  We analyze the Mott-insulator phases of dipolar bosonic gases placed in
neighboring but unconnected 1D traps. Whereas for short-range interactions the
1D systems are independent, the non-local dipole-dipole interaction induces a
direct Mott-insulator to pair-superfluid transition which significantly
modifies the boundaries of the lowest Mott-insulator phases. The lowest
boundary of the lowest Mott regions becomes progressively constant as a
function of the hopping rate, eventually inverting its slope, leading to a
re-entrant configuration which is retained in 2D. We discuss the consequences
of this effect on the spatial Mott-insulator plateaux in experiments with
additional harmonic confinement, showing that anti-intuitively the plateaux may
become wider for increasing hopping. Our results are also applicable to
non-dipolar boson-boson mixtures.
