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.

Scented winter flowers

To me there is nothing in the garden that is as uplifting as fragrance, particularly in the darkest depths of winter. Catching an unexpected whiff of the scent of summer on a cold, grey day when dashing out the front door or walking to the bus stop is one of the everyday surprises which makes gardening so magical.

However, as a self-confessed fair-weather gardener who hates the cold, for me there is just one downside to many winter flowering shrubs: you have to get out in the freezing drizzle to actually smell them. I barely last a few minutes at a time. Fortunately, a small handful of these beauties also happen to make excellent cut flowers, so you can surround yourself with the scent of the outdoors all day. Having experimented with loads each winter, I have come up with my top four that smell as good in the house as they do in the garden.

Wintersweet, or Chimonanthus praecox, lives a secret double life as a mild-mannered garden shrub all summer long, with plain green leaves that are easily overlooked. Yet come this time of year, its bare branches erupt into waxy yellow flowers with deep burgundy throats and a scent that will stop you dead in your tracks. Spicy, sweet and intensely fragrant, it is well worth the few years' wait for the plants to reward you with flowers.

If you only have a tiny spot to play with, you couldn't do much better than Daphne bholua, especially if it is overshadowed by trees and tall buildings. These shade-loving, tiny, evergreen shrubs produce delicate white or pink blooms that look like they are made from sugar icing. And the scent – oh, the scent. Deep, rich and classically floral, it reminds me of vintage perfume.

Sarcococca hookeriana is another excellent candidate for smaller, shady spots, producing a jasmine-like scent so powerful you will almost certainly smell it before you see it.

Last but not least comes Viburnum x bodnantense, a large shrub with small pompoms in delicate white or pastel pink. With its extremely long flowering season, starting from mid-autumn until early spring, you'll get a conveyor of scented blooms right when you need them most.

No garden? No problem

Even if you don't have any outside space at all, there are many winter flowering house plants you can grow for unbeatable fragrance indoors. I am a huge fan of the ivory, scented flowers of trailing cactus Epiphyllum anguliger, with its mad, fishbone-shaped foliage. For lovers of the classics there are always the white, rose-like flowers of gardenia, with an infamously intense perfume and the old-school bridal bouquet favourite of stephanotis, whose lighter, fresher scent can still fill a room.

Bumblebees Use Temperature Patterns to Choose Flowers, Says New Study

 A wide range of flowers produce not just signals that we can see and smell, but also ones that are invisible such as heat. According to new research from the University of Bristol, UK, bumblebees can use these temperature patterns as a cue to recognize flowers and make informed foraging choices based upon them.

Bees experience the world in a different way to humans. The plants that they visit exploit the bee’s senses to make sure that a searching bee can easily find, handle and pollinate flowers.

For example, bumblebees can learn to choose between flowers that are different temperatures, using heat as a way of identifying the best flowers.

Some wild flowers are warmer than others when they grow in their natural environment.

"Recent advances in technology mean that scientists are now able to take a more detailed look at flower temperature than ever before," said lead author Dr. Heather Whitney from the University of Bristol’s School of Biological Sciences and colleagues.

"We used this technology to look at 118 species of plant, including daisies, rockroses and poppies."

The majority of flowers examined by the team had complex patterns of heat across their petals, echoing the colorful patterns that we see with our own eyes.

On average these patterns were 4-5 degrees Celsius warmer than the rest of the flower, although the patterns could be as much as 11 degrees Celsius warmer.

Dr. Whitney and co-authors made artificial flowers that copied these heat patterns, but did not include the corresponding color patterns.

While these artificial flowers look identical to human eyes, and we are not able to tell them apart, it is a different case for foraging bumblebees.

Bumblebees were found to be able to use these patterns to distinguish between different flowers and the rewards that they provide.

"The presence of multiple cues on flowers is known to enhance the ability of bees to forage efficiently, so maximizing the amount of food they can take back to sustain the rest of their colony," Dr. Whitney said.

"Climate change might have additional previously unexpected impacts on bee-flower interactions by disrupting these hidden heat patterns."

On the Dry Side: South Africa offers treasure trove of winter-growing bulbs

 South Africa has an extraordinary number of plant species found nowhere else, including hundreds of species of bulbs. Some of these bulbs are well-established in the gardening world, such as Agapanthus or Amaryllis belladonna, but others are little known except to bulb aficionados. They vary greatly in size — from large ones, with bulbs as big as a football, down to miniatures, with bulbs smaller than a pea.

While some grow and flower during the summer months, others spring to life toward the end of the year and grow through the winter. The winter growers come from the western part of the country, which has a Mediterranean climate much like that of California. With very little rainfall during the summer months, these plants respond by sleeping through the dry summers and waking up when the rainy season begins in autumn.

Often, they are so strongly adapted to this regimen that they do not last long when grown in places with wet summers. Happily for us, they present little difficulty in the coastal parts of California, where winters are not too cold and the rainfall arrives just when they need it.

Among South Africa’s treasure trove of winter-growing bulbs is the large genus Lachenalia, with 133 species. These are small plants with delightful flowers, the great majority of them found in the southwest corner of the country, in the winter-rainfall zone. Many of them have spires of tiny short-tubular flowers, but some of the showiest kinds have larger, vividly colored long-tubular flowers, which are pollinated by nectar-feeding birds.

One such species is Lachenalia punctata, which grows mostly in sandy coastal locations both north and south of Cape Town, though there are a few places where it occurs farther inland. This plant has long been known by the name Lachenalia rubida, but recent research shows that the older name, Lachenalia punctata, refers to the same species, and should be used because it was published first, in 1788.

Lachenalia punctata emerges from its summer dormancy in the fall, coming up about late October to November at the Ruth Bancroft Garden in Walnut Creek. The flowers develop rapidly, beginning to bloom even before the leaves have developed fully. Each mature bulb produces a single slender flower stalk, which may in some cases grow to a height of 10 inches, though they are usually shorter than this. The cylindrical flowers are 2½ to 3½ inches long and come in various shades of red or pink. In some cases, the red comes in the form of speckles on a background of pale yellow, and this is the source of the name “punctata,” which means spotted.

The flowers are not the only part of the plant with spots, since the pointed leaves often have dark purple spots, though these are not always present. They grow through the winter months, going dormant again when summer approaches.

Lachenalia punctata makes a fine garden plant or potted specimen, requiring sun and good drainage. Heavier soils should be amended for successful growing.