An Experimental Test of the Condition Dependent Handicap Hypothesis Using Gryllus Pennsylvanicus

Abstract

Viability-based indicator models predict a positive correlation between ornamentation and longevity. Although ornament manipulations can reveal attraction and survival effects, they can inaccurately estimate the costs of ornamentation arising from correlated life-history constraints. Cotton circumvented this problem by applying a weight manipulation to stalk-eyed flies and asking whether males with bigger stalks lived longer. She found that ornamentation was positively correlated with longevity in weight manipulated males. Building upon Cotton's findings, I applied a weight and a diet manipulation to field crickets (Gryllus pennsylvanicus) and quantified their acoustic signalling and longevity. High effort signallers survived longer across all treatments. Further, males that signaled more attractively also survived longer when they experienced a weight manipulation and/or a poor diet. The weight manipulation did not directly affect longevity, because weight manipulated males dealt with the manipulation by reducing their signalling effort. Overall, my results provide support for viability-based indicator models. I would like to extend my gratitude to my supervisor Dr. Susan Bertram, for patiently and tirelessly assisting me with my research and writing. She has pushed me to become a better academic, a competent writer, and in general be less accident prone. Though, despite her best efforts I still find a way to injure myself weekly. Without her assistance I would not have been able to complete my thesis. I am also grateful to the staff and faculty of the biology department at Carleton University for their assistance during my Masters. I would like to personally thank Ed Bruggink and Andras Dobai for helping with greenhouse maintenance, equipment repairs, and the occasional cricket wrangling. I would also like to thank my committee members Drs. Jean-Guy Godin and Julie Morand-Ferron for assisting with experimental design and providing constant and invaluable feedback. I would like to extend a big thanks to all members of the Bertram lab who have made the past couple years fly by. I would like to thank Sean Neave, Daniel Gladish, Kathryn Hunt, and Michelle Leveillee for weighing hundreds of crickets and keeping them alive far longer than they wanted to. I would personally like to thank Dr. Genevieve Ferguson for allowing me to constantly pick brain about everything cricket related, for guiding me through the painful EARS analysis protocols (which I stumbled on at every step), and providing a much needed sounding board to all my problems. I would also like to thank my fellow Masters student Maria Doria for frequently reminding me about upcoming meetings, offering much needed snacks (usually mini eggs), and for always being up for a Stella at Mike's Place. Without Dr. Ferguson or Maria my past couple years would have been incredibly dull. iii The competition of my Masters thesis would not have been possible without the constant support of my friends and family. I would like to lovingly thank my fiancée, Emily Montpeti...

Signaling Vigor in Gryllodes Sigillatus: Relationship with Age and Foreign Body Ingestion

“…In general, males that signaled most often [high time spent calling (TSC)] lived longer. Males on lower quality diets died sooner and signaled less often (lower TSC), suggesting that males may be honestly signaling their condition (Tremblay, 2019). Further supporting Tremblay's (2019) findings that longer lived males signal more and are therefore in better condition, both Gryllus veletis and Gryllodes sigillatus males have been found to have a positive correlation between TSC and longevity (Bertram & Fitzsimmons, 2011;Houslay et al, 2015).…”

“…When females finish eating the spermatophylax, they remove the ampulla, completing sperm transfer, regardless of whether there is still sperm left in the ampulla or not. Females often favour males that spend more time signaling (i.e., signal with more vigour) so males in better condition that live longer would be more likely to secure a mate, indicating that vigorous calls may be a fitness advantage (Tremblay, 2019;Bertram et al, 2021). Mate attraction signaling is often correlated with body condition (e.g., body mass) and body size.…”

“…Further, to test the conditiondependent handicap hypothesis using Gryllus pennsylvanicus, Tremblay (2019) manipulated adult diet and glued a weight to the pronotum of a subset of the males to see whether males that signaled more vigorously were better able to withstand the diet or weight stress and survive longer. Males that signaled louder and with a higher chirp rate (more vigorously) survived longer even if they were faced with a challenging diet or weight compared to males that chirped softer or at a lower chirp rate (Tremblay, 2019). In general, males that signaled most often [high time spent calling (TSC)] lived longer.…”