Lloyd E A, Gould S J
Department of Philosophy, University of California, Berkeley, CA 94720, USA.
Proc Natl Acad Sci U S A. 1993 Jan 15;90(2):595-9. doi: 10.1073/pnas.90.2.595.
Most analyses of species selection require emergent, as opposed to aggregate, characters at the species level. This "emergent character" approach tends to focus on the search for adaptations at the species level. Such an approach seems to banish the most potent evolutionary property of populations--variability itself--from arguments about species selection (for variation is an aggregate character). We wish, instead, to extend the legitimate domain of species selection to aggregate characters. This extension of selection theory to the species level will concentrate, instead, on the relation between fitness and the species character, whether aggregate or emergent. Examination of the role of genetic variability in the long-term evolution of clades illustrates the cogency of broadening the definition of species selection to include aggregate characters. We reinterpret, in this light, a classic case presented in support of species selection. As originally presented, the species selection explanation of volutid neogastropod evolution was vulnerable to a counterinterpretation at the organism level. Once this case is recast within a definition of species selection that reflects the essential structure and broad applicability of hierarchical selection models, the organism-level reinterpretation of variability loses its force. We conclude that species selection on variability is a major force of macroevolution.
大多数物种选择分析需要物种层面的突现性状，而非聚合性状。这种“突现性状”方法往往侧重于在物种层面寻找适应性。这种方法似乎将种群最强大的进化特性——变异性本身——排除在关于物种选择的争论之外（因为变异是一种聚合性状）。相反，我们希望将物种选择的合理范围扩展到聚合性状。将选择理论扩展到物种层面，将转而关注适合度与物种性状之间的关系，无论该性状是聚合的还是突现的。对遗传变异性在类群长期进化中的作用的考察，说明了将物种选择的定义扩大到包括聚合性状的合理性。据此，我们重新解读了一个支持物种选择的经典案例。最初提出时，腹足纲新腹足类动物进化的物种选择解释容易在个体层面遭到反驳。一旦这个案例在反映层次选择模型基本结构和广泛适用性的物种选择定义中重新构建，个体层面关于变异性的重新解释就失去了说服力。我们得出结论，对变异性的物种选择是宏观进化的主要力量。
