The Yellowstone Permutation

Define a sequence of positive integers by the rule that a(n) = n for 1 <= n = 4, a(n) is the smallest number not already in the sequence which has a common factor with a(n-2) and is relatively prime to a(n-1). We show that this is a permutation of the positive integers. The remarkable graph of this sequence consists of runs of alternating even and odd numbers, interrupted by small downward spikes followed by large upward spikes, suggesting the eruption of geysers in Yellowstone National Park. On a larger scale the points appear to lie on infinitely many distinct curves. There are several unanswered questions concerning the locations of these spikes and the equations for these curves.Comment: 10 pages, 6 figures. Mar 7 2015: mostly stylistic change

Populus tremuloides seedling establishment: An underexplored vector for forest type conversion after multiple disturbances

Ecosystem resilience to climate change is contingent on post-disturbance plant regeneration. Sparse gymnosperm regeneration has been documented in subalpine forests following recent wildfires and compounded disturbances, both of which are increasing. In the US Intermountain West, this may cause a shift to non-forest in some areas, but other forests may demonstrate adaptive resilience through increased quaking aspen (Populus tremuloides Michx.) dominance. However, this potential depends on ill-defined constraints of aspen sexual regeneration under current climate. We created an ensemble of species distribution models for aspen seedling distribution following severe wildfire to define constraints on establishment. We recorded P. tremuloides seedling locations across a post-fire, post-blowdown landscape. We used 3 algorithms (Mahalanobis Typicalities,Multilayer Perceptron Artificial Neural Network, and MaxEnt) to create spatial distribution models for aspen seedlings and to define constraints. Each model performed with high accuracy and was incorporated into an ensemble model, which performed with the highest overall accuracy of all the models. Populus tremuloides seedling distribution is constrained primarily by proximity to unburned aspen forest and annual temperature ranges, and secondarily by light availability, summer precipitation, and fire severity. Based on model predictions and validation data, P. tremuloides seedling regeneration is viable throughout 54% of the post-fire landscape, 97% of which was previously conifer-dominated. Aspen are less susceptible to many climatically-sensitive disturbances (e.g. fire, beetle outbreak, wind disturbance), thus, aspen expansion represents an important adaptation to climate change. Continued aspen expansion into post-disturbance landscapes through sexual reproduction at the level suggested by these results would represent an important adaptation to climate change and would confer adaptive forest resilience by maintaining forest cover, but would also alter future disturbance regimes, biodiversity, and ecosystem services.Ye

Microbial communities and arsenic biogeochemistry at the outflow of an alkaline sulfide-rich hot spring.

Alkaline sulfide-rich hot springs provide a unique environment for microbial community and arsenic (As) biogeochemistry. In this study, a representative alkaline sulfide-rich hot spring, Zimeiquan in the Tengchong geothermal area, was chosen to study arsenic geochemistry and microbial community using Illumina MiSeq sequencing. Over 0.26 million 16S rRNA sequence reads were obtained from 5-paired parallel water and sediment samples along the hot spring's outflow channel. High ratios of As(V)/AsSum (total combined arsenate and arsenite concentrations) (0.59-0.78), coupled with high sulfide (up to 5.87 mg/L), were present in the hot spring's pools, which suggested As(III) oxidation occurred. Along the outflow channel, AsSum increased from 5.45 to 13.86 μmol/L, and the combined sulfide and sulfate concentrations increased from 292.02 to 364.28 μmol/L. These increases were primarily attributed to thioarsenic transformation. Temperature, sulfide, As and dissolved oxygen significantly shaped the microbial communities between not only the pools and downstream samples, but also water and sediment samples. Results implied that the upstream Thermocrinis was responsible for the transformation of thioarsenic to As(III) and the downstream Thermus contributed to derived As(III) oxidation. This study improves our understanding of microbially-mediated As transformation in alkaline sulfide-rich hot springs

The Binary Enots Wolley Sequence

It is an open conjecture that the Enots Wolley sequence is surjective onto the set of positive integers with a binary weight of at least 2. In this paper, this property is proved for an analog of the Enots Wolley sequence which operates on the binary representation of a number rather than the prime factorization

Compression and Conditional Emulation of Climate Model Output

Numerical climate model simulations run at high spatial and temporal resolutions generate massive quantities of data. As our computing capabilities continue to increase, storing all of the data is not sustainable, and thus it is important to develop methods for representing the full datasets by smaller compressed versions. We propose a statistical compression and decompression algorithm based on storing a set of summary statistics as well as a statistical model describing the conditional distribution of the full dataset given the summary statistics. The statistical model can be used to generate realizations representing the full dataset, along with characterizations of the uncertainties in the generated data. Thus, the methods are capable of both compression and conditional emulation of the climate models. Considerable attention is paid to accurately modeling the original dataset--one year of daily mean temperature data--particularly with regard to the inherent spatial nonstationarity in global fields, and to determining the statistics to be stored, so that the variation in the original data can be closely captured, while allowing for fast decompression and conditional emulation on modest computers

Phylogeography of the thermophilic Cyanobacterium Mastigocladus Laminosus

We have taken a phylogeographic approach to investigate the demographic and evolutionary processes that have shaped the geographic patterns of genetic diversity for a sample of isolates of the cosmopolitan thermophillic cyanobacterial Mastigocladus laminosus morphotype collected from throughout most of its range. Although M. laminosus is found in thermal areas throughout the world, our observation that populations are typically genetically differentiated on local geographic scales suggests the existence of dispersal barriers, a conclusion corroborated by evidence for genetic isolation by distance. Genealogies inferred using nitrogen metabolism gene sequence data suggest that a significant amount of the extant global diversity of M. laminosus can be traced back to a common ancestor associated with the western North American hot spot currently located below Yellowstone National Park. Estimated intragenic recombination rates are comparable to those of pathogenic bacteria known for their capacity to exchange DNA, indicating that genetic exchange has played an important role in generating novel variation during M. laminosus diversification. Selection has constrained protein changes at loci involved in the assimilation of both dinitrogen and nitrate, suggesting the historic use of both nitrogen sources in this heterocystous cyanobacterium. Lineage-specific differences in thermal performance were also observed

Initial and future stand development following mountain pine beetle in harvested and uncut lodgepole pine forests

2010 Spring.Covers not scanned.Includes bibliographical references.The extent and severity of over tory lodgepole pine (Pinus contorta Dougl.) mortality from mountain pine beetle (Dendroctonus ponderosae Hopkins) has created management concerns associated with forest regeneration, wildfire risk, human safety, and scenic, wildlife and watershed resources in western North America. In northern Colorado and southern Wyoming the long-term ecological and socioeconomic consequences of the outbreak hinge upon the response of tree regeneration in both harvested and untreated forests. To characterize initial and future forest development following mountain pine beetle mortality I conducted two studies. First, I used historic U.S. Forest Service stand and seedling survey records to compare the density and species composition of advance regeneration in uncut stands and post-harvest recruits in clearcut harvest units during pre-outbreak (1980-1996) and outbreak (2002-2007) period. Second, I compared the effects of various intensities of forest management on site conditions, seedling establishment and growth of advance regeneration to uncut areas in beetle-infested lodgepole pine stands. Advance regeneration averaged 3,953 stems ha-1 and was at least as high in beetle-infested stands compared to the pre-outbreak period. Lodgepole pine advance regeneration showed increased leader growth from 2008 to 2009 in harvested and untreated stands in response to canopy removal and decreased canopy foliage following overstory mortality. The density of seedling recruitment was three times higher in harvested than untreated stands (6,487 versus 2,021 seedlings ha-1), and did not differ between outbreak and pre-outbreak stands. Growth simulations showed uncut and partial cut stands will be dominated by subalpine fir (Abies lasiocarpa), while clearcut stand will be dominated by lodgepole pine and have attributes similar to pre-outbreak stands within a century

Adaptation to a geothermal soil mosaic shapes genome-wide patterns of diversity and differentiation in Yellowstone monkeyflowers (M. guttatus)

Local adaptation across habitat mosaics can generate phenotypic divergence in the face of gene flow; however, adaptive divergence in reproductive traits may also create barriers to genetic exchange within and among distinct habitats. In plants, life-history, phenology, and mating system traits may lead to divergent selection over short (microgeographic) spatial scales. Changes to these traits are likely to directly affect patterns of gene flow and genomic diversity. In this study, we combined field, common garden, and population genomic approaches to investigate phenotypic and genetic variation in Mimulus guttatus (yellow monkeyflowers) adapted to a complex geothermal soil mosaic in Yellowstone National Park (YNP). A previously-identified major locus underlying life-history divergence (out6) strongly sorts by habitat (thermal annual habitats [AH] vs. non-thermal perennial habitats [PH]) across YNP. Plants from AH and PH were also differentiated for self-pollination potential and flowering time traits in the common garden, consistent with adaptation to spring-flowering in thermal habitats. Genome-wide sequence data (ddRADSeq) reveals one highly differentiated (and ecologically extreme) AH population (AHQT), while the other AH and PH plants form four geographic populations. F’ST between the geographic regions varied but remained relatively high (~0.10) across all comparisons. F’ST between AH-AH sub-populations pairs were marginally more differentiated than PH-PH pairs (F’ST = 0.13 vs. 0.10, respectively). Slightly elevated differentiation of thermal annual populations mirrors the isolation of AHQT from all other populations and suggests that increased selfing and phenological assortative mating in thermal habits generate structure through reduced gene flow and increased drift. Individual inbreeding coefficients (FIS) were positively associated with mean progeny stigma-anther distance and significantly elevated in thermal annual habitats. This is consistent with the inference that thermal habitats select for efficient self-pollination, with consequences for individual and population variation. Overall, multi-trait adaptation to geothermal soils occurs despite ongoing gene flow with nearby nonthermal populations, and parallel selective pressures in extreme thermal soils have reassembled similar adaptive phenotypes on distinct genetic backgrounds. To varying degrees, thermal annuals exhibit genomic signatures of elevated population differentiation that suggest they may be in the early stages of developing local reproductive isolation