Can We Understand Evolution Without Symbiogenesis?

Abstract

This work is a contribution to the literature and knowledge on evolution that takes into account the biological data obtained on symbiosis and symbiogenesis. Evolution is traditionally considered a gradual process essentially consisting of natural selection, conducted on minimal phenotypical variations that are the result of mutations and genetic recombinations to form new species. However, the biological world presents and involves symbiotic associations between different organisms to form consortia, a new structural life dimension and a symbiont-induced speciation. The acknowledgment of this reality implies a new understanding of the natural world, in which symbiogenesis plays an important role as an evolutive mechanism. Within this understanding, symbiosis is the key to the acquisition of new genomes and new metabolic capacities, driving living forms' evolution and the establishment of biodiversity and complexity on Earth. This chapter provides information on some of the key figures and their major works on symbiosis and symbiogenesis and reinforces the importance of these concepts in our understanding of the natural world and the role they play in the establishing of the evolutionary complexity of living systems. In this context, the concept of the symbiogenic superorganism is also discussed.

Symbiosis, History of

“…Symbiosis refers to the phenomenon whereby two or more organisms with distinct genealogical, evolutionary histories live in close association with one another ( de Bary, 1878Bary, , 1879. Together, the host and its symbionts form a new biological entity that is sometimes called a superorganism (Spencer, 1876;Carrapiço, 2015), holobiont (Margulis, 1991;Guerrero et al, 2013), or symbiome (Sapp, 2003: 33); and this newly formed entity is considered to be a single unit, either of natural selection (through its hologenome, Rosenberg et al, 2007;Zilber-Rosenberg and Rosenberg, 2008), or of other evolutionary mechanisms. Symbionts can be acquired both vertically (during phylogenesis) and horizontally (during ontogenesis).…”

“…By the midnineteenth century, used to designate group cooperation and communal group living that advances effects unobtainable by the individuals, which is why the whole becomes more than the sum of its individual parts First introduced in biology in bio-economic, systems theoretical and hierarchical approaches to life (see e.g., Corning, 2013Corning, , 2014 References: http://www.oed.com/; https://www.wiktionary.org/; http://www.etymonline. com/ (Carrapiço, 2015;Gontier, 2015; Social Darwinians thus focused on competition, and many symbiologists understood these theories as direct extensions of liberal thought into biology. Symbiosis scholars critiqued by emphasizing that the sociopolitical and biological realms display many instances of social and mutualistic behavior, which they equally understood as 'lawful.…”

“…The positive effects of symbiosis also remained a topic of interest, especially in what regards its impact on ecology and the biosphere. Frank (1885) first described 'root symbiosis' ('Wurzelsymbiose') that occurs between fungi and the roots of trees and plants, and he introduced the concept of Mycorrhiza (Carrapiço, 2015). At de Bary's lab, Winogradsky (1893 discovered nitrogen-fixing bacteria in the soil, which he called 'autotrophic' for their ability to synthesize chemical elements instead of devouring organic matter.…”

Symbiogenesis, History of

“…Boveri (1904), for example, although a founder of chromosome theory, merely stated that Mendelian factors are transmitted via chromosomes. He also conjectured that the 'protoplasm' (cytoplasm) and chromosomes of the cell originated through symbiosis, an idea that was already introduced in 1893 by Shôsaburô Watasé (Sapp, 1994;Carrapiço, 2010Carrapiço, , 2015.…”

“…As early as the twentieth century, such ecological and systems theoretical approaches led Reinheimer (1913) to provide a ''bio-economic'' view of life, wherein he introduced the concept of a ''web of life'' (Carrapiço, 2015). And many symbiologists today continue to link their theories to the idea that earth or 'Gaia' is a living superorganism (Lovelock, 1972;Lovelock and Margulis, 1974;Volk, 1998).…”