Department of Ecology and Evolutionary Biology, Yale University, New Haven, CT 06511, USA.
J Evol Biol. 2010 Dec;23(12):2614-24. doi: 10.1111/j.1420-9101.2010.02130.x. Epub 2010 Oct 14.
Although negative frequency-dependent fitness is argued to allow the stable coexistence of two alternative reproductive types (such as resource defenders and reproductive parasites), no existing theory has considered a third strategy where resource defenders invest differentially in defence against reproductive parasites. Here, we present the results of a three-strategy game, where reproductive parasites interact with two resource defenders: 'Susceptibles' defend more resources but lose more reproductive success to parasites. 'Immunes' lose less to parasites, but immunity carries a reproductive cost. We show that the inclusion of a third strategy dramatically changes the evolutionary dynamics, such that for a wide range of parameter values, our model predicts the continuous sequential invasion of the three strategies instead of stable coexistence. Our results therefore limit the generality of the prediction that frequency-dependent fitness necessarily allows alternative reproductive tactics to coexist at equilibrium and may also explain the observed dynamics of some multiple-strategy systems.
虽然负频率依赖适合度被认为可以允许两种替代生殖类型（如资源守护者和生殖寄生虫）的稳定共存，但现有的理论还没有考虑到第三种策略，即资源守护者会对防御生殖寄生虫进行不同程度的投资。在这里，我们提出了一个三策略博弈的结果，其中生殖寄生虫与两种资源守护者相互作用：“易感者”保护更多资源，但因寄生虫而失去更多生殖成功。“免疫者”受寄生虫的影响较小，但免疫会带来生殖成本。我们表明，引入第三种策略会极大地改变进化动态，使得在广泛的参数值范围内，我们的模型预测三种策略会连续地依次入侵，而不是稳定共存。因此，我们的结果限制了频率依赖适合度必然允许替代生殖策略在平衡时共存的普遍性预测，也可能解释了一些多策略系统的观察到的动态。
