Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, Ontario, Canada.
Department of Biological Sciences, University of Toronto Scarborough, Scarborough, Ontario, Canada.
Mol Ecol. 2023 Jul;32(13):3403-3418. doi: 10.1111/mec.16964. Epub 2023 Apr 29.
Predicting how quickly populations expand their range and whether they will retain genetic diversity when they are introduced to new regions or track environmental conditions suited to their survival is an important applied and theoretical challenge. The literature suggests that long-distance dispersal, landscape heterogeneity and the evolution of dispersal influence populations' expansion rates and genetic diversity. We used individual-based spatially explicit simulations to examine these relationships for Tench (Tinca tinca), an invasive fish expanding its geographical range in eastern North America since the 1990s. Simulated populations varied greatly in expansion rates (1.1-28.6 patches year ) and genetic diversity metrics, including changes in observed heterozygosity (-19 to +0.8%) and effective number of alleles (-0.32 to -0.01). Populations with greater dispersal distances expanded faster than those with smaller dispersal distances but exhibited considerable variation in expansion rate among local populations, implying less predictable expansions. However, they tended to retain genetic diversity as they expanded, suggesting more predictable evolutionary trajectories. In contrast, populations with smaller dispersal distances spread predictably more slowly but exhibited more variability among local populations in genetic diversity losses. Consistent with empirical data, populations spreading in a longer, narrower dispersal corridor lost more neutral genetic variation to the stochastic fixation of alleles. Given the unprecedented pace of anthropogenic environmental change and the increasing need to manage range-expanding populations, our results have conservation ramifications as they imply that the evolutionary trajectories of populations characterised by shorter dispersal distances spreading in narrower landscapes are more variable and, therefore, less predictable.
预测种群扩张速度以及在引入新区域或追踪适应其生存的环境条件时是否会保留遗传多样性，是一个重要的应用和理论挑战。文献表明，长距离扩散、景观异质性和扩散的演化会影响种群的扩张速度和遗传多样性。我们使用基于个体的空间显式模拟来研究这些关系，研究对象是自 20 世纪 90 年代以来在北美东部地理范围不断扩大的入侵鱼类——丁鱥（Tinca tinca）。模拟种群在扩张速度（1.1-28.6 个斑块/年）和遗传多样性指标方面存在很大差异，包括观察到的杂合度变化（-19 至+0.8%）和有效等位基因数变化（-0.32 至-0.01）。扩散距离较大的种群比扩散距离较小的种群扩张速度更快，但局部种群的扩张速度存在很大差异，这意味着扩张的可预测性较低。然而，它们在扩张过程中往往会保留遗传多样性，这表明进化轨迹的可预测性更高。相比之下，扩散距离较小的种群扩张速度可预测性较慢，但局部种群的遗传多样性损失存在更大的变异性。与实证数据一致的是，在较长、较窄的扩散走廊中扩散的种群会因等位基因的随机固定而失去更多的中性遗传变异。考虑到人类引起的环境变化的空前速度以及管理范围不断扩大的种群的日益增长的需求，我们的研究结果具有保护意义，因为它们意味着具有较短扩散距离和在较窄景观中扩散的种群的进化轨迹具有更大的变异性，因此更难以预测。
