Serpentine soils and the ecology and evolution of fungal-plant symbiotic partners.

摘要

Extreme environments tend to host depauperate and specialized biological communities. Serpentine soils, stressful due to high heavy metal levels, poor nutrient contents, and unbalanced calcium to magnesium ratios, exemplify this phenomenon by imposing well-known constraints on plants. Here, I study the effects of serpentine soil on the ecology and evolution of a fungalplant symbiotic system to investigate adaptive responses in symbiotic partners under the same environmental constraint. I focused on serpentine ectomycorrhizal (ECM) fungal communities associated with Quercus ilex subsp. ballota and used a combination of field, greenhouse, and molecular approaches to examine community- and population-level differentiation patterns in the fungi and the plant. I found rich and phylogenetically diverse serpentine fungal communities, as well as widespread serpentine tolerance in ECM fungi. Although serpentine soil is a distinct environment hosting different fungal communities, I found no indication of it being physiologically challenging. I also report the existence of local adaptation in Q. ilex subsp. ballota, with serpentine ecotypic differentiation evidenced by disproportional root allocation, as well as limits to gene flow among populations and significant population-genetic structure. My results show that serpentine soils influence the ecology and evolution of symbiotic partners differently, with differential patterns detectable only at the plant-level.