Extended phenotypes are traits that exist outside the physical body of organisms. Despite their role in the lives of the organisms that express them and other organisms influenced by extended phenotypes, the consistency and covariance with morphological and behavioural traits of extended phenotypes has rarely been evaluated. We repeatedly measured an extended phenotype involved in prey acquisition (web structure) of wild orb-weaving spiders (Micrathena vigorsii), which re-build their webs daily. We related web structure to behaviours and spider body length. Web diameter and web density were repeatable among individuals, reaction to a predation threat was very marginally so, and response to a prey stimulus and web evenness were not repeatable. Larger spiders spun wider webs, had webs with increased thread spacing, and the spider possibly tended to react more slowly to a predation threat. When a spider built a relatively larger web it was also a relatively less dense and less even web. The repeatability of web construction and relationship with spider body size we found may be common features of intra-population variation in web structure in spiders. By estimating the consistency and covariances of extended phenotypes we can begin to evaluate what maintains their variation and how they might evolve.
Swanson and the staff of the Andes and Amazon Field School at Iyarina for making our stay as comfortable and enjoyable as possible. Comments from three anonymous reviewers improved the manuscript. We have no conflicts of interest. D.N.F. and J.N.P. designed the study. J.Y. acquired the permits. D.N.F. collected and analysed the data and drafted the manuscript. All authors contributed to revisions of the manuscript and approved the final version. The work was supported by a Canada 150 Research Chair award to J.N.P.
- extended phenotype
- web structure