Natural selection is the main mechanism to explain the diversity of living organisms. However, natural selection is limited in absence of environmental variation. Yet, our knowledge on how evolution works under different environmental circumstances is extremely limited in wild populations, because most of our understanding of how natural selection operates has been focused in studies based on single years and populations. In this talk, I will show how different sources of environmental variation like food abundance, parasites or climatic conditions influence the variance of the expression of sexual traits in long-term (Common kestrels – Falco tinnunculus) or multiple studied populations (Red grouse – Lagopus lagopus scoticus). Also, I am particularly interested on showing some preliminary analyses looking at first, the influence of environmental heterogeneity on both additive genetic variance and selection (i.e. microevolution) in common kestrels. Second, exploring the evolutionary potential of multiple populations and species to respond to environmental change by analysing evolutionary biology using bio-geographical tools.