Small, isolated populations are constantly threatened by loss of genetic diversity due to drift. Such situations are found, for instance, in laboratory culturing. In guarding against diversity loss, monitoring of potential changes in population structure is paramount; this monitoring is most often achieved using microsatellite markers, which can be costly in terms of time and money when many loci are scored in large numbers of individuals. Here, we present a case study reducing the number of microsatellites to the minimum necessary to correctly detect the population structure of two Drosophila nigrosparsa populations. The number of loci was gradually reduced from 11 to 1, using the Allelic Richness (AR) and Private Allelic Richness (PAR) as criteria for locus removal. The effect of each reduction step was evaluated by the number of genetic clusters detectable from the data and by the allocation of individuals to the clusters; in the latter, excluding ambiguous individuals was tested to reduce the rate of incorrect assignments. We demonstrate that more than 95% of the individuals can still be correctly assigned when using eight loci and that the major population structure is still visible when using two highly polymorphic loci. The differences between sorting the loci by AR and PAR were negligible. The method presented here will most efficiently reduce genotyping costs when small sets of loci (“core sets”) for long-time use in large-scale population screenings are compiled.

偏僻的小种群不断受到因漂移造成的遗传多样性丧失的威胁。例如在实验室培养中发现了这种情况。为了防止多样性丧失，监测人口结构的潜在变化至关重要。这种监视通常是使用微卫星标记来实现的，当在大量个体中对许多基因座进行评分时，这在时间和金钱上可能是昂贵的。在这里，我们提供一个案例研究，将微卫星的数量减少到正确检测两个黑腹果蝇的种群结构所需的最小数量人口。使用等位基因丰富度（AR）和私人等位基因丰富度（PAR）作为去除基因座的标准，基因座的数量从11个逐渐减少到1个。通过从数据中检测到的遗传簇的数量以及个体对簇的分配来评估每个减少步骤的效果。在后者中，测试排除不明确的个体以减少错误分配的发生率。我们证明使用八个基因座时仍可以正确分配95％以上的个体，并且使用两个高度多态性基因座时仍可看到主要的种群结构。通过AR和PAR对基因座进行排序之间的差异可以忽略不计。