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Extreme environments as potential drivers of convergent evolution by exaptation: the Atacama Desert Coastal Range case.

Azua-Bustos A, González-Silva C, Arenas-Fajardo C, Vicuña R - Front Microbiol (2012)

Bottom Line: The third case is Chroococcidiopsis, a genus of Cyanobacteria commonly found in deserts around the world that has also been described in warm springs.Thus, we show that the traits found in the closest ancestors of the aforementioned species (which inhabited other unrelated extreme environments) seem to be now useful for the described species in their current subaerial habitats and may likely correspond to cases of exaptations.Altogether, the Coastal Range of the Atacama Desert may be considered as a place where key steps on the colonization of land by phototrophic organisms seem to be being repeated by convergent evolution of extant microalgae and Cyanobacteria.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular Genetics and Microbiology, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile Santiago, Chile.

ABSTRACT
We have recently discovered a variety of unrelated phototrophic microorganisms (two microalgae and one cyanobacteria) in specialized terrestrial habitats at The Coastal Range of the Atacama Desert. Interestingly, morphological and molecular evidence suggest that these three species are all recent colonists that came from aquatic habitats. The first case is Cyanidiales inhabiting coastal caves. Cyanidiales are microalgae that are commonly found in warm acid springs, but have also been recently discovered as cave flora in Italy. The case is Dunaliella biofilms colonizing spider webs in coastal caves; Dunaliella are microalgae typically found in hypersaline habitats. The third case is Chroococcidiopsis, a genus of Cyanobacteria commonly found in deserts around the world that has also been described in warm springs. Thus, we show that the traits found in the closest ancestors of the aforementioned species (which inhabited other unrelated extreme environments) seem to be now useful for the described species in their current subaerial habitats and may likely correspond to cases of exaptations. Altogether, the Coastal Range of the Atacama Desert may be considered as a place where key steps on the colonization of land by phototrophic organisms seem to be being repeated by convergent evolution of extant microalgae and Cyanobacteria.

No MeSH data available.


Related in: MedlinePlus

Scanning and transmission electron micrographs of the cave Dunaliella. (A) SEM micrograph of a group of cells of cave Dunaliella attached to the spider web's silk threads. (B) TEM micrograph of a cave Dunaliella cell. CW, cell wall; C, chlorosplast; P, pyrenoid; Sb, starch bodies.
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Figure 4: Scanning and transmission electron micrographs of the cave Dunaliella. (A) SEM micrograph of a group of cells of cave Dunaliella attached to the spider web's silk threads. (B) TEM micrograph of a cave Dunaliella cell. CW, cell wall; C, chlorosplast; P, pyrenoid; Sb, starch bodies.

Mentions: Typically, aquatic Dunaliella species grow as free ranging individuals, as opposed to the cave Dunaliella, which grows in colonies. Scanning electron microscopy (SEM) shows one of these colonies firmly attached to the spider web threads (Figure 4A). Interestingly, a stage growth named as the “palmella” stage has been reported for D. salina and D. viridis subjected to conditions of reduced salinity (Brock, 1975). In the palmella stage, cells lose their flagella, become more rounded and excrete a layer of exopolysaccharides (EPS) in which they repeatedly divide, thus forming colonies (Borowitzka and Silva, 2007). These morphological characteristics are strikingly similar to the ones observed in the colonies of cave Dunaliella covering the spider webs. Consistent with this, other phylogenetically close species to our cave Dunaliella are two strains of D. viridis (SPMO 980625-IE and SPMO202, isolated from the Salt Plains National Wildlife Refuge, Oklahoma, USA) (Assunção et al., 2012).


Extreme environments as potential drivers of convergent evolution by exaptation: the Atacama Desert Coastal Range case.

Azua-Bustos A, González-Silva C, Arenas-Fajardo C, Vicuña R - Front Microbiol (2012)

Scanning and transmission electron micrographs of the cave Dunaliella. (A) SEM micrograph of a group of cells of cave Dunaliella attached to the spider web's silk threads. (B) TEM micrograph of a cave Dunaliella cell. CW, cell wall; C, chlorosplast; P, pyrenoid; Sb, starch bodies.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3526103&req=5

Figure 4: Scanning and transmission electron micrographs of the cave Dunaliella. (A) SEM micrograph of a group of cells of cave Dunaliella attached to the spider web's silk threads. (B) TEM micrograph of a cave Dunaliella cell. CW, cell wall; C, chlorosplast; P, pyrenoid; Sb, starch bodies.
Mentions: Typically, aquatic Dunaliella species grow as free ranging individuals, as opposed to the cave Dunaliella, which grows in colonies. Scanning electron microscopy (SEM) shows one of these colonies firmly attached to the spider web threads (Figure 4A). Interestingly, a stage growth named as the “palmella” stage has been reported for D. salina and D. viridis subjected to conditions of reduced salinity (Brock, 1975). In the palmella stage, cells lose their flagella, become more rounded and excrete a layer of exopolysaccharides (EPS) in which they repeatedly divide, thus forming colonies (Borowitzka and Silva, 2007). These morphological characteristics are strikingly similar to the ones observed in the colonies of cave Dunaliella covering the spider webs. Consistent with this, other phylogenetically close species to our cave Dunaliella are two strains of D. viridis (SPMO 980625-IE and SPMO202, isolated from the Salt Plains National Wildlife Refuge, Oklahoma, USA) (Assunção et al., 2012).

Bottom Line: The third case is Chroococcidiopsis, a genus of Cyanobacteria commonly found in deserts around the world that has also been described in warm springs.Thus, we show that the traits found in the closest ancestors of the aforementioned species (which inhabited other unrelated extreme environments) seem to be now useful for the described species in their current subaerial habitats and may likely correspond to cases of exaptations.Altogether, the Coastal Range of the Atacama Desert may be considered as a place where key steps on the colonization of land by phototrophic organisms seem to be being repeated by convergent evolution of extant microalgae and Cyanobacteria.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular Genetics and Microbiology, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile Santiago, Chile.

ABSTRACT
We have recently discovered a variety of unrelated phototrophic microorganisms (two microalgae and one cyanobacteria) in specialized terrestrial habitats at The Coastal Range of the Atacama Desert. Interestingly, morphological and molecular evidence suggest that these three species are all recent colonists that came from aquatic habitats. The first case is Cyanidiales inhabiting coastal caves. Cyanidiales are microalgae that are commonly found in warm acid springs, but have also been recently discovered as cave flora in Italy. The case is Dunaliella biofilms colonizing spider webs in coastal caves; Dunaliella are microalgae typically found in hypersaline habitats. The third case is Chroococcidiopsis, a genus of Cyanobacteria commonly found in deserts around the world that has also been described in warm springs. Thus, we show that the traits found in the closest ancestors of the aforementioned species (which inhabited other unrelated extreme environments) seem to be now useful for the described species in their current subaerial habitats and may likely correspond to cases of exaptations. Altogether, the Coastal Range of the Atacama Desert may be considered as a place where key steps on the colonization of land by phototrophic organisms seem to be being repeated by convergent evolution of extant microalgae and Cyanobacteria.

No MeSH data available.


Related in: MedlinePlus