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Evolution Gets Colorful August 24, 2009

Posted by Mrs Weird Scientist in Brain Power, Environment, Evolution, Tough Stuff.
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Summer is still going strong but soon it will be fall – a time when we can enjoy the pretty autumn leaves. Or as I always like to do, throw leaves at my wee dog and race through the massive piles of foliage.

Unless you’ve traveled a bit and have a sharp eye for detail, you might not have noticed that autumn leaves are usually red in America but yellow in Europe. Seems strange, doesn’t it? If you’re wondering why, then you’re not the only one. Two professors thought about these differences too and they came up with a cool theory.

Prof. Simcha Lev-Yadun of the Department of Science Education at the University of Haifa-Oranim in Israel and Prof. Jarmo Holopainen of the University of Kuopio in Finland had their work published in New Phytologist.

Stepping Back In Time

Red leaves in America serve as a warning flag to ward off insects. But in Europe, none of these evolutionary 'tricks' are needed, which means leaves are yellow.

To find out more, we have to step back 35 million years to sort out the mystery. Up until that time, huge areas of the globe were rich in evergreen forests. Then, a bunch of ice ages and dry spells came into the picture. Lots of the tree species evolved to become deciduous – meaning they lose their leaves depending on the season. Some trees even started to produce red leaves to keep the pesky insects away. But, something else came into play and you might be surprised to learn just what it was!

Look To The Mountains

It’s true. We have to check out the orientation of the mountains to get the scoop on why the leaves evolved to be red in America but yellow in Europe. In North America, north-to-south mountain chains created a protected area, enabling the plants and animals to migrate south or north. Joining them were the insects. So, the leaves in America remained red to continue warding off these annoying bugs.

But in Europe, the mountains are oriented from east-to-west, leaving no protected areas as the ice and other environmental conditions came to visit. Loads of the tree species just couldn’t survive the extreme cold. When they died, so did those insects that needed the trees for their survival. By the time the ice ages were over, those trees that had managed to survive didn’t have to deal with the now-extinct insects. So, no need for red leaves to keep them away!

Curious Minds Want To Know

I asked Simcha Lev-Yadun how he ended up studying leaves. While my background is in the life sciences (medicine and nutrition), I always wonder how people end up in the many different, neat areas of science. He explained:

I wanted to be a biologist and archaeologist since I was ten years old. For me, science is a lifestyle, not a job. At the age of 57…I look backwards and see that I made the right decision.

He also shared his plans to meet up in Scandinavia with his colleague Jarmo Holopainen, where they hope to find out even more about why plants have such cool and different colors.

My Wishful Thinking

While my dog Tiko probably doesn’t care much about leaf color when he dashes through the crisp autumn leaves, I like to understand what makes one leaf a bright yellow and another a brilliant red. Now, if only leaves could somehow evolve to become fluorescent pink, my favorite color. Somehow though, I just don’t see it happening!

Comments»

1. telson - August 31, 2009

It has been thought that there have been several Ice Ages on the Earth. It has even been said that tropical and hot areas like the Sahara, Africa, Saudi Arabia, Yemen, Australia, India, Madagascar, and South America were covered with a large continental glacier tens of millions of years ago. The latest Ice Age is assumed to have started “just” about 500,000 years ago and ended 10,000 years ago. The ice sheets are believed to have covered at their widest 55 million square meters, and the thickness of the ice was at most over 3 kilometers (about 1.8 miles).

What should we think about the Ice Age? Have we any reason to believe in it? Maybe the signs that have been interpreted as signs of an Ice Age were caused by something else?

2. S. Lev-Yadun - August 31, 2009

Ice ages were a reality, especially during the last 2 million years.
There is a good book (and many others): Imbrie, J. & Palmer-Imbrie, K. 1979. Ice ages. Solving the mystery. Enslow Publishers.
I am certain that a good encyclopedia will also give the basic facts and figures.
Ice ages were a reality that significantly influenced the world in the last 2 million years or so. The tropics, the Sahara or the Near East were not covered by glaciation, but moderately influenced by the much more drastic climatic changes in the temperate region.

3. Mr.Science - February 5, 2010

So the Evolution as you said about the the leaves not needing the color red to keep insects away is kind of like an adaptation of some sort to protect the plant from insects an I correct.

4. Miss Weird Scientist - February 5, 2010

Yes, it’s an adaptation. Without those insects, the trees don’t need that red color to ward them off!

5. Mr.Science - February 5, 2010

cool thankyou for clearing my thoughts.

6. Mr.Science - February 6, 2010

oh and is that the only varible you can find to this strange adaptation or could it do with climate or polution or some other varible.

7. Miss Weird Scientist - February 7, 2010

Mister Science, you got it! It was the geographic orientation that ultimately left these trees susceptible to the influence of the climate. So, the climate definitely played a part too.

8. Mr.Science - February 20, 2010

oh cool you certintly did your research ha ha ha thankyou.


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