Earth Sciences

Permanent URI for this communityhttps://scholarworks.montana.edu/handle/1/43

By virtue of our outstanding location in the scenic and rugged mountains of southwest Montana, Earth Science students have many opportunities to participate in field trips that will facilitate the study of earth processes, earth resources, earth history, and environments that people have modified. These field trips are an integral part of many courses, as well as extracurricular activities sponsored by the department. Fieldwork is a very important component of our instructional programs at both the undergraduate and graduate levels.Because of the research conducted by faculty in the department, an undergraduate student may have the opportunity to work on active research projects. In particular, we offer the opportunity to do a "Senior Thesis" to our top students in each senior class. The senior thesis enables a student to work on an actual research project under the supervision of a faculty member, write a research report (a mini-thesis), and present the results at a professional conference. This is excellent preparation for graduate school and/or the workplace. Our Master's theses frequently involve field-testing of state-of-the-art hypotheses proposed elsewhere, as well as formulation of the next generation of hypotheses, which will shape our disciplines in the decades to come. Most Master's thesis work in the Department is published in the peer-reviewed professional literature after presentation at regional or national professional meetings.

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    Evolutionary Divergence of Marinobacter Strains in Cryopeg Brines as Revealed by Pangenomics
    (Frontiers Media SA, 2022-06) Cooper, Zachary S.; Rapp, Josephine Z.; Shoemaker, Anna M. D.; Anderson, Rika E.; Zhong, Zhi-Ping; Deming, Jody W.
    Marinobacter spp. are cosmopolitan in saline environments, displaying a diverse set of metabolisms that allow them to competitively occupy these environments, some of which can be extreme in both salinity and temperature. Here, we introduce a distinct cluster of Marinobacter genomes, composed of novel isolates and in silico assembled genomes obtained from subzero, hypersaline cryopeg brines, relic seawater-derived liquid habitats within permafrost sampled near Utqiaġvik, Alaska. Using these new genomes and 45 representative publicly available genomes of Marinobacter spp. from other settings, we assembled a pangenome to examine how the new extremophile members fit evolutionarily and ecologically, based on genetic potential and environmental source. This first genus-wide genomic analysis revealed that Marinobacter spp. in general encode metabolic pathways that are thermodynamically favored at low temperature, cover a broad range of organic compounds, and optimize protein usage, e.g., the Entner–Doudoroff pathway, the glyoxylate shunt, and amino acid metabolism. The new isolates contributed to a distinct clade of subzero brine-dwelling Marinobacter spp. that diverged genotypically and phylogenetically from all other Marinobacter members. The subzero brine clade displays genomic characteristics that may explain competitive adaptations to the extreme environments they inhabit, including more abundant membrane transport systems (e.g., for organic substrates, compatible solutes, and ions) and stress-induced transcriptional regulatory mechanisms (e.g., for cold and salt stress) than in the other Marinobacter clades. We also identified more abundant signatures of potential horizontal transfer of genes involved in transcription, the mobilome, and a variety of metabolite exchange systems, which led to considering the importance of this evolutionary mechanism in an extreme environment where adaptation via vertical evolution is physiologically rate limited. Assessing these new extremophile genomes in a pangenomic context has provided a unique view into the ecological and evolutionary history of the genus Marinobacter, particularly with regard to its remarkable diversity and its opportunism in extremely cold and saline environments.
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    The diverse terminology of reptile eggshell microstructure and its effect on phylogenetic comparative analyses
    (Wiley, 2022-06) Legendre, Lucas J.; Choi, Seung; Clarke, Julia A.
    Reptile eggshell ensures water and gas exchange during incubation and plays a key role in reproductive success. The diversity of reptilian incubation and life history strategies has led to many clade-specific structural adaptations of their eggshell, which have been studied in extant taxa (i.e. birds, crocodilians, turtles, and lepidosaurs). Most studies on non-avian eggshells were performed over 30 years ago and categorized reptile eggshells into two main types: “hard” and “soft” – sometimes with a third intermediate category, “semi-rigid.” In recent years, however, debate over the evolution of eggshell structure of major reptile clades has revealed how definitions of hard and soft eggshells influence inferred deep-time evolutionary patterns. Here, we review the diversity of extant and fossil eggshell with a focus on major reptile clades, and the criteria that have been used to define hard, soft, and semi-rigid eggshells. We show that all scoring approaches that retain these categories discretize continuous quantitative traits (e.g. eggshell thickness) and do not consider independent variation of other functionally important microstructural traits (e.g. degree of calcification, shell unit inner structure). We demonstrate the effect of three published approaches to discretizing eggshell type into hard, semi-rigid, and soft on ancestral state reconstructions using 200+ species representing all major extant and extinct reptile clades. These approaches result in different ancestral states for all major clades including Archosauria and Dinosauria, despite a difference in scoring for only 1–4% of the sample. Proposed scenarios of reptile eggshell evolution are highly conditioned by sampling, tree calibration, and lack of congruence between definitions of eggshell type. We conclude that the traditional “soft/hard/semi-rigid” classification of reptilian eggshells should be abandoned and provide guidelines for future descriptions focusing on specific functionally relevant characteristics (e.g. inner structures of shell units, pores, and membrane elements), analyses of these traits in a phylogenetic context, and sampling of previously undescribed taxa, including fossil eggs.
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