Microclimate drives demographic compensation in a narrow endemic tropical species

Demographic compensation occurs when reductions in some vital rates are offset by increases in others, allowing populations to maintain similar performance across varying environments. This mechanism may help explain species' ecological distributions and range limits, yet its role at microenvironmental scales remains poorly understood. We investigated demographic compensation in Ipomoea cavalcantei, a narrow-range but locally abundant species endemic to Amazonian ironstone outcrops, by comparing populations in two contrasting habitats: open- and shrubby-canga. Using 3 yr of demographic data, we built matrix population models and conducted a life table response experiment. We also carried out germination and seedling establishment experiments under different temperature and light conditions simulating both habitats to identify the potential environmental drivers and their effects on key life-cycle events. Despite contrasting environmental conditions, both populations exhibited similar population growth rates (λ), with opposing contributions of growth and fecundity - evidence of demographic compensation. The open-canga population had lower growth but higher recruitment, driven by favorable temperature regimes for seed dormancy release and germination. Reduced growth was associated with physiological stress under high irradiance and shallow soils. Our results show that demographic compensation allows I. cavalcantei to persist across microhabitats, highlighting the importance of fine-scale environmental heterogeneity in shaping species distributions.