Review Article
Evolving Ecosystems: Inheritance and Selection in the Light of the Microbiome

https://doi.org/10.1016/j.arcmed.2018.01.002Get rights and content

The importance of microorganisms in human biology is undeniable. The amount of research that supports that microbes have a fundamental role in animal and plant physiology is substantial and increasing every year. Even though we are only beginning to comprehend the broadness and complexity of microbial communities, evolutionary theories need to be recast in the light of such discoveries to fully understand and incorporate the role of microbes in our evolution. Fundamental evolutionary concepts such as diversity, heredity, selection, speciation, etc., which constitute the modern synthesis, are now being challenged, or at least expanded, by the emerging notion of the holobiont, which defines the genetic and metabolic networks of the host and its microbes as a single evolutionary unit. Several concepts originally developed to study ecosystems, can be used to understand the physiology and evolution of such complex systems that constitute “individuals.” In this review, we discuss these ecological concepts and also provide examples that range from squids, insects and koalas to other mammals and humans, suggesting that microorganisms have a fundamental role not only in physiology but also in evolution. Current evolutionary theories need to take into account the dynamics and interconnectedness of the host-microbiome network, as animals and plants not only owe their symbiogenetic origin to microbes, but also share a long evolutionary history together.

Section snippets

The Object of Selection

Natural selection has been a controversial subject since Darwinian times. With the discovery of genes and the formulation of the modern synthesis some scientists thought that selection should act upon genes, since they were the subject of mutation and thus were the raw material of evolution (1). However, evolutionary biologists such as Ernst Mayr and Sewall Wright argued that selective pressures do not only act on single genes. Based on the observation that many genes' functionalities depend on

Conclusions and Perspectives

In this review we have covered a wide range of topics related to the evolution of holobionts. We have shown that the holobiont concept, in addition to being consistent with experimental observations, also provides a new perspective to reformulate fundamental evolutionary questions. Since hosts and microorganisms have coevolved through millions of years, it is reasonable to expect the latter to be well suited to hold information about past and present environmental conditions (together with

Acknowledgments

The authors thank Prof. Michele Gold Morgan and Prof. Teresa Bosques for their critical reading of the manuscript and their many valuable suggestions. AF thanks El Colegio Nacional for its generous support. SSM thanks Catedras CONACYT 2017 program for its support.

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