Foraging behavior and extended phenotype independently affect foraging success in spiders

• Published in: Behavioral ecology 2020-10, Vol.31 (5), p.1242-1249
• Main Authors: DiRienzo, N, Schraft, H A, Montiglio, P O, Bradley, C T, Dornhaus, A
• Format: Article
• Language: English
• ISSN: 1045-2249; 1465-7279
• DOI: 10.1093/beheco/araa080

Abstract Multiple phenotypic traits often interact with each other to determine an individual’s fitness. Behavioral and extended phenotypic traits, such as architectural constructions, can contribute to fitness in an integrated way. The goal of this study was to understand how the interaction between behavioral and extended phenotypic traits can affect foraging success. We tested this question using black widow spiders, where spiders that are aggressive in a foraging context tend to build more gumfooted silk lines that aid in prey capture, while non-aggressive spiders build webs with fewer gumfooted lines. We repeatedly assessed behavior and web structure to quantify relationships between these traits, and then allowed spiders to forage for live prey on their own web or the web of a conspecific that differed in structure. Thus, we assessed how varying combinations of behavior and web structure affect foraging success, and if correlational selection might act on them. We confirmed that aggressiveness and number of gumfooted lines are positively correlated and found that capture success increased with both aggressiveness and the number of gumfooted lines. Yet, we did not find any evidence for correlational selection: aggressiveness and number of gumfooted lines appeared to affect foraging success independently of each other. These findings highlight that a correlation between traits that contribute towards the same ecological function does not necessarily imply correlational selection. Taking advantage of the experimental convenience afforded by extended phenotypic traits can provide insight into the functional consequences of phenotypic variation within and between individuals. Animal architectural constructions such as spider webs provide important fitness benefits. Yet, how effective these constructions are depends on how they interact with the behavior of the animal using them. In black widows, aggressive spiders tend to build a large number of foraging silk lines, and this trait combination is especially successful at catching prey. However, the two traits appear to have evolved independently and became linked for a reason other than prey capture.