02267nas a2200265   4500008004100000022001400041245008300055210006900138260001200207490000700219520143800226653002201664653002001686653002401706653002401730653002301754100002501777700002101802700002301823700001701846700002101863700002401884700002201908856007101930       2025                        eng d  a1523-043000aSoil biota sensitivity to hydroclimate variability in a polar desert ecosystem0 aSoil biota sensitivity to hydroclimate variability in a polar de  c05/20250 v573 a<p>An anomalous warm weather event in the Antarctic McMurdo Dry Valleys on 18 March 2022 created an opportunity to characterize soil biota communities most sensitive to freeze&ndash;thaw stress. This event caused unseasonal melt within Taylor Valley, activating stream water and microbial mats around Canada Stream. Liquid water availability in this polar desert is a driver of soil biota distribution and activity. Because climate change impacts hydrological regimes, we aimed to determine the effect on soil communities. We sampled soils identified from this event that experienced thaw, nearby hyper-arid areas, and wetted areas that did not experience thaw to compare soil bacterial and invertebrate communities. Areas that exhibited evidence of freeze&ndash;thaw supported the highest live and dead nematode counts and were composed of soil taxa from hyper-arid landscapes and wetted areas. They received water inputs from snowpacks, hyporheic water, or glacial melt, contributing to community differences associated with organic matter and salinity gradients. Inundated soils had higher organic matter and lower conductivity (p &lt;&nbsp;.02) and hosted the most diverse microbial and invertebrate communities on average. Our findings suggest that as liquid water becomes more available under predicted climate change, soil communities adapted to the hyper-arid landscape will shift toward diverse, wetted soil communities.</p>10aclimate variation10aextreme weather10aMcMurdo Dry Valleys10amicrobial community10asoil invertebrates1 aSnyder, Meredith, D.1 aAdams, Byron, J.1 aBorgmeier, Abigail1 aJorna, Jesse1 aPower, Sarah, N.1 aSalvatore, Mark, R.1 aBarrett, John, E.  uhttps://www.tandfonline.com/doi/full/10.1080/15230430.2025.248528302399nas a2200217   4500008004100000245008500041210006900126260005400195490000700249520171000256653001501966653001701981653002401998653001402022653002402036653001002060653002402070100002502094700002102119856004102140       2022                        eng d00aEffect of climate history on the genetic structure of an Antarctic soil nematode0 aEffect of climate history on the genetic structure of an Antarct  aProvo, UT, USAbBrigham Young Universityc12/20220 vMS3 a<p>Historical climate disturbances such as glacial cycling and fluctuating stream, lake, and sea levels strongly influence the distribution and evolutionary trajectories of Antarctic terrestrial species. Antarctic invertebrates, with limited long-range mobility, including the ubiquitous sentinel nematode species <i>Scottnema lindsayae</i>, are especially sensitive to climate disturbances. We tested hypotheses associated with the historical geographic and population genetic structure of this species as it occurs across the McMurdo Dry Valleys (MDVs) of Antarctica. In order to reconstruct the influence of climate disturbance and ecological conditions on this species, partial mitochondrial COI gene sequences were sequenced and analyzed from individual <i>S. lindsayae</i> collected from sites across the MDVs reflecting a opposing gradients of climate disturbance during the Last Glacial Maximum (LGM). We found that populations were strongly geomorphic barriers with distinct haplotypes associated with valleys except among valleys that experienced glacial advance and retreat during the LGM. One monophyletic clade corresponds with valley systems that were undisturbed during the LGM indicating putative refugia areas. A second monophyletic clade corresponds to recent dispersal and expansion of evolutionarily younger populations into valleys that were strongly reworked by glacial activity during the LGM. Our work shows that contemporary populations of these animals are strongly structured by prior climate history. Such findings can be useful for interpreting long-term monitoring of demographic shifts of soil organisms in response to changing climate trends in the McMurdo Dry Valleys.</p>10aAntarctica10abiogeography10aclimate disturbance10aevolution10aMcMurdo Dry Valleys10apolar10apopulation genetics1 aJackson, Abigail, C.1 aAdams, Byron, J.  uhttp://hdl.lib.byu.edu/1877/etd1262202236nas a2200241   4500008004100000245006500041210006400106260001200170300000900182490000700191520155500198653001501753653002401768653001801792653002601810653001201836653002201848100002501870700001701895700001501912700002101927856004601948       2022                        eng d00aGlacial legacies: Microbial communities of Antarctic refugia0 aGlacial legacies Microbial communities of Antarctic refugia  c10/2022  a14400 v113 a<p>In the cold deserts of the McMurdo Dry Valleys (MDV) the suitability of soil for microbial life is determined by both contemporary processes and legacy effects. Climatic changes and accompanying glacial activity have caused local extinctions and lasting geochemical changes to parts of these soil ecosystems over several million years, while areas of refugia may have escaped these disturbances and existed under relatively stable conditions. This study describes the impact of historical glacial and lacustrine disturbance events on microbial communities across the MDV to investigate how this divergent disturbance history influenced the structuring of microbial communities across this otherwise very stable ecosystem. Soil bacterial communities from 17 sites representing either putative refugia or sites disturbed during the Last Glacial Maximum (LGM) (22&ndash;17 kya) were characterized using 16 S metabarcoding. Regardless of geographic distance, several putative refugia sites at elevations above 600 m displayed highly similar microbial communities. At a regional scale, community composition was found to be influenced by elevation and geographic proximity more so than soil geochemical properties. These results suggest that despite the extreme conditions, diverse microbial communities exist in these putative refugia that have presumably remained undisturbed at least through the LGM. We suggest that similarities in microbial communities can be interpreted as evidence for historical climate legacies on an ecosystem-wide scale.</p>10aAntarctica10aMcMurdo Dry Valleys10ametabarcoding10amicrobial communities10arefugia10asoil biodiversity1 aJackson, Abigail, C.1 aJorna, Jesse1 aChaston, J1 aAdams, Byron, J.  uhttps://www.mdpi.com/2079-7737/11/10/144002380nas a2200253   4500008004100000245012200041210006900163260001200232300000900244490000600253520157500259653001501834653002701849653002401876653001901900653001601919653001901935653002701954100002501981700002902006700002602035700002102061856004402082       2021                        eng d00aPhagotrophic protists and their associates: Evidence for preferential grazing in an abiotically driven soil ecosystem0 aPhagotrophic protists and their associates Evidence for preferen  c08/2021  a15550 v93 a<p>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.</p>10aAntarctica10aco-occurrence networks10aMcMurdo Dry Valleys10aRhogostoma sp.10aSandona sp.10asoil food webs10avariation partitioning1 aThompson, Andrew, R.1 aRoth-Monzón, Andrea, J.1 aAanderud, Zachary, T.1 aAdams, Byron, J.  uhttps://www.mdpi.com/2076-2607/9/8/155503820nas a2200217   4500008004100000245015200041210006900193260004000262490000800302520300700310653003203317653003303349653001703382653002403399653002103423653002503444653003903469100002503508700002103533856004803554       2019                        eng d00aHeterotrophic protists as useful models for studying microbial food webs in a model soil ecosystem and the universality of complex unicellular life0 aHeterotrophic protists as useful models for studying microbial f  aProvo, UTbBrigham Young University0 vPhD3 a<p>Heterotrophic protists, consisting largely of the Cercozoa, Amoebozoa, Ciliophora, Discoba and some Stramenopiles, are a poorly characterized component of life on Earth. They play an important ecological role in soil communities and provide key insights into the nature of one of life&rsquo;s most enigmatic evolutionary transitions: the development of the complex unicell. Soil ecosystems are crucial to the functioning of global biogeochemical cycles (e.g. carbon and nitrogen) but are at risk of drastic change from anthropogenic climate change. Heterotrophic protists are the primary regulators of bacterial diversity in soils and as such play integral roles in biogeochemical cycling, nutrient mobilization, and trophic cascades in food webs under stress. Understanding the nature of these changes requires examining the rates, diversity, and resiliency of interactions that occur between soil organisms. However, soils are the most taxonomically diverse ecosystems on Earth and disentangling the complexities of dynamic and varied biotic interactions in them requires a unique model system. The McMurdo Dry Valleys of Antarctica, one of the harshest terrestrial environments on Earth, serve as a model soil ecosystem owing to their highly reduced biological diversity. Exploring the functioning of heterotrophic protists in these valleys provides a way to test the applicability of this model system to other soil food webs. However, very little is known about their taxonomic diversity, which is a strong predictor of function. Therefore, I reviewed the Antarctic literature to compile a checklist of all known terrestrial heterotrophic protists in Antarctica. I found significant geographical, methodological, and taxonomic biases and outlined how to address these in future research programs. I also conducted a molecular survey of whole soil communities using 18 shotgun metagenomes representing major landscape features of the McMurdo Dry Valleys. The results revealed the dominance of Cercozoa and point to an Antarctic heterotrophic protist soil community that is taxonomically diverse and reflects the structure and composition of communities at lower latitudes. To investigate whether biotic interactions or abiotic factors were a larger driver for Antarctic heterotrophic protists, I conducted variation partitioning using environmental data (e.g. moisture, pH and electrical conductivity). Biotic variables were more significant and accounted for more of the variation than environmental variables. Taken together, it is clear that heterotrophic protists play key ecological roles in this ecosystem. Deeper insights into the ecology of these organisms in the McMurdo Dry Valleys also have implications for the search for complex unicellular life in our universe. I discuss the theoretical underpinnings of searching for these forms of life outside of Earth, conclude that they are likely to occur, and postulate how future missions could practically search for complex unicells.</p>10aheterotrophic soil protists10akey evolutionary innovations10alife on Mars10aMcMurdo Dry Valleys10anetwork analysis10ashotgun metagenomics10auniversal complex unicellular life1 aThompson, Andrew, R.1 aAdams, Byron, J.  uhttps://www.proquest.com/docview/2310631977