  The main orbital signatures of the secular evolution of an isolated
self-gravitating stellar Mestel disc are recovered using a dressed
Fokker-Planck formalism in angle-action variables. The shot-noise-driven
formation of narrow ridges of resonant orbits is recovered in the WKB limit of
tightly wound transient spirals, for a tepid Toomre-stable tapered disc. The
relative effect of the bulge, the halo, the disc temperature and the spectral
properties of the shot noise are investigated in turn. For such galactic discs
all elements seem to impact the locus and direction of the ridge. For instance,
when the halo mass is decreased, we observe a transition between a regime of
heating in the inner regions of the disc through the inner Lindblad resonance
to a regime of radial migration of quasi-circular orbits via the corotation
resonance in the outer part of the disc. The dressed secular formalism captures
both the nature of collisionless systems (via their natural frequencies and
susceptibility), and their nurture via the structure of the external perturbing
power spectrum. Hence it provides the ideal framework in which to study their
long term evolution.
