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Surprising Spiders

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Two recent studies published in the Proceedings of the National Academy of Sciences by CNR insect biologists provide new insights into the behavior and evolution of spiders.

One study, by Assistant Professor Eileen Hebets, found that it isnít just vertebrates who use learning, memory, and social experience to choose a mate. Spiders do, too.

Hebets found that a sexually immature female wolf spider that has been courted by a mature male is substantially more likely, later in life, to choose a mate similar to the one she first encountered (not entirely unlike marrying the man who reminds you of a high school crush).

Scientists have rarely had much regard for what happens in spidersí lives before sexual maturity, at least when it came to positing arthropod sexual selection theories. Females have generally been assumed to possess a genetic preference for a certain phenotype in their mates, but Hebetsí findings suggest that social experience and memory may be more important.

In a separate study, Professor Rosemary Gillespie reported that the similarities between the webs of different spider species in Hawaii provide fresh evidence that behavioral tendencies can evolve rather predictably, even in widely separated geographic places.

She found that separate species of Tetragnatha spiders, located on different islands and sharing no common ancestry, constructed webs of nearly identical shape, structure, and function. Gillespie and her colleagues concluded that the spidersí ability to construct nearly identical webs must have evolved independently, driven by matching environmental conditions.

The idea that traits can evolve independently isnít new, but this process never before had been applied to behaviors as complex as spinning a web.

-Sara Bernard and Cyril Manning


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