Did Flowering Plants Evolve On A Lost Continent, Like Darwin Imagined?

In his vast correspondence with other contemporary naturalists, Charles Darwin mentions an “abominable mystery”. This mystery was the origin of angiosperms or plants with flowers. The fossil record showed that flowering plants appear relatively suddenly all around the world in the mid-Cretaceous, in contrast with Darwin's belief of a gradual, slow evolution. Darwin explained the apparent sudden evolution using gaps in the fossil record.

Perhaps, he suggested, the ancestor of modern flowering plants evolved in a remote place, from where the new group quickly spread. Plants with flowers are far more likely to become fertilized, thanks to the help of insects or the wind, can quickly produce seeds and colonize new terrain. So to solve this mystery it was just necessary to find the remote place where the first flowering plants evolved. Darwin proposed an interesting explanation why this place was not found during his lifetime: "I have sometimes fancied that development might have slowly gone for an immense period in some isolated continent or large island, perhaps near the South Pole.”

Darwin speculated that the first flowers evolved on a continent, from there spread over the globe, meanwhile the continent with the transitional fossils disappeared beneath the sea, far out of reach of any fossil collector or naturalist.

Since Darwin, many plant fossils have been found, but the origin of flowering plants still remains elusive. Possible sites of origin of the angiosperms were placed in the Arctic region, Southeast or East Asia, South America and Africa. Some fossil leaves of the Triassic and Jurassic resemble leaves of modern angiosperms but there is no direct evidence to link the fossils to the group. The oldest known fossils of angiosperms, showing some typical parts of a flower, like carpels and stamens (the reproductive organs of a flowering plant) but lacking others, like petals (modified, brightly colored leaves to attract pollinators),  were found in China, dating to the early Cretaceous. Archaefructus, discovered in 1998, was a plant growing in wet environments or even water, as the sediments, where the fossil is preserved, and the morphology of the leaves suggest.

The connection of Archaefructus with water supports also another idea about the evolution of flowering plants. The Cretaceous radiation probably begins somewhere in the wet tropics. The new plants then spread quickly from their place of origin and in just forty million years flowering plants make up already more than seventy-five percent of all known land plants. But according to botanists Archaefructus, despite its primitive traits, cannot be considered the first flowering plant, but just a very basal form, relocating the possible origin of angiosperms outside of China.

A modern discovery may vindicate Darwin's very speculative idea about the true origin of flowering plants. The continent of Zealandia, located east of modern Australia, disappeared in the sea in the late Cretaceous. If the first flowering plants evolved on the lost continent of Zealandia, this would explain the apparent lack of fossil forms.  From Zealandia, maybe with a tropical, wet climate at the time, the new group would quickly spread over Australia and Asia, united at the time in a single landmass, coinciding with the discovery of primitive flowering plants in fossil sites of China and Mongolia. There is also some evidence to support this hypothesis observing the distribution of modern species. Research suggests that Zealandia played an important role to explain the dispersal and evolution of animals, providing a dry land bridge, in the South Pacific. It's likely that also plants used this land bridge.

This is supported by the distribution of flowering plants still sharing some traits with their primitive ancestor.  Many primitive flowering plants are found clustering around the former location of Zealandia, supposed origin of the primitive ancestor.  The genus Amborella is found only on the island of  New Caledonia,  southwest Pacific Ocean. Austrobaileya is found only in the tropical forests of Queensland, Australia. Degeneria, a genus in the family Magnoliaceae, a very old group inside the flowering plants, is only found on Fidschi, a remote island north of New Zealand.

Researcher Studies Pollinator Plots for Warm Season Grass Lawns

FAYETTEVILLE, Ark. — The nation's pollinators are in need of food and housing. Michelle Wisdom is stepping up.

Wisdom, a graduate student in horticulture, is researching ways to incorporate bulbs and other flowers into lawns and other turfgrass areas as a means of providing much needed habitat for pollinating insects.

Bees may be the most widely recognized pollinators of flowering plants, and they are the main pollen spreaders for fruits and vegetables, according to information from the USDA Natural Resource Conservation Service. But many animals help spread pollen about.

Other insects like butterflies, moths and beetles contribute to pollination. So do birds and bats.

Pollinators are in trouble, according the NRCS and other sources. They face challenges from environmental contaminants, disease and parasites. But the most pressing challenge is loss of habitat.

Wisdom said urban spread is the biggest contributer to habitat loss. According to USDA sources, more than 50 million acres of manicured lawns, golf courses, roadsides and other managed turfgrass surfaces make grass the largest agricultural crop in the U.S. Add Monoculture farmlands and the result is that pollinator habitats have become fragmented.

When Wisdom was looking for a master's thesis research project in horticulture, turfgrass professor Mike Richardson suggested she work on the use of bulb flowers in warm-season turfgrasses.

Richardson had done some research on using bulbs to add color to dormant, warm-season grass lawns in early spring, before the grass begins greening up. He had identified a couple bulbs that could persist in lawns planted with aggressive bermudagrass varieties. He thought Wisdom might be able to continue and expand that early work.

Wisdom, a hobbyist beekeeper, wanted to expand that research to study the potential of flowers to add pollinator habitat to warm-season grass lawns.

She began by looking at more efficient methods for planting large numbers of bulbs. If you're doing a few, just dig a hole put one in. If you're planting several dozen, that's a lot of work. She found that opening a trench with a sod cutter, tossing them in and covering them up works well.

"After two years, you can't tell the difference," she said.

Wisdom observed them to see if bees or other pollinators would use them early in the spring. She was delighted to see bees feeding on the flowers as early as February.

"Bees will come out of the hive on mild winter days to relieve themselves," she said. "And while they're out, they'll feed if blooms are available."

Wisdom also wanted to see if she could find flowering plants that could coexist with bermudagrass or buffalograss during the insects' active season. She said her goal was to create a succession of blooms from early spring through late fall.

"A succession of blooms is best for pollinators," she said. "Most require diverse pollen sources for good health. And they also need a season-long succession of food sources."

The trick with the later flowers was finding plants that not only could coexist with the grasses, but also survive repeated mowings. She was able to find a combination of bulbs, white clovers and a couple other flowering plants that provided a succession of blooms.

In addition to contributing to pollinator habitat, the white clovers are legumes that make their own nitrogen and leave enough of it in the soil to help fertilize the grass.

The combination provided a succession of blooms from as early as January through as late as November. So far, the plants have persisted for two years in her test plots.

Wisdom concedes that those who want a nice, green, manicured lawn will probably not want clover and other plants popping up through the grass.But results of her research will be useful to homeowners who don't mind allowing other plants in their lawns in order to lend a hand to pollinating insects.

Wisdom said another area that would be ideal for adding pollinator habitat would be grassy roadsides. The need, there, would be to use low-height plants that won't block drivers' visibility on the roadways.

About the Division of Agriculture: The University of Arkansas System Division of Agriculture's mission is to strengthen agriculture, communities, and families by connecting trusted research to the adoption of best practices. Through the Agricultural Experiment Station and the Cooperative Extension Service, the Division of Agriculture conducts research and extension work within the nation's historic land grant education system.

The Division of Agriculture is one of 20 entities within the University of Arkansas System. It has offices in all 75 counties in Arkansas and faculty on five system campuses.

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