Synchronous population dynamics in California butterflies explained by climatic forcing

Area of Science:

• Ecology
• Population Biology
• Zoology

Background:

• Understanding spatial synchrony in population dynamics is crucial for population biology.
• Climatic variation and dispersal are proposed drivers of synchronous population dynamics.
• The relative importance of climate versus dispersal in natural populations remains unclear.

Purpose of the Study:

• To compare the predictive power of dispersal-driven versus climate-driven models for interspecific variation in population synchrony.
• To investigate the influence of climate sensitivity and dispersal propensity on butterfly population synchrony.

Main Methods:

• Utilized 27 years of observational data for 65 butterfly species across 10 sites in Northern California.
• Assessed spatial synchrony as a response variable.
• Employed a comparative approach to model interspecific variation in synchrony based on climate response and dispersal.

Main Results:

• Variation in climate sensitivity explained 50% of interspecific variation in synchrony, while dispersal propensity explained 23%.
• Sensitivity to the El Niño Southern Oscillation was the strongest predictor of synchrony.
• Combined models of climate and dispersal did not significantly improve performance, highlighting climate's primacy.

Conclusions:

• Climate sensitivity is the dominant factor driving spatial synchrony in butterfly populations.
• Dispersal plays a secondary role in determining population synchrony.
• The relationship between spatial synchrony and population decline is theoretically consistent but weak, suggesting limited utility for understanding current declines.