Climate variability disrupts microbial mutualism-driven population persistence.

Area of Science:

• Ecology
• Evolutionary Biology
• Plant-Microbe Interactions

Background:

• Understanding species interactions is key to predicting population dynamics and responses to global change.
• Microbial mutualisms can influence plant persistence across large scales, particularly by mitigating environmental stressors like drought.

Purpose of the Study:

• To investigate how microbial mutualisms, specifically Epichloë fungal endophytes, promote the long-term, range-wide persistence of their host grass, Bromus laevipes.
• To assess the impact of climate variability on the prevalence and effectiveness of these mutualistic relationships.

Main Methods:

• Integrated 13 years of range-wide field surveys of approximately 90 Bromus laevipes populations.
• Utilized demographic modeling based on 6-year common garden experiments across the host grass's distribution.
• Quantified endophyte prevalence and population extinction rates in relation to climate variability.

Main Results:

• Mutualistic Epichloë endophytes significantly promoted population-level persistence and growth of Bromus laevipes.
• Non-mutualistic populations were four times more likely to experience local extinction compared to mutualistic ones.
• Endophyte prevalence decreased eightfold more in historically mutualistic populations subjected to high climate variability.

Conclusions:

• Mutualisms can be critical for underpinning population persistence and buffering plants against environmental stress.
• These mutualistic relationships are vulnerable to global change, particularly climate variability.
• The potential decline of mutualisms has significant implications for long-term plant population viability and species distributions.