@article {4645, title = {Phagotrophic protists and their associates: Evidence for preferential grazing in an abiotically driven soil ecosystem}, journal = {Microorganisms}, volume = {9}, year = {2021}, month = {08/2021}, pages = {1555}, abstract = {

The complex relationship between ecosystem function and soil food web structure is governed by species interactions, many of which remain unmapped. Phagotrophic protists structure soil food webs by grazing the microbiome, yet their involvement in intraguild competition, susceptibility to predator diversity, and grazing preferences are only vaguely known. These species-dependent interactions are contextualized by adjacent biotic and abiotic processes, and thus obfuscated by typically high soil biodiversity. Such questions may be investigated in the McMurdo Dry Valleys (MDV) of Antarctica because the physical environment strongly filters biodiversity and simplifies the influence of abiotic factors. To detect the potential interactions in the MDV, we analyzed the co-occurrence among shotgun metagenome sequences for associations suggestive of intraguild competition, predation, and preferential grazing. In order to control for confounding abiotic drivers, we tested co-occurrence patterns against various climatic and edaphic factors. Non-random co-occurrence between phagotrophic protists and other soil fauna was biotically driven, but we found no support for competition or predation. However, protists predominately associated with Proteobacteria and avoided Actinobacteria, suggesting grazing preferences were modulated by bacterial cell-wall structure and growth rate. Our study provides a critical starting-point for mapping protist interactions in native soils and highlights key trends for future targeted molecular and culture-based approaches.

}, keywords = {LTER-MCM, Antarctica, co-occurrence networks, McMurdo Dry Valleys, Rhogostoma sp., Sandona sp., soil food webs, variation partitioning}, doi = {10.3390/microorganisms9081555}, url = {https://www.mdpi.com/2076-2607/9/8/1555}, author = {Thompson, Andrew R. and Roth-Monz{\'o}n, Andrea J. and Aanderud, Zachary T. and Adams, Byron J.} } @article {4734, title = {Phagotrophic protists (protozoa) in Antarctic terrestrial ecosystems: Diversity, distribution, ecology, and best research practices}, journal = {Polar Biology}, volume = {44}, year = {2021}, month = {08/2021}, pages = {1467-1484}, abstract = {

Phagotrophic protists (formerly protozoa) are a highly diverse, polyphyletic grouping of generally unicellular, heterotrophic eukaryotes that are key regulators of the soil microbiome. The biodiversity and ecology of soil phagotrophic protists are still largely uncharacterized, especially in the Antarctic, which possesses some of the harshest terrestrial environments known and potentially many physiologically unique and scientifically interesting species. Antarctic soil systems are also highly limited in terms of moisture, temperature, and carbon, and the resulting reduced biological complexity can facilitate fine-tuned investigation of the drivers and functioning of microbial communities. To facilitate and encourage future research into protist biodiversity and ecology, especially in context of the broader functioning of Antarctic terrestrial communities, I review the biodiversity, distribution, and ecology of Antarctic soil phagotrophic protists. Biodiversity appears to be highly structured by region and taxonomic group, with the Antarctic Peninsula having the highest taxonomic diversity and ciliates (Ciliophora) being the most diverse taxonomic group. However, richness estimates are likely skewed by disproportionate sampling (over half of the studies are from the peninsula), habitat type bias (predominately moss-associated soils), investigator bias (toward ciliates and the testate amoeba morphogroup), and methodological approach (toward cultivation and morphological identification). To remedy these biases, a standardized methodology using both morphological and molecular identification and increased emphasis on microflagellate and naked amoeba morphogroups is needed. Additionally, future research should transition away from biodiversity survey studies to dedicated ecological studies that emphasize the function, ecophysiology, endemicity, dispersal, and impact of abiotic drivers beyond moisture and temperature.

}, keywords = {LTER-MCM, abiotic drivers of protist communities, Antarctic protozoa, Corythion dubium, phagotrophic soil protists, protist diversity}, issn = {0722-4060}, doi = {10.1007/s00300-021-02896-3}, url = {https://link.springer.com/article/10.1007/s00300-021-02896-3}, author = {Thompson, Andrew R.} } @article {4360, title = {Provisional checklist of terrestrial heterotrophic protists from Antarctica}, journal = {Antarctic Science}, year = {2019}, month = {11/2019}, abstract = {

Heterotrophic soil protists encompass lineages that are both evolutionarily ancient and highly diverse, providing an untapped wealth of scientific insight. Yet the diversity of free-living heterotrophic terrestrial protists is still largely unknown. To contribute to our understanding of this diversity, we present a checklist of heterotrophic protists currently reported from terrestrial Antarctica, for which no comprehensive evaluation currently exists. As a polar continent, Antarctica is especially susceptible to rising temperatures caused by anthropogenic climate change. Establishing a baseline for future conservation efforts of Antarctic protists is therefore important. We performed a literature search and found 236 taxa identified to species and an additional 303 taxa identified to higher taxonomic levels in 54 studies spanning over 100 years of research. Isolated by distance, climate and the circumpolar vortex, Antarctica is the most extreme continent on Earth: it is not unreasonable to think that it may host physiologically and evolutionarily unique species of protists, yet currently most species discovered in Antarctica are considered cosmopolitan. Additional sampling of the more extreme intra-continental zones will probably result in the discovery of more novel and unique taxa.

}, keywords = {LTER-MCM}, doi = {10.1017/S0954102019000361}, url = {https://www.cambridge.org/core/journals/antarctic-science/article/provisional-checklist-of-terrestrial-heterotrophic-protists-from-antarctica/DC08D89ABDC5AF2CC83E38B1C6F1F78C}, author = {Thompson, Andrew R. and Powell, Gareth S. and Byron Adams} }