`--abskew` *real*
: Set the minimum abundance skew ratio between a chimera and its
  potential parent. The assumption is that chimeras appear later in
  the PCR amplification process and are therefore less abundant than
  their parents. Any positive value equal or greater than 1.0 can be
  used. Default is 1.0, which means that the parents should be at
  least as abundant than the chimera.
