The effect of dielectric polarization of the electrode on anomalous temperature effects in the electrical double layer

Monte Carlo simulations and a modified Poisson–Boltzmann (MPB) theory are used to investigate the temperature dependence of the capacitance (around the potential of zero charge) of an electric double layer in the presence of surface polarization due to a dielectric boundary. Within the context of the restricted primitive model planar double layer, whose solvent dielectric constant is ε₂, the cases when the electrode is an insulator (ε₁ = 1), when the electrode and the electrolyte have the same permittivity (ε₁ = ε₂, no polarization), and when the electrode is a conductor (ε₁ → ∞) are studied for the case where the electrolyte concentration is 0.1 M. The simulations reveal a capacitance anomaly, that is, a positive temperature dependence of the capacitance at low temperatures for the former two situations. The MPB theory also shows this effect for these two situations and is in qualitative or better agreement with the simulation data. In these two cases, both the simulations and theory show a dramatic increase of the diffuse layer potential in the temperature regime where capacitance anomaly occurs. However, in the latter situation, where the electrode is metallic, the capacitance always has a negative temperature derivative for the MPB theory and probably also for the simulation data.     

A simple,band‐mounted device to measure behaviorally modified thermal microclimates experienced by birds

Birds encounter climate at the scale of microclimates that can vary rapidly in time and space and so understanding potential vulnerability and adaptations to those microclimates requires fine‐scale measurements that accurately track thermal exposures. However, few options exist for recording the microclimates actually experienced by birds (realized microclimates). We constructed and tested a simple, low‐cost, temperature logger for recording the realized microclimates of ground‐nesting birds. We developed attachment protocols for band‐mounting Thermochron iButtons on Ring‐billed Gull (Larus delawarensis) chicks. We tested these mounted, temperature‐logging devices on 20 chicks weighing > 200 g (device weight was 4 g), attaching devices for 48 h and observing behavior before and after attachment and removal. Devices recorded temperature immediately surrounding the leg at 2‐min intervals. Recorded temperatures were strong predictors of observed thermoregulatory behaviors (panting and sitting), outperforming predictions based on air temperatures measured by basic, static approaches. Through comparison with matched controls (chicks with just a band), we detected no adverse physiological effects of devices, no effects on social or feeding behavior, and only a short‐term decrease in inactivity immediately after device attachment (likely due to increased preening). By attaching iButtons to the legs of birds, we quantified realized thermal exposure, integrating air temperature, modes of environmental heat transfer, and bird behavior at microclimatic scales. Although not yet validated for broader use, our approach (including possible miniaturization) should be suitable to measure thermal exposure of adults, not just chicks, allowing collection of data concerning thermal exposures during flight under field conditions. At ~ $25 USD per device, our approach facilitates experimental protocols with robust sample sizes, even for relatively modest budgets.     

Correction of a bootstrap approach to testing for evolution along lines of least resistance

Testing for an association between the leading vectors of multivariate trait (co)variation within populations (the ‘line of least resistance’) and among populations is an important tool for exploring variational bias in evolution. In a recent study of stickleback fish populations, a bootstrap‐based test was introduced that takes into account estimation error in both vectors and hence improves the previously available bootstrap method. Because this test was implemented incorrectly, however, I here describe the correct test protocol and provide a reanalysis of the original data set. The application of this new test protocol should improve future investigations of evolution along lines of least resistance and other vector comparisons.     

The natural history, thermal physiology, and ecological impacts of intertidal mesopredators, Oedoparena spp. (Diptera: Dryomyzidae)

Abstract. The ecological roles of small (1–1000 mg) predators in benthic marine systems are poorly understood. We investigated the natural history and predatory impact of one group of such mesopredators—larvae of dipteran flies in the genus Oedoparena —which prey on intertidal barnacles. We 1) quantified patterns of larval Oedoparena distribution and abundance in the Northwest Straits of Washington State, USA, 2) determined larval physiological tolerance limits in the laboratory, and 3) conducted a manipulative field experiment to assess the role of microhabitat temperature on predation rates in Oedoparena . Members of Oedoparena in Washington are univoltine, with peak larval abundance in late spring and early summer. Infestation frequencies in the barnacles Balanus glandula and Chthamalus dalli were as high as 22% and 35%, respectively. In laboratory studies, larvae of O . glauca were able to tolerate temperatures up to 37°C; however, this temperature is often exceeded in high intertidal habitats. In a field manipulation using experimental shades, we demonstrate that the alleviation of physiological stress greatly increased the abundance of larvae of Oedoparena spp. As a result of increased larval densities under shades, adult B. glandula mortality increased from 5% to nearly 30%, and C. dalli mortality increased from less than 20% to over 60%. Because high intertidal barnacles serve as food and habitat for a diverse array of species, Oedoparena spp. have the potential to play a major role in structuring high intertidal communities, particularly in cooler microhabitats.     

Long‐term population dynamics of a coral reef gastropod and responses to disturbance

The age‐specific density of the red‐lipped stromb Strombus luhuanus (Mollusca: Gastropoda) was monitored over 13 years (1981–1993) at four locations on the intertidal reef flat at Heron Island, Great Barrier Reef. Densities were highly variable, but there were persistent, location‐specific differences in population density, age structure and adult body size, the latter indicating that the populations were not extensively linked by adult movement. There was relatively high recruitment at most locations in 1984, 1989 and 1993, each occurring approximately 2 years after El Niño/Southern Oscillation events, although recruit density during these years varied in both space and time. The studied strombs experienced three disturbance events: (i) experimental harvesting at two locations (1984–1985); (ii) siltation from a harbour dredging operation (1987–1988); and (iii) a severe cyclone (1992). Resilience to harvesting at a local scale (0.5–2 ha) was high: density had recovered within a year, due to immigration of adults and older juveniles. Strombus luhuanus responded much more strongly to broad‐scale changes to its environment than to localized harvesting. After dredging, there was a progressive density decline coupled with low recruitment at two locations, and a later decline at a third location, followed by a recruitment‐driven rebound after the cyclone. Generalized environmental effects of siltation and the cyclone were also reflected in substantial changes in algal cover. Long‐term variations in environmental conditions probably cause high temporal variation over large spatial scales through effects on the survival of larvae or recruits. Localized short‐term field monitoring of such species would give a misleading picture of key factors affecting population dynamics.     

Diversity and distribution of reptiles in Romania

The reptile fauna of Romania comprises 23 species, out of which 12 species reach here the limit of their geographic range. We compiled and updated a national database of the reptile species occurrences from a variety of sources including our own field surveys, personal communication from specialists, museum collections and the scientific literature. The occurrence records were georeferenced and stored in a geodatabase for additional analysis of their spatial patterns. The spatial analysis revealed a biased sampling effort concentrated in various protected areas, and deficient in the vast agricultural areas of the southern part of Romania. The patterns of species richness showed a higher number of species in the warmer and drier regions, and a relatively low number of species in the rest of the country. Our database provides a starting point for further analyses, and represents a reliable tool for drafting conservation plans.     

Mate detection success of maleClethrionomys rufocanus in relation to the spatial distribution of sexually receptive females

Summary Mate detection success of male grey-sided voles,Clethrionomys rufocanus, in relation to the spatial distribution of sexually receptive females was studied in an experimental island population. The spatiotemporal distribution of receptive females was controlled by containing females in small, mobile wire-mesh cages, whereas the response by free-ranging males was monitored by means of radiotelemetry. Males were on average more successful in finding oestrous females when females were spatially clumped than when females were spatially overdispersed. In addition, the variance (CV) in male mate detecting success was highest when females had an overdispersed spatial distribution. These results are consistent with predictions from a theoretical model (Ims, 1988b) analysing the effect of mate distribution on male mating success, and with empirical results on prey detection success of predators searching for prey.