Untangling spider webs
For decades, the story of spider evolution went like this: As insects became more and more diverse, with some species taking to the skies, spiders evolved new hunting strategies, including the ability to weave orb-shaped webs to trap their prey. From that single origin, orb-weaver spiders diverged along different evolutionary paths, leading to the present day, when several species weave similar — though not identical — webs. It’s a good story, but there’s a problem. Harvard scientists now know it’s not true. The largest-ever phylogenetic study of spiders shows that the two groups that weave orb-shaped webs do not share a single origin. Conducted by postdoctoral student Rosa Fernández, Alexander Agassiz Professor of Zoology Gonzalo Giribet, and Professor Gustavo Hormiga of George Washington University, the study is described in a July 17 paper in Current Biology. “Using thousands of genes, we did a comparative phylogenetic analysis, and what we now know is there is...