Hickerson Michael J, Meyer Christopher P, Moritz Craig
Museum of Vertebrate Zoology, University of California, Berkeley, CA 94720-3160, USA.
Syst Biol. 2006 Oct;55(5):729-39. doi: 10.1080/10635150600969898.
With increasing force, genetic divergence of mitochondrial DNA (mtDNA) is being argued as the primary tool for discovery of animal species. Two thresholds of single-gene divergence have been proposed: reciprocal monophyly, and 10 times greater genetic divergence between than within species (the "10x rule"). To explore quantitatively the utility of each approach, we couple neutral coalescent theory and the classical Bateson-Dobzhansky-Muller (BDM) model of speciation. The joint stochastic dynamics of these two processes demonstrate that both thresholds fail to "discover" many reproductively isolated lineages under a single incompatibility BDM model, especially when BDM loci have been subject to divergent selection. Only when populations have been isolated for > 4 million generations did these thresholds achieve error rates of < 10% under our model that incorporates variable population sizes. The high error rate evident in simulations is corroborated with six empirical data sets. These properties suggest that single-gene, high-throughput approaches to discovering new animal species will bias large-scale biodiversity surveys, particularly toward missing reproductively isolated lineages that have emerged by divergent selection or other mechanisms that accelerate reproductive isolation. Because single-gene thresholds for species discovery can result in substantial error at recent divergence times, they will misrepresent the correspondence between recently isolated populations and reproductively isolated lineages (= species).
随着研究力度的不断加大，线粒体DNA（mtDNA）的遗传差异被视为发现动物物种的主要工具。目前已提出了单基因差异的两个阈值：相互单系性，以及物种间的遗传差异比物种内的遗传差异大10倍（“10倍规则”）。为了定量探索每种方法的实用性，我们将中性合并理论与经典的贝茨森-多布赞斯基-穆勒（BDM）物种形成模型相结合。这两个过程的联合随机动力学表明，在单一不相容BDM模型下，这两个阈值都无法“发现”许多生殖隔离的谱系，尤其是当BDM基因座受到趋异选择时。只有当种群隔离超过400万代时，在我们纳入可变种群大小的模型下，这些阈值才能实现低于10%的错误率。模拟中明显的高错误率在六个实证数据集中得到了证实。这些特性表明，用于发现新动物物种的单基因、高通量方法将使大规模生物多样性调查产生偏差，特别是会遗漏通过趋异选择或其他加速生殖隔离的机制而出现的生殖隔离谱系。由于用于物种发现的单基因阈值在最近的分化时间可能会导致大量误差，它们将错误地反映最近隔离的种群与生殖隔离谱系（=物种）之间的对应关系。
