The distribution of abundance and genome size (GS, 2C-value) variability of the saw-toothed grain beetle Oryzaephilus surinamensis was studied on the opposite slopes of the microsite "Evolution Canyon" ("EC"), Mt.Carmel, Israel. As controls, we used one sample of beetle population from a grain silo in Haifa Bay. The study showed that O. surinamensis is abundant in acorns of Quercus calliprinos (Palestine oak). The observed number of adults of O. surinamensis per acorn ranged from 0 to 12 at "EC" and 54% of acorns were not infected. At "EC", O. surinamensis was more abundant on the "European, garrigue-like" north-facing slope ("ES") than on the "African, savannah-like" south-facing slope ("AS"), reflecting the interslope differences in the number of oak trees. There was a significant positive correlation between beetle abundance and number of acorns. Both the number of acorns and the number of beetles decreased with the "ES" altitude. No significant intersample differences were found in the infestation rate (number of beetles per acorn) at "EC". The study of the GS variability showed significant differences between the natural population at "EC" and the indoor silo pest population. Likewise, we found significant differences between males and females at both "EC" and in the silo, probably associated with the heteromorphism of the sex chromosomes. At "EC", the slopes had significantly more effect than the intraslope stations on the female GS differences, indicating larger genomes in females at "AS" than at "ES". The multispecies comparison of four diploid species (O. surinamensis, and the plants Ceratonia siliqua, Cyclamen persicum and Lotus peregrinus) supports the premise that increased tolerance to drought stress is associated with larger GS.