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Over millions of years, evolution can do some wild things. In New Zealand, where almost no mammals live natively, birds took on every role in the food chain, from herbivores who waddled on the ground to fruit eaters who lived in the trees, to a giant terrifying eagle with a ten foot wingspan. In Hawaii, something similarly bizarre happened to a species of spider, as we learn from a new study in an upcoming issue of Current Biology from researchers at UC Berkeley.
Ariamnes stick spiders, strange, elongated insects that often look like sticks or leaves, probably first came to the Hawaiian islands two or three million years ago. Since landing on the islands, the spiders diversified to fill every nook and cranny of their new environment, ultimately evolving into 14 separate species across the islands.
These spiders have developed different adaptations to suit their environments. Their three variations, known as ecomorphs, include a brown spider that lives among rocks, a gold spider that lives under leaves, and a white spider that lives on lichen.
But what’s so incredible about the spiders’ evolution is not just how well they adapted to their new environment, a process known as adaptive radiation. It’s that they all did so in the same way, separately. Researchers have found that ariamnes spiders on different Hawaiian islands all underwent basically the same evolutionary process, filling the same niches. So there are white ariamnes spiders on every island, but they are actually more closely related to their gold or red ancestors on their own island than they are to similar looking spiders on other islands.
“This very predictable repeated evolution of the same forms is fascinating because it sheds light on how evolution actually happens,” Rosemary Gillespie, professor of Systematic Entomology at UC Berkeley and the lead author of the paper told Phys.org. “Such outstanding predictability is rare and is only found in a few other organisms that similarly move around the vegetation.”
Finds like these are an incredible opportunity for scientists to study the mechanics of evolution. But as more and more invasive species come to the Hawaiian islands, the time to do so is running out.
“We need to be able to figure out this diversity and document it and describe what’s so special about it, so that people know about it,” Gillespie told Phys.org. “It’s being lost and it’s a desperate situation.”
Excerpted from article in Popular Mechanics dated Mar 18