  By considering $f(R)$ gravity models, the cosmic evolution is modified with
respect to the standard $\Lambda$CDM scenario. In particular, the thermal
history of particles results modified. In this paper, we derive the evolution
of relics particles (WIMPs) assuming a reliable $f(R)$ cosmological solution
and taking into account observational constraints. The connection to the PAMELA
experiment is also discussed. Results are consistent with constraints coming
from BICEP2 and PLANCK experiments.
