Historic hybridization and persistence of a novel mito-nuclear combination in red-backed voles (genus Myodes)

<p>Abstract</p> <p>Background</p> <p>The role of hybridization in generating diversity in animals is an active area of discovery and debate. We assess hybridization across a contact zone of northern (<it>Myodes rutilus</it>) and southern (<it>M. gapperi</it>) red-backed voles using variation in skeletal features and both mitochondrial and nuclear loci. This transect extends approximately 550 km along the North Pacific Coast of North America and encompasses 26 populations (n = 485). We establish the history, geographic extent and directionality of hybridization, determine whether hybridization is ongoing, and assess the evolutionary stability of novel genomic combinations.</p> <p>Results</p> <p>Identification of <it>M. rutilus </it>and <it>M. gapperi </it>based on the degree of closure of the post-palatal bridge was concordant with the distribution of diagnostic nuclear MYH6 alleles; however, an 80 km zone of introgressed populations was identified. The introgressant form is characterized by having mitochondrial haplotypes closely related to the northern <it>M. rutilus </it>on a nuclear background and morphological characteristics of southern <it>M. gapperi</it>.</p> <p>Conclusion</p> <p>Introgression appears to have been historic as pure populations of <it>M. rutilus </it>are now isolated to the north from introgressants or pure <it>M. gapperi </it>by the LeConte Glacier. As we do not find pure <it>M. rutilus </it>or <it>M. gapperi </it>individuals throughout the distribution of the introgressant form, it appears that the introgressants are a self-sustaining entity not requiring continued hybridization between pure parental forms to generate this novel combination of characters.</p

The Heather Vole, Genus Phenacomys, in Alaska

Four specimens of heather vole (genus Phenacomys) collected in the coastal mountains of Southeast Alaska document the first Recent records of this vole in Alaska. Alternative hypotheses on the relationship of these newly-discovered populations to extant and historical populations are outlined, and additional studies proposed

Australia's arid-adapted butcherbirds experienced range expansions during Pleistocene glacial maxima

A model of range expansions during glacial maxima (GM) for cold-adapted species is generally accepted for the Northern Hemisphere. Given that GM in Australia largely resulted in the expansion of arid zones, rather than glaciation, it could be expected that arid-adapted species might have had expanded ranges at GM, as cold-adapted species did in the Northern Hemisphere. For Australian biota, however, it remains paradigmatic that arid-adapted species contracted to refugia at GM. Here we use multilocus data and ecological niche models (ENMs) to test alternative GM models for butcherbirds. ENMs, mtDNA and estimates of nuclear introgression and past population sizes support a model of GM expansion in the arid-tolerant Grey Butcherbird that resulted in secondary contact with its close relative - the savanna-inhabiting Silver-backed Butcherbird - whose contemporary distribution is widely separated. Together, these data reject the universal use of a GM contraction model for Australia's dry woodland and arid biota

Topographic shading influences cryoconite morphodynamics and carbon exchange

Cryoconite holes are the most active and diverse microbial habitats on glacier and ice-sheet surfaces. In this article the authors demonstrate that the shape of cryoconite holes varies depending on ice-surface topography and that this has implications for the carbon cycling regime within. Net ecosystem production is shown to be controlled primarily by sediment thickness within holes. The authors show that irregular hole shapes are indicative of hole migration away from topographic shade, which promotes carbon fixation at the mesoscale on ice surfaces. A cellular automaton is used in conjunction with sediment-delivery experiments to show that migration is the result of simple sediment transfer processes, implying a relationship between ice-surface evolution and cryoconite biogeochemistry that has not previously been examined.The authors gratefully acknowledge funding from the British Society for Geomorphology, Mount Everest Foundation, Gino Watkins Memorial Fund, Andrew Croft Memorial Fund, Scottish Arctic Club, Gilchrist Educational Fund, and Rolex Awards for Enterprise and Gradconsult. JC also acknowledges UK-funded Natural Environment Research Council Consortium Grant “Black and Bloom” (NE/ M021025/1)

Glacier algae: a dark past and a darker future

“Glacier algae” grow on melting glacier and ice sheet surfaces across the cryosphere, causing the ice to absorb more solar energy and consequently melt faster, while also turning over carbon and nutrients. This makes glacier algal assemblages, which are typically dominated by just three main species, a potentially important yet under-researched component of the global biosphere, carbon, and water cycles. This review synthesizes current knowledge on glacier algae phylogenetics, physiology, and ecology. We discuss their significance for the evolution of early land plants and highlight their impacts on the physical and chemical supraglacial environment including their role as drivers of positive feedbacks to climate warming, thereby demonstrating their influence on Earth’s past and future. Four complementary research priorities are identified, which will facilitate broad advances in glacier algae research, including establishment of reliable culture collections, sequencing of glacier algae genomes, development of diagnostic biosignatures for remote sensing, and improved predictive modeling of glacier algae biological-albedo effects

Bootstrap Exploration of the Duration of Surface Electromyography Sampling in Relation to the Precision of Exposure Estimation

Objectives: This study examined the effect of sampling duration, in units of work cycles, on the precision of estimates of exposure to forceful exertion obtained with surface electromyography (EMG). Methods: Recordings of the activity of the flexor digitorum superficialis, extensor digitorum, and upper trapezius muscles over 30 consecutive work cycles were obtained for a random sample of 25 manufacturing workers, each of whom was performing a unique production task representing a portion of the whole job. The mean root-meansquare amplitude and the 10th, 50th, and 90th percentiles of the distribution function of the amplitude probability were calculated for each cycle. Bootstrap analyses were used to examine the precision of the summary measures as the sampling duration increased incrementally from 1 to 30 work cycles. Precision was estimated by calculating the coefficient of variation (CV) of the bootstrap distributions at each sampling duration increment. Results: The average minimum sampling duration for a bootstrap distribution CV of 15% ranged from 2.0 (SD 1.5) cycles to 7.5 (SD 9.6) cycles, depending on muscle and summary measure. For a 5% CV, the average minimum sampling duration ranged from 11.9 (SD 9.0) to 20.9 (SD 10.5) cycles. Conclusions: The results suggest that sampling as few as three work cycles was sufficient to obtain a bootstrap distribution CV of 15% for some of the muscles and summary measures examined in this study. While limited to machine-paced, cyclic manufacturing work, these results will assist the development of exposure assessment strategies in future epidemiologic studies of physical risk factors and musculoskeletal disorders

Light absorption and albedo reduction by pigmented microalgae on snow and ice

Pigmented microalgae inhabiting snow and ice environments lower the albedo of glacier and ice-sheet surfaces, significantly enhancing surface melt. Our ability to accurately predict their role in glacier and ice-sheet surface mass balance is limited by the current lack of empirical data to constrain their representation in predictive models. Here we present new empirical optical properties for snow and ice algae and incorporate them in a radiative transfer model to investigate their impact on snow and ice surface albedo. We found ice algal cells to be more efficient absorbers than snow algal cells, but their blooms had comparable impact on surface albedo due to the different photic conditions of their habitats. We then used the model to reconstruct the effect of ice algae on bare ice albedo spectra collected at our field site in southern Greenland, where blooms dropped the albedo locally by between 3 and 43%, equivalent to 1-10 L m(-2) d(-1) of melted ice. Using the newly parametrized model, future studies could investigate biological albedo reduction and algal quantification from remote hyperspectral and multispectral imagery

732-1 An Institutional Experience with Second and Third Stage Palliative Procedures for Hypoplastic Left Heart Syndrome: The Impact of the Bidirectional Cavopulmonary Shunt

We reviewed 71 consecutive pts who underwent stage II and III operations following stage I palliation for hypoplastic left heart syndrome (HLHS) at our institution since 1983. 6 surgeons participated in the care of these pts. Follow-up is 97% complete. We examined 17 potential risk factors for mortality, including preoperative anatomic and physiologic factors, and procedural features of the stage II operation. Multivariate analysis revealed that the only significant risk factor for stage II mortality was the performance of a non-fenestrated completion Fontan procedure (p&lt;0.001). There were 9 hospital deaths (69%) in the 13 pts undergoing the Fontan procedure at stage II. In contrast, 49 pts underwent bidirectional cavopulmonary shunting (47) or hemi-Fontan procedure(2) as an intermediate step to the Fontan procedure with 4 (8%) early deaths. The first bidirectional cavopulmonary shunt was performed in this population in 1988. Median age at this stage II procedure was 8.4 months. Surgical augmentation of the pulmonary arteries was performed in 18 (37%) pts at the time of stage II surgery and was not associated with increased operative risk. Also, HLHS anatomic subtype was not a risk factor for stage II mortality or pre-stage III attrition. There have been 2 (4%) intermediate deaths prior to the performance of a stage III procedure, which at our institution is the fenestrated Fontan procedure. This has been performed in 25 pts at a median age of 30 months with 1 early death and no mortality at a median follow-up of 22 months. There are presently 34 HLHS pts who have modified Fontan anatomy following a course of surgical palliation performed entirely at this institution. Follow-up in this group ranges up to 92 months, with a median of 28 months. 33 of these patients are NYHA class 1 or 2.2 pts have required pacemaker implantation, but there have otherwise been no surgical reinterventions in pts who have completed palliation. We conclude that the incorporation of the bidirectional cavopulmonary shunt into a course of surgical palliation for HLHS has dramatically reduced mortality in this challenging group of pts, allowing them to undergo the modified fenestrated Fontan procedure with low operative mortality and good intermediate outcome

Diel Variation in the Vertical Distribution of Deep-Water Scattering Layers in the Gulf of Mexico

Sound scattering layers (SSLs) are important components of oceanic ecosystems with ubiquitous distribution throughout the world\u27s oceans. This vertical movement is an important mechanism for exchanging organic matter from the surface to the deep ocean, as many of the organisms comprising SSLs serve as prey resources for linking the lower trophic levels to larger predators. Variations in abundance and taxonomic composition of mesopelagic organisms were quantified using repeated discrete net sampling and acoustics over a 30-h survey, performed during 26–27 June 2011 at single site (27°28’51”N and 88°27’54”W) in the northern Gulf of Mexico. We acoustically classified the mesopelagic SSL into four broad taxonomic categories, crustacean and small non-swimbladdered fish (CSNSBF), large non-swimbladdered fish (LNSBF), swimbladdered fish (SBF) and unclassified and we quantified the abundance of mesopelagic organisms over three discrete depth intervals; epipelagic (0–200 m); upper mesopelagic (200–600 m) and lower mesopelagic (600–1000 m). Irrespective of the acoustic categories at dusk part of the acoustic energy redistributed from the mesopelagic into the upper epipelagic (shallower than 100 m) remaining however below the thermocline depth. At night higher variability in species composition was observed between 100 and 200 m suggested that a redistribution of organisms may also occur within the upper portion of the water column. Along the upper mesopelagic backscatter spectra from CSNSBF migrated between 400 and 460 m while spectra from the other categories moved to shallower depths (300 and 350 m), resulting in habitat separation from CSNSBF. Relatively small vertical changes in both acoustic backscatter and center of mass metrics of the deep mesopelagic were observed for CNSBF and LNSBF suggesting that these animals may be tightly connected to deeper (below 1000 m) mesopelagic habitats, and do not routinely migrate into the epipelagic