The preserved petals and pollen of a new ancient flowering species have been discovered in mid-Tertiary amber from the Dominican Republic. According to findings published in Nature Plants this week, these are the first neotropical flowers found in amber from a representative of the asterids – one of today’s most diverse plant groups with over 80,000 species ranging from peppers and potatoes to sunflowers, mint, and coffee.
Amber is the fossilized resin of ancient trees. When small insects or other organisms become trapped in resin before it solidifies, they remain mostly unchanged for millions of years in the amber that results. While Dominican amber has proven to be a rich source of vascular plant remains, no fossilized examples of asterids from been reported until now.
Oregon State University’s George Poinar and Lena Struwe of Rutgers University studied flowers encased in two separate pieces of amber from Hymenaea protera trees from a mine in the Cordillera Septentrional mountain range between Puerto Plata and Santiago on the Caribbean island of Hispaniola. A neotropical Caribbean forest existed there in the mid-Tertiary period, long before the North and South American continents were connected by the Panama land bridge.
The preserved flowers, which were less than a centimeter long, consisted of a trumpet-shaped fused petal (or corolla) tube, recurved petal lobes, the stamen and small anthers with spherical pollen, and a long, protruding style. The flowers belong to the genus Strychnos, like the Strychnos nux-vomica tree, from which poisonous strychnine is extracted. The duo named the new species Strychnos electri, which refers to “elektron,” the Greek word for amber. Because precise dating of Dominican amber is difficult, the team turned to two different types of evidence that suggest the fossils formed as recently as 15 million to 20 million years ago or as long as 30 million to 45 million years ago.
Strychnos electri provides evidence that highly derived asterid groups were already present in neotropical forests by the mid-Tertiary, suggesting that many other relatives of modern New World asterids had also evolved by this time, though their remains have yet to be discovered.
The fused petal tube, style, and anthers visible in the mouth of the flower of Strychnos electri. George Poinar