in scattered locations only. However, the bleak is spreading in the region, potentially increasing the risks of hybridization with other Squalius species. To gather a more comprehensive picture on the current geography of hybridization, we compiled records on hybrids between bleak and chub in Portugal and conducted genetical assessments of hybrids between bleak and S. carolitertii. We found that hybridization with bleak is widespread throughout Portuguese river basins and involves at least S. alburnoides, S. pyrenaicus and S. carolitertii. Hybridization with bleak may not only cause waste of reproductive effort and damage the genetic integrity of these endemic species but also promote shifts in the reproductive dynamics of the S. alburnoides hybrid complex, which includes individuals with various ploidy levels and combinations of parental genomes, reproducing sexually and asexually. We recommend that future studies characterize the fitness of bleak hybrids and their ecological and genetic interactions with native fish, in order to design effective conservation measures.
