Persistence of alternative reproductive tactics: a test of game-theoretic predictions

Abstract

In many species, males produce signals to attract females. However, in some species and populations, only some males produce these signals, with other males competing for and intercepting reproductive opportunities. In these systems, at least three tactics are expected: Always Signal, signal only when others are not (Assess) and Never Signal. The expected representation of these tactics within a population is frequently unknown in part because the costs of signalling (C) and the fitness value of a single reproductive bout (V) are difficult to quantify. Using a game-theoretic model, we predicted that the Always Signal strategy should only be present in a population if the fitness value of calling is greater than twice the cost (2C < V). We found that males that Always Signal are apparently absent in decorated crickets, Gryllodes sigillatus, at least in our sampling of a laboratory-housed population. Moreover, males were not strict assessors and instead signalled infrequently (30% of the time) when signalling by others was constant. Males also exhibited substantial among-individual variation in the propensity to call when other males were not signalling (τ = 0.3). Our results indicate a high relative cost of signalling (2C > V). The presence of among-individual variation in propensity to call is also suggestive of underlying genetic variation and a mixed evolutionarily stable strategy. More generally, the apparent high cost of signalling and the presence of variation in calling propensity suggest that reduced-cost strategies should spread quickly in populations.