Department of Bioagricultural Sciences and Pest Management, Colorado State University, Fort Collins, CO 80523-1177;
Department of Entomology, Michigan State University, East Lansing, MI 48824.
Proc Natl Acad Sci U S A. 2017 Dec 19;114(51):13501-13506. doi: 10.1073/pnas.1712934114. Epub 2017 Nov 28.
Colonization and expansion into novel landscapes determine the distribution and abundance of species in our rapidly changing ecosystems worldwide. Colonization events are crucibles for rapid evolution, but it is not known whether evolutionary changes arise mainly after successful colonization has occurred, or if evolution plays an immediate role, governing the growth and expansion speed of colonizing populations. There is evidence that spatial evolutionary processes can speed range expansion within a few generations because dispersal tendencies may evolve upwards at range edges. Additionally, rapid adaptation to a novel environment can increase population growth rates, which also promotes spread. However, the role of adaptive evolution and the relative contributions of spatial evolution and adaptation to expansion are unclear. Using a model system, red flour beetles (), we either allowed or constrained evolution of populations colonizing a novel environment and measured population growth and spread. At the end of the experiment we assessed the fitness and dispersal tendency of individuals originating either from the core or edge of evolving populations or from nonevolving populations in a common garden. Within six generations, evolving populations grew three times larger and spread 46% faster than populations in which evolution was constrained. Increased size and expansion speed were strongly driven by adaptation, whereas spatial evolutionary processes acting on edge subpopulations contributed less. This experimental evidence demonstrates that rapid evolution drives both population growth and expansion speed and is thus crucial to consider for managing biological invasions and successfully introducing or reintroducing species for management and conservation.
在全球范围内，生物的分布和丰度由其向新的生境的殖民和扩张决定。殖民事件是快速进化的熔炉，但目前尚不清楚进化变化是主要发生在成功殖民之后，还是进化立即发挥作用，控制着殖民种群的生长和扩张速度。有证据表明，空间进化过程可以在几代内加速范围扩张，因为在分布范围边缘，扩散趋势可能向上进化。此外，对新环境的快速适应可以提高种群增长率，从而促进扩散。然而，适应性进化的作用以及空间进化和适应对扩张的相对贡献尚不清楚。利用一个模型系统——红粉甲虫（Tribolium castaneum），我们要么允许种群在新环境中进化，要么限制其进化，并测量种群的生长和扩散。在实验结束时，我们评估了来自进化种群核心或边缘的个体与来自非进化种群的个体的适合度和扩散倾向，或者在一个共同的花园中。在六代内，进化种群的生长速度增加了两倍，扩散速度快了 46%。更大的种群规模和更快的扩张速度主要是由适应驱动的，而作用于边缘亚种群的空间进化过程的贡献较小。这一实验证据表明，快速进化既驱动了种群的生长，也驱动了种群的扩张速度，因此对于管理生物入侵以及成功引入或重新引入物种进行管理和保护至关重要。
