Focardi S, Tinelli A
Istituto Nazionale per la Fauna Selvatica, via Ca' Fornacetta 9, I-40064 Ozzano dell' Emilia, Italy.
Tenuta Presidenziale di Castelporziano, via Pontina 690, 00128 Roma, Italy.
Behav Processes. 1996 Jun;36(3):227-37. doi: 10.1016/0376-6357(95)00032-1.
The object of this paper is to verify whether in specific cases the variance of mating success among lekking males may be due exclusively to a random mechanism, as opposed to the adaptive mechanisms of mate choice which are usually postulated in the literature in the framework of sexual selection theory. In fact, some studies attempted to compare observed distributions of male mating success with a Poisson 'null' distribution based on the conjecture of random mating; the conjecture is usually rejected. In this paper we construct a plausible model (the 'null' hypothesis) for a strictly random non-adaptive pattern of social behaviour of lekking males and females and we perform several simulations for reasonable choices of parameter values. It should be observed that some of the simulations based on our random model lead to a distribution of male mating success which is Poisson-like. However, contrary to predictions, in several simulations a random process of mate choice lead to non-Poissonian distributions. Accordingly, the fact that, when performing a statistical test on several sets of field data, we find both cases which are in agreement with Poisson distribution, or a normal one, and cases which are not, does not allow us to reject the assumption of random male reproductive success. Thus it is legitimate to conjecture that in many cases the inter-individual variability of male mating success might indeed be determined by random processes. If this conjecture were to be confirmed by further studies, the actual significance of sexual selection in the evolution of lekking species should be reassessed, and a novel approach in the analysis of field data would be called for.
本文的目的是验证在特定情况下，求偶场中雄性交配成功率的差异是否可能完全归因于随机机制，而非文献中通常在性选择理论框架下假定的配偶选择适应性机制。事实上，一些研究试图将观察到的雄性交配成功率分布与基于随机交配猜想的泊松“零”分布进行比较；该猜想通常被拒绝。在本文中，我们为求偶场中雄性和雌性严格随机的非适应性社会行为模式构建了一个合理的模型（“零假设”），并针对合理的参数值选择进行了多次模拟。应该注意的是，基于我们的随机模型进行的一些模拟得出了类似泊松分布的雄性交配成功率分布。然而，与预测相反，在几次模拟中，随机的配偶选择过程导致了非泊松分布。因此，在对几组实地数据进行统计检验时，我们既发现了与泊松分布或正态分布一致的情况，也发现了不一致的情况，这一事实并不允许我们拒绝雄性繁殖成功率随机的假设。因此，可以合理推测，在许多情况下，雄性交配成功率的个体间差异可能确实由随机过程决定。如果这一推测能得到进一步研究的证实，那么在求偶物种进化中性选择的实际意义就需要重新评估，并且需要一种新的实地数据分析方法。
