The web architecture of Latrodectus hesperus black widow spiders (Araneae: Theridiidae) shows genetic variation and sexual dimorphism, but no plasticity according to the experience of the site of prey capture

Abstract

Animals create extended phenotypes to adaptively modify and interact with their environment. Animals also respond to changes in the environment by adaptively modifying their behavior or body in a process called phenotypic plasticity. Extended phenotypes might be especially prone to plasticity as they are often the products of behavior. We tested for plasticity in black widow web architecture in response to long-term variation in prey capture location. We also estimated genetic variation, genetic variation in plasticity, and sexual dimorphism in web architecture. We found no overall plasticity in response to variation in prey capture location. However, web architecture differed between spider families, and spider families differed in their plastic response. Web architecture also differed between male and female spiders, and male and female spiders differed in their plastic response. We conclude that black widows do not adjust web architecture in response to long-term inputs from the external environment and that internal inputs are responsible for more of the variation in web architecture than external inputs. We suggest that in order to fully understand variation in extended phenotypes, it is important to investigate potential environmental and physiological or genetic sources of variation, and to examine these potential sources at different time scales. Animals can alter their extended phenotypes in response to short- or long-term variation in the external environment, or to internal sources of variation, such as genetic variation or sexual dimorphism. Studies asking how extended phenotypes vary at more than one time scale and that simultaneously test for variation due to different sources of variation are rare. Here, we ask how an extended phenotype varies in response to environmental variation at short and long time scales, whether the extended phenotype has a genetic component of variation, and whether the extended phenotype is sexually dimorphic. We found that the extended phenotype did not respond to long-term environmental variation but did differ in response to all tested internal inputs. These results suggest that variation in extended phenotypes should be considered at multiple time scales and across external and internal sources of variation.