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1. Revisiting Diagrams of Ice Growth Environments

   https://doi.org/10.1175/BAMS-D-21-0271.1  

   Hueholt, Daniel M. ; Yuter, Sandra E. ; Miller, Matthew A. ( November 2022 , Bulletin of the American Meteorological Society)

   Ice habit diagrams published prior to 2009—and many since—do not accurately describe in situ observations of ice shapes as a function of temperature and moisture. Laboratory studies and analysis of field observations by Bailey and Hallett in a series of papers in 2002, 2004, and 2009 corrected several errors from earlier studies, but their work has not been widely disseminated. We present a new, simplified diagram based on Bailey and Hallett’s work that focuses on several ice growth forms arising from the underlying surface processes by which mass is added to a crystal: tabular, columnar, branched, side branched, two types of polycrystalline forms, and a multiple growth regime at low ice supersaturations. To aid interpretation for a variety of applications, versions of the ice growth diagram are presented in terms of relative humidity with respect to water as well as the traditional formats of relative humidity with respect to ice and vapor density excess. These diagrams are intended to be understandable and useful in classroom settings at the sophomore undergraduate level and above. The myriad shapes of pristine snow crystals can be described as the result of either a single growth form or a sequence of growth forms. Overlays of data from upper-air soundings on the ice growth diagrams aid interpretation of expected physical properties and processes in conditions of ice growth.

    

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2. Alternate Growth Forms Can Protect Climate-Threatened Trees from Freezing Stressors

   https://doi.org/10.1093/forsci/fxac038  

   Buma, Brian ( October 2022 , Forest Science)

   Climate change creates a variety of novel stressors for species, such as a decline in snowpack. Loss of snow has many impacts, including the loss of thermal insulation of soils. Winter/spring freezing of soils has been tied to forest mass mortality in multiple locations around the world. Many species, however, can take alternative growth forms, such as tall tree forms and short shrub-like forms. Shrub-forms may provide a unique protection from the snow loss phenomenon by providing a similar thermal insulation as snowpack. That hypothesis is tested here using yellow-cedar, a species undergoing mass mortality due to snow loss. Temperature loggers were placed under both tree- and shrub-form cedars, including areas where the species was experimentally removed. The number of soil freezing days was high in open areas, areas of tree mortality, and where the shrub-form was removed, but was almost zero in areas where the shrub-form was left intact. This suggests that growth-form temperature moderation is possible and may provide an important resistance to the mortality mechanism. In other areas around the world where snow loss is resulting in soil freezing and mortality, growth forms should be investigated as a potential moderating mechanism for this particular climate change stress.

    

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3. Filling in Gaps in the Ceratopsid Histologic Database: Histology of Two Basal Centrosaurines and an Assessment of the Utility of Rib Histology in the Ceratopsidae

   https://doi.org/10.1002/ar.24099  

   Hedrick, Brandon P. ; Goldsmith, Erika ; Rivera‐Sylva, Hector ; Fiorillo, Anthony R. ; Tumarkin‐Deratzian, Allison R. ; Dodson, Peter ( March 2019 , The Anatomical Record)

   Bone histology grants substantial insight into the growth and biology of fossil vertebrates. Many of the major non‐avian dinosaurian clades have been extensively sampled for bone histologic data allowing reconstruction of their growth as well as the assessment of the evolution of growth changes along phylogenies. However, horned ceratopsians are poorly represented in paleohistologic studies. Further, the ceratopsian taxa that have been examined are unevenly sampled phylogenetically with very basal forms and highly derived forms making up the majority of studied taxa. In order to rectify this, we have histologically sampledAvaceratopsfrom Montana andYehuecauhceratopsfrom northern Mexico to assess how mid‐sized basal centrosaurines grew relative to more basal and derived forms. Based on results from these taxa, basal centrosaurines present a mosaic of growth characters intermediate between those seen in basal ceratopsians and more derived centrosaurines. Further,Yehuecauhceratopshas many lines of arrested growth preserved, suggesting that the large number of lines of arrested growth found in a high‐latitudePachyrhinosaurusspecimen may be a result of phylogeny rather than geography. Since lines of arrested growth are not preserved in long bones of many ceratopsians, especially chasmosaurines, we also histologically sampled ribs ofAvaceratopsandPachyrhinosaurus. However, the largest ribs were highly remodeled obscuring lines of arrested growth, making it unlikely that rib histology will clarify growth trends in ceratopsians. These centrosaurines add to the growing ceratopsian histological database and demonstrate that basal centrosaurines grew in a manner intermediate between non‐ceratopsid taxa and derived centrosaurines. Anat Rec, 303:935–948, 2020. © 2019 Wiley Periodicals, Inc.

    

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4. Moss phyllid morphology varies systematically with substrate slope

   https://doi.org/10.5091/plecevo.2021.1839  

   Turberville, Caleb M. ; Fuentes-González, Jesualdo A. ; Rogers, Sydney ; Pienaar, Jason ( November 2021 , Plant Ecology and Evolution)

   Background and aims – Tracheophyte leaf morphology is well studied but it is unclear if the findings generalize to poikilohydric plants. We tested combinations of hypotheses to determine if microhabitat characteristics, including light exposure, moisture availability, and substrate slope, controlled for morphological differences between upright and prostrate growth forms, affect phyllid surface area and costa length of mosses.Material and methods – We quantified mean phyllid surface-area and costa lengths for four replicates of 38 moss species from Alabama. Phylogenetic comparative methods that model adaptation were used to evaluate the relative evidence for each hypothesis using information criteria. To further explore mechanistic explanations involving substrate slope, we tested whether mosses on vertical substrates differed from those on horizontal substrates in the average amount of water-retaining, nutrient-rich litter they accumulated.Key results – Substrate slope and growth form combined were the best predictors of phyllid surface area. Mosses growing on vertical substrates exhibited smaller phyllid surface area for both growth forms. Although growth form and phyllid length best explained costa length variation, a more complex model including substrate slope performed nearly as well. Within the prostrate growth forms, species growing on vertical substrates exhibit longer relative costa than those on horizontal substrates. We also estimated rapid rates of adaptation for both traits.Conclusion – The smaller phyllid surface area of both upright and prostrate growth forms is possibly an adaptive response to reduced habitat moisture-retention or nutrient quality that vertical substrates offer. The longer costa lengths of prostrate mosses growing on vertical surfaces relative to prostrate mosses on horizontal surfaces, possibly make up for the decreased ability of smaller phyllids to rapidly reabsorb water when it is available. Further work is required to determine if it is truly substrate slope itself that matters or other variables associated with the differences in slope, and to determine how general this phenomenon is. 

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5. The Relationship Between Microbiomes and Selective Regimes in the Sponge Genus Ircinia

   https://doi.org/10.3389/fmicb.2021.607289  

   Kelly, Joseph B. ; Carlson, David E. ; Low, Jun Siong ; Rice, Tyler ; Thacker, Robert W. ( March 2021 , Frontiers in Microbiology)

   null (Ed.)

   Sponges are often densely populated by microbes that benefit their hosts through nutrition and bioactive secondary metabolites; however, sponges must simultaneously contend with the toxicity of microbes and thwart microbial overgrowth. Despite these fundamental tenets of sponge biology, the patterns of selection in the host sponges’ genomes that underlie tolerance and control of their microbiomes are still poorly understood. To elucidate these patterns of selection, we performed a population genetic analysis on multiple species of Ircinia from Belize, Florida, and Panama using an F ST -outlier approach on transcriptome-annotated RADseq loci. As part of the analysis, we delimited species boundaries among seven growth forms of Ircinia . Our analyses identified balancing selection in immunity genes that have implications for the hosts’ tolerance of high densities of microbes. Additionally, our results support the hypothesis that each of the seven growth forms constitutes a distinct Ircinia species that is characterized by a unique microbiome. These results illuminate the evolutionary pathways that promote stable associations between host sponges and their microbiomes, and that potentially facilitate ecological divergence among Ircinia species. 

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