From inland vigour to coastal caution: contrasting germination strategies of a tropical hydrochoric bromeliad

Distinct environmental factors can drive divergent selection, shaping contrasting ecological strategies across populations. Coastal habitats characterized by extreme abiotic conditions, such as high salinity and low water availability, impose intense selective pressures on plants. By contrast, inland tropical environments with species-rich communities, due to abundant freshwater availability, favour traits associated with rapid seedling establishment. Here, we investigate the germination and seedling performance of Pitcairnia flammea, an endemic tropical bromeliad with a potential hydrochoric dispersal, across coastal and inland populations. Our results reveal that inland populations exhibit rapid and consistent germination across water availability gradients, reflecting a potential competitive strategy in freshwater-rich riparian environments. Conversely, coastal populations display delayed germination and reduced success under drought and saline conditions, suggesting an avoidance strategy to mitigate abiotic stress. Floating seeds demonstrated enhanced germinability and reduced mortality, highlighting hydrochory as a central dispersal strategy under both freshwater and saline conditions. These findings offer novel insights into the adaptive significance of germination strategies in bromeliads, highlighting the dual roles of abiotic filters in shaping coastal populations and competitive strategies in inland populations. Our study highlights the effect of both abiotic and biotic pressures on shaping the divergent selection of tropical populations distributed across environmental gradients.