This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: The two warmest time periods on Earth in the past 140 million years drove both mass extinctions and explosions in plant diversity, according to researchers in Australia and Austria who say this could explain how flowering plants became dominant among land plants. The study, published in Nature Plants, examined fossilized pollen and spores to show that the mid-Cretaceous and early Cenozoic periods of extreme global warmth were central to plant evolution.
This applies not only to flowering plants, but also to the other main land plant groups. Land plants are critical for life on land. The energy they capture from the sun underpins the existence of almost all terrestrial animals, fungi and bacteria.
Lead author Kale Sniderman, honorary research fellow at the University of Melbourne, said that flowering plants are the most productive and diverse group of land plants with approximately 400,000 species globally. "They dominate most ecosystems on land. They are the most important terrestrial players in capturing carbon dioxide from the air.
They have evolved complex relationships with animals, fungi and bacteria," Sniderman said. "This created vast numbers of species, each specializing in eating, pollinating, dispersing seed and decomposing flowering plants of different species or in different ways." It's not clear how flowering plants came to rule the world. In the middle of the Cretaceous Period, during 'peak dinosaur' time (~100 million years ago), flowering plants began to displace older plant groups that had dominated the land for 200 million years before.
Climate may have been important in driving this transition, but until now a clear link between climate and plant diversity has been elusive due to bias in fossil records. "The number of available fossils varies over geological time and between regions. Because of this, simple counts of fossilized species can give a misleading sense of diversity over evolutionary time," Sniderman said.
The researchers compiled data on over 60,000 individual fossil occurrences and applied methods that overcome the major biases in the fossil record. They then generated revised estimates of fossil pollen and spore diversity for successive time periods throughout the past 130 million years. "Our research shows that both extinction and the emergence of new but evolutionarily related land plants occurred mostly during two intervals of globally extremely warm climate," said Greg Jordan, professor of botany at the University of Tasmania and a co-author of the study.
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