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The influence of environmental setting on the community ecology of Ediacaran organisms.

ABSTRACT: The broad-scale environment plays a substantial role in shaping modern marine ecosystems, but the degree to which palaeocommunities were influenced by their environment is unclear. To investigate how broad-scale environment influenced the community ecology of early animal ecosystems, we employed spatial point process analyses (SPPA) to examine the community structure of seven late Ediacaran (558-550 Ma) bedding-plane assemblages drawn from a range of environmental settings and global localities. The studied palaeocommunities exhibit marked differences in the response of their component taxa to sub-metre-scale habitat heterogeneities on the seafloor. Shallow-marine (nearshore) palaeocommunities were heavily influenced by local habitat heterogeneities, in contrast to their deeper-water counterparts. The local patchiness within shallow-water communities may have been further accentuated by the presence of grazers and detritivores, whose behaviours potentially initiated a propagation of increasing habitat heterogeneity of benthic communities from shallow to deep-marine depositional environments. Higher species richness in shallow-water Ediacaran assemblages compared to deep-water counterparts across the studied time-interval could have been driven by this environmental patchiness, because habitat heterogeneities increase species richness in modern marine environments. Our results provide quantitative support for the 'Savannah' hypothesis for early animal diversification-whereby Ediacaran diversification was driven by patchiness in the local benthic environment.

SUBMITTER: Mitchell EG

PROVIDER: S-EPMC7333898 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:The impact of key environmental factors, salinity, prey, and temperature, on the survival and ecology of Bdellovibrio and like bacteria (BALOs), including the freshwater/terrestrial, non-halotolerant group and the halophilic Halobacteriovorax strains, has been assessed based on a review of data in the literature. These topics have been studied by numerous investigators for nearly six decades now, and much valuable information has been amassed and reported. The collective data shows that salinity, prey, and temperature play a major role in, not only the growth and survival of BALOs, but also the structure and composition of BALO communities and the distribution of the predators. Salinity is a major determinant in the selection of BALO habitats, distribution, prey bacteria, and systematics. Halophilic BALOs require salt for cellular functions and are found only in saltwater habitats, and prey primarily on saltwater bacteria. To the contrary, freshwater/terrestrial BALOs are non-halotolerant and inhibited by salt concentrations greater than 0.5%, and are restricted to freshwater, soils, and other low salt environments. They prey preferentially on bacteria in the same habitats. The halophilic BALOs are further separated on the basis of their tolerance to various salt concentrations. Some strains are found in low salt environments and others in high salt regions. In situ studies have demonstrated that salinity gradients in estuarine systems govern the type of BALO communities that will persist within a specific gradient. Bacterial prey for BALOs functions more than just being a substrate for the predators and include the potential for different prey species to structure the BALO community at the phylotype level. The pattern of susceptibility or resistance of various bacteria species has been used almost universally to differentiate strains of new BALO isolates. However, the method suffers from a lack of uniformity among different laboratories. The use of molecular methods such as comparative analysis of the 16S rDNA gene and metagenomics have provided more specific approaches to distinguished between isolates. Differences in temperature growth range among different BALO groups and strains have been demonstrated in many laboratory experiments. The temperature optima and growth range for the saltwater BALOs is typically lower than that of the freshwater/terrestrial BALOs. The collective data shows not only that environmental factors have a great impact on BALO ecology, but also how the various factors affect BALO populations in nature.

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The influence of environmental setting on the community ecology of Ediacaran organisms.

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