A new study looks at the evolution of various spider species scattered across Hawaii. While they bear significant differences in appearance and methods of hunting, they aren't actually related, and this could shed light into the factors that constrain evolutionary change.
The study was led by University of California, Berkeley biologists. In a nutshell, what they discovered was that it's possible for different species to evolve in similar ways despite being far away from each other.
Hawaiian Stick Spiders
About 2 to 3 million years ago, stick spiders came to Hawaii. Each time a spider traveled to a different Hawaiian island, it evolved into various species — one species found a way to survive on rocks. Another found a way to live under leaves. This is one of the characteristics of adaptive radiation, and understanding it enhances our grasp of the evolution theory. It remains largely a mystery, and it is what caused the said spiders to evolve into 14 different species when they came to Hawaii.
While the spiders in question share a similar body type, each is its own unique species, complete with different traits and hunting methods. However, there's an odd phenomenon. There are stick spiders of the same color — red and yellow, for example — on different islands, yet they're completely different species. How so?
Evolution has led these spiders to evolve in predictable and programmed ways.
To published March 8 in Current Biology, the study suggest the spiders in question are ecomorphs, or animals that bear aesthetic similarities and habitat but aren't actually closely related. Ecomorphs, as the study claims, have a special element in their DNA that enables them to evolve quickly but at the same time places a limit on what they can evolve into.
Meaning, some species may be programmed to evolve in certain ways and repeat the process over and over, which explains why, in all the islands, yellow and red stick spiders evolve independently despite their different genetic makeup.
"Such outstanding predictability is rare and is only found in a few other organisms that similarly move around the vegetation," said the study's lead author, Rosemary Gillespie.
Gillespie hopes her team's research encourages other scientists to delve into the diversity of Hawaii's animal landscape.
"Often, I hear people saying, 'Oh, Hawaii's so well studied. What else is there to look at?' But there are all these unknown radiations that are just sitting there, all these weird and wonderful organisms," she said. "We need everyone to understand what's there and how extraordinary it is. And then we need to see what we can do to protect and conserve what still waits to be described."