  We explore the impact of cosmic reionization on nearby isolated dwarf
galaxies using a compilation of SFHs estimated from deep HST data and a
cosmological hydrodynamical simulation of the Local Group. The nearby dwarfs
show a wide diversity of star formation histories; from ancient systems that
have largely completed their star formation $\sim 10$ Gyr ago to young dwarfs
that have formed the majority of their stars in the past $\sim 5$ Gyr to
two-component systems characterized by the overlap of comparable numbers of old
and young stars. Taken as an ensemble, star formation in nearby dwarfs dips to
lower-than-average rates at intermediate times ($4<t$/Gyr $<8$), a feature that
we trace in the simulation to the effects of cosmic reionization. Reionization
heats the gas and drives it out of the shallow potential wells of low mass
halos, affecting especially those below a sharp mass threshold that corresponds
to a virial temperature of $\sim 2 \times 10^4 $ $\mathrm{K}$ at $z_{\rm
reion}$.
  The loss of baryons leads to a sharp decline in the star forming activity of
early-collapsing systems, which, compounded by feedback from early star
formation, empties halos of gas and leaves behind systems where a single old
stellar component prevails. In halos below the threshold at $z_{\rm reion}$,
reionization heating leads to a delay in the onset of star formation that lasts
until the halo grows massive enough to allow some of the remaining gas to cool
and form stars. Young stellar components therefore dominate in dwarfs whose
halos assemble late and thus form few stars before reionization. Two-component
systems may be traced to late mergers of individual examples of the two
aforementioned cases. The relative dearth of intermediate-age stars in nearby
dwarfs might thus be the clearest signature yet identified of the imprint of
cosmic reionization on the star formation history of dwarf galaxies.
