Grant Peter R, Grant B Rosemary
Department of Ecology and Evolutionary Biology, Princeton University, Washington Road, Princeton, NJ 08544-1003, USA. prgrantprinceton.edu.
Science. 2002 Apr 26;296(5568):707-11. doi: 10.1126/science.1070315.
Evolution can be predicted in the short term from a knowledge of selection and inheritance. However, in the long term evolution is unpredictable because environments, which determine the directions and magnitudes of selection coefficients, fluctuate unpredictably. These two features of evolution, the predictable and unpredictable, are demonstrated in a study of two populations of Darwin's finches on the Galápagos island of Daphne Major. From 1972 to 2001, Geospiza fortis (medium ground finch) and Geospiza scandens (cactus finch) changed several times in body size and two beak traits. Natural selection occurred frequently in both species and varied from unidirectional to oscillating, episodic to gradual. Hybridization occurred repeatedly though rarely, resulting in elevated phenotypic variances in G. scandens and a change in beak shape. The phenotypic states of both species at the end of the 30-year study could not have been predicted at the beginning. Continuous, long-term studies are needed to detect and interpret rare but important events and nonuniform evolutionary change.
从对选择和遗传的了解出发，短期内进化是可以预测的。然而，从长期来看，进化是不可预测的，因为决定选择系数方向和大小的环境会发生不可预测的波动。进化的这两个特征，即可预测和不可预测，在对加拉帕戈斯群岛达芙妮主岛上的两种达尔文雀种群的研究中得到了体现。从1972年到2001年，勇地雀（中型地雀）和仙人掌地雀在体型和两种喙部特征方面发生了多次变化。自然选择在这两个物种中频繁发生，且从单向到振荡、从偶发到渐进各不相同。杂交虽很少发生，但反复出现，导致仙人掌地雀的表型方差增加以及喙形发生变化。在这项为期30年的研究结束时，这两个物种的表型状态在一开始是无法预测的。需要进行持续的长期研究来检测和解释罕见但重要的事件以及非均匀的进化变化。
