A ‘tree city of the world’: spatiotemporal variation in floral resource availability for flower visitors in a highly forested city in Brazil

Urban trees provide critical trophic subsidies for flower visitors, yet the spatiotemporal availability of floral resources in tropical cities remains poorly understood. We evaluated tree composition, floral traits, pollination systems, and spatiotemporal resource distribution along public sidewalks in Campo Grande, Brazil, an internationally recognized “Tree City of the World”. We surveyed 1,934 established trees across 200 stratified urban blocks, classifying species by origin, floral morphology, phenology, and pollination system. Fabaceae dominated in richness (33 species). Non-native species comprised 54% of total richness and 72% of individuals (> 1,400 trees). Floral traits were predominantly generalized: dish-shaped flowers (38%), white coloration (70%), actinomorphic symmetry (83%), and nectar rewards (62%). Accordingly, pollination systems were dominated by morphologies suited for diverse small insects (53.8% of species) and bees (29.5%), whereas specialized forms for moths/hawkmoths (9%), hummingbirds (7%), and bats (0.7%) were underrepresented. Flowering occurred year-round, peaking in September, non-natives peaked in September (buffering the late dry season), while natives peaked in October (onset of the rainy season). Spatially, resources for bees and small insects formed continuous corridors across the urban grid, whereas resources for specialized visitors were restricted to discrete, poorly connected patches. Despite international forestry recognition, Campo Grande’s street trees exhibit functional and spatial biases favoring generalists over specialized guilds. These findings underscore the urgency of planting native Cerrado species with diverse floral traits, enhancing spatial connectivity, and integrating phenological criteria to sustain resilient flower-visiting communities.