Science: Spiders go way back

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Research show that spiders first emerged about 230 million years ago

There are thousands of species of orb-weaving spiders, found on every continent but Antarctica. Now, researchers report that these spiders that build spiral-shaped webs first emerged about 230 million years ago, during the Middle Triassic period.

They then rapidly diversified and a wide variety of orb weavers emerged by the middle of the Jurassic period, about 170 million years ago, according to a study in the journal Proceedings Of The Royal Society B.

In the past, scientists thought that orb weavers diversified when flying insects did — that the spiders needed to specialise to catch different insects.

But the new research indicates that “there is no real direct relationship,” says the study’s first author, Dimitar Dimitrov, an evolutionary biologist at the University of Copenhagen. In fact, he said, flying insects diversified 100 million years after the orb weavers.

He believes that orb weavers diversified for another reason: To create specialised habitats. Some create webs ideal for tree branches, while others specialise in webs better suited for tree trunks and tall grasses.

“When you see them today they might be in the same place, at the same time, but occupying different niches,” he says. Dr Dimitrov and his colleagues used DNA samples of existing spiders, along with fossil remains, to create an evolutionary tree and a timeline.

“We were able to find that the orbs have a single origin,” he says.  - NYT

Orb-weaving spiders can be found on every continent except Antarctica


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