Department of Botany, University of Wisconsin-Madison, 430 Lincoln Drive, Madison, WI 53706, USA.
Syst Biol. 2009 Feb;58(1):74-86. doi: 10.1093/sysbio/syp011. Epub 2009 May 19.
Because species names play an important role in scientific communication, it is more important that species be understood to be taxa than that they be equated with functional ecological or evolutionary entities. Although most biologists would agree that taxa are composed of organisms that share a unique common history, 2 major challenges remain in developing a species-as-taxa concept. First, grouping: in the face of genealogical discordance at all levels in the taxonomic hierarchy, how can we understand the nature of taxa? Second, ranking: what criteria should be used to designate certain taxa in a nested series as being species? The grouping problem can be solved by viewing taxa as exclusive groups of organisms- sets of organisms that form a clade for a plurality of the genome (more than any conflicting set). However, no single objective criterion of species rank can be proposed. Instead, the species rank should be assigned by practitioners based on the semisubjective application of a set of species-ranking criteria. Although these criteria can be designed to yield species taxa that approximately match the ecological, evolutionary, and morphological entities that taxonomists have traditionally associated with the species rank, such a correspondence cannot be enforced without undermining the assumption that species are taxa. The challenge and art of monography is to use genealogical and other kinds of data to assign all organisms to one and only one species-ranked taxon. Various implications of the species-as-ranked-taxa view are discussed, including the synchronic nature of taxa, fossil species, the treatment of hybrids, and species nomenclature. I conclude that, although challenges remain, adopting the view that species are ranked taxa will facilitate a much-needed revolution in taxonomy that will allow it to better serve the biodiversity informatic needs of the 21st century.
因为物种名称在科学交流中起着重要作用，所以理解物种是分类单元比将其等同于功能生态或进化实体更为重要。尽管大多数生物学家都同意分类单元是由具有独特共同历史的生物体组成的，但在发展物种作为分类单元的概念方面仍存在 2 大挑战。首先是分组：面对分类层次结构中所有级别的系统发育分歧，我们如何理解分类单元的本质？其次是排序：应该使用什么标准来将嵌套系列中的某些分类单元指定为物种？通过将分类单元视为生物体的排他性组——一组形成多个基因组（超过任何冲突组）的生物体的集合，可以解决分组问题。然而，不能提出物种等级的单一客观标准。相反，物种等级应由从业者根据一组物种等级标准的半主观应用来分配。尽管这些标准可以设计为产生与传统上与物种等级相关联的生态、进化和形态实体大致匹配的物种分类单元，但如果不破坏物种是分类单元的假设，就无法强制实施这种对应关系。专论的挑战和艺术是使用系统发育和其他类型的数据将所有生物体分配到一个且仅一个具有物种等级的分类单元中。讨论了物种作为等级分类单元观点的各种含义，包括分类单元的同步性质、化石物种、杂种的处理以及物种命名法。我得出结论，尽管仍然存在挑战，但采用物种是等级分类单元的观点将促进分类学急需的革命，使其能够更好地满足 21 世纪生物多样性信息学的需求。
