Naturalis Biodiversity Centre, PO Box 9517, Leiden, 2300 RA, The Netherlands; Department of Bioinformatics and Genetics, Swedish Museum of Natural History, PO Box 50007, Stockholm, SE-104 05, Sweden; Department of Zoology, Stockholm University, Stockholm, SE-10691, Sweden.
Biol Rev Camb Philos Soc. 2014 Feb;89(1):199-214. doi: 10.1111/brv.12051. Epub 2013 Jul 19.
The debate over species concepts has produced a huge body of literature on how species can, may or should be delimited. By contrast, very few studies have documented how species taxa are delimited in practice. The aims of the present study were to (i) quantify the use of species criteria in taxonomy, (ii) discuss its implications for the debate over species concepts and (iii) assess recent claims about the impact of different species concepts on taxonomic stability and the 'nature' of species. The application of six species criteria was examined in taxonomic studies of birds published between 1950 and 2009. Three types of taxonomic studies were included: descriptions of new species (N = 329), proposals to change the taxonomic rank of species and subspecies (N = 808) and the taxonomic recommendations of the American Ornithologists' Union Committee on Classification and Nomenclature (N = 176). In all three datasets, diagnosability was the most frequently applied criterion, followed by reproductive isolation and degree of difference. This result is inconsistent with the popular notion that the Biological Species Concept is the dominant species concept in avian taxonomy. Since the 1950s, avian species-level taxonomy has become increasingly pluralistic and eclectic. This suggests that taxonomists consider different criteria as complementary rather than as rival approaches to species delimitation. Application of diagnosability more frequently led to the elevation of subspecies to species rank than application of reproductive isolation, although the difference was small. Hypotheses based on diagnosability and reproductive isolation were equally likely to be accepted in a mainstream checklist. These findings contradict recent claims that application of the Phylogenetic Species Concept causes instability and that broader application of the Biological Species Concept can stabilise taxonomy. The criteria diagnosability and monophyly, which are commonly associated with Phylogenetic Species Concepts, were used throughout the study period. Finally, no support was found for the idea that Phylogenetic Species Concepts have caused a change in the 'nature' of species taxa. This study demonstrates that there is a discrepancy between widely held perceptions of how species are delimited and the way species are actually delimited by taxonomists. Theoretically oriented debates over species concepts thus may benefit from empirical data on taxonomic practice.
物种概念的争论产生了大量关于物种如何、可能或应该被界定的文献。相比之下，很少有研究记录物种分类群在实践中是如何被界定的。本研究的目的是：(i) 量化分类学中物种标准的使用，(ii) 讨论其对物种概念争论的影响，(iii) 评估关于不同物种概念对分类稳定性和物种“本质”的影响的最新说法。检查了 1950 年至 2009 年期间发表的鸟类分类学研究中应用的六个物种标准。包括三种类型的分类学研究：新物种的描述（N=329）、物种和亚种分类地位变更的提议（N=808）和美国鸟类学家协会分类与命名委员会的分类学建议（N=176）。在所有三个数据集，可诊断性是最常应用的标准，其次是生殖隔离和差异程度。这一结果与流行的观点即生物物种概念是鸟类分类学中占主导地位的物种概念不一致。自 20 世纪 50 年代以来，鸟类种级分类学变得越来越多元化和折衷。这表明分类学家认为不同的标准是互补的，而不是竞争的物种界定方法。与生殖隔离相比，应用可诊断性更有可能导致亚种升为物种，尽管差异很小。基于可诊断性和生殖隔离的假设在主流清单中同样有可能被接受。这些发现与最近的说法相矛盾，即应用系统发育物种概念会导致不稳定，而更广泛地应用生物物种概念可以使分类学稳定。在整个研究期间，普遍与系统发育物种概念相关的标准可诊断性和单系性得到了应用。最后，没有证据支持这样的观点，即系统发育物种概念已经导致了物种分类群“本质”的变化。本研究表明，人们对物种如何界定的普遍看法与分类学家实际界定物种的方式之间存在差异。因此，关于物种概念的理论性争论可能会受益于关于分类学实践的实证数据。
