Optimization of Resource Allocation Can Explain the Temporal Dynamics and Honesty of Sexual Signals

Abstract

In species in which males are free to dynamically alter their allocation to sexual signaling over the breeding season, the optimal investment in signaling should depend on both a male's state and the level of competition he faces at any given time. We developed a dynamic optimization model within a game-theoretical framework to explore the resulting signaling dynamics at both individual and population levels and tested two key model predictions with empirical data on three-spined stickleback (Gasterosteus aculeatus) males subjected to dietary manipulation (carotenoid availability): (1) fish in better nutritional condition should be able to maintain their signal for longer over the breeding season, resulting in an increasingly positive correlation between nutritional status and signal (i.e., increasing signal honesty), and (2) female preference for more ornamented males should thus increase over the breeding season. Both predictions were supported by the experimental data. Our model shows how such patterns can emerge from the optimization of resource allocation to signaling in a competitive situation. The key determinants of the honesty and dynamics of sexual signaling are the condition dependency of male survival, the initial frequency distribution of nutritional condition in the male population, and the cost of signaling.

Food restriction promotes signaling effort in response to social challenge in a short-lived electric fish

“…6B). This finding was unexpected, since in most species males trade off between time spent signaling and time spent foraging (Abrahams, 1993;Fernald and Hirata, 1977;Griffiths, 1996;Lindstrom et al, 2009;Nolan, 1978). For many taxa, male sexual displays are incompatible with feeding behavior and in others, spatial separation between preferred feeding and signaling grounds prevents simultaneous foraging and reproductive signaling.…”

Dynamic resource allocation between pre- and postcopulatory episodes of sexual selection determines competitive fertilization success

“…The intensity of carotenoid-based breeding signals should provide females with honest information about male foraging ability [63] and the amount of carotenoids available for immunostimulation [24] or antioxidant functions [64]. Our results indicate that this may only account for well-fed males while under food limitation some dishonesty may occur [60]. This could lead to evolutionary constraints on the direction of pre-and postcopulatory sexually selected traits, which may have considerable consequences even on population level.…”

Social and Environmental Regulation of Signal Plasticity and Signal Reliability in the Electric Fish Brachyhypopomus gauderio

“…6b). This finding was unexpected, since in most species males trade off between time spent signaling and time spent foraging (Fernald and Hirata, 1977;Nolan Jr, 1978;Abrahams, 1993;Griffiths, 1996;Lindstrom et al, 2009). For many taxa, male sexual displays are incompatible with feeding behavior and in others, spatial separation between preferred feeding and signaling grounds prevents simultaneous foraging and reproductive signaling.…”

“…Males also tend to signal more intensively when they are close to their last reproductive opportunity Proulx et al 2002;Hall et al 2009). Older males may benefit by reallocating energy from self-maintenance and survival to signalling if their survival probability has been reduced by age or time of season (Kokko 1997;Proulx et al 2002;Lindstrom et al 2009). Still, theory is unclear what effect signal enhancement should have on the reliability of the signal (Johnstone et al 2009).…”

“…However, when the costs of signalling outweigh its benefits, signal reliability can also be reduced by 'cheating down' wherein high-quality individuals reduce their signalling output and reallocate that energy to self-maintenance as an investment in future reproduction (Lindstrom et al 2009) or predation avoidance (Endler 1987). An expensive signal that can be attenuated to reduce costs under low competition is effectively a 'disposable handicap'.…”