Department of Physics, Boston University, Boston, MA, 02215, USA.
Departments of Physics and Integrative Biology, University of California, Berkeley, CA, 94720, USA.
Ecol Lett. 2019 Nov;22(11):1817-1827. doi: 10.1111/ele.13364. Epub 2019 Sep 8.
Theory predicts rapid genetic drift during invasions, yet many expanding populations maintain high genetic diversity. We find that genetic drift is dramatically suppressed when dispersal rates increase with the population density because many more migrants from the diverse, high-density regions arrive at the expansion edge. When density dependence is weak or negative, the effective population size of the front scales only logarithmically with the carrying capacity. The dependence, however, switches to a sublinear power law and then to a linear increase as the density dependence becomes strongly positive. We develop a unified framework revealing that the transitions between different regimes of diversity loss are controlled by a single, universal quantity: the ratio of the expansion velocity to the geometric mean of dispersal and growth rates at expansion edge. Our results suggest that positive density dependence could dramatically alter evolution in expanding populations even when its contribution to the expansion velocity is small.
理论预测入侵过程中会发生快速的遗传漂变，但许多扩张种群仍保持着高度的遗传多样性。我们发现，当扩散率随种群密度增加时，遗传漂变会被显著抑制，因为来自多样化、高密度地区的更多移民会到达扩张的前沿。当密度依赖性较弱或为负时，前沿的有效种群规模仅与承载能力呈对数比例缩放。然而，随着密度依赖性变得很强，这种依赖性会从亚线性幂律转变为线性增加。我们提出了一个统一的框架，揭示了不同多样性损失模式之间的转变是由一个单一的、普遍的数量控制的：扩张速度与扩张前沿的扩散和增长率的几何平均值之比。我们的研究结果表明，即使密度依赖性对扩张速度的贡献很小，它也可能会极大地改变扩张种群中的进化。
