Grazing mediates microclimate effects on lichen performance near its warm-range margin.

Area of Science:

• Ecology
• Climate Change Biology
• Biotic Interactions

Background:

• Climate directly affects species physiology and indirectly influences interactions.
• Understanding the relative importance of these pathways is crucial for predicting species responses to environmental change.
• The impact of microclimate on cold-adapted species, considering biotic interactions, is poorly understood.

Purpose of the Study:

• Investigate how microclimate influences the growth of a cold-adapted lichen (Peltigera aphthosa).
• Determine if microclimate effects are direct or indirect, mediated by mollusc grazing.
• Assess if these microclimatic effects and grazing susceptibility differ among populations of varying origins.

Main Methods:

• Transplant experiment with Peltigera aphthosa from five populations across a latitudinal gradient in Sweden.
• Monitoring lichen growth and grazing damage at 56 forest sites over one year.
• Utilizing piecewise Structural Equation Models to quantify direct and indirect effects of microclimate on growth via grazing.

Main Results:

• No direct effects of microclimate on lichen growth were observed.
• Microclimate indirectly affected lichen growth through mollusc grazing.
• Increased grazing damage occurred with warmer temperatures and higher humidity, negatively impacting lichen growth. Populations varied in grazing susceptibility.

Conclusions:

• Indirect microclimatic effects mediated by biotic interactions are significant for species performance at their warm-range margins.
• Intraspecific variation in grazing susceptibility, alongside the absence of direct microclimatic effects, necessitates considering biotic interactions and population differences in climate change predictions.
• Transplant experiments across microclimatic gradients are valuable for understanding species adaptation and performance.