Reproductive isolation and the expansion of an invasive hybrid swarm

• Published in: Biological invasions 2010-08, Vol.12 (8), p.2825-2836
• Main Authors: Blum, Michael J, Walters, David M, Burkhead, Noel M, Freeman, Byron J, Porter, Brady A
• Format: Article
• Language: English
• Subjects: Animal reproduction; Biomedical and Life Sciences; Cyprinella lutrensis; Cyprinella venusta stigmatura; Cyprinidae; Developmental Biology; ecological invasion; Ecology; egg hatchability; Fecundity; Females; fertilization (reproduction); Fish; Freshwater; Freshwater & Marine Ecology; freshwater fish; gender differences; gene flow; genetic variation; Hatching; heterosis; hybrid swarms; Hybridization; Hybrids; interspecific hybridization; Invasions; invasive species; larvae; Life Sciences; males; mortality; Nonnative species; Original Paper; Plant Sciences; Population genetics; reproductive isolation; River basins; Rivers; Spawning; viability; zygote
• ISSN: 1387-3547; 1573-1464
• DOI: 10.1007/s10530-010-9688-9

Biological invasions involving hybridization proceed according to prezygotic and postzygotic reproductive isolating mechanisms. Yet few comparisons of reproductive isolation have been carried out to understand how different mechanisms prevent or promote invasions involving hybridization. Here we present a study of prezygotic and postzygotic isolation between non-native red shiner (Cyprinella lutrensis) and native blacktail shiner (C. venusta stigmatura) from the Coosa River basin (USA) to better understand the formation and expansion of invasive hybrid swarms. We conducted spawning trials to measure mating preferences and raised broods from crosses to assay hybrid viability through early juvenile development. Females of both species were more responsive to conspecific mates, although blacktail shiner females responded more often to heterospecific mates than did red shiner females. Fecundity of red shiner females was also higher than blacktail shiner females. Heterospecific crosses resulted in lower fertilization and egg hatching rates, but we found no other evidence of inviability. Rather, we found comparatively low larval mortality of F₁ hybrids, which is suggestive of heterosis. These findings support prior inferences of assortative mating from genetic descriptions of hybridization, and that the invasion in the Coosa River is likely proceeding due to interspecific competition and intrinsic hybrid viability.