title: Phylogenomics resolves a spider backbone phylogeny and rejects a prevailing paradigm for orb web evolution.
abstract: Spiders represent an ancient predatory lineage known for their extraordinary biomaterials, including venoms and silks. These adaptations make spiders key arthropod predators in most terrestrial ecosystems. Despite ecological, biomedical, and biomaterial importance, relationships among major spider lineages remain unresolved or poorly supported. Current working hypotheses for a spider "backbone" phylogeny are largely based on morphological evidence, as most molecular markers currently employed are generally inadequate for resolving deeper-level relationships. We present here a phylogenomic analysis of spiders including taxa representing all major spider lineages. Our robust phylogenetic hypothesis recovers some fundamental and uncontroversial spider clades, but rejects the prevailing paradigm of a monophyletic Orbiculariae, the most diverse lineage, containing orb-weaving spiders. Based on our results, the orb web either evolved much earlier than previously hypothesized and is ancestral for a majority of spiders or else it has multiple independent origins, as hypothesized by precladistic authors. Cribellate deinopoid orb weavers that use mechanically adhesive silk are more closely related to a diverse clade of mostly webless spiders than to the araneoid orb-weaving spiders that use adhesive droplet silks. The fundamental shift in our understanding of spider phylogeny proposed here has broad implications for interpreting the evolution of spiders, their remarkable biomaterials, and a key extended phenotype--the spider web.
authors.affiliation: Department of Biological Sciences and Auburn University Museum of Natural History, Auburn University, Auburn, AL 36849, USA. Electronic address: jbond@auburn.edu.
authors.forename: Jason E
authors.initials: JE
authors.lastname: Bond
authors.affiliation: Department of Biological Sciences and Auburn University Museum of Natural History, Auburn University, Auburn, AL 36849, USA.
authors.forename: Nicole L
authors.initials: NL
authors.lastname: Garrison
authors.affiliation: Department of Biological Sciences and Auburn University Museum of Natural History, Auburn University, Auburn, AL 36849, USA.
authors.forename: Chris A
authors.initials: CA
authors.lastname: Hamilton
authors.affiliation: Department of Biological Sciences and Auburn University Museum of Natural History, Auburn University, Auburn, AL 36849, USA.
authors.forename: Rebecca L
authors.initials: RL
authors.lastname: Godwin
authors.affiliation: Department of Biology, San Diego State University, San Diego, CA 92182, USA.
authors.forename: Marshal
authors.initials: M
authors.lastname: Hedin
authors.affiliation: Department of Biology, University of Vermont, 120A Marsh Life Science Building, 109 Carrigan Drive, Burlington, VT 05405, USA.
authors.forename: Ingi
authors.initials: I
authors.lastname: Agnarsson
mesh_terms: D000818:Animals; D060829:Arthropod Proteins / Q000235:genetics*; D005075:Biological Evolution; D008969:Molecular Sequence Data; D010802:Phylogeny; D011235:Predatory Behavior; D017422:Sequence Analysis, DNA; D013112:Spiders / Q000145:classification* / Q000235:genetics* / Q000502:physiology
chemical_list: D060829:Arthropod Proteins