摘要
目前在我国古生物学研究中存在着许多有关物种判别的问题。在相当程度上这是与居群概念的贫乏和传统的林奈式类型-形态学研究方法的影响分不开的。广泛存在于物种间的形态间断为识别物种带来了方便,但它与生殖隔离并不完全吻合。若只考虑形态特征,所判定的化石种大多只相当于表型单元。本文探讨如何将形态标准与居群、群落-生态和时空等项标准相结合来区分物种与表型单元。以上这些标准分别反映了物种的生物学特性的不同方面,而生殖一遗传标准是将它们有机地联系在一起的共同基础。古生物学必须站在理性的高度上俯瞰生命发展过程中的物种,从现代生物学的知识库中汲取养料。化石种研究现状的改观尚有待于我们付出艰巨的努力。通过这种努力将使古生物学进入一个新的、更严格的科学发展阶段。
Among palaeontologists almost every one has recognized the vexation of species problem in palaeontology. This has been usually attributed to the presence of the time dimension which makes it impossible to apply the commonly accepted biological species definition and at the same time recognize species as discrete, nonarbitrary entities (Raup and Stanley, 1978, p. 109). But this problem is more theoretical than real. In fact, palaeontologists have seldom met evolutionary continua in the fossil record which make them difficult in delimiting species. Even when evolutionary continua do occur, subdivision need not be entirely arbitrary (Imbrie, 1956). We believe that species should be objective entities with difinite temporal and spatial distributions. 'A species is a single lineage linked up with other lineages by speciation events which is a reproductive and genetic community composed of ancestral-descendant populations with its own evolutionary position and historical fate, and which maintains its distinctive identity from other such lineages and occupies or occupied a specific niche in nature' (Fang, 1990, p. 45). Here speciation is defined as the evolutionary process of species formation including phyletic speciation (= phyletic transition, Raup and Stanley, 1978)——the appearance of a new species by the gradual evolution of an entire lineage. The speciation event, which is not all equal to the branching points in this paper, occurs when the genetic homesotasis of a species is transformed into another.
The species problem has been made to appear more difficult than it is by a confusion of the concepts underlying the terms of phenon and species (Mayr, 1969), especially in palaeontology. According to Mayr (1969, 1982), phenon is a sample of pheno-typically similar specimens. There is hardly a species that does not contain several if not dozens of phena which may come from sexual dimorphism, age differences, seasonal variants alternation of generations, genetic polymorphism, and so on and have no taxonomic status. If we recognize species merely on the basis of morphological differences, it may be only a phenon or a morphospecies, but not a real biological species. In addition to the morphological criterion, here population, community-ecological niche, and spatiotemporal distribution criteria are presented for species discrimination. It can be inferred based on various types of evidence although fossils cannot be tested for reproductive isolation. There is a complete difference between basing only on morphological criterion and using morphological evidence as inference for the application of a biological concept. So long as we make every effort to distinguish species from phena, much improvement seems possible in the species problem of palaeontology. After untiring efforts it is not impossible for palaeontologists to recognize the same sort of species as neontologists do, or nearly so.
出处
《古生物学报》
CAS
CSCD
北大核心
1991年第5期537-555,共19页
Acta Palaeontologica Sinica
关键词
表型单元
形态种
生物种
化石种
phenon, morphospecies, population criterion, community-ecological niche criterion, spatio-temporal distribution criterion
