Warming and elevated CO2 induces changes in the reproductive dynamics of a tropical plant species

Tropical plant species are vulnerable to climate change and global warming. Since flowering is a critical factor for plant reproduction and seed-set, warming and elevated atmospheric carbon dioxide concentrations (eCO(2)) are crucial climate change factors that can affect plant reproductive dynamics and flowering related events in the tropics. Using a combined free-air CO2 enrichment and a free-air temperature-controlled enhancement system, we investigate how warming (+2 degrees C above ambient, eT) and elevated [CO2] (similar to 600 ppm, eCO(2)) affect the phenological pattern, plant-insect interactions, and outcrossing rates in the tropical legume forage species Stylosanthes capitata Vogel (Fabaceae). In comparison to the control, a significantly greater number of flowers (NF) per plot (-62%) were observed in eT. Furthermore, in warmed plots flowers began opening approximately 1 h earlier (similar to 09:05), with a canopy temperature of similar to 23 degrees C, than the control (similar to 09:59) and eCO(2) (similar to 09:55) treatments. Flower closure occurred about 3 h later in eT (similar to 11:57) and control (similar to 13:13), with a canopy temperature of similar to 27 degrees C. These changes in flower phenology increased the availability of floral resources and attractiveness for pollinators such as Apis mellifera L. and visitors such as Paratrigona lineata L., with significant interactions between eT treatments and insect visitation per hour/day, especially between 09:00-10:40. In comparison to the control, the additive effects of combined eCO(2) + eT-enhanced the NF by 137%, while the number of A. mellifera floral visits per plot/week increased by 83% during the period of greatest flower production. Although we found no significant effect of treatments on mating system parameters, the overall mean multilocus outcrossing rate (tm = 0.53 +/- 0.03) did confirm that S. capitate has a mixed mating system. The effects of elevated [CO2] and warming on plant-pollinator relationships observed here may have important implications for seed production of tropical forage species in future climate scenarios. (C) 2021 Elsevier B.V. All rights reserved.