Data from: Alternative reproductive tactics arising from a continuous behavioral trait: callers vs. satellites in field crickets

Alternative reproductive tactics may arise when natural enemies use sexual signals to locate the signaler. In field crickets, elevated costs to male calling due to acoustically orienting parasitoid flies create opportunity for an alternative tactic, satellite behavior, where noncalling males intercept females attracted to callers. Although the caller-satellite system in crickets that risk detection by parasitoids resembles distinct behavioral phenotypes, a male’s propensity to behave as caller or satellite can be a continuously variable trait over several temporal scales, and an individual may pursue alternate tactics at different times. We modeled a caller-satellite-parasitoid system as a spatially explicit interaction among male and female crickets using individual-based simulation. Males varied in their propensity to call versus behave as a satellite from one night to the next. We varied mortality, density, sex ratio, and female mating behavior, and recorded lifetime number of mates as a function of a male’s probability of calling (vs. acting as a satellite) along a gradient in parasitism risk. Frequently, the optimal behavior switched abruptly from being pure caller (call every night) to pure satellite (never call) as parasitism rate increased. However, mixed strategies prevailed even with high parasitism risk under conditions of higher background mortality rate, decreasing density, increasing female-biased sex ratio, and increasing female choosiness. In natural populations, high parasitoid pressure alone would be unlikely to yield fixation of pure satellite behavior.当天敌借助性信号定位信号发送者时，往往会出现替代性繁殖策略（alternative reproductive tactics）。在田野蟋蟀（field crickets）中，依靠声学定向的寄生蝇会提升雄性鸣唱的代价，这为替代性策略——卫星行为（satellite behavior）——创造了条件：不鸣唱的雄性可拦截被鸣唱雄性吸引而来的雌性。尽管面临寄生蝇检测风险的蟋蟀鸣唱者-卫星系统呈现出鲜明的行为表型，但雄性作为鸣唱者或卫星个体的行为倾向，在多个时间尺度上均可表现为连续可变的性状，且单个个体可在不同时段切换繁殖策略。我们采用基于个体的模拟（individual-based simulation）方法，构建了鸣唱者-卫星-寄生蝇的空间显式交互模型，模拟雌雄蟋蟀间的互动。雄性个体每晚的鸣唱与卫星行为倾向存在个体差异。我们调整了死亡率、种群密度、性比（sex ratio）以及雌性交配行为等参数，并以寄生风险梯度下雄性的鸣唱概率（相较于采取卫星行为的概率）为自变量，记录其终生交配次数。通常而言，随着寄生率升高，最优繁殖策略会从纯鸣唱者（每晚鸣唱）骤然切换为纯卫星个体（永不鸣唱）。但在较高背景死亡率、种群密度降低、雌性偏向性比升高以及雌性择偶偏好（female choosiness）增强的条件下，即便寄生风险较高，混合繁殖策略仍占主导地位。在自然种群中，仅靠高寄生压力不太可能导致纯卫星行为的固定化。