Gene pool conservation and computer analysis
Gene pool conservation and computer analysis
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基因库保护和计算机分析
DOI：
10.1111/j.1748-1090.1977.tb00870.x
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发表时间：
1977
影响因子：
--
通讯作者：
N. Flesness
中科院分区：
文献类型：
--
作者：
N. Flesness
过去十年在种群生物学方面的研究表明，自然种群的基因多样性比人们之前认为的要多得多。然而，在本世纪的大部分时间里，基因变异的重要性一直是显而易见的。它在两个层面上很重要--人口和个人。在种群内部，遗传变异是变化的基础。当环境发生变化时，人口必须以同样的速度变化，否则就会灭绝。它能适应的速度受到它包含多少相关基因变异的限制。如果没有，它就根本无法适应。那些从事植物研究的人更好地认识到了这一点的重要性：农业种子生产者以及保护组织发现，为了应对不断演变的疾病株，有必要保持遗传多样性的储备。还有第二种方式，遗传多样性可能对种群很重要。个体之间的遗传差异可能使他们能够利用略有不同的资源。在减少竞争的过程中，它们将允许更大的人口规模，并可能提高人口的稳定性。目前尚不清楚这一影响的程度。在个体水平上，遗传变异--或杂合性--与种群中的遗传变异相关，但并不完全相同。两者都随着近亲交配而衰退。在小而封闭的种群中，例如许多现有的动物园种群，一些近亲交配是不可避免的；在大多数方面，这种近亲交配被发现是个别有害的。跳蚤、苍蝇、老鼠、螨虫、老鼠、鸡、猪、牛、鹌鹑和人类都表现出近亲交配损害，通常被称为近亲交配抑郁。这表现为“活力”的普遍丧失，以及生存能力、生长速度、生育能力、繁殖力、哺乳能力和竞争能力的下降。在近亲交配的不同程度上都可以检测到损害，已发表的报告显示近亲交配系数为0。Z~=0.75(0.23是兄妹交配产生的近亲交配量)。一些动物园种群，例如Przewalski Eqtius przewalskii，在个别情况下近亲繁殖系数已经高达0.6或更高。近亲繁殖衰退可能包括生育力下降，近亲繁殖迅速的小种群可能会灭绝。通过兄弟姐妹交配产生近交系实验动物的尝试导致了大约95%的病例灭绝。较慢的近亲交配速度造成的损害要小得多，因为选择有机会抵消有害影响。在一种情况下，将近亲交配率降至最低可能并不可取。在目前旨在有意驯化某些野生物种的计划中，例如阿拉斯加的麝牛Ovihos nioschatus和苏联的Taurotresus oryx，对特定特征的刻意选择涉及到某种程度的近亲繁殖。斯拉提斯(1975)最近从这个角度讨论了动物园的近亲繁殖，并找到了推荐近亲繁殖的理由。然而，重要的是要认识到，只有在目标是改变相关动物的情况下，这些建议才是有效的，而不是如果它是为了保护现有的动物。此外，家畜的繁育者拥有一个庞大的种群，一旦出现近亲繁殖问题，他就可以从这些种群中进行杂交；对于那些与较不幸运的物种的最后残余物结婚的人来说，这样的选择是不可用的。
The work of the last ten years in population biology has shown that natural populations are much more genetically diverse than had previously been thought. The importance of genetic variation, however, has been clear for much of this century. It is important at two levels-the population and the individual. Within the population, genetic variation is the basis for change. When the environment changes, the population must change equally as fast, or become extinct. How rapidly it can adapt is limited by how much relevant genetic variation it contains. If it has none, it cannot adapt at all. The importance of this has been better appreciated by those who work with plants: agricultural seed producers, as well as conservation groups, have found it necessary to maintain genetically diverse stocks in order to deal with continually evolving strains of disease. There is a second way in which genetic diversity may be important to populations. Genetic differences between individuals may allow them to utilise slightly different resources. In thus reducing competition, they would allow a larger size of population and probably improve stability of numbers. The magnitude of this effect is still not known. On an individual level, genetic variation-or heterozygosity-is related but not identical to genetic variation in populations. Both decline with inbreeding. In small, closed populationssuch as many existing zoo populations-some inbreeding is inevitable; in most respects it has been found to be individually harmful. Fleas, flies, mice, mites, rats, chickens, pigs, cattle, quail and humans all show inbreeding damage, usually called inbreeding depression. This shows up as a general loss of ‘vigour’and reduced viability, growth rate, fertility, fecundity, lactation and competitive ability. Damage is detectable at various levels of inbreeding, published reports showing deterioration at inbreeding coefficients of 0. z~ to 0.75 (0.23 is the amount of inbreeding from a brother-sister mating). Some zoo populations, for example the Przewalski horse Eqtius przewalskii, have already attained an inbreeding coefficient in individual instances as high as 0.6 or more.Inbreeding depression can include lowered fertility, and small populations which are inbred rapidly can become extinct. Attempts to produce inbred lines of laboratory animals by brothersister matings result in about 95% of cases in extinction. A slower rate of inbreeding causes much less damage as selection has an opportunity to counteract the deleterious effects. There is one situation where to minimise the rate of inbreeding might not be desirable. In current programmes aimed at the intentional domestication of certain wild species, eg the musk-ox Ovihos nioschatus in Alaska and the eland Taurotragus oryx in the Soviet Union, the deliberate selection of particular traits involves some degree of inbreeding. Slatis (1975) has recently discussed inbreeding in zoos from this perspective and has found reasons for recommending it. Nevertheless it is important to realise that the recommendations hold only if the goal is to change the animal concerned, not if it is to preserve it as it exists today. Further, the breeder of domestic animals has at his command a large population from which he may outcross as soon as inbreeding problems arise; to those who husband the last remnants of a less fortunate species, such an option is not available.