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The Cerrado (South American savannah) is a complex mixture of grassland and tree and shrub woodland, it is a hotspot for biodiversity conservation and provides essential ecosystem services. However, this important ecosystem has been historically undervalued and understudied, and is under immediate threat from land use change and climate change. Some areas are already experiencing rapid warming and climate models predict temperature increases of between 1 and 5°C across the Cerrado biome by the end of this century, potentially affecting many aspects of plant growth and function. Crop research has revealed that sexual reproduction, particularly pollen (male gametophyte) development, is one of the most sensitive stages of flowering plant development to temperature, with higher-than-average temperatures repeatedly shown to reduce pollen viability and fruit and seed production. In the Cerrado, a reduction in the quantity or quality of pollen, fruits, or seeds produced by native species could not only affect their reproductive ability and therefore the future community structure of the Cerrado, but also the survival of insects and animals (and sometimes humans) who rely on these products. However, our understanding of the impacts of high temperatures on reproduction in non-crop species is very limited, and even more so in larger, woody species. In order to investigate how higher temperatures predicted for the Cerrado will impact sexual reproduction in native woody species, we carried out direct heating experiments on adult individuals of common tree species Byrsonima pachyphylla and Davilla elliptica. We developed novel passive heating methodologies to warm both individual inflorescences and whole trees in situ during floral bud and fruit development, and analysed the effects of higher daytime temperatures on pollen viability (through pollen staining and germination) and fruit production (following hand pollination). Surprisingly, our results show some indication that higher daytime temperatures may increase pollen viability in these two species. However, we also present evidence that for B. pachyphylla higher temperatures could reduce the proportion of pollinated flowers that develop into mature fruit, which could have implications for species persistence and community structure in the future. To the best of our knowledge these are the first warming experiments to be carried out in situ on Cerrado vegetation, and although only on a small scale, they provide an initial insight into the effects that climate change could have on the continued reproductive success of Cerrado species.

Keywords:

Cerrado
Trees
Reproduction
Heating experiment
Pollen viability
Fruit set
Climate change

Georgina Werkmeister, David Galbraith, Milene Alves, Márcia Cardoso da Silva, Jairo Matos da Rocha, Paulo Alves da Silva, Bruno Gonçalves Lopes, Daniel Ferreira de Oliveira, Regiane Batista Santos, Denilson Mendes Santos, Beatriz Marimon, Ben Hur Marimon Júnior, David Ashley, Santiago Clerici, Oliver Phillips, Emanuel Gloor

Presentation within symposium:

S-19 Tropical forest response to temperature: a pantropical synthesis of elevation gradients, and leaf thermoregulation studies

Investigating the effects of higher temperatures on Cerrado tree reproduction

-Review-