Philip J. Turk

Flight responses by a migratory soaring raptor to changing meteorological conditions.

Soaring birds that undertake long-distance migration should develop strategies to minimize the energetic costs of endurance flight. This is relevant because condition upon completion of migration has direct consequences for fecundity, fitness and thus, demography. Therefore, strong evolutionary pressures are expected for energy minimization tactics linked to weather and topography. Importantly, the minute-by-minute mechanisms birds use to subsidize migration in variable weather are largely unknown, in large part because of the technological limitations in studying detailed long-distance bird flight. Here, we show golden eagle (Aquila chrysaetos) migratory response to changing meteorological conditions as monitored by high-resolution telemetry. In contrast to expectations, responses to meteorological variability were stereotyped across the 10 individuals studied. Eagles reacted to increased wind speed by using more orographic lift and less thermal lift. Concomitantly, as use of thermals decreased, variation in flight speed and altitude also decreased. These results demonstrate how soaring migrant birds can minimize energetic expenditures, they show the context for avian decisions and choices of specific instantaneous flight mechanisms and they have important implications for design of bird-friendly wind energy.

Soil-mediated local adaptation alters seedling survival and performance

Background and aimsSoils can act as agents of natural selection, causing differential fitness among genotypes and/or families of the same plant species, especially when soils have extreme physical or chemical properties. More subtle changes in soils, such as variation in microbial communities, may also act as agents of selection. We hypothesized that variation in soil properties within a single river drainage can be a selective gradient, driving local adaptation in plants.MethodsUsing seeds collected from individual genotypes of Populus angustifolia James and soils collected from underneath the same trees, we use a reciprocal transplant design to test whether seedlings would be locally adapted to their parental soil type.ResultsWe found three patterns: 1. Soils from beneath individual genotypes varied in pH, soil texture, nutrient content, microbial biomass and the physiological status of microorganisms. 2. Seedlings grown in local soils experienced 2.5-fold greater survival than seedlings planted in non-local soils. 3. Using a composite of height, number of leaves and leaf area to measure plant growth, seedlings grew ∼17.5% larger in their local soil than in non-local soil.ConclusionsThese data support the hypothesis that variation in soils across subtle gradients can act as an important selective agent, causing differential fitness and local adaptation in plants.

Use of multiple modes of flight subsidy by a soaring terrestrial bird, the golden eagle Aquila chrysaetos, when on migration

Large birds regularly use updrafts to subsidize flight. Although most research on soaring bird flight has focused on use of thermal updrafts, there is evidence suggesting that many species are likely to use multiple modes of subsidy. We tested the degree to which a large soaring species uses multiple modes of subsidy to provide insights into the decision-making that underlies flight behaviour. We statistically classified more than 22 000 global positioning satellite–global system for mobile communications telemetry points collected at 30-s intervals to identify the type of subsidized flight used by 32 migrating golden eagles during spring in eastern North America. Eagles used subsidized flight on 87% of their journey. They spent 41.9% ± 1.5 (, range: 18–56%) of their subsidized northbound migration using thermal soaring, 45.2% ± 2.1 (12–65%) of time gliding between thermals, and 12.9% ± 2.2 (1–55%) of time using orographic updrafts. Golden eagles responded to the variable local-scale meteorological events they encountered by switching flight behaviour to take advantage of multiple modes of subsidy. Orographic soaring occurred more frequently in morning and evening, earlier in the migration season, and when crosswinds and tail winds were greatest. Switching between flight modes allowed migration for relatively longer periods each day and frequent switching behaviour has implications for a better understanding of avian flight behaviour and of the evolution of use of subsidy in flight.

Perceived distance and obesity: It's what you weigh, not what you think.

Action abilities are constrained by physical body size and characteristics, which, according to the action-specific account of perception, should influence perceived space. We examined whether physical body size or beliefs about body size affect distance perception by taking advantage of naturally-occurring dissociations typical in people who are obese but believe themselves to weigh less. Normal weight, overweight, and obese individuals made verbal distance estimates. We also collected measures of beliefs about body size and measures of physical body size. Individuals who weighed more than others estimated distances to be farther. Furthermore, physical body weight influenced perceived distance but beliefs about body size did not. The results illustrate that whereas perception is influenced by physical characteristics, it is not influenced by beliefs. The results also have implications for perception as a contributing factor for lifestyle choices: people who weigh more than others may choose to perform less physically demanding actions not as a result of how they perceive their bodies, but as a result of how they perceive the environment.

The effect of a flaxseed oil-enhanced diet on the product quality of farmed brook trout (Salvelinus fontinalis) fillets.

The effects of dietary modification with flaxseed oil-enhanced (Flax) feed on the product quality of brook trout fillets were examined. Trout were fed a commercial feed supplemented with fish oil (CD) or flaxseed oil (Flax) for 165 d before harvesting. Proximate composition and fatty acid profile were determined on fillets. Quality parameters of the raw fillets were examined over the storage period by measuring color (L*, a*, b*), muscle pH, and thiobarbituric acid reactive substances test. Evaluations on the cooked fillets included sensory evaluation with triangle tests and a paired preference test. There were no differences in proximate composition between the groups; however, the total omega-3 fatty acids were greater in Flax fillets (P<0.05). Diet and day were shown to interact in their effect on whiteness, pH, and lipid oxidation (P<0.05); however, linear regression did not determine that malondialdehyde concentration was associated with time in either diet type implying that lipid oxidation in the vacuum-packed fish was controlled at storage temperatures (4°C). Sensory panelists were able to choose the odd sample in a replicated triangle test analyzed using the β-binomial model, and there was preference for Flax fillets (P<0.05). Results indicate that a Flax-enhanced diet would have favorable effects on product quality of farmed brook trout.

Changes in cell shape are correlated with metastatic potential in murine and human osteosarcomas

ABSTRACT Metastatic cancer cells for many cancers are known to have altered cytoskeletal properties, in particular to be more deformable and contractile. Consequently, shape characteristics of more metastatic cancer cells may be expected to have diverged from those of their parental cells. To examine this hypothesis we study shape characteristics of paired osteosarcoma cell lines, each consisting of a less metastatic parental line and a more metastatic line, derived from the former by in vivo selection. Two-dimensional images of four pairs of lines were processed. Statistical analysis of morphometric characteristics shows that shape characteristics of the metastatic cell line are partly overlapping and partly diverged from the parental line. Significantly, the shape changes fall into two categories, with three paired cell lines displaying a more mesenchymal-like morphology, while the fourth displaying a change towards a more rounded morphology. A neural network algorithm could distinguish between samples of the less metastatic cells from the more metastatic cells with near perfect accuracy. Thus, subtle changes in shape carry information about the genetic changes that lead to invasiveness and metastasis of osteosarcoma cancer cells. Summary: Human and murine invasive osteosarcoma cancer cell lines, developed by selection in vivo from a less invasive parental line, show distinguishable differences in shape from the parental line that fall into two categories: more mesenchymal or more amoeboid.

The Effects of Misconceptions on the Properties of Friedman's Test

Friedmans test is a widely used rank-based alternative to the analysis of variance (ANOVA) F-test for identifying treatment differences in a randomized complete block design. Many texts provide incomplete or misleading information about when Friedmans test may be appropriately applied. We discuss the assumptions needed for the test and common misconceptions. We show via simulation that when the variance or skew of the treatment distributions differ, application of Friedmans test to detect differences in treatment location can result in Type I error probabilities larger than the nominal α, and even when α is unaffected, the power of the test can be less than expected.

White-footed mice (Peromyscus leucopus) select fruits of native species over invasive honeysuckle fruits

Abstract White-footed mouse (Peromyscus leucopus) consumption of plant fruits can significantly affect vegetative community structure. However, little is known about the effects of relative selection between different fruit species on the establishment and spread of invasive shrubs. Depending on foraging activity, white-footed mice may provide resistance against exotic establishment, have no impact, or even contribute to invasive spread. Selection of invasive Morrows honeysuckle (Lonicera morrowii) and 5 native soft-mast species was studied across 3 cover types (forest, field, and edge) and 2 seasons in southwestern Pennsylvania. Foraging stations, containing equal quantities of each species, were randomly placed in each of the cover types. In addition, nutrient composition and total energy were measured. Fruit consumption was nonrandom based on compositional analysis (P < 0.05). Honeysuckle was consumed over native staghorn sumac (Rhus typhina); otherwise, it was consumed less than all natives. Honeysuckle fruits had significantly less lipids (0.67%) than all natives (P < 0.05), and one of the lowest protein contents (0.66%). Total energy was important in distinguishing the highest selected fruits: black cherry (Prunus serotina; 0.45 kcal) and common dewberry (Rubus flagellaris; 0.36 kcal). Selection of high-nutrient native fruits over those of honeysuckle may confer additional competitive advantages to the seeds of this invasive shrub. In this way, white-footed mice may contribute to the establishment of Morrows honeysuckle in multiple cover types.

Hibernacula Use and Hibernation Phenology in the Common Snapping Turtle (Chelydra serpentina) in Canaan Valley, West Virginia

Abstract We captured 32 Common Snapping Turtles (Chelydra serpentina) in a Canaan Valley, West Virginia lake and equipped them with radio-transmitters during 1988 through 2007 to describe their hibernation behavior and examine the relative importance of temporal and environmental effects on hibernation. We monitored entry date, exit date, and location of hibernacula. The mean date of entry into hibernation was 9 October, and the mean date of exit from hibernation was 13 April, with a mean duration of 185 days. Turtles moved a mean distance of 117 m to hibernacula and were located most often along small streams bordered by speckled alder (Alnus rugosa). Hibernation entry date was influenced by lake temperature and hibernation exit date was influenced by water temperature at hibernacula sites. We suggest that small streams are important to Common Snapping Turtles as hibernacula because they provide protection from predators and remain above freezing temperatures.

Amphibian reproductive success as a gauge of functional equivalency of created wetlands in the Central Appalachians

Abstract Context. Evaluating the adequacy of created wetlands to replace the functions of lost natural wetlands is important because wetland mitigation is a major tool used to offset wetland losses. However, measurements such as vegetative cover and presence of wildlife may not provide sufficient evidence that created wetlands are functioning properly. Thus, examining the ecology of wetland biota such as that of amphibians may be a more useful surrogate for function. Aims. The objectives of this study were to compare the abundance of amphibian metamorphs and survival and growth of larval amphibians in created wetlands, relative to natural wetlands. Methods. Amphibian metamorphs were trapped in created and natural wetlands during the spring (April–May) and summer (June–August) of 2009 and 2010, and 165 green frog (Lithobates clamitans) larvae were raised during the spring of 2010 in laboratory aquaria containing water from created or natural wetlands. Key results. Abundance of spring peeper (Pseudacris crucifer) metamorphs decreased significantly from 2009 to 2010 and abundance of green frog metamorphs increased with habitat complexity, but both were unaffected by wetland type. Detection probability of metamorphs of both species was low, increased with water temperature and declined with month of observation. Survival, growth curves and mass were similar among green frog larvae raised in created and natural wetland aquaria. Conclusions. Our results suggest that the created and natural wetlands we examined function similarly with respect to providing adequate breeding habitat for green frogs and spring peepers. Implications. Wetlands created to offset the loss of natural wetlands, although generally not designed for the purpose of wildlife habitat, can function as adequate breeding habitat for generalist amphibians such as green frogs and spring peepers.