Cycles and synchrony: two historical 'experiments' and one experience.

Area of Science:

• Ecology
• Epidemiology
• Mathematical Biology

Background:

• Theoretical models predict enhanced spatial synchrony in cyclic populations due to nonlinear phase-locking.
• Previous studies show varying synchrony patterns in childhood diseases (measles, whooping cough) across vaccination eras.
• Historical rodent population data suggest a loss of cyclicity linked to reduced regional synchrony.

Purpose of the Study:

• To investigate the relationship between spatial synchrony and population cycles.
• To reanalyze historical rodent data for synchrony and cyclicity patterns.
• To explore the role of imperfect phase-locking in maintaining regionwide synchrony.

Main Methods:

• Analysis of spatial synchrony in childhood disease epidemics (measles, whooping cough) before and during vaccination.
• Reanalysis of historical rodent population records.
• Utilizing a coupled map lattice model to simulate population dynamics.

Main Results:

• Measles showed higher synchrony and cyclicity before vaccination; whooping cough showed higher synchrony during vaccination.
• Loss of cyclicity in rodent populations correlated with a loss of regional synchrony.
• The coupled map lattice model demonstrated that imperfect phase-locking can explain regionwide synchrony.

Conclusions:

• Nonlinear phase-locking is a key mechanism enhancing spatial synchrony in cyclic populations.
• Changes in environmental factors (like vaccination) can alter population synchrony and cyclicity.
• Imperfect phase-locking offers a viable explanation for observed regionwide synchrony in cyclic populations.