Herron Matthew D, Rashidi Armin, Shelton Deborah E, Driscoll William W
Department of Ecology and Evolutionary Biology, University of Arizona, 1041 Lowell St, Tucson, 85721, AZ, U.S.A.
Biol Rev Camb Philos Soc. 2013 Nov;88(4):844-61. doi: 10.1111/brv.12031. Epub 2013 Mar 1.
Biology needs a concept of individuality in order to distinguish organisms from parts of organisms and from groups of organisms, to count individuals and compare traits across taxa, and to distinguish growth from reproduction. Most of the proposed criteria for individuality were designed for 'unitary' or 'paradigm' organisms: contiguous, functionally and physiologically integrated, obligately sexually reproducing multicellular organisms with a germ line sequestered early in development. However, the vast majority of the diversity of life on Earth does not conform to all of these criteria. We consider the issue of individuality in the 'minor' multicellular taxa, which collectively span a large portion of the eukaryotic tree of life, reviewing their general features and focusing on a model species for each group. When the criteria designed for unitary organisms are applied to other groups, they often give conflicting answers or no answer at all to the question of whether or not a given unit is an individual. Complex life cycles, intimate bacterial symbioses, aggregative development, and strange genetic features complicate the picture. The great age of some of the groups considered shows that 'intermediate' forms, those with some but not all of the traits traditionally associated with individuality, cannot reasonably be considered ephemeral or assumed transitional. We discuss a handful of recent attempts to reconcile the many proposed criteria for individuality and to provide criteria that can be applied across all the domains of life. Finally, we argue that individuality should be defined without reference to any particular taxon and that understanding the emergence of new kinds of individuals requires recognizing individuality as a matter of degree.
生物学需要一个个体性的概念，以便将生物体与生物体的部分以及生物体群体区分开来，对个体进行计数并比较不同分类群的特征，以及区分生长和繁殖。大多数提出的个体性标准是为“单一”或“范式”生物体设计的：连续的、功能和生理上整合的、专性有性繁殖的多细胞生物体，其生殖细胞系在发育早期就被隔离。然而，地球上绝大多数生命的多样性并不符合所有这些标准。我们考虑“小型”多细胞分类群中的个体性问题，这些分类群共同涵盖了真核生物生命之树的很大一部分，回顾它们的一般特征，并专注于每个类群的一个模式物种。当为单一生物体设计的标准应用于其他类群时，它们对于给定单元是否为个体的问题往往给出相互矛盾的答案或根本没有答案。复杂的生命周期、紧密的细菌共生关系、聚集发育和奇特的遗传特征使情况变得复杂。所考虑的一些类群的悠久历史表明，“中间”形式，即具有一些但并非所有传统上与个体性相关特征的形式，不能合理地被视为短暂的或被假定为过渡性的。我们讨论了最近一些调和众多提出的个体性标准并提供可应用于所有生命领域的标准的尝试。最后，我们认为个体性的定义不应参考任何特定的分类群，并且理解新个体类型的出现需要认识到个体性是一个程度问题。
