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Flowering patterns are crucial to understand the dynamics of plant reproduction and resource availability for pollinators. Seasonal climate constrains flower and leaf phenology, where leaf and flower colors likely differ between seasons. Color is the main floral trait attracting pollinators; however, seasonal changes in the leaf-background coloration affect the perception of flower color contrasts by pollinators. For a seasonally dry woody cerrado community (Brazilian savanna) mainly pollinated by bees, we verified whether seasonality affects flower color diversity over time and if flower color contrasts of bee-pollinated species differ between seasons due to changes in the leaf-background coloration. For 140 species, we classified flower colors based on human-color vision, and for 99 species, we classified flower colors based on bee-color vision (spectral measurements). We described the community’s flowering pattern according to the flower colors using a unique 11 years phenological database. For the 43 bee-pollinated species in which reflectance data were also available, we compared flower color diversity and contrasts against the background between seasons, considering the background coloration of each season. Flowering was markedly seasonal, peaking at the end of the dry season (September), when the highest diversity of flower colors was observed. Yellow flowers were observed all year round, whereas white flowers were seasonal, peaking during the dry season, and pink flowers predominated in the wet season, peaking in March. Bee-bluegreen flowers peaked between September and October. Flowers from the wet and dry seasons were similarly conspicuous against their corresponding background. Regardless of flowering season, the yellowish background of the dry season promoted higher flower color contrast for all flower species, whereas the greener background of the wet season promoted a higher green contrast. Temporal patterns of flower colors and color contrasts were related to the cerrado seasonality, but also to bee’s activity, visual system, and behavior. Background coloration affected flower contrasts, favoring flower conspicuousness to bees according to the season. Thus, our results provide new insights regarding the temporal patterns of plant–pollinator interactions.

Flower color is a primary pollinator attractant and generally adjusted to the cognitive system of the pollinators. The perception of flower color depends on the visual system of pollinators and also on environmental factors such as light conditions and the background against which flowers are displayed. METHODS:Using bee-pollinated Fabaceae species as a model, we analyzed flower color diversity and compared flower color signals considering both the standard green and the natural leaf background of two tropical seasonally dry vegetations-a mountain rupestrian grassland (campo rupestre) and a woody savanna (cerrado)-compared to a nontropical Mediterranean shrubland. RESULTS: By using natural background, bees discriminated color for 58% of the flowers in the campo rupestre and for only 43% in cerrado. Both vegetations were surpassed by 75% of bee color discrimination in Mediterranean vegetation. Chromatic contrast and purity were similar among the three vegetation types. Green contrast and brightness were similar between the tropical vegetations but differed from the Mediterranean shrubland. Green contrast differences were lost when using a standard green background, and most variables (purity, green contrast, and brightness) differed according to the background (natural or standard green) in all vegetations. CONCLUSIONS:The natural background influenced bee perception of flower color regardless of vegetation. The background of the campo rupestre promoted green contrast for flowers, ensuring flower detection by pollinators and, along with bees, may also act as a selective pressure driving the diversity of flower colors in Fabaceae species. We highlight the importance of considering the natural background coloration when analyzing flower color signals.

Cerrado remnants can hold an important diversity of plant species of environmental and ecological relevance. We presented a checklist of vascular plants based on 12 years of inventory carried out in 36 plots (10 m x 2 m; 0.18 ha in total) and during unsystematic walks in a remnant area of cerrado sensu stricto located at Itirapina municipality, state of São Paulo, southeastern Brazil. The list comprised 195 plant species, corresponding to 54 families and 131 genera. The richest families were Fabaceae (25 species), Asteraceae (16), Myrtaceae (16), Rubiaceae (11), Bignoniaceae and Malpighiaceae (10 each), Melastomataceae (9), and Erythroxylaceae, Sapindaceae and Annonaceae (6). Predominant life forms included shrubs and trees, with 68% of the species, followed by lianas with 12%, sub-shrub and herbs with 10% each. Bees were the dominant pollinators (67,5%) and the majority of species had seeds dispersed by animals (56.8%), mostly by birds, followed by wind (33.3%) and self-dispersed (11.2%). More than 60% of the total species were classified as “typical” Cerrado species. Bowdichia virgilioides was the only species classified as Near Threatened (NT) and 157 were regarded as Data Deficient (DD). Our dataset provides floristic, structural, and ecological information for one of the targeted areas for Cerrado survey at São Paulo state, contributing to the understanding of diversity patterns and future conservation and restoration actions in this threatened hotspot.