Abstract
Barriers to microbial migrations can lead adaptive radiations and increased endemism. We propose that extreme unbalanced nutrient stoichiometry of essential nutrients can be a barrier to microbial immigration over geological timescales. At the oasis in the Cuatro Ciénegas Basin in Mexico, nutrient stoichiometric proportions are skewed given the low phosphorus availability in the ecosystem. We show that this endangered oasis can be a model for a lost world. The ancient niche of extreme unbalanced nutrient stoichiometry favoured survival of ancestral microorganisms. This extreme nutrient imbalance persisted due to environmental stability and low extinction rates, generating a diverse and unique bacterial community. Several endemic clades of Bacillus invaded the Cuatro Cienegas region in two geological times, the late Precambrian and the Jurassic. Other lineages of Bacillus, Clostridium and Bacteroidetes migrated into the basin in isolated events. Cuatro Ciénegas Basin conservation is vital to the understanding of early evolutionary and ecological processes.
Highlights
A ‘lost world’ is both a poetic metaphor and a scientific idea; in both cases, the term pertains to the conservation or re-creation of the deep past in a particular place
We observed a vast microbial diversity within roughly a square kilometer, through PCR amplification and sequencing of 16S rRNA genes from environmental DNA (Figure 2). This diversity can be expressed in operational taxonomic units (OTUs), used to classify groups of related individuals that have 16S rRNA gene sequences exhibiting at least 97% identity
The Churince’s total Bacteria and Archaea richness is represented by a total of 5,167 OTUs assigned to samples from the water column, aquatic sediments, and soil
Summary
A ‘lost world’ is both a poetic metaphor and a scientific idea; in both cases, the term pertains to the conservation or re-creation of the deep past in a particular place. The exception seems to be the abundant and morphologically diverse stromatolites and microbial mats found in the endangered oasis of Cuatro Cienegas Basin (CCB) in Northern Mexico In this extremely diverse wetland (Minckley, 1969), the recycling of the deep aquifer by magmatic heat replicates many conditions of ancient oceans (Wolaver et al, 2013), including its extremely unbalanced nutrient stoichiometry (Elser et al, 2006) and sulphur and magnesium minerals that replicate marine osmolarity (Wolaver et al, 2013; De Anda et al, 2017; Rebollar et al, 2012), despite being low in NaCl. isotopic analysis suggests that the deep aquifer maintained the ancestral marine conditions in the wetland by dissolving the existing minerals from its
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