Spiders are one of the oldest and most varied fauna groups in terrestrial habitats. Hisfossil record begins in Devonian(380 million years ago). With about 40,000 described species, arthropods are the dominant predators of microfauna in the natural environment.
About 200 million years ago,in the middle Triassic, orbicular spiders emerged, which diversified rapidly during the end of the Triassic and the beginning of the Jurassic. What are the causes of this evolutionary process? To answer the question, the new study has been based on the analysis of the molecular differences in the sequence of six genes from a taxonomic sample that includes 291 species of spiders, with representatives of 21 of the 22 families of orbicular spiders existing. (Deinopoidea, Araneoidea and Nicodamidae).
Traditionally, the process of diversification of webs had been linked to the spread of insects, the main prey of spiders, and flowering plants (angiosperms). However, in the work, the authors outline a new hypothesis to describe the evolutionary scenario: that the modifications of the cobwebs are aimed at occupying new natural habitats (trunks, stems, etc.) and exploiting resources in a more efficient way. .
“It is not weaving webs, which has allowed the diversification of spiders, but producing silk, and it is not the same. The silk threads, generated by many species of arachnids, are used to anchor, move, build nests, protect the spawn, etc. ”, says Arnedo. “Thegreat diversification broke out with sticky silk, a more efficient and easy-to-produce material for the spider. In our study, we found that all the evolutionary innovations that have taken place from an ancestral orbital web appear independently, have a lower energy cost for the spider and require fewer behavioral patterns “, adds the researcher. This tells us that, rather than following the evolutionary process of insects, spiders designed new strategies to occupy the maximum ecological space possible.
