title: Biomaterial evolution parallels behavioral innovation in the origin of orb-like spider webs.
abstract: Correlated evolution of traits can act synergistically to facilitate organism function. But, what happens when constraints exist on the evolvability of some traits, but not others? The orb web was a key innovation in the origin of >12,000 species of spiders. Orb evolution hinged upon the origin of novel spinning behaviors and innovations in silk material properties. In particular, a new major ampullate spidroin protein (MaSp2) increased silk extensibility and toughness, playing a critical role in how orb webs stop flying insects. Here, we show convergence between pseudo-orb-weaving Fecenia and true orb spiders. As in the origin of true orbs, Fecenia dragline silk improved significantly compared to relatives. But, Fecenia silk lacks the high compliance and extensibility found in true orb spiders, likely due in part to the absence of MaSp2. Our results suggest how constraints limit convergent evolution and provide insight into the evolution of nature's toughest fibers.
authors.affiliation: Department of Biology and Integrated Bioscience Program, University of Akron, Akron, Ohio, USA. blackledge@uakron.edu
authors.forename: Todd A
authors.initials: TA
authors.lastname: Blackledge
authors.forename: Matjaž
authors.initials: M
authors.lastname: Kuntner
authors.forename: Mohammad
authors.initials: M
authors.lastname: Marhabaie
authors.forename: Thomas C
authors.initials: TC
authors.lastname: Leeper
authors.forename: Ingi
authors.initials: I
authors.lastname: Agnarsson
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001097:Arachnida / Q000145:classification / Q000378:metabolism; D001522:Behavior, Animal / Q000502:physiology*; D005075:Biological Evolution; D055119:Elastic Modulus; D005349:Fibroins / Q000737:chemistry / Q000378:metabolism; D008969:Molecular Sequence Data; D010802:Phylogeny; D047011:Silk / Q000737:chemistry* / Q000145:classification / Q000378:metabolism; D013112:Spiders / Q000378:metabolism
chemical_list: D047011:Silk; D005349:Fibroins