Templeton Alan R
Department of Biology, Washington University, St. Louis, Missouri 63130-4899, USA.
Bioessays. 2008 May;30(5):470-9. doi: 10.1002/bies.20745.
A founder event occurs when a new population is established from a small number of individuals drawn from a large ancestral population. Mayr proposed that genetic drift in an isolated founder population could alter the selective forces in an epistatic system, an observation supported by recent studies. Carson argued that a period of relaxed selection could occur when a founder population is in an open ecological niche, allowing rapid population growth after the founder event. Selectable genetic variation can actually increase during this founder-flush phase due to recombination, enhanced survival of advantageous mutations, and the conversion of non-additive genetic variance into additive variance in an epistatic system, another empirically confirmed prediction. Templeton combined the theories of Mayr and Carson with population genetic models to predict the conditions under which founder events can contribute to speciation, and these predictions are strongly confirmed by the empirical literature. Much of the criticism of founder speciation is based upon equating founder speciation to an adaptive peak shift opposed by selection. However, Mayr, Carson and Templeton all modeled a positive interaction of selection and drift, and Templeton showed that founder speciation is incompatible with peak-shift conditions. Although rare, founder speciation can have a disproportionate importance in adaptive innovation and radiation, and examples are given to show that "rare" does not mean "unimportant" in evolution. Founder speciation also interacts with other speciation mechanisms such that a speciation event is not a one-dimensional process due to either selection alone or drift alone.
当一个新种群由从一个大的祖先种群中抽取的少数个体建立起来时，就会发生奠基者事件。迈尔提出，在一个孤立的奠基者种群中，基因漂变可能会改变上位系统中的选择力，这一观点得到了近期研究的支持。卡森认为，当奠基者种群处于开放的生态位时，可能会出现一段选择放松的时期，这使得在奠基者事件之后种群能够快速增长。在这个奠基者 - 快速增长阶段，由于重组、有利突变的存活率提高以及上位系统中非加性遗传方差向加性方差的转化，可选择的遗传变异实际上会增加，这是另一个得到实证证实的预测。坦普尔顿将迈尔和卡森的理论与种群遗传模型相结合，以预测奠基者事件能够促成物种形成的条件，这些预测得到了实证文献的有力证实。对奠基者物种形成的许多批评是基于将奠基者物种形成等同于由选择所反对的适应性峰值转移。然而，迈尔、卡森和坦普尔顿都构建了选择与漂变的正向相互作用模型，并且坦普尔顿表明奠基者物种形成与峰值转移条件不相符。尽管罕见，但奠基者物种形成在适应性创新和辐射中可能具有不成比例的重要性，文中给出了一些例子来说明在进化中“罕见”并不意味着“不重要”。奠基者物种形成还与其他物种形成机制相互作用，因此物种形成事件并非仅由选择或仅由漂变导致的一维过程。
