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 non-calling 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, 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 vs. behave as a satellite from one night to the next. We varied mortality, density, sex ratio, and female mating behavior, and recorded lifetime number 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个体时，可能会演化出替代性生殖策略（alternative reproductive tactics）。在田野蟋蟀中，依赖声学定向的寄生蝇会抬高雄性鸣唱的代价，这为该策略——卫星行为（satellite behavior）——创造了演化空间：不鸣唱的雄性可拦截被鸣唱雄性吸引而来的雌性。尽管面临寄生蝇探测风险的蟋蟀鸣唱者-卫星系统（caller-satellite system）看似拥有截然不同的行为表型，但雄性作为鸣唱者或卫星个体的行为倾向实则为连续可变性状，且单个个体可在不同时段采取不同策略。本研究采用基于个体的模拟（individual-based simulation）方法，将鸣唱者-卫星-寄生蝇系统建模为田野蟋蟀雌雄个体间的空间显式互作模型。雄性个体的鸣唱倾向与卫星行为倾向会在不同夜晚间发生变化。我们调控了死亡率、种群密度、性比及雌性交配行为等参数，并以寄生风险梯度为自变量，记录了雄性鸣唱概率（相较于充当卫星个体）与其终身交配次数之间的对应关系。随着寄生率升高，最优策略往往会从纯粹的鸣唱者（每晚鸣唱）骤然切换为纯粹的卫星个体（永不鸣唱）。但在本底死亡率较高、种群密度降低、雌性偏倚性比升高以及雌性择偶偏好增强的条件下，即便寄生风险较高，混合策略仍会占据主导地位。在自然种群中，仅靠高寄生压力，不太可能使纯粹的卫星行为策略在种群中固定下来。