Kieser J A, Groeneveld H T
Med Hypotheses. 1985 Jul;17(3):219-25. doi: 10.1016/0306-9877(85)90126-4.
A model for continuous and discontinuous evolutionary change is proposed that accommodates both punctuated equilibrium and phyletic gradualism. Natural selection operating on a gaussian distribution of phenotypes subjected to severe stress will result in a skewing of the normal distribution in the direction of the favoured phenotype. If a reproductive isolation threshold is imposed upon this model, rapid crossing of the threshold by large numbers of individuals within the skewed distribution will result in the sudden achievement of a critical descendant population mass. Mild directional selection however, will result in gentle shifts of the gaussian mean thus leading us to suggest that stasis and incipient speciatior are extremes of the same spectrum, defined by the rates of mean-shift in response to varying severities of selection pressure. Both punctuated and gradualistic evolution as accommodated in our model may further be described within Thom's cusp catastrophe theory.
提出了一个连续和不连续进化变化的模型，该模型兼顾了间断平衡和线系渐变论。在受到严重压力的表型高斯分布上起作用的自然选择，将导致正态分布朝着有利表型的方向倾斜。如果对该模型施加一个生殖隔离阈值，在倾斜分布内大量个体快速跨越该阈值将导致关键后代种群数量的突然达到。然而，温和的定向选择将导致高斯均值的缓慢变化，从而使我们认为停滞和初始物种形成是同一谱系的极端情况，由响应不同选择压力强度的均值变化率所定义。我们模型中包含的间断和渐变进化都可以在托姆的尖点突变理论中进一步描述。
