Impacts of higher daytime temperatures on viable pollen and fruit production in common Cerrado tree Byrsonima pachyphylla (Malpighiaceae)

Already threatened by deforestation, the Brazilian Cerrado—a complex and biodiverse tropical savannah that provides important ecosystem services—could experience climate warming of 1–5°C by 2100. This could negatively impact sexual reproduction (considered particularly sensitive to temperature stress) in native plant species, potentially limiting the production of viable pollen, fruits, and seeds; however, such impacts are largely unstudied in wild tropical species. To investigate the potential effects of higher temperatures on Cerrado species reproduction, developing inflorescences of common and widespread tree Byrsonima pachyphylla (Malpighiaceae) were passively heated in situ from an early bud stage (by 3–4°C during the daytime). Viability of pollen samples (analyzed through in vitro pollen germination and differential pollen staining) and fruit set (the proportion of hand-pollinated flowers that developed into mature fruit) were compared between heated and control (ambient temperature) inflorescences, hypothesizing that both would be lower in heated inflorescences. However, higher daytime temperatures had no impact on viable pollen production, suggesting a strong resilience to warming. Nevertheless, fruit set was significantly reduced, which could have serious implications for future species recruitment and potentially Cerrado community structure, insect and animal food chains, and human populations, especially if representative of other Cerrado species. To the best of our knowledge, this experiment is the first manipulative warming of Cerrado vegetation in situ. It provides initial insights into the effects that increasing temperatures could have on future reproductive success and demonstrates the importance of considering reproduction when evaluating the possible impacts of climate change on tropical ecosystems.