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The forces driving evolution remain controversial. In fungi, are they Darwinian, Neo-Lamarckian or both? To help provide an answer, we performed an experimental study involving transplantation of soil at ’Evolution Canyon’, Israel, from a south-facing, tropical, savanna, high solar radiation, ’African’ slope (AS) to a north-facing temperate forested ’European’ slope (ES), 250 m apart, and vice versa. We hypothesized that the new microclimatic conditions would influence the abundance of a soil fungus, Aspergillus niger, and the concentration of melanin in its conidia, associated with the level of solar radiation. The results verified this hypothesis. ES-to-AS soil transplantation increased the relative abundance of A. niger ten-fold and significantly increased the conidial melanin concentration in the transplanted population in comparison with the native ES population. By contrast, AS-to-ES soil transplantation reduced the relative abundance of the fungus ten-fold and highly significantly decreased the concentration of conidial melanin in the transplanted population, as compared to the native AS soil. The results show how these fungal populations adapted to changing environmental conditions of high vs. low solar radiation. Further genomic, transcriptomic and epigenomic studies are needed to understand the evolutionary mechanisms driving such fungal adaptations.