Differences in the Cyanobacterial Community Composition of Biocrusts From the Drylands of Central Mexico. Are There Endemic Species?
Por:
Becerra-Absalon, Itzel, Angeles Munoz-Martini, M., Montejano, Gustavo, Mateo, Pilar
Publicada:
3 may 2019
Resumen:
In drylands worldwide, biocrusts, topsoil microbial communities, are
prevalent, contributing to the biostabilization of soils and allowing
the subsequent establishment and growth of vascular plants. In early
successional biocrusts, cyanobacteria are the first dominant colonizers
of bare ground, largely determining their functioning. However, there
are large gaps in our knowledge of the cyanobacterial diversity in
biocrusts, particularly in understudied geographic regions, such as the
tropical latitudes. We analyzed the diversity of the cyanobacteria
inhabiting the biocrusts of semideserts from Central Mexico in two
localities belonging to the same desert system (Chihuahuan Desert) that
are separated by a cordillera that crosses the center of Mexico.
Morphological identification of the cyanobacteria was carried out after
cultivation in parallel with the direct observation of the environmental
samples and was supported by genetic characterization through analysis
of the 16S rRNA gene of the isolated strains and by next-generation
sequencing of the soil samples. Taxonomic assignment revealed a clear
dominance of heterocystous cyanobacteria at one of the studied locations
(Actopan, Hidalgo state). Although heterocystous forms were abundant at
the other location (Atexcac, Puebla state), almost a third of the
cyanobacterial phylotypes were represented by unicellular/colonial
cyanobacteria, mostly Chroococcidiopsis spp. Only 28.4% of the
phylotypes were found to be common to both soils. Most of the other
taxa, however, were biocrust-type specific, and approximately 35% of
the phylotypes were found to be unique to the soil they were collected
in. In addition, differences in the abundances of the shared
cyanobacteria between the locations were also found. These differences
in the cyanobacterial distribution were supported by the distinct
responses of the isolated strains representative of the sites to extreme
heat and desiccation in bioassays. Some cyanobacteria with high
abundance or only present at the hottest Actopan site, such as Scytonema
hyalinum, Scytonema crispum, Nostoc commune, Nostoc sp., and Calothn'x
parietina, survived extreme heat and desiccation. However, Tolypothrix
distorta and Chroococcidiopsis spp. were clearly sensitive to these
extreme conditions in relation to their lower abundances at Actopan as
opposed to Atexcac. Since novel biocrust-associated phylotypes were also
found, the emergence of endemic cyanobacterial taxa is discussed.
Filiaciones:
Univ Autonoma Madrid, Dept Biol, Fac Ciencias, Madrid, Spain
Univ Nacl Autonoma Mexico, Fac Ciencias, Dept Biol Comparada, Mexico City, DF, Mexico
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