Altered Fire Regimes Influence Plant-Pollinator Networks in a Subtropical Pine Forest

Regular fire shapes ecosystem function in fire-dependent forests, yet fire exclusion is widespread, with unclear consequences for species interactions. Because pollination depends on interactions rather than species alone, prolonged fire exclusion may erode ecological function in ways undetected by species inventories. We examined how time since fire (TSF) and historical fire frequency shaped flowering plants, pollinators, and their interactions across a 40-year fire-history chronosequence in globally imperiled pine rockland forests of the Florida Keys, USA, where contemporary fire return intervals often exceed the historical 6–9-year range. Time since fire was the strongest predictor of network structure: modularity, specialization, and interaction diversity declined as time without fire increased, while within-guild niche overlap increased, indicating more generalized interaction structure in long-unburned plots. Fire frequency had no comparable effect on network structure. Species-level diversity instead diverged across the two fire-history axes: pollinator diversity was unrelated to either metric, flowering-plant richness declined with TSF, and abundance-weighted flowering diversity was associated with fire frequency. These results indicate that plant-pollinator interactions are more sensitive to altered fire regimes than pollinator diversity alone. For managers balancing fuel reduction and biodiversity objectives, restoring fire recency can rebuild network complexity, but sustaining historical floral-resource structure requires recurrent burning.