Genômica e biologia de fungos
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Evolution under Ecological Stress: Fungal Divergent Adaptive Melanization at Evolution Canyons in Israel

Eviatar Nevo

Environmental stress, both biotic and antibiotic, is a major driving force of evolution. I revisit our earlier study on the effects of solar radiation on melanin concentration in the soil fungus Aspergillus niger, at Evolution Canyon I (EC I), Mount Carmel, the first and most explored of four Evolution Canyons, investigated in Israel. The Evolution "Canyon" model is a microsite, optimal for studying biodiversity evolution, adaptation and incipient sympatric ecological speciation. At AC I, the tropical African (AS), south facing slope (SFS) receives 200-800% more solar radiation than the temperate European slope. We measured conidial melanin concentration of 80 strains of A. niger from the opposite slopes and from sunny versus shady micro niches in each slope. A. niger on AS had threefold more melanin than on the ES. As expected, AS strains of A. niger resisted UVA irradiation better than ES strains and the same was demonstrated by A. niger strains from sunny as compared with abutting shady micro niches on the ES. We concluded that melanin shelters A. niger adaptively from solar radiation. We conduct reciprocal transfer experiment of A. niger from AS to the ES and vice versa, in an attempt to highlight melanin evolutionary dynamics on the opposite slopes.