A Year in my Yard: Why are there Flowers?
Before I get to the flowers I have to acknowledge that this is my 100th blog post! I guess that is some kind of arbitrary milestone!!
Now, back to my yard…
Spring is a time of immense change, I have been challenged to keep up with all the different sizes and shapes of flowers at all levels in my yard. I know there are even some flowers I have missed simply because they were completely inaccessible. The black cherry tree in my backyard had blooms but only at the top of the 40-foot canopy. This diversity in location and variety of flowers raises the question of “Why flowers?”
Flowering plants are the younger of the two major tribes of plants. The gymnosperms or non-flowering plants dominated the land for much of the history of life on land. Gymnosperms include the cycads, conifers, and the gingkos. These plants rely on the wind and water to spread their pollen from tree to tree with pollination happening only by chance. About 200 million years ago in the Triassic period, the first great age of dinosaurs, a new type of plant appeared, the angiosperms. These plants had the ability to increase the chances of pollination by recruiting a pollen delivery service advertised with a flower.
Those primitive angiosperms did not have large blooms and color, those would come later. They did have a small offering of nectar, sugary sap, provided for those insects. As the insects feast on the nectar, they pick up pollen grains. When those insects visit another plant they transfer the pollen directly to the reproductive style. This direct mode of fertilization is much more efficient than the wind-driven process used by the gymnosperms.
Now 200 million years later that same process has been tweaked and modified millions of times leading to a reproductive arms race that includes bribery, trickery, kidnapping and even seduction. Flowers of all shapes, colors and sizes have evolved in direct response to the insects, mammals, birds and reptiles that pollinate them. Give too much nectar and the pollinator won’t visit another flower, give too little and they won’t visit at all. Each flower has honed into a niche to exploit a unique set of pollinators.
The diversity of flowers exploded only during the twilight of the dinosaurs in the cretaceous period a short 80-million years ago. Approximately 40 million years ago the next great family of plants appeared the grasses. These plants eliminated the need for the pollinators and reverted to the wind driven pollination of the gymnosperms. These new plants quickly took over the planet and gave us the grasslands and savannahs that we know today. More importantly, those grasses gave rise to the very plants on which our species survives rice, wheat and corn are all grasses.
The flowers we see today are the direct result of over 200 million years of coevolution with their pollinators. We now face the real possibility of losing pollinators due to a rapidly changing environment as a result of human activities. If we lose the pollinators we will inevitably and more subtly lose plants for which they pollinate. The mysterious collapse of bees and other pollinators is an indicator of much larger forces in action, forces which I hope we begin to respect and understand before we reach a tipping point.
Enjoy the diversity of flowers we have, recognize the evolutionary journey they have taken to reach their modern form. Bask in their fragrance and beauty but do not take them for granted as they, like all life, are subject to extinction. For the first time in the history of life one organism has the conscious decision to determine the fate of another. To protect the beauty of flowers we must first acknowledge the system in which they exist. We cannot hope to keep one part of an intricate machine just as we cannot remove pieces and expect it to continue working. With flowers we must protect thier pollinators, their habitat and all the other neccessities they require for life if we are to ensure the perpetuation of the species.
So, why are there flowers?? The flowers we have today are the decendents of those very early angiosperms that emerged in the Triassic period. Their efficient mode of reproduction led to the production of more offspring and increased diversity leaving the gymnosperms in their wake. The angiosperms simply outcompete the gymnosperms in many of the ecosystems around the planet. There are flowers because they are the most efficient method of reproduction a plant has ever achieved.