Rodríguez-Ramilo S T, Morán P, Caballero A
Departamento de Bioquímica, Genética e Inmunología, Universidad de Vigo, 36310 Vigo, Spain.
Genetics. 2006 Feb;172(2):1043-54. doi: 10.1534/genetics.105.051003. Epub 2005 Nov 19.
Equalization of parental contributions is one of the most simple and widely recognized methods to maintain genetic diversity in conservation programs, as it halves the rate of increase in inbreeding and genetic drift. It has, however, the negative side effect of implying a reduced intensity of natural selection so that deleterious genes are less efficiently removed from the population with possible negative consequences on the reproductive capacity of the individuals. Theoretical results suggest that the lower fitness resulting from equalization of family sizes relative to that for free contribution schemes is expected to be substantial only for relatively large population sizes and after many generations. We present a long-term experiment with Drosophila melanogaster, comparing the fitness performance of lines maintained with equalization of contributions (EC) and others maintained with no management (NM), allowing for free matings and contributions from parents. Two (five) replicates of size N = 100 (20) individuals of each type of line were maintained for 38 generations. As expected, EC lines retained higher gene diversity and allelic richness for four microsatellite markers and a higher heritability for sternopleural bristle number. Measures of life-history traits, such as egg-to-adult viability, mating success, and global fitness declined with generations, but no significant differences were observed between EC and NM lines. Our results, therefore, provide no evidence to suggest that equalization of family sizes entails a disadvantage on the reproductive capacity of conserved populations in comparison with no management procedures, even after long periods of captivity.
亲本贡献均等化是保护计划中维持遗传多样性的最简单且被广泛认可的方法之一，因为它能将近亲繁殖和遗传漂变的增加率减半。然而，它有一个负面影响，即意味着自然选择强度降低，从而使有害基因从种群中被清除的效率降低，可能对个体的繁殖能力产生负面后果。理论结果表明，相对于自由贡献方案，家庭规模均等化导致的较低适应性预计仅在相对较大的种群规模和多代之后才会显著。我们对黑腹果蝇进行了一项长期实验，比较了采用贡献均等化（EC）维持的品系和不进行管理（NM）、允许自由交配和亲本自由贡献的品系的适应性表现。每种品系大小为N = 100（20）的个体各有两个（五个）重复，维持38代。正如预期的那样，对于四个微卫星标记，EC品系保留了更高的基因多样性和等位基因丰富度，并且胸侧板刚毛数的遗传力更高。诸如卵到成虫的存活率、交配成功率和总体适应性等生活史特征的指标随世代下降，但在EC和NM品系之间未观察到显著差异。因此，我们的结果没有提供证据表明，与不进行管理程序相比，即使经过长时间的圈养，家庭规模均等化对保护种群的繁殖能力有不利影响。
