Kolbe Jason J, Glor Richard E, Schettino Lourdes Rodríguez, Lara Ada Chamizo, Larson Allan, Losos Jonathan B
Department of Biology, Campus Box 1137, Washington University, St. Louis, MO 63130, USA.
Conserv Biol. 2007 Dec;21(6):1612-25. doi: 10.1111/j.1523-1739.2007.00826.x.
Invasive species are classically thought to suffer from reduced within-population genetic variation compared to their native-range sources due to founder effects and population bottlenecks during introduction. Reduction in genetic variation in introduced species may limit population growth, increase the risk of extinction, and constrain adaptation, hindering the successful establishment and spread of an alien species. Results of recent empirical studies, however, show higher than expected genetic variation, rapid evolution, and multiple native-range sources in introduced populations, which challenge the classical scenario of invasive-species genetics. With mitochondrial DNA (mtDNA) sequence data, we examined the molecular genetics of 10 replicate introductions of 8 species of Anolis lizards. Eighty percent of introductions to Florida and the Dominican Republic were from multiple native-range source populations. MtDNA haplotypes restricted to different geographically distinct populations in the native range of a species commonly occurred as intrapopulation polymorphisms in introduced populations. Two-thirds of introduced populations had two or more sources, and admixture elevated genetic variation in half of the introduced populations above levels typical of native-range populations. The mean pairwise sequence divergence among haplotypes sampled within introduced populations was nearly twice that within native-range populations (2.6% vs. 1.4%). The dynamics of introductions from multiple sources and admixture explained the observed genetic contrasts between native and introduced Anolis populations better than the classical scenario for most introduced populations. Elevated genetic variation through admixture occurred regardless of the mode or circumstances of an introduction. Little insight into the number of sources or amount of genetic variation in introduced populations was gained by knowing the number of physical introductions, the size of a species' non-native range, or whether it was a deliberate or accidental introduction. We hypothesize that elevated genetic variation through admixture of multiple sources is more common in biological invasions than previously thought. We propose that introductions follow a sequential, two-step process involving a reduction in genetic variation due to founder effects and population bottlenecks followed by an increase in genetic variation if admixture of individuals from multiple native-range sources occurs.
传统观点认为，由于引入过程中的奠基者效应和种群瓶颈，入侵物种与它们在原生范围内的种群相比，其种群内部的遗传变异会减少。引入物种的遗传变异减少可能会限制种群增长、增加灭绝风险并限制适应性，从而阻碍外来物种的成功建立和扩散。然而，最近的实证研究结果显示，引入种群中的遗传变异高于预期、进化迅速且有多个原生范围来源，这对入侵物种遗传学的传统观点提出了挑战。我们利用线粒体DNA（mtDNA）序列数据，研究了8种安乐蜥属蜥蜴10次重复引入的分子遗传学。引入到佛罗里达州和多米尼加共和国的种群中，80%来自多个原生范围的源种群。在一个物种原生范围内局限于不同地理区域种群的mtDNA单倍型，在引入种群中通常以种群内多态性的形式出现。三分之二的引入种群有两个或更多来源，并且基因混合使一半引入种群的遗传变异高于原生范围种群的典型水平。引入种群中采样的单倍型之间的平均成对序列差异几乎是原生范围种群内的两倍（2.6%对1.4%）。对于大多数引入种群而言，来自多个来源的引入和基因混合动态比传统观点更能解释观察到的原生和引入安乐蜥种群之间的遗传差异。无论引入的方式或情况如何，通过基因混合都会增加遗传变异。通过了解物理引入的数量、物种非原生范围的大小，或者引入是有意还是无意的，对于引入种群的来源数量或遗传变异量几乎没有深入了解。我们推测，通过多个来源的基因混合而增加的遗传变异在生物入侵中比以前认为的更为常见。我们提出，引入遵循一个连续的两步过程，首先由于奠基者效应和种群瓶颈导致遗传变异减少，如果发生来自多个原生范围来源个体的基因混合，则随后遗传变异增加。
