Cacti explosion!

I’ve posted a lot of “creativity” lately, but not much on the matter of curiosities 😉 here’s something I wrote up after interviewing a researcher at Brown, the school I attend as an undergrad majoring in biology.  Enjoy!

Research Into Succulent Plants Yields New Insight Into Formation of New Species Millions of Years Ago

Brown University biologists and colleagues have uncovered new evidence suggesting that cacti evolution accelerated with the origin of many new species 5 to 10 million years ago and coincided with global diversification of succulent plants.  Interestingly, this time period, the late Miocene, was marked by arid conditions and a precipitous drop in carbon dioxide as well as the evolution of a new form of photosynthesis (C4) that maximizes moisture conservation.

Researchers emphasize that learning more about the coincidence of these three events can help scientists obtain insight into what drives plant evolution and why.

The team began research with the intent of determining the origin of cacti.  Erika Edwards, an assistant professor in the Department of Ecology and Evolutionary Biology at Brown, explained that by sequencing the DNA of different plants, the scientists were able to compare across species and reconstruct branches of the evolutionary tree or phylogeny for succulent plants and flowering plants in general.

Although the scientists were able to deduce that cacti first originated about 35 million years ago, they were more surprised that cacti greatly diversified only 5 to 10 million years ago.  Curiously, a new type of photosynthesis (C4) adapted to arid conditions as well as all succulent plants chose this time to diversify as well.

If succulent plants were around 35 million years ago, why did they wait so long until diversifying into the myriad succulent life forms we see today?

The answer to this question lies in the global environment of the time period, known as the late Mioscene in geological time.  The researchers knew that the evolution of all three life forms at the same time could not be mere coincidence, and did some digging into environmental conditions to find an explanation.

Succulent plants, which have evolved the ability to hold water and include such familiar species as cacti, aloe, and ice plants, seemed to have evolved these adaptations during the late Mioscene because of the arid conditions and low carbon dioxide levels accompanying the period.  “The landscape was fundamentally changing” on a global scale, Erika Edwards explains.

Similarly, C4 plants are much better equipped to handle lowered carbon dioxide conditions, so they also took their chance to diversify during the same time period.

As to how plants will respond to the rapid increase in carbon dioxide at present, Edwards simply stated, “we don’t know!”  She emphasized that further research into plant physiology, anatomy, and evolution can help scientists obtain insight into the upper limits to plants’ physical abilities to handle temperature and drought and predict how plants will fare in the perilous, rapidly approaching future of global climate.

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