The Oldest TomatilloThese photos are different examples of a pair of plants that were buried in a la

The Oldest TomatilloThese photos are different examples of a pair of plants that were buried in a lake in Patagonia, Argentina 52 million years ago, and their discovery has helped scientists rewrite the history of plants you might have in your kitchen today.Potatoes, tomatoes, tomatillos, chilis, bell peppers, tobacco, and eggplant all belong to the family Solanaceae, also called the Nightshade plants. The greatest inherent diversity in these plants comes from continents that were once part of the Gondwana supercontinent, including South America, Australia, Antarctica, India, and Africa. This diversity suggests that those plants likely evolved on Gondwana and radiated out across the globe from there.When modern scientists investigate a series of related organisms, they can often piece together relationships using DNA – the more similar two organisms are, the more recently they diverged from a single common ancestor. While DNA is incredibly powerful for illustrating relationships between organisms, it is much more difficult to use DNA to understand how long ago species diverged as rates of change in DNA are difficult to calculate and some species that do evolve are likely to go extinct without leaving records. Thus, finding well-dated fossils in the geologic record that can be directly related to modern organisms gives scientists a clock, a way to determine how long ago these divergences happened.These fossils are exceptionally preserved plants from lake sediments found associated with a volcanic caldera and discovered by scientists at Penn State. They likely fell into the lake along the edge of a rainforest and were rapidly buried either by sediments from the rainforest or from volcanic ash – the ash was a last gasp of the volcanic output associated with the breakup of Gondwana. The organic material was turned into coal/graphite during fossilization, but it still preserves features including the flower and the berry. The size, shape, and other morphological features are characteristic of Solanaceae, closest in morphology to the tomatillo. Each of the two discovered fossils are shown here compared with modern examples to illustrate matching details like the shape of leaves and location of various veins.Estimates based on how different the DNA was between species of this family placed the origin of these plants between 30 and 50 million years ago. Finding a well-developed example of one that is 52 million years old implies that those species originated much earlier than those estimates. Discovering these fossils therefore helps scientists understand the evolution and radiation of the entire group, and also suggests that there may be other records of the emergence of this family buried in even older sediments across the fragments of Gondwana. How far back can this line be pushed? The author of this study now believes that future discoveries could push its lineage all the way back to the Cretaceous, over 65 million years ago.-JBBImage credit and original paper:http://science.sciencemag.org/content/355/6320/71.fullPress version:http://n.pr/2igmNrG -- source link
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