The Spider Silk Standardization Initiative (S3I): A powerful tool to harness biological variability and to systematize the characterization of major ampullate silk fibers spun by spiders from suburban Sydney, Australia

The true stress-true strain curves of 11 Australian spider species from the Entelegynae lineage were tensile tested and classified based on the values of the alignment parameter, α*, in the framework of the Spider Silk Standardization Initiative (S3I). The application of the S3I methodology allowed the determination of the alignment parameter in all cases, and were found to range between α* = 0.03 and α* = 0.65. These data, in combination with previous results on other species included in the Initiative, were exploited to illustrate the potential of this approach by testing two simple hypotheses on the distribution of the alignment parameter throughout the lineage: (1) whether a uniform distribution may be compatible with the values obtained from the studied species, and (2) whether any trend may be established between the distribution of the α* parameter and phylogeny. In this regard, the lowest values of the α* parameter are found in some representatives of the Araneidae group, and larger values seem to be found as the evolutionary distance from this group increases. However, a significant number of outliers to this apparent general trend in terms of the values of the α* parameter are described.