Simulation of Seed Digestion by Birds: How Does It Reflect the Real Passage Through a Pigeon’s Gut?

Simulation of seed passage through a bird’s gut is an important tool for comparing the effect of bird digestion and thus the potential for plant dispersal by endozoochory. However, sufficient methodology is missing. Thus, we subjected seeds of 20 plant species to seven different simulations of gut passage and to the real passage through a pigeon’s gut to determine which simulation type best reflects the effects of real bird digestion. We also measured various seed traits to identify the traits responsible for differences between species. Results show that four out of seven simulations were significant predictors of seed survival after gut passage. The fit between direct digestion by the pigeon and the different simulation treatments was, however, species-specific and depends not only on the commonly tested traits such as seed mass and water permeability, but also on other unmeasured traits. Seed mass was the best predictor of differences between real digestion and simulation. Selecting one type of simulation to be a good predictor of seed survival after gut passage is difficult. The strongest simulation (24-h scarification and 240-min acid immersion) is the best predictor and may be used to compare the ability of seeds to be dispersed by bird endozoochory. Such knowledge can be included in databases of species traits, as is currently done for many other species traits.     

Conserving the Birds of Uganda’s Banana-Coffee Arc: Land Sparing and Land Sharing Compared

Reconciling the aims of feeding an ever more demanding human population and conserving biodiversity is a difficult challenge. Here, we explore potential solutions by assessing whether land sparing (farming for high yield, potentially enabling the protection of non-farmland habitat), land sharing (lower yielding farming with more biodiversity within farmland) or a mixed strategy would result in better bird conservation outcomes for a specified level of agricultural production. We surveyed forest and farmland study areas in southern Uganda, measuring the population density of 256 bird species and agricultural yield: food energy and gross income. Parametric non-linear functions relating density to yield were fitted. Species were identified as “winners” (total population size always at least as great with agriculture present as without it) or “losers” (total population sometimes or always reduced with agriculture present) for a range of targets for total agricultural production. For each target we determined whether each species would be predicted to have a higher total population with land sparing, land sharing or with any intermediate level of sparing at an intermediate yield. We found that most species were expected to have their highest total populations with land sparing, particularly loser species and species with small global range sizes. Hence, more species would benefit from high-yield farming if used as part of a strategy to reduce forest loss than from low-yield farming and land sharing, as has been found in Ghana and India in a previous study. We caution against advocacy for high-yield farming alone as a means to deliver land sparing if it is done without strong protection for natural habitats, other ecosystem services and social welfare. Instead, we suggest that conservationists explore how conservation and agricultural policies can be better integrated to deliver land sparing by, for example, combining land-use planning and agronomic support for small farmers.     

The Fitness Check of the Birds and Habitats Directives: A discourse analysis of stakeholders’ perspectives

In 2015, the European Union’s Birds and Habitats Directives underwent an evaluation in which selected national stakeholders provided their perspectives on the directives’ implementation. Analyzing the views of different stakeholder groups from eight European member states, this study found that these views could be synthesized into three more general perspectives. The first perspective focuses on problems, indicating that these are caused by legislative drawbacks in the directives. The second perspective holds that problems are generated by improper implementation by member states. The third perspective commends the benefits of the directives in face of the existing implementation problems. Interest groups and to a minor extent governmental bodies espoused the first perspective, and environmental non-governmental organizations especially favored the third. The struggle between these three perspectives reflects ongoing debates regarding positive and negative aspects of the directives and possibilities for improving their implementation. We conclude that the relevance and impact of conservation policies should never be seen as self-evident. In order to reach the conservation goals envisaged, continuous efforts are needed to enforce and maintain environmental legislation.     

Fast and fuel efficient? Optimal use of wind by flying albatrosses

The influence of wind patterns on behaviour and effort of free-ranging male wandering albatrosses (Diomedea exulans) was studied with miniaturized external heart-rate recorders in conjunction with satellite transmitters and activity recorders. Heart rate was used as an instantaneous index of energy expenditure. When cruising with favourable tail or side winds, wandering albatrosses can achieve high flight speeds while expending little more energy than birds resting on land. In contrast, heart rate increases concomitantly with increasing head winds, and flight speeds decrease. Our results show that effort is greatest when albatrosses take off from or land on the water. On a larger scale, we show that in order for birds to have the highest probability of experiencing favourable winds, wandering albatrosses use predictable weather systems to engage in a stereotypical flight pattern of large looping tracks. When heading north, albatrosses fly in anticlockwise loops, and to the south, movements are in a clockwise direction. Thus, the capacity to integrate instantaneous eco-physiological measures with records of large-scale flight and wind patterns allows us to understand better the complex interplay between the evolution of morphological, physiological and behavioural adaptations of albatrosses in the windiest place on earth.     

Simulated Birdwatchers’ Playback Affects the Behavior of Two Tropical Birds

Although recreational birdwatchers may benefit conservation by generatinginterest in birds, they may also have negative effects. One such potentiallynegative impact is the widespread use of recorded vocalizations, or “playback,”to attract birds of interest, including range-restricted and threatened species.Although playback has been widely used to test hypotheses about the evolution ofbehavior, no peer-reviewed study has examined the impacts of playback in abirdwatching context on avian behavior. We studied the effects of simulatedbirdwatchers’ playback on the vocal behavior of Plain-tailed WrensThryothorus euophrys and Rufous Antpittas Grallariarufula in Ecuador. Study species’ vocal behavior was monitored foran hour after playing either a single bout of five minutes of song or a controltreatment of background noise. We also studied the effects of daily five minuteplayback on five groups of wrens over 20 days. In single bout experiments,antpittas made more vocalizations of all types, except for trills, afterplayback compared to controls. Wrens sang more duets after playback, but did notproduce more contact calls. In repeated playback experiments, wren responseswere strong at first, but hardly detectable by day 12. During the study, onestudy group built a nest, apparently unperturbed, near a playback site. Theplayback-induced habituation and changes in vocal behavior we observed suggestthat scientists should consider birdwatching activity when selecting researchsites so that results are not biased by birdwatchers’ playback. Increasedvocalizations after playback could be interpreted as a negative effect ofplayback if birds expend energy, become stressed, or divert time from otheractivities. In contrast, the habituation we documented suggests that frequent,regular birdwatchers’ playback may have minor effects on wren behavior.     

Influence of the solar wind on the distribution of the electric potential near the Moon’s surface

The Moon’s surface illuminated by the Sun acquires an electric charge due to photoelectron emission and interaction with the solar wind plasma. The influence of the solar wind on the nonmonotonic distribution of the electric potential near the Moon’s surface is studied in a wide range of the densities of emitted photoelectrons. It is found that, for any photoelectron density, the surface potential reaches its minimum value for a slow solar wind. Although the electron thermal velocity can exceed the solar wind velocity by several times, taking into account the directed flow velocity in the electron velocity distribution function substantially affects the value of the potential in the lunar regolith regions not enriched with hydrogen, for which the photoelectric work function under solar irradiation is significantly higher than for regions enriched with hydrogen.     

Thermoregulation: What Role for UCPs in Mammals and Birds?

Mammals and birds are endotherms and respond to cold exposure by the means of regulatory thermogenesis, either shivering or non-shivering. In this latter case, waste of cell energy as heat can be achieved by uncoupling of mitochondrial respiration. Uncoupling proteins, which belong to the mitochondrial carrier family, are able to transport protons and thus may assume a thermogenic function. The mammalian UCP1 physiological function is now well understood and gives to the brown adipose tissue the capacity for heat generation. But is it really the case for its more recently discovered isoforms UCP2 and UCP3? Additionally, whereas more and more evidence suggests that non-shivering also exists in birds, is the avian UCP also involved in response to cold exposure? In this review, we consider the latest advances in the field of UCP biology and present putative functions for UCP1 homologues.     

Was Dinosaurian Physiology Inherited by Birds? Reconciling Slow Growth in Archaeopteryx

Background

Archaeopteryx is the oldest and most primitive known bird (Avialae). It is believed that the growth and energetic physiology of basalmost birds such as Archaeopteryx were inherited in their entirety from non-avialan dinosaurs. This hypothesis predicts that the long bones in these birds formed using rapidly growing, well-vascularized woven tissue typical of non-avialan dinosaurs.

Methodology/Principal Findings

We report that Archaeopteryx long bones are composed of nearly avascular parallel-fibered bone. This is among the slowest growing osseous tissues and is common in ectothermic reptiles. These findings dispute the hypothesis that non-avialan dinosaur growth and physiology were inherited in totality by the first birds. Examining these findings in a phylogenetic context required intensive sampling of outgroup dinosaurs and basalmost birds. Our results demonstrate the presence of a scale-dependent maniraptoran histological continuum that Archaeopteryx and other basalmost birds follow. Growth analysis for Archaeopteryx suggests that these animals showed exponential growth rates like non-avialan dinosaurs, three times slower than living precocial birds, but still within the lowermost range for all endothermic vertebrates.

Conclusions/Significance

The unexpected histology of Archaeopteryx and other basalmost birds is actually consistent with retention of the phylogenetically earlier paravian dinosaur condition when size is considered. The first birds were simply feathered dinosaurs with respect to growth and energetic physiology. The evolution of the novel pattern in modern forms occurred later in the group''s history.     

Proarrhythmia Induced by Propafenone: What is the Mechanism?

Propafenone, a Class IC antiarrhythmic drug, is an orally active sodium channel-blocking agent. It is effective in supraventricular tachyarrhythmias and is particularly useful in converting atrial fibrillation to sinus rhythm. In therapeutic doses, it may cause non-cardiac and cardiac toxicity, including proarrhythmia.     

Are novel ecosystems suitable habitats for native birds? Birds’ association with spontaneous vegetation patches in the argentinean pampas

Biodiversity and Conservation - Novel ecosystems are characterized by species compositions and relative abundances that differ from those that occurred previously and have the potential for...     

Zooplankton communities of the Arctic’s Canada Basin: the contribution by smaller taxa

Zooplankton was sampled at ten stations in the Canada Basin during August 2002 using both 53- and 236-m mesh nets to examine the contribution by smaller and less studied species. Copepod nauplii, the copepods Oithona similis, Oncaea borealis and Microcalanus pygmaeus, and the larvacean Fritillaria borealis typica dominated the upper 100 m of the water column numerically, while biomass was dominated by the copepods Calanus hyperboreus, Calanus glacialis and Paraeuchaeta glacialis, and the chaetognath Eukrohnia hamata. Zooplankton biomass ranged from 3.7 to 14.5 mg AFDW m^–3, with a mean of 9.6 mg AFDW m^–3 . While the three microcopepods contributed less than 5% of the biomass, estimates of their potential growth rates suggest they might contribute upwards of 25% of the metazoan zooplankton production. The true rates of growth and development of these microcopepods in the Arctic need to be determined to conclusively ascertain their importance.     

Can the stress protein response be controlled by ‘membrane-lipid therapy’?

In addition to high temperature, other stresses and clinical conditions such as cancer and diabetes can lead to the alteration of heat-shock protein (HSP) levels in cells. Moreover, HSPs can associate with either specific lipids or with areas of special membrane topology (such as lipid rafts), and changes in the physical state of cellular membranes can alter hsp gene expression. We propose that membrane microheterogeneity is important for regulating the HSP response. In support of this hypothesis, when particular membrane intercalating compounds are used to alter membrane properties, the simultaneous normalization of dysregulated expression of HSPs causes beneficial responses to disease states. Therefore, these compounds (such as hydroxylamine derivatives) have the potential to become a new class of pharmaceuticals for use in 'membrane-lipid therapy'.     

Understanding the somitogenesis clock: What’s missing?

The segmentation of vertebrate embryos depends on a complex genetic network that generates highly dynamic gene expression. Many of the elements of the network have been identified, but their interaction and their influence on segmentation remain poorly understood. A few mathematical models have been proposed to explain the dynamics of subsets of the network, but the mechanistic bases remain controversial. This review focuses on outstanding problems with the generation of somitogenesis clock oscillations, and the ways they could regulate segmentation. Proposals that oscillations are generated by a negative feedback loop formed by Lunatic fringe and Notch signaling are weighed against a model based on positive feedback, and the experimental basis for models of simple negative feedback involving Her/Hes genes or Wnt targets is evaluated. Differences are then made explicit between the many 'clock and wavefront' model variants that have been proposed to explain how the clock regulates segmentation. An understanding of the somitogenesis clock will require addressing experimentally the many questions that arise from the study of simple models.     

Tumor suppression by p53: fall of the triumvirate?

p53 is a key tumor suppressor protein that has numerous functions. Its primary mode of action has generally been ascribed to the induction of cell-cycle arrest, apoptosis, or senescence upon stress. Li et al. challenge this dogma with evidence that all three of these programs are dispensable for p53's tumor suppressive role.