Ecophysiology of Lichens and Their Ecosystem Roles

Lichens represent a symbiotic partnership between a fungal partner (mycobiont) and one or more photosynthetic partners (photobionts), typically green algae or cyanobacteria. Their poikilohydric nature allows them to equilibrate rapidly with environmental humidity, governing hydration dynamics, photosynthetic activity and metabolic turnover. Lichen thalli exhibit a suite of morphological and biochemical traits—such as melanisation, hydrophobic cortex layers and specialised photoprotective pigments—that mediate energy capture and stress tolerance across diverse habitats. Through these adaptations, lichens contribute to nutrient cycling by fixing atmospheric nitrogen, enhancing soil formation on bare substrates and intercepting airborne pollutants. They function as bioindicators of air quality and climate change, while influencing microclimates in forest canopies and polar regions by modulating light, moisture and thermal regimes. Recent advances in trait-based ecology have linked within-thallus variability to community distribution and ecosystem functioning, underscoring lichens’ roles in carbon sequestration, water interception and symbiont turnover in response to changing vapour pressure deficits. Understanding their ecophysiology is therefore critical for predicting shifts in biodiversity, ecosystem services and biogeochemical cycles under global change.

Research from Nature Portfolio

A recent study examined how melanin concentration within the lichen thallus influences heat‐stress resilience. Researchers established a critical thermal threshold near 35 °C for symbiotic metabolism by monitoring chlorophyll fluorescence and membrane integrity. Contrary to expectations, highly melanised thalli proved more susceptible to heat damage, exhibiting reduced photosystem II efficiency and increased lipid peroxidation. This work reveals a trade-off between UV screening and thermal sensitivity, suggesting that pigment composition modulates antioxidant responses and recovery dynamics after extreme temperature events. Insights from this investigation inform models of lichen persistence under intensifying heatwaves and guide assessments of physiological plasticity across pigment gradients.

Ecophysiology of Lichens and Their Ecosystem Roles publication trend

The graph below shows the total number of articles in ecophysiology of lichens and their ecosystem roles across all publications each year (not limited to Nature Index journals).

Technical terms

Poikilohydric: Describes organisms whose internal water content varies with ambient humidity, lacking active water regulation.

Poikilothermic: Refers to organisms whose body temperature fluctuates with environmental temperature.

Thallus: The vegetative body of a lichen, comprising fungal and photosynthetic tissues.

Photobiont: The photosynthetic partner in the lichen symbiosis, typically a green alga or cyanobacterium.

Mycobiont: The fungal partner in the lichen symbiosis, responsible for thallus architecture and substrate attachment.

Photosystem II (PSII): A key protein complex in the thylakoid membrane where light-driven water splitting initiates photosynthesis.

Vapour Pressure Deficit (VPD): The difference between the amount of moisture in the air and the maximum it can hold when saturated, influencing water loss and gas exchange.

References

1. Lichen hydration, moisture dynamics and climate change: A synthesis of established methods and potential new directions. Fungal Biology Reviews (2025).
2. Desiccation Tolerance of Epiphytic Macrolichens in an Evergreen Temperate Rain Forest (Alerce Costero National Park, Chile). Plants (2024).
3. Effect of thallus melanisation on the sensitivity of lichens to heat stress. Scientific Reports (2023).