  This work aims to investigate the behaviour of the lithium abundance in stars
with and without detected planets. Our study is based on a sample of 1332 FGK
main-sequence stars with measured lithium abundances, for 257 of which planets
were detected. Our method reviews the sample statistics and is addressed
specifically to the influence of tides and orbital decay, with special
attention to planets on close orbits, whose stellar rotational velocity is
higher than the orbital period of the planet. In this case, tidal effects are
much more pronounced. The analysis also covers the orbital decay on a short
timescale, with planets spiralling into their parent star. Furthermore, the
sample allows us to study the relation between the presence of planets and the
physical properties of their host stars, such as the chromospheric activity,
metallicity, and lithium abundance. In the case of a strong tidal influence, we
cannot infer from any of the studies described that the behaviour of Li differs
between stars that host planets and those that do not. Our sample includes
stars with super-solar metallicity ([Fe/H]>0.15 dex) and a low lithium
abundance (A(Li) <1.0 dex). This enabled us to analyse scenarios of the origin
and existence of these stars. Considering the possible explanation of the F
dip, we show that it is not a plausible scenario. Our analysis is based on a
kinematic study and concludes that the possible time that elapsed in the travel
from their birth places in the central regions of the Galaxy to their current
positions in the solar neighbourhood is not enough to explain the high lithium
depletion. It is remarkable that those of our high-metallicity low-lithium
stars with the greatest eccentricity (e>0.2) are closest to the Galactic
centre. A dedicated study of a set of high-metallicity low-Li stars is needed
to test the migration-depletion scenario.
