Tuesday 1 March 2016

Genomic evidence sheds new light on our understanding of spider evolution

Date: February 23, 2016
Source: PeerJ

After a burst of work in the 1980s, it was believed that science had a sound understanding of the evolution of spiders. However, in a new study employing cutting edge bioinformatics and next generation sequencing techniques, scientists have reconstructed the spider 'tree of life' to come to intriguing new conclusions about the evolution of the web, something which has important implications for the overall story of spider evolution.

The arachnid order to which spiders belong, Araneae, is an incredibly ancient and diverse group comprising over 45,000 described species with nearly three times as many awaiting discovery; by all counts they are the largest known animal group that is exclusively predatory. In addition to remarkable diversity, ecology, and abundance, spiders are known for some extraordinary biomolecules , such as venoms and silks. Although few spider venoms are dangerous to humans, they hold enormous medical promise as insecticides and therapeutics. And, no other animal can claim a more varied and elegant use of silk -- a super strong material being used to create biometic material such as artificial nerve constructs, implant coatings, and drug delivery systems.

Despite their amazing diversity, and important biomolecules, our understanding of spider evolution has long been an open question. The orb web, the spiral wheel shaped web made by many spider species, once considered "the crowning achievement of aerial spiders" has captured the imagination of evolutionary biologists for over a century as a consequence of its intricate beauty. Initially thought to have evolved independently at least twice across the group's evolutionary history, complex associated morphologies and behaviors studied extensively in the 1980s suggested otherwise, sparking a shift in thinking that ultimately concluded that the orb web and the taxa that spin it all shared a common ancestor. Subsequent evolutionary changes in thread chemistry along with a vertically oriented orb web were thought to have sparked a tremendous bout of species diversification.

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