Predation Danger Can Explain Changes in Timing of Migration: The Case of the Barnacle Goose

Understanding stopover decisions of long-distance migratory birds is crucial for conservation and management of these species along their migratory flyway. Recently, an increasing number of Barnacle geese breeding in the Russian Arctic have delayed their departure from their wintering site in the Netherlands by approximately one month and have reduced their staging duration at stopover sites in the Baltic accordingly. Consequently, this extended stay increases agricultural damage in the Netherlands. Using a dynamic state variable approach we explored three hypotheses about the underlying causes of these changes in migratory behavior, possibly related to changes in (i) onset of spring, (ii) potential intake rates and (iii) predation danger at wintering and stopover sites. Our simulations showed that the observed advance in onset of spring contradicts the observed delay of departure, whereas both increased predation danger and decreased intake rates in the Baltic can explain the delay. Decreased intake rates are expected as a result of increased competition for food in the growing Barnacle goose population. However, the effect of predation danger in the model was particularly strong, and we hypothesize that Barnacle geese avoid Baltic stopover sites as a response to the rapidly increasing number of avian predators in the area. Therefore, danger should be considered as an important factor influencing Barnacle goose migratory behavior, and receive more attention in empirical studies.     

Trade-Offs between Predation Risk and Growth Benefits in the Copepod Eurytemora affinis with Contrasting Pigmentation

Intraspecific variation in body pigmentation is an ecologically and evolutionary important trait; however, the pigmentation related trade-offs in marine zooplankton are poorly understood. We tested the effects of intrapopulation phenotypic variation in the pigmentation of the copepod Eurytemora affinis on predation risk, foraging, growth, metabolic activity and antioxidant capacity. Using pigmented and unpigmented specimens, we compared (1) predation and selectivity by the invertebrate predator Cercopagis pengoi, (2) feeding activity of the copepods measured as grazing rate in experiments and gut fluorescence in situ, (3) metabolic activity assayed as RNA:DNA ratio in both experimental and field-collected copepods, (4) reproductive output estimated as egg ratio in the population, and (5) total antioxidant capacity. Moreover, mitochondrial DNA (mtDNA) COI gene variation was analysed. The pigmented individuals were at higher predation risk as evidenced by significantly higher predation rate by C. pengoi on pigmented individuals and positive selection by the predator fed pigmented and unpigmented copepods in a mixture. However, the antioxidant capacity, RNA:DNA and egg ratio values were significantly higher in the pigmented copepods, whereas neither feeding rate nor gut fluorescence differed between the pigmented and unpigmented copepods. The phenotypic variation in pigmentation was not associated with any specific mtDNA genotype. Together, these results support the metabolic stimulation hypothesis to explain variation in E. affinis pigmentation, which translates into beneficial increase in growth via enhanced metabolism and antioxidant protective capacity, together with disadvantageous increase in predation risk. We also suggest an alternative mechanism for the metabolic stimulation via elevated antioxidant levels as a primary means of increasing metabolism without the increase in heat absorbance. The observed trade-offs are relevant to evolutionary mechanisms underlying plasticity and adaptation and have the capacity to modify strength of complex trophic interactions.     

烟草愈伤组织生长和衰老期间呼吸代谢的改变

前人(Ross和Thorpe 1973,Thorpe和Laishley 1973,Brown和Thorpe 1982)曾报道了烟草愈伤组织芽形成期间呼吸速率、线粒体活性、底物代谢途径和有关呼吸酶活性的变化。我们对烟草愈伤组织呼吸代谢的研究证明:组织分化和芽原基的形成与HMP途径运行升高相联系(毕玉蓉和梁厚果1987);愈伤组织的呼吸链存     

A Novel Paradigm for Nonassociative Long-Term Memory in Drosophila: Predator-Induced Changes in Oviposition Behavior

Learning processes in Drosophila have been studied through the use of Pavlovian associative memory tests, and these paradigms have been extremely useful in identifying both genetic factors and neuroanatomical structures that are essential to memory formation. Whether these same genes and brain compartments also contribute to memory formed from nonassociative experiences is not well understood. Exposures to environmental stressors such as predators are known to induce innate behavioral responses and can lead to new memory formation that allows a predator response to persist for days after the predator threat has been removed. Here, we utilize a unique form of nonassociative behavior in Drosophila where female flies detect the presence of endoparasitoid predatory wasps and alter their oviposition behavior to lay eggs in food containing high levels of alcohol. The predator-induced change in fly oviposition preference is maintained for days after wasps are removed, and this persistence in behavior requires a minimum continuous exposure time of 14 hr. Maintenance of this behavior is dependent on multiple long-term memory genes, including orb2, dunce, rutabaga, amnesiac, and Fmr1. Maintenance of the behavior also requires intact synaptic transmission of the mushroom body. Surprisingly, synaptic output from the mushroom body (MB) or the functions of any of these learning and memory genes are not required for the change in behavior when female flies are in constant contact with wasps. This suggests that perception of this predator that leads to an acute change in oviposition behavior is not dependent on the MB or dependent on learning and memory gene functions. Because wasp-induced oviposition behavior can last for days and its maintenance requires a functional MB and the wild-type products of several known learning and memory genes, we suggest that this constitutes a paradigm for a bona fide form of nonassociative long-term memory that is not dependent on associated experiences.     

ENSO,Nest Predation Risk,Food Abundance,and Male Status Fail to Explain Annual Variations in the Apparent Survival Rate of a Migratory Songbird

Adult mortality can be a major driver of population decline in species whose productivity is relatively low. Yet, little is known about the factors influencing adult survival rates in migratory bird species, nor do we know much about the longer-term effects of habitat disturbance on the fitness of individuals. The Ovenbird (Seiurus aurocapilla) is one of the vertebrate species most sensitive to forest management, yet it is still common and widespread. We monitored the fate of 330 colour-banded Ovenbird males in four pairs of 25-ha plots during 9 successive breeding seasons. One plot of each pair was treated through selection harvesting (30–40% basal area removed) during the first winter. We tested the following hypotheses: (1) higher physiological costs in harvested plots as a result of lower food abundance will reduce apparent survival rate (ASR) relative to controls; (2) lower ASR following years with low nest survival and higher probability of renesting; (3) fluctuations in ASR reflecting El Niño Southern Oscillation (ENSO); and (4) higher ASR in returning males than in recruits (unbanded immigrants) owing to greater site familiarity in the former. We tested the relative importance of these hypotheses, or combinations thereof, by generating 23 models explaining variation in ASR. The year-dependent model received the most support, showing a 41% decrease in ASR from 2007 to 2014. The important year-to-year variation we observed in ASR (Σw_i = 0.99) was not explained by variation in nest predation risk nor by ENSO. There was also little evidence for an effect of selection harvesting on ASR of Ovenbird males, despite a slight reduction in lifespan relative to males from control plots (2.7 vs 2.9 years). An avenue worth exploring to explain this intriguing pattern would be to determine whether conditions at migratory stopover sites or in the wintering area of our focal population have gradually worsened over the past decade.     

Nature of Predation Risk Cues in Container Systems: Mosquito Responses to Solid Residues From Predation

In aquatic systems, prey animals associate predation risk with cues that originate either from the predator or from injured conspecifics. Sources and benefits of these cues have received considerable attention in river, lake, and pond ecosystems but are less well understood in small container ecosystems that can hold less than a liter of water. Mosquitoes Aedes triseriatus (Say) and Aedes albopictus (Skuse) encounter predatory Corethrella appendiculata (Grabham) and Toxorhynchites rutilus (Coquillett) in small containers and show antipredatory behavioral responses. We investigated the sources of the predation cues to which these prey larvae respond. We tested whether Ae. albopictus larvae show behavioral responses to cues emanating from the predator or from damage to prey caused by the act of predation. We also tested whether Ae. triseriatus respond to cues present in fluid or solid residues from predator activity. Ae. albopictus showed behavioral modifications only in response to waterborne cues from a feeding predator and not to cues from a starving predator, indicating that Ae. albopictus respond to cues created by the act of predation, which could include substances derived from damaged prey or substances in predator feces. Ae. triseriatus showed behavioral responses to solid residues from predation but not to fluid without those solids, indicating that the cues to which they respond originate in predator feces or uneaten prey body parts. Our results suggest that cues in this system may be primarily chemicals that are detected upon contact with solid residues that are products of the feeding processes of these predators.     

Influence of Some Potential Predation Risk Factors and Interaction between Predation Risk and Cost of Fleeing on Escape by the Lizard Sceloporus virgatus

Escape theory predicts that flight initiation distance (predator–prey distance when escape begins) increases as predation risk increases and decreases as cost of fleeing increases. Scant information is available about the effects of some putative predation risk factors and about interaction between simultaneously operating risk and cost of fleeing factors on flight initiation distance and distance fled. By simulating an approaching predator, I studied the effects of body temperature (BT), distance to nearest refuge, and eye contact with a predator, as well as simultaneous effects of predator approach speed and female presence/absence on escape behavior by a small ectothermic vertebrate, the lizard Sceloporus virgatus. Flight initiation distance decreased as BT increased, presumably because running speed increases as BT increases, facilitating escape. Distance to nearest refuge was unrelated to BT or flight initiation distance. Substrate temperature was only marginally related, and air temperature was not related to flight initiation distance. Eye contact did not affect flight initiation during indirect approaches that bypassed lizards by a minimum of 1 m, but an effect of eye contact found in other studies during direct approach might occur. Predator approach speed and presence of a female interactively affected flight initiation distance, which increased as speed increased and decreased when a female was present. In the presence of a female, flight initiation distance was far shorter than when no female was present. The high cost of forgoing a mating opportunity accounts for the interaction because the difference between female presence and absence is greater when risk is greater.     

Response to Predation Risk in Urban and Rural House Sparrows

Habitat urbanization may change the density of predators, and it is often assumed that such changes lead to altered predation risk for urban populations of their prey. Although it is difficult to study predation hazard directly, behavior responses of prey species may be informative in inferring such habitat differences. In this study, we compared the risk‐taking behavior of urban and rural house sparrows (Passer domesticus) after simulated attacks by two of their important predators (sparrowhawk Accipiter nisus and domestic cat Felis catus). The birds were startled by moving dummies of these predators and respective control objects, and their risk taking was estimated as their latency to feed after the startle. We found that sparrows responded more strongly (had longer post‐startle feeding latencies) to sparrowhawk attacks than to the control object, and their responses differed between the habitats. First, risk taking of urban birds strongly decreased with age (older birds had longer latencies than young birds), while there was no such age difference in rural birds. Second, young urban birds responded less strongly, while older urban birds responded more strongly to the sparrowhawk than the same age groups of rural birds, respectively. We did not succeed in evoking antipredatory response by simulated cat attacks, because birds responded similarly to the dummy and the control object. Our results support that predation risk, posed at least by avian predators, is different in urban and rural habitats of house sparrows. The increased wariness of older, hence presumably more experienced, urban birds implies that sparrows may be more exposed to predation in cities.     

Paternal Genetic Effects on Foraging Decision-Making Under the Risk of Predation

Foraging behavior under the risk of predation has interested biologists for decades. Here, we examine paternal genetic effects on foraging decisions of bluegill (Lepomis macrochirus) larvae sired by males adopting alternative life histories. We use split in vitro fertilization to generate maternal half‐siblings sired by either a ‘parental’ male or a ‘cuckolder’ male. Immediately, upon the switch to exogenous feeding, we fed the larvae ad libitum for 2 d. We then starved the larvae for between 12 and 17 h, following which we subjected them to a dichotomous choice foraging trial, where one side of a test tank posed a risky foraging habitat and the other posed a safe foraging habitat. Equal amounts of food were simultaneously introduced to both sides of the tank and the proportion of individuals on either side was recorded. There were significantly fewer cuckolder offspring foraging on the risky side of the tank when compared with their parental half‐siblings indicating that cuckolder offspring took fewer risks than parental offspring. These results demonstrate a paternal genetic effect (sire life history) on foraging behavior. We ruled out energetic state as a possible explanation for this difference because the half‐siblings did not differ in body length or mass. Instead, previous research suggests that cuckolder offspring have higher conversion efficiency (efficiency of converting food into soma) than parental offspring and therefore the differences in foraging behavior observed here may, in part, be attributed to genetic differences in conversion efficiency.     

Changes in Starch Synthesis and Metabolism Within Developing Bulbs of Lycoris radiata During the Vegetative Growth Stage

Journal of Plant Growth Regulation - Lycoris is a genus of plants with flowering bulbs that have high ornamental, medicinal, and ecological value. The slow growth of Lycoris bulbs under natural...     

Selection and Reduced Population Size Cannot Explain Higher Amounts of Neandertal Ancestry in East Asian than in European Human Populations

It has been hypothesized that the greater proportion of Neandertal ancestry in East Asians than in Europeans is due to the fact that purifying selection is less effective at removing weakly deleterious Neandertal alleles from East Asian populations. Using simulations of a broad range of models of selection and demography, we have shown that this hypothesis cannot account for the higher proportion of Neandertal ancestry in East Asians than in Europeans. Instead, more complex demographic scenarios, most likely involving multiple pulses of Neandertal admixture, are required to explain the data.     

Understanding the Folding-Function Tradeoff in Proteins

When an amino-acid sequence cannot be optimized for both folding and function, folding can get compromised in favor of function. To understand this tradeoff better, we devise a novel method for extracting the “function-less” folding-motif of a protein fold from a set of structurally similar but functionally diverse proteins. We then obtain the β-trefoil folding-motif, and study its folding using structure-based models and molecular dynamics simulations. CompariA protein sequence serves two purpson with the folding of wild-type β-trefoil proteins shows that function affects folding in two ways: In the slower folding interleukin-1β, binding sites make the fold more complex, increase contact order and slow folding. In the faster folding hisactophilin, residues which could have been part of the folding-motif are used for function. This reduces the density of native contacts in functional regions and increases folding rate. The folding-motif helps identify subtle structural deviations which perturb folding. These may then be used for functional annotation. Further, the folding-motif could potentially be used as a first step in the sequence design of function-less scaffold proteins. Desired function can then be engineered into these scaffolds.     

Changes in Respiratory Metabolism during Callus Growth and Adventitious Root Formation in Jerusalem Artichoke Tuber Tissues

The CN-resistant alternative oxidase pathway was examined inrelation to the formation of callus and adventitious roots ofJerusalem artichoke tuber tissues. During the early stage ofincubation at 28?C, respiration was significantly activatedand the O₂-uptake rate via the Cyt pathway increased 2.5–2.6times by the second day of culture regardless of the presenceof 2,4-D. However, further increases and preservation of highlevels of Cyt pathway activities were observed only in the callusformingtissues. The capacity of the alternative pathway also increased,but the actually operating fraction was very small (0–4%of total respiration). On the other hand, during the later stagesof culture in which adventitious roots emerged from the callus,activation of the alternative pathway was observed. These resultssuggested that the alternative pathway was not involved in callusgrowth but was related to root formation in callus tissues ofJerusalem artichoke tubers. (Received October 29, 1986; Accepted April 20, 1987)     

Field Assessment of the Predation Risk - Food Availability Trade-Off in Crab Megalopae Settlement

Settlement is a key process for meroplanktonic organisms as it determines distribution of adult populations. Starvation and predation are two of the main mortality causes during this period; therefore, settlement tends to be optimized in microhabitats with high food availability and low predator density. Furthermore, brachyuran megalopae actively select favorable habitats for settlement, via chemical, visual and/or tactile cues. The main objective in this study was to assess the settlement of Metacarcinus edwardsii and Cancer plebejus under different combinations of food availability levels and predator presence. We determined, in the field, which factor is of greater relative importance when choosing a suitable microhabitat for settling. Passive larval collectors were deployed, crossing different scenarios of food availability and predator presence. We also explore if megalopae actively choose predator-free substrates in response to visual and/or chemical cues. We tested the response to combined visual and chemical cues and to each individually. Data was tested using a two-way factorial design ANOVA. In both species, food did not cause significant effect on settlement success, but predator presence did, therefore there was not trade-off in this case and megalopae respond strongly to predation risk by active aversion. Larvae of M. edwardsii responded to chemical and visual cues simultaneously, but there was no response to either cue by itself. Statistically, C. plebejus did not exhibit a differential response to cues, but reacted with a strong similar tendency as M. edwardsii. We concluded that crab megalopae actively select predator-free microhabitat, independently of food availability, using chemical and visual cues combined. The findings in this study highlight the great relevance of predation on the settlement process and recruitment of marine invertebrates with complex life cycles.     

Frequency of Encounter with Risk and the Tradeoff between Pursuit and Antipredator Behaviors in Crayfish: A Test of the Risk Allocation Hypothesis

Prey animals encountering multiple stimuli must often make behavioral tradeoffs. Many environmental cues may influence the tradeoff observed, but recent theoretical work suggests that temporal variation in risk should influence how prey animals behave during any given period of risk. As time spent under risk of predation increases, prey animals will increase their allocation of foraging during periods of risk. This model is known as the risk allocation hypothesis (RAH) ( Lima & Bednekoff 1999 ). We tested the RAH using the crayfish Orconectes virilis. We selected two frequency regimes (exposure to risk every 6 or 12 h) and three cues suggestive of increasing risk (water, snapping turtle cue, and conspecific alarm cue). Test animals were exposed to one of the six frequency × risk combinations for 24 h, followed immediately by the simultaneous introduction of a food and a risk cue. Three behaviors (burrow use, non‐ambulatory motion, and locomotion) were then recorded for 5 min. Responses were significantly influenced by the interaction of risk and frequency. Further analysis indicated that responses were not consistently influenced by frequency alone. While our results do not support the predictions of the RAH for our frequency regimes, qualitative comparison with an earlier, similar study ( Hazlett 1999 ) suggests that risk allocation is occurring in this system. We recommend that frequency of encounter with risk be considered in future studies. Ignoring temporal variation may lead to over‐ or underestimation of the subject's natural responses.     

Fixed vs. Random Temporal Predictability of Predation Risk: An Extension of the Risk Allocation Hypothesis

Predation is a strong selective force acting on prey animals. Predation is by nature highly variable in time; however, this aspect of predation risk has traditionally been overlooked by behavioural ecologists. Lima and Bednekoff proposed the predation risk allocation hypothesis (RAH), predicting how temporal variation in predation risk drives prey antipredator behaviours. This model is based on the concept that prey adaptively allocate their foraging and antipredator efforts across high‐ and low‐risk situations, depending on the duration of high‐ vs. low‐risk situations and the relative risk associated with each of them. An unstudied extension of the RAH is the effect of predictability of predation risk. A predictable risk should lead to prey displaying minimal vigilance behaviours during predictable low‐risk periods and the strongest antipredator behaviours during risky periods. Conversely, an unpredictable predation risk should result in prey displaying constant vigilance behaviour, with suboptimal foraging rates during periods of safety but antipredator behaviours of lower intensity during periods of risk. We tested this extension of the RAH using convict cichlids exposed to high‐risk alarm cues at two frequencies of risk (1× vs. 3×) per day, on either a fixed or random schedule for 5 d. We then tested the fish for a response to high‐risk cues (alarm cues) and to low‐risk cues (disturbance resulting from the introduction of distilled water). Our study supports previous results on the effects of risk frequency and cue intensity on cichlid behaviour. We failed to show an effect of risk predictability on the behavioural responses of cichlids to high‐risk alarm cues, but predictability did influence responses to low‐risk cues. We encourage further studies to test the effect of predictability in other systems.