Melanin's Role in Balancing Mechanical Strength and Reproductive Output in Environmentally Stressed Fungal Spores

Fungal spores must withstand varying environmental stressors during dispersal and dormancy, yet the impact of these stressors on the mechanical, structural, and surface properties of the spore wall remains largely uncharacterized, particularly in basidiomycete species. The spore wall structure, composition, mechanical behavior, and wettability of eight basidiomycete species spanning two ecologically distinct groups are examined in this study. Montagnea arenaria, Battarrea stevensii, Ganoderma applanatum, and Ustilago maydis represent an environmentally stressed group, and Hericium erinaceus, Hypsizygus ulmarius, Lentinula edodes , and Pleurotus djamor represent a less stressed group. Stereomicroscopic, spectroscopic, and nanomechanical analyses reveal that all four stressed species produce pigmented spores with higher melanin content, thicker walls, higher mechanical strength, and hydrophobic surfaces, resulting in a higher biosynthetic energy cost. In contrast, the less stressed group produces hyaline, hydrophilic spores with thinner walls, which confer lower mechanical strength but produce a lower biosynthetic energy footprint. These findings provide the first detailed structural and mechanical characterization of basidiomycete spores, demonstrating that ecological context is reflected in spore wall composition, architecture, and mechanical properties.