The Pace of Life Syndrome describes a spectrum of strategies where individuals may develop to sexual maturation rapidly at the expense of self-investment, while others may spend more time immature but invest more heavily in long-term survival. Those that undergo rapid maturation are expected to be under higher metabolic demand due to the high cost of development, resulting in smaller size as adults and potentially more aggressive behaviors to maximize foraging. Comprehensive research into this PoLS hypothesis has been lacking. In laboratory settings, resources are often unlimited for animals, muting tradeoffs. Also, studies often ignore sex, which can be problematic due to differing selection pressures. Finally, researchers often focus on single traits find correlations instead of modelling a wider range to uncover relationships. In this study, we tested the PoLS hypothesis by investigating the relationship between behavior, immunocompetence, size, and body condition in the wolf spider, Tigrosa Helluo, freshly captured across the active season. We aimed to explore the traits that co-occur in these spiders, with adult body size as a proxy for growth, and thus, the pace of life. We hoped to identify trade-offs between or among these traits to allow for further exploration.
Results/Conclusions
We found suites of traits that tended to co-occur in these spiders, and trade-offs in these suites using principal component analysis. In females, PC1 (explaining 20.7% of variation) found that fatter individuals had higher amounts of protein in hemolymph, higher lytic activities, and lower encapsulation scores. PC2 (18.7%) found that smaller females had higher encapsulation rates, traveled further in a novel environment, and appeared darker in color. In males, PC1 (22.1%) found that larger individuals displayed higher rates of lytic activity, traveled less distance, and were lighter in coloration. PC2 (18.3%) found that fatter males possessed higher hemolymph protein, lower encapsulation scores, and were more asymmetrical. We also found that these suites differed not only between sexes, but also by month of collection using redundancy analysis. Our results support the PoLS hypothesis as adults that were larger in size, and thus thought to have taken longer to grow between molts and mature, appeared to invest more in immunity while also displaying more timid behavior. These results also suggest that an individual’s pace of life is playing a role in displayed behavior, and that researchers need to examine sexes independently and account for seasonal variation when investigating the PoLS hypothesis.