Systematics, phylogeny, and evolution of orb-weaving spiders.

The orb-weaving spiders (Orbiculariae) comprise more than 25% of the approximately 44,000 known living spider species and produce a remarkable variety of webs. The wheel-shaped orb web is primitive to this clade, but most Orbiculariae make webs hardly recognizable as orbs. Orb-weavers date at least to the Jurassic. With no evidence for convergence of the orb web, the monophyly of the two typical orb web taxa, the cribellate Deinopoidea and ecribellate Araneoidea, remains problematic, supported only weakly by molecular studies. The sister group of the Orbiculariae also remains elusive. Despite more than 15 years of phylogenetic scrutiny, a fully resolved cladogram of the Orbiculariae families is not yet possible. More comprehensive taxon sampling, comparative morphology, and new molecular markers are required for a better understanding of orb-weaver evolution.