Search for: All records

Relating physiological stress to habitat quality could refne conservation eforts. Habitat quality, which is often inferred from patch occupancy or demographic rates, might be measured in a more timely and nuanced way using metrics of physiological stress. To understand whether stressassociated hormones vary with metrics of habitat quality, we measured fecal glucocorticoid metabolite (FGM) levels in the American pika (Ochotona princeps), a small mammal with welldefned habitat (talus), which can vary in quality depending on the presence of subsurface ice features. In spring and fall 2018, we collected feces noninvasively from pika territories in taluses “with” or “without” subsurface ice to capture seasonal variation in FGM between habitat types. We used linear mixed efects models to explore the interactions among season, habitat metrics (including subsurface ice status), and subsurface temperature as predictors of FGM. We found support for interacting efects on FGM levels, which covaried with season, elevation, putative ice presence, graminoid to forb ratio, graminoid cover, and measures of acute subsurface heat exposure. However, only one subsurface temperature metric difered according to putative presence of subsurface ice. Our results contribute to the growing evidence that FGMs might be developed as a tool to assess habitat quality. 

Research over the last decade has revealed the importance of the cutaneous microbiome for the health and immune function of amphibians. Thousands of Bacteria and Archaeans species living in and on the skin are able to outcompete pathogenic species of fungus or types of viruses. The relationship between microbes and their host is so intimate that the term "metaorganism" has been used to describe this phenomenon. We are, however, at the early stages of understanding what determines the composition of the cutaneous microbiome and the relative effects of factors like genetics and habitat use. Could it be that there is a species-specific “microbiome fingerprint” that is consistent across different sites? Do species inhabiting similar microhabitats host similar microbes? We have replicated a similar study performed in Sosbee Cove in Union County, with a site in Cherokee County, with multiple species that are comparable across the two sites. We present our project designed to answer these questions and report preliminary results. 

Abstract Captive breeding has become a critical tool for the restoration of amphibian populations decimated by diseases. However, much is unknown about effects of long-term captivity on amphibian health and particularly immune system function. Therefore, we have begun a project to understand the effects of captivity and captive breeding on the cutaneous microbiome of lungless salamanders. The community of microbes living in and on the skin of lungless salamanders (Plethodontidae) is an important predictor of the organisms’ ability to ward off diseases like chytridiomycosis. We compare the microbiome of wild and long-term (8 years) captive or captive-bred Ocoee and Blue Ridge two-lined salamanders (Desmognathus ocoee and Eurycea wilderae, respectively) all from the Charles H. Wharton Conservation Center in Union County, GA. Microbiome communities were estimated by amplifying the V4 region of the 16S rDNA gene and then comparing with sequences from the Greengenes database. We present our study design and preliminary results. 

In the directed setting, the spaces of directed paths between fixed initial and terminal points are the defining feature for distinguishing different directed spaces. The simplest case is when the space of directed paths is homotopy equivalent to that of a single path; we call this the trivial space of directed paths. Directed spaces that are topologically trivial may have non-trivial spaces of directed paths, which means that information is lost when the direction of these topological spaces is ignored. We define a notion of directed collapsibility in the setting of a directed Euclidean cubical complex using the spaces of directed paths of the underlying directed topological space, relative to an initial or a final vertex. In addition, we give sufficient conditions for a directed Euclidean cubical complex to have a contractible or a connected space of directed paths from a fixed initial vertex. We also give sufficient conditions for the path space between two vertices in a Euclidean cubical complex to be disconnected. Our results have applications to speeding up the verification process of concurrent programming and to understanding partial executions in concurrent programs. 

Ecosystems across the United States are changing in complex and surprising ways. Ongoing demand for critical ecosystem services requires an understanding of the populations and communities in these ecosystems in the future. This paper represents a synthesis effort of the U.S. National Science Foundation-funded Long-Term Ecological Research (LTER) network addressing the core research area of “populations and communities.” The objective of this effort was to show the importance of long-term data collection and experiments for addressing the hardest questions in scientific ecology that have significant implications for environmental policy and management. Each LTER site developed at least one compelling case study about what their site could look like in 50–100 yr as human and environmental drivers influencing specific ecosystems change. As the case studies were prepared, five themes emerged, and the studies were grouped into papers in this LTER Futures Special Feature addressing state change, connectivity, resilience, time lags, and cascading effects. This paper addresses the “connectivity” theme and has examples from the Phoenix (urban), Niwot Ridge (alpine tundra), McMurdo Dry Valleys (polar desert), Plum Island (coastal), Santa Barbara Coastal (coastal), and Jornada (arid grassland and shrubland) sites. Connectivity has multiple dimensions, ranging from multi-scalar interactions in space to complex interactions over time that govern the transport of materials and the distribution and movement of organisms. The case studies presented here range widely, showing how land-use legacies interact with climate to alter the structure and function of arid ecosystems and flows of resources and organisms in Antarctic polar desert, alpine, urban, and coastal marine ecosystems. Long-term ecological research demonstrates that connectivity can, in some circumstances, sustain valuable ecosystem functions, such as the persistence of foundation species and their associated biodiversity or, it can be an agent of state change, as when it increases wind and water erosion. Increased connectivity due to warming can also lead to species range expansions or contractions and the introduction of undesirable species. Continued long-term studies are essential for addressing the complexities of connectivity. The diversity of ecosystems within the LTER network is a strong platform for these studies. 

Organic semiconductor materials have recently gained momentum due to their non‐toxicity, low cost, and sustainability. Xylindein is a remarkably photostable pigment secreted by fungi that grow on decaying wood, and its relatively strong electronic performance is enabled by π–π stacking and hydrogen‐bonding network that promote charge transport. Herein, femtosecond transient absorption spectroscopy with a near‐IR probe was used to unveil a rapid excited‐state intramolecular proton transfer reaction. Conformational motions potentially lead to a conical intersection that quenches fluorescence in the monomeric state. In concentrated solutions, nascent aggregates exhibit a faster excited state lifetime due to excimer formation, confirmed by the excimer→charge‐transfer excited‐state absorption band of the xylindein thin film, thus limiting its optoelectronic performance. Therefore, extending the xylindein sidechains with branched alkyl groups may hinder the excimer formation and improve optoelectronic properties of naturally derived materials.