 However, the gene-centered viewpoint was not the primary research focus or challenge for a large subset of field researchers, consisting of naturalists, zoologists and ecologists. Their focus was similarly on natural selection as the only evolutionary force which can produce adaptation, the fit between an organism and its environment. However, its focus is on the role of environment in adaptation. Ecological genetics is the study of evolutionary processes, especially adaptation by natural selection, in an ecological context in order to account for phenotypic patterns observed in nature. Where evolutionary genetics tends toward a branch of applied mathematics founded on Mendelian axioms, ecological genetics is grounded in the reciprocal interaction between theory and empirical observations from field and laboratory.