Araneid Phylogeny and Evolution of Spider Silk Phenotypes Collaborative research: Todd A. Blackledge, Nikolaj Scharff and John W. Wenzel

Spiders produce different types of silks that have remarkable physical properties. Some spider silk can even absorb more energy before breaking than high performance manmade materials. Orb webs are an outstanding example of how a combination of properties from two types of silk fibers, stiff supporting threads and stretchy capture spirals, function to absorb the high energy impacts of flying insect prey. Yet, orb webs spun by different species of spiders can have radically different shapes. This project seeks to understand how the mechanical function of spider silk may evolve in relation to changes in the way different species of spiders spin webs. The research will involve three steps. 1) It will produce the first robust hypothesis for evolutionary relationships among orb-weaving spiders by using novel DNA data and expanded data on morphology. 2) It will measure the shapes of webs and quantify the material properties for the two constituent fibers of orb webs, frame threads and sticky capture silk. This will include testing the strength, stretchiness, and toughness of the silk fibers spun by an ecologically diverse sampling of orb-weaving spiders. 3) These two types of data will then be combined to examine the how the biomechanical properties of silks coevolve with web shape among different of orb-weaving spiders that have both similar and very different ecologies from one another.

This project will have three primary broader impacts; 1) facilitating biotechnological exploitation of spider silks, 2) mentoring of underrepresented students in science, and 3) contributing to public scientific literacy. The extreme performance of spider silk makes it a desirable model for the development of biomimetic superfibers and fabrics. This project will demonstrate how web shape can be used by bioprospectors as an indicator for spiders that spin mechanically unusual silks. It will also determine the degree to which different mechanical properties of silks can change independently of one another. This knowledge is essential for efforts to bioengineer recombinant spider silk for customized applications that require unique combinations of strength and stretchiness. Undergraduates will be actively involved in basic scientific research each year of this project through the development and completion of independent projects. These projects will relate to web evolution and silk mechanics and some of these students will even participate in field research excursions to Africa and South America, where they will gain exposure to biodiversity related research and to new cultures. This is particularly relevant, because U Akron students are predominately from heavily populated northeastern Ohio and a majority of biology students are female, with more than 30% from under-represented minority ethnic groups. Many of these students have not been exposed to basic scientific research or to career possibilities in the sciences. Finally, the investigators will use the media’s interest in spider webs and silk to enhance the public’s knowledge of biodiversity and the often-misunderstood process of evolution. They will also use the research to introduce high school students to the relationship between basic scientific research and industry through established summer internship programs at U Akron.

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