  Multiple scattering and induced parton splitting lead to a medium
modification of the QCD evolution for jet fragmentation functions and the final
hadron spectra. Medium-induced parton splittings not only lead to energy loss
of leading partons and suppression of leading hadron spectra, but also modify
the flavor composition of a jet due to induced flavor conversion via gluon
emission, quark pair production and annihilation. Through a numerical study of
the medium-modified QCD evolution, leading $K^-$ strange meson spectra are
found to be particularly sensitive to the induced flavor conversion in
semi-inclusive deeply inelastic scatterings (SIDIS) off a large nucleus. The
induced flavor conversion can lead to increased number of gluons and sea quarks
in a jet and, as a consequence, enhance the leading $K^-$ spectra to counter
the effect of parton energy loss in SIDIS with large momentum fractions $x_B$
where the struck quarks are mostly valence quarks of the nucleus.
