Allopolyploidy   occurs  when  an  individual  has  multiple  sets  of
   chromosome sets derived from different species.
   Nondisjunction  of species B can yield diploid gametes which produce a
   sterile hybrid with species (A).
   If  its  gamete  fuses with a haploid gamete from species A, a fertile
   allopolyploid offspring may result - a new species.