A group of international researchers, including botanists from the University of Vienna, Austria, has conducted a comprehensive analysis of fossilized flowers, comparing their morphological variety with that of present-day species.
Their findings were striking: during the Cretaceous period, flowering plants exhibited a remarkably diverse array of flower types soon after their emergence, surpassing the diversity observed in modern times. The study unveiling these discoveries has been recently published in the esteemed journal New Phytologist.
With an estimated count of over 300,000 species, flowering plants (angiosperms) stand as the largest plant group thriving today. Their origins trace back at least 140 million years, coinciding with the era of dinosaurs.
Over the past few decades, the unearthing and documentation of fossilized flowers from various geological periods have provided insights into ancient floral diversity. However, the pertinent questions remained: How does this historical diversity compare to the current panorama?
Furthermore, what evolutionary changes have influenced flower morphology across time? Addressing these queries, an international research team comprising experts from the National Autonomous University of Mexico, the Botanic Gardens of Sydney, Australia, and the University of Vienna, Austria, embarked on a study to delve into these intriguing aspects—and their findings shed light on the subject.
For this study, the researchers examined 30 floral characteristics in 1,201 living and 121 fossil angiosperms to measure floral diversity and to investigate patterns of floral evolution over time and across lineages.
“Interestingly, it turned out that the Early Cretaceous flowers were on average more different from each other than today’s flowers, even though there are many more species of flowering plants on Earth today,” explains Marion Chartier from the Department of Botany and Biodiversity Research at the University of Vienna.
“Our results are fascinating because we only know a relatively small number of flowers from the Early Cretaceous, but this small number showed more variability than a thousand living species sampled for the study,” Andrea López, co-leading author from the National Autonomous University of Mexico, adds.
A similar evolutionary pattern, with a high degree of morphological diversity at a time when the number of species was relatively low, is also known in several animal groups (e.g., dinosaurs or fish).
“For flowering plants, one possible explanation for this pattern is that when the group first evolved, floral organization was more flexible and novel flower types could evolve more easily. This flexibility may have allowed flowering plants, within a few million years of their origin, to adapt to the different animals that pollinated their flowers and dispersed their fruits” explains Dr Maria von Balthazar from the University of Vienna.
The collection of the vast dataset of floral traits required for this study was made possible by the eFLOWER project, coordinated by Hervé Sauquet of the Botanic Gardens of Sydney and Jürg Schönenberger of the University of Vienna. “Our analyses clearly show that the morphological diversity of a given group does not necessarily correlate with species richness of that same group. In fact, some of the most species-rich groups of flowering plants, such as orchids and the daisy family, have managed to produce thousands of species while maintaining the same floral organization”, Schönenberger states.
However, the intriguing revelations didn’t stop at the initial diversity in flower structures. The researchers additionally demonstrated that specific combinations of characteristics were theoretically viable but seemingly never manifested through evolution. Simultaneously, certain highly successful flower types emerged multiple times independently.
Header Image Credit : Julia Asenbaum