How Cacti Defy Darwin

0 0 1 minute read

https://www.profitableratecpm.com/f4ffsdxe?key=39b1ebce72f3758345b2155c98e6709c

In interpreting the intimate relationships between pollinators and orchids, Charles Darwin proposed that the specialized shapes and colors of flowers lead to diversification. After all, it seems logical that as flowers adapt to better match the specific color preferences, body shapes, or mouthparts of pollinators, new species emerge.

But a recent study by biologists at the University of Reading published in Biology letters evaluated Darwin’s hypothesis and found evidence to the contrary in cacti (family Cactaceae). The researchers compared the flower lengths of 774 cactus species representing almost all cactus subfamilies, whose flowers spanned 185 times in size ranging from 0.08 inches to 1.5 inches. Next, they mapped flower length on a cactus phylogenetic tree, from which they estimated speciation rates over geologic time since cacti first appeared on Earth.

“We expected that cacti with longer, more specialized flowers would create the most new species,” lead author Jamie Thompson said in a press release.

Read more: “Why is everything an orchid? »

Instead, the researchers found that flower size had only a minimal impact on how quickly new species emerged, and that it was the cacti whose flowers (regardless of size) changed the fastest that were most likely to split into new species.

The overall pace of cactus evolution revealed in the study was also surprising. Despite how slowly cacti grow, “the cactus family is one of the most rapidly evolving groups of plants on Earth. Knowing how quickly cacti evolve reveals that deserts, often thought of as harsh and unchanging, are actually hotbeds of rapid natural change,” Thompson said.

So the cactus family, numbering about 1,850 species, spread rapidly across the Americas over the course of 20 to 35 million years, which may seem like forever, but is actually only a short evolutionary time span, and it appears that it was their floral diversity, rather than a specific adaptation of pollinators, that led the way.

So while desert landscapes may seem, as Thompson says, harsh and unchanging, you can be sure that the cacti found there are evolving.