Research on symbiotic communities (microbiomes) of multicellular organisms seems to be changing our understanding of how species of plants and animals have evolved over millions of years. The quintessence of these discoveries is the emergence of the hologenome theory of evolution, founded on the concept that a holobiont (a host along with all of its associated symbiotic microorganisms) acts a single unit of selection in the process of evolution. Although the hologenome theory has become very popular among certain scientific circles, its principles are still being debated. In this paper, we argue, firstly, that only a very small number of symbiotic microorganisms are sufficiently integrated into multicellular organisms to act in concert with them as units of selection, thus rendering claims that holobionts are units of selection invalid. Secondly, even though holobionts are not units of selection, they can still constitute genuine units from an evolutionary perspective, provided we accept certain constraints: mainly, they should be considered units of co-operation. Thirdly, we propose a reconciliation of the role of symbiotic microorganisms with the theory of speciation through the use of a developed framework. Mainly, we will argue that, in order to understand the role of microorganisms in the speciation of multicellular organisms, it is not necessary to consider holobionts units of selection; it is sufficient to consider them units of co-operation.

中文翻译：

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有关进化的全基因组理论和微生物在物种形成中的作用的一些理论见解。

多细胞生物共生群落（微生物群落）的研究似乎正在改变我们对动植物物种数百万年如何进化的理解。这些发现的精髓是进化全基因组学理论的出现，其基础是全生命体（宿主及其所有相关共生微生物）在进化过程中起着单一选择单元的作用。尽管全息基因组学理论在某些科学界已经非常流行，但其原理仍在争论中。在本文中，我们认为，首先，只有极少数的共生微生物能够充分整合到多细胞生物中，以作为选择单位与它们协同作用，因此使全生命周期生物是选择单位无效。其次，即使全生命周期不是选择的单位，但从进化的角度来看，它们仍然可以构成真正的单位，前提是我们接受某些限制：主要地，应将它们视为合作单位。第三，我们提出通过使用已开发的框架来协调共生微生物与物种形成理论的作用。主要是，我们将争辩说，为了了解微生物在多细胞生物物种形成中的作用，没有必要考虑选择全生命周期单元。将它们视为合作单位就足够了。我们建议通过使用已开发的框架来协调共生微生物与物种形成理论的作用。主要是，我们将争辩说，为了了解微生物在多细胞生物物种形成中的作用，没有必要考虑选择全生命周期单元。将它们视为合作单位就足够了。我们建议通过使用已开发的框架来协调共生微生物与物种形成理论的作用。主要是，我们将争辩说，为了了解微生物在多细胞生物物种形成中的作用，没有必要考虑选择全生命周期单元。将它们视为合作单位就足够了。