Blackledge's results provided compelling evidence that 3-D web-weavers are better defended against attack than their 2-D web-weaving relatives. The researchers found that 3-D web-weavers accounted for fewer than one in five spiders captured by wasps. However, this proportion is "flip-flopped" around from the proportion of spiders available to wasps, said Blackledge.
In fact, 3-D web-weavers comprise an average of four in five web-building spiders actually found in the in the environment.
"3-D web-builders appear to be somehow protected from predation," said Blackledge. "Perhaps something about 3-D webs make them less attractive to predators," he added.
The classic, flat, 2-D orb web, though efficient at catching flying insects with little silk, leaves spiders more readily exposed to predators, said Blackledge. On the other hand, the 3-D web provides physical protection and early warming of attack. The concept that the predators might have influenced the evolution of web architecture attracted much attention in recent years, said Shear, who is the Charles Patterson Distinguished Professor of Biology at Hampton-Sydney College. However, this study is one of the first tests of the theory that "defense against predators is an important selective force on spider web architecture," he said.
Blackledge is "testing experimentally…assumptions that have been taken for granted by spider folk for a long time," said Shear.
The study is documented in last month's issue of the journal Ecology Letters.
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