Hyphal morphology and substrate porosity -rather than melanization- drive penetration of black fungi into carbonate substrates

•Morphological flexibility of rock-inhabiting MCF depends on nutrient availability.•MCF can colonize and penetrate the substrates regardless the production of melanin.•Substrate porosity affects the penetration pattern of different growth-forms of MCF.•Artificial standardized marble pellets accelerate lab testing of fungal penetration.•Conservation treatments should be preceded by lab tests on colonization patterns.