1972). Nowadays, however, it is no longer possible to ignore that in a ubiquous way,
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 (Carrapiço 2015a; Gontier 2016; Margulis and Fester 1991). Within
this understanding, symbiosis is the key to the acquisition of new genomes and new
metabolic capacities, driving not only the evolution of living forms but also the
establishment of biodiversity and evolutionary complexity of living systems
(Archibald 2014; Carrapiço 2006, 2010a, 2012, 2015a, b; Corning 1983, 2005,
2018, 2020; Margulis and Fester 1991; Margulis and Sagan 2002; Reid 2007;
Sapp 2003, 2009; Selosse 2017; Villarreal and Ryan 2011). Despite the existence
of open-minded ideas on co-operative and synergistic approaches to the evolutive
process, symbiosis and symbiogenesis have traditionally been considered by the
majority of the scientific community as the “stepdaughters or stepsons” of the
evolutionary theory (Carrapiço 2010a, 2012, 2015a, b; Corning 2005, 2018; Pereira
et al. 2012; Sapp 1994, 2003; Suárez 2018), or in the case of symbioses, as biological
anecdotes (Selosse 2000). These ideas reveal a limited understanding of evolutive
process and do not correspond to the reality nor to the structure of the web of life in
our planet and to the understanding of the role of symbionts as key actors and not
only as supporting ones.
27.2 The symbiont’s Long Road in Time
In 1867, the Swiss botanist Simon Schwendener proposed at the Swiss Natural
History Society annual meeting, held in Rheinfelden, the dual hypothesis, relating
to the structure and organization of lichens (Carrapiço 2015a). This hypothesis
indicated that lichens are an association of two or three organisms, a fungus and
an alga or a cyanobacterium, behaving as “master and slave” (Honegger 2000; Sapp
1994, 2003; Selosse 2000, 2017) (Fig. 27.1). The idea that an organism could be
formed by two or more genetically separate organisms living together and working
as one unit was regarded as so unusual at the time that it was largely rejected by the
scientific community. Although the dual hypothesis was an innovative concept for
the biology of the nineteenth century, as well as an epistemological rupture in the
traditional concept of organism, it was considered by several experts of the lichenological field of the time as a “pure fantasy” (Carrapiço 2015a; Nylander 1896).
The symbiosis concept introduced in 1878 by the German biologist Heinrich Anton
de Bary (1831–1888) and defined as the “the living together of unlike named
organism” (Carrapiço 2015a; De Bary 1878, 1879) (Fig. 27.2) was another important
step in recognizing the role of symbionts. This author used lichens and Azolla (aquatic
fern) as biological examples to build this important concept in science (Carrapiço
2010b). The definition of symbiosis includes actually parasitism, commensalism, and
mutualism (Villarreal and Ryan 2011), and it can be considered as a continuous
596
F. Carrapiço
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 (Carrapiço 2015a; Gontier 2016; Margulis and Fester 1991). Within
this understanding, symbiosis is the key to the acquisition of new genomes and new
metabolic capacities, driving not only the evolution of living forms but also the
establishment of biodiversity and evolutionary complexity of living systems
(Archibald 2014; Carrapiço 2006, 2010a, 2012, 2015a, b; Corning 1983, 2005,
2018, 2020; Margulis and Fester 1991; Margulis and Sagan 2002; Reid 2007;
Sapp 2003, 2009; Selosse 2017; Villarreal and Ryan 2011). Despite the existence
of open-minded ideas on co-operative and synergistic approaches to the evolutive
process, symbiosis and symbiogenesis have traditionally been considered by the
majority of the scientific community as the “stepdaughters or stepsons” of the
evolutionary theory (Carrapiço 2010a, 2012, 2015a, b; Corning 2005, 2018; Pereira
et al. 2012; Sapp 1994, 2003; Suárez 2018), or in the case of symbioses, as biological
anecdotes (Selosse 2000). These ideas reveal a limited understanding of evolutive
process and do not correspond to the reality nor to the structure of the web of life in
our planet and to the understanding of the role of symbionts as key actors and not
only as supporting ones.
27.2 The symbiont’s Long Road in Time
In 1867, the Swiss botanist Simon Schwendener proposed at the Swiss Natural
History Society annual meeting, held in Rheinfelden, the dual hypothesis, relating
to the structure and organization of lichens (Carrapiço 2015a). This hypothesis
indicated that lichens are an association of two or three organisms, a fungus and
an alga or a cyanobacterium, behaving as “master and slave” (Honegger 2000; Sapp
1994, 2003; Selosse 2000, 2017) (Fig. 27.1). The idea that an organism could be
formed by two or more genetically separate organisms living together and working
as one unit was regarded as so unusual at the time that it was largely rejected by the
scientific community. Although the dual hypothesis was an innovative concept for
the biology of the nineteenth century, as well as an epistemological rupture in the
traditional concept of organism, it was considered by several experts of the lichenological field of the time as a “pure fantasy” (Carrapiço 2015a; Nylander 1896).
The symbiosis concept introduced in 1878 by the German biologist Heinrich Anton
de Bary (1831–1888) and defined as the “the living together of unlike named
organism” (Carrapiço 2015a; De Bary 1878, 1879) (Fig. 27.2) was another important
step in recognizing the role of symbionts. This author used lichens and Azolla (aquatic
fern) as biological examples to build this important concept in science (Carrapiço
2010b). The definition of symbiosis includes actually parasitism, commensalism, and
mutualism (Villarreal and Ryan 2011), and it can be considered as a continuous
596
F. Carrapiço