Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, AZ 85721, USA.
Philos Trans R Soc Lond B Biol Sci. 2010 Apr 12;365(1543):1111-26. doi: 10.1098/rstb.2009.0285.
The link between adaptation and evolutionary change remains the most central and least understood evolutionary problem. Rapid evolution and diversification of avian beaks is a textbook example of such a link, yet the mechanisms that enable beak's precise adaptation and extensive adaptability are poorly understood. Often observed rapid evolutionary change in beaks is particularly puzzling in light of the neo-Darwinian model that necessitates coordinated changes in developmentally distinct precursors and correspondence between functional and genetic modularity, which should preclude evolutionary diversification. I show that during first 19 generations after colonization of a novel environment, house finches (Carpodacus mexicanus) express an array of distinct, but adaptively equivalent beak morphologies-a result of compensatory developmental interactions between beak length and width in accommodating microevolutionary change in beak depth. Directional selection was largely confined to the elimination of extremes formed by these developmental interactions, while long-term stabilizing selection along a single axis-beak depth-was mirrored in the structure of beak's additive genetic covariance. These results emphasize three principal points. First, additive genetic covariance structure may represent a historical record of the most recurrent developmental and functional interactions. Second, adaptive equivalence of beak configurations shields genetic and developmental variation in individual components from depletion by natural selection. Third, compensatory developmental interactions among beak components can generate rapid reorganization of beak morphology under novel conditions and thus greatly facilitate both the evolution of precise adaptation and extensive diversification, thereby linking adaptation and adaptability in this classic example of Darwinian evolution.
适应与进化变化之间的联系仍然是最核心和最不被理解的进化问题。鸟类喙的快速进化和多样化是这种联系的一个典型例子，然而，使喙能够精确适应和广泛适应的机制还知之甚少。通常观察到的喙的快速进化变化特别令人困惑，因为新达尔文主义模型需要在发育上不同的前体中协调变化，并且功能和遗传模块之间存在对应关系，这应该排除进化多样化。我表明，在殖民新环境后的前 19 代中，家雀（Carpodacus mexicanus）表达了一系列不同的，但适应性等效的喙形态——这是由于喙长度和宽度之间的补偿性发育相互作用，以适应喙深度的微进化变化。定向选择主要局限于消除这些发育相互作用形成的极端，而沿着单个轴——喙深度——的长期稳定选择反映在喙的加性遗传协方差的结构中。这些结果强调了三个主要观点。首先，加性遗传协方差结构可能代表最频繁发生的发育和功能相互作用的历史记录。其次，喙结构的适应性等效性保护了个体成分的遗传和发育变异不受自然选择的消耗。第三，喙成分之间的补偿性发育相互作用可以在新条件下快速重组喙形态，从而极大地促进精确适应和广泛多样化的进化，从而在这个经典的达尔文进化例子中联系适应和适应能力。
