We report experiments on convection driven by a radial electrical forc
e in suspended annular smectic-A liquid crystal films. In the absence
of an externally imposed azimuthal shear, a stationary 1D pattern cons
isting of symmetric vortex pairs is formed via a supercritical transit
ion at the onset of convection. Shearing reduces the symmetries of the
base state and produces a traveling 1D pattern whose basic periodic u
nit is a pair of asymmetric vortices. For a sufficiently large shear,
the primary bifurcation changes from supercritical to subcritical. We
describe measurements of the resulting hysteresis as a function of the
shear at radius ratio eta similar to 0.8. [S0031-9007(97)05181-8].