The role of genetic variation in adaptation and population persistence in a changing environment
The role of genetic variation in adaptation and population persistence in a changing environment
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DOI：
10.1111/j.1558-5646.1996.tb04504.x
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发表时间：
1996-02-01
期刊：
影响因子：
3.3
通讯作者：
Shannon, S
中科院分区：
文献类型：
--
作者：
Lande, R;Shannon, S
最近的保护工作主要集中在小种群的遗传事件上，例如濒临灭绝的受威胁或濒危物种。然而，世界范围内人口减少和灭绝的压倒性原因是栖息地的破坏和外来物种的引入，寄生虫，捕食者和竞争对手。恢复和维护健康的栖息地和生态系统应该是一门成熟的保护生物学科学所非常关注的。长期保护生物多样性不仅需要了解小种群的人口统计学和遗传学，而且需要了解丰富物种的生态学和进化。在这里，我们表明，在恒定或不可预测的环境中，遗传方差降低人口的平均适应度，增加灭绝的风险。在可预测的，高度可变的环境中，遗传变异可能是必要的适应性进化和种群持久性。生态学家和进化生物学家感兴趣的大多数性状是受许多基因和环境因素影响的数量性状。用数量遗传学方法也可以分析分生和阈生性状（Wright 1968，第15章;法尔科纳1989）。对化石记录的研究证明，数量性状在适应性进化中具有重要意义（Simpson 1953;卡罗尔1988）。虽然适应性进化可以通过大影响的突变发生，但区分一个物种内不同种群和密切相关物种的数量性状的差异通常具有多基因基础（Wright 1968，ch. 15; Lande 1981; Coyne 1985）。数量性状遗传变异对种群持久性和适应性的重要性目前还没有全面的评价。在短期内，遗传变异性往往不如种群持续性的其他决定因素那么重要（Lande 1988），但从长期来看，它可以在允许种群持续和适应不断变化的环境方面发挥决定性作用。对单个数量性状选择的平均表型进化速率与性状的加性遗传方差和定向选择强度的乘积成正比（Lande 1976;法尔科纳1989）。然而，遗传变异被认为不是长期进化的限速因素。相反，进化和适应性辐射的长期速率受到生态机会的限制（Simpson 1953，pp. 77-80; Wright 1968，p. 520）。短期观点和长期观点并不矛盾，这可以从一个常见情况的模型中看出，在这个模型中，自然选择作用于一个数量性状（而不是适合度本身），有利于一个中间型。在这种情况下，性状的进化速率不仅受到性状加性遗传方差大小的限制，而且还受到环境变化时最佳表型变化速率的限制。一个中间最优模型，如下面的模型也表明，遗传变异可能是有益的或有害的，这取决于环境变化的模式。
Much recent conservation effort has focused on genetic events in small populations, such as threatened or endangered species on the verge of extinction. However, the overwhelming causes of population reductions and extinctions worldwide are habitat destruction and the introduction of exotic species of parasites, predators, and competitors. The restoration and maintenance of healthy habitats and ecosystems should be of great concern to a mature science of conservation biology. The long-term preservation of biodiversity requires understanding not only the demography and genetics of small populations but also the ecology and evolution of abundant species. Here we show that in constant or unpredictable environments genetic variance reduces population mean fitness and increases the risk of extinction. In predictable, highly variable environments genetic variance may be essential for adaptive evolution and population persistence. Most of the characters of interest to ecologists and evolutionary biologists are quantitative characters influenced by many genes and environmental factors. Meristic and thresh-old characters also are amenable to analysis using quanti-tative genetic methods (Wright 1968, ch. 15; Falconer 1989). As examination of the fossil record attests, quantitative characters are of great importance in adaptive evolution (Simpson 1953; Carroll 1988). Although adaptive evolution can occur by mutations of large effect, the divergence in the quantitative traits that distinguish both different populations within a species and closely related species usually has a polygenic basis (Wright 1968, ch. 15; Lande 1981; Coyne 1985). No comprehensive evaluation of the importance of genetic variability in quantitative traits to population persistence and adaptation exists currently. In the short-term, genetic vari-ability is often less critical than other determinants of population persistence (Lande 1988), but in the long-term, it can play the decisive role in allowing a population to persist and adapt in a changing environment. The rate of evolution in the mean phenotype in response to selection on a single quantitative character is proportional to the product of the additive genetic variance in the character and the intensity of direc-tional selection (Lande 1976; Falconer 1989). However, genetic variability is thought not to be the rate-limiting factor in long-term evolution. Instead, long-term rates of evolution and adaptive radiation are constrained by ecological opportunity (Simpson 1953, pp. 77-80; Wright 1968, p. 520). That the short-and the long-term views are not inconsistent can be seen in a model of the common situation in which natural selection acting on a quantitative character (other than fitness itself) favors an intermediate phenotype. In this situation the rate of evolution in the character is limited not only by the magnitude of the additive genetic variance in the character but also by the rate of change in the optimum phenotype as the environment changes. An intermediate-optimum model such as that which follows also demonstrates that genetic variability may be either beneficial or detrimental, depending on the pattern of environmental change.