PLOS ONE2013-10-16 2:10 AM

How Many Species Are There on Earth and in the Ocean?陆地和海洋中有多少物种?

Abstract The diversity of life is one of the most striking aspects of our planet; hence knowing how many species inhabit Earth is among the most fundamental questions in science. Yet the answer to this question remains enigmatic, as efforts to sample the world's biodiversity to date have been limited and thus have precluded direct quantification of global species richness, and because indirect estimates rely on assumptions that have proven highly controversial. Here we show that the higher taxonomic classification of species (i.e., the assignment of species to phylum, class, order, family, and genus) follows a consistent and predictable pattern from which the total number of species in a taxonomic group can be estimated. This approach was validated against well-known taxa, and when applied to all domains of life, it predicts ~8.7 million (±1.3 million SE) eukaryotic species globally, of which ~2.2 million (±0.18 million SE) are marine. In spite of 250 years of taxonomic classification and over 1.2 million species already catalogued in a central database, our results suggest that some 86% of existing species on Earth and 91% of species in the ocean still await description. Renewed interest in further exploration and taxonomy is required if this significant gap in our knowledge of life on Earth is to be closed. 论文摘要 生物种类繁多是我们这个星球上最让人惊奇的地方之一;因此到底有多少物种居住在地球上便成了一个最基本的科学问题之一。然而问题的答案仍旧是个谜,至今为止人们对这个世界的生物多样性了解很有限,如此也很难对地球物种的确切数量进行计算,因为间接估算所仰赖的基础本身就很有争议。这里我们展示的是物种的上层分类(例如,将物种分为门、纲、目、科、属)所依据的这个连续且可预见的模式,从这个模式中我们可以估算某一个分类群组中的物种数量。这种方法已经被证实和众所周知的分类法不同,而且在应用到各种生物领域时,它能估算出870万(±130万SE)全球真核物种,其中220万(±18万)为海洋生物。尽管经过250年的分类工作,已经有超过120万的物种被分类入册了,但我们的结果仍然指出大概86%的陆地生物及91%的海洋生物还未被分类入册。如果我们想要填补地球生物知识的鸿沟,那必须对生物分类学进行更深入的探索。 Author Summary Knowing the number of species on Earth is one of the most basic yet elusive questions in science. Unfortunately, obtaining an accurate number is constrained by the fact that most species remain to be described and because indirect attempts to answer this question have been highly controversial. Here, we document that the taxonomic classification of species into higher taxonomic groups (from genera to phyla) follows a consistent pattern from which the total number of species in any taxonomic group can be predicted. Assessment of this pattern for all kingdoms of life on Earth predicts ~8.7 million (±1.3 million SE) species globally, of which ~2.2 million (±0.18 million SE) are marine. Our results suggest that some 86% of the species on Earth, and 91% in the ocean, still await description. Closing this knowledge gap will require a renewed interest in exploration and taxonomy, and a continuing effort to catalogue existing biodiversity data in publicly available databases. 作者总结 地球物种的数量是一个悬而未决的最基本的科学问题之一。很不幸,由于大多数物种依旧没有被分门别类,而且间接解决这个问题的方法很受争议,所以一直未能得到准确数量。在这里,我们依据一个连续模式把物种分类整理为更上层的分类群组(从属到门),从中可以估算出任何分类群组的生物总数。用这个模式把地球上各个生物王国进行分类,就可以估算出全球大约870万(±130万SE)物种,其中有220万(±18万)为海洋生物。我们的结果显示大约86%的陆地生物及91%的海洋生物还未被分类描述。要填补这块知识鸿沟需要更深入地探索和分类,并且要持续不懈地在可用的公共数据中对存活物种进行分类。

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