Egg-laying Patterns Research Articles

Predation of eggs and incubating females in willow ptarmigan Lagopus l. lagopus

Nest predation is a major cause of reproductive loss in many ground-nesting birds. During 15 consecutive years the predation of nests and females throughout the incubation season were recorded in a willow ptarmigan Lagopus l. lagopus population in central Norway. The temporal predation patterns, factors affecting the predation probability and age-specific nesting patterns in this species were studied. There was a large annual variation in predation rate of both nests (0-50%) and incubating females (0-29%) in this area during the study period. The mean annual predation rate of nests (15%) was on average three times higher than the predation of incubating willow ptarmigan females (5%). Predation rate was not constant throughout the incubation season, and the nest predation rate increased with increasing number of available nests. The predation events started after the mean initiation day of incubation, and coincided with the highest number of available nests. None of the parameters we tested in a logistic regression analysis (physical condition, nest cover, experience and date for initiation of egg-laying) could predict the predation probability of nests and incubating females. However, “good” nest cover tended to have some predictive value on the predation probability. Yearling incubating females had significantly lower physical body condition than adults, and also there were differences in choice of nest site in relation to cover between the two age groups. Initiation of egg-laying in adult females tended to be distributed more evenly over the season, whereas yearling females had a more aggregated egg-laying pattern, compared to adults.

Red-Wattled Lapwing (Vanellus indicus): A Traditional Rain Forecaster for Tribal Farmers of Southwestern Rajasthan

Abstract An intensive survey was carried out over the past 8 years in tribal-dominated areas of southwestern Rajasthan to document red-wattled lapwing (Vanellus indicus) behavior as a rain forecaster, relevant to farm planning and better crop production. The present study included tribal farmers, agriculture scientists, extension workers, ornithologists, and farm workers. The precision of their observations was compared with a contemporaneous study of 10–15 red-wattled lapwing nests across the 46-ha operational area of the Agricultural Research Sub-Station (ARSS) and Adaptive Trial Center (ATC), Sumerpur, Pali, Rajasthan (25.1526°N latitude, 73.0823°E longitude). Local knowledge was gathered through surveys and focus group discussions with the respondents to discuss lapwing behavior as a rain prediction indicator. Meteorological data were gathered from the ATC farm observatory. The findings revealed that the older tribal farmers have an assortment of knowledge about the behavior of red-wattled lapwing as rain prediction indicators such as nesting sites, egg position, egg arrangement, nesting material, numbers of eggs, and egg-laying patterns. These predictions have a direct correlation with modern meteorological observations. It was also noted that the elder tribal farmers planned their farms using lapwing indicators in order to increase crop production, whereas younger generations overlook the traditional rain prediction indicators and have significant knowledge about meteorological data-based weather forecasting. Both the elder and younger tribal farmers were equally interested in meteorological weather forecast announcements, but due to network connectivity challenges, residents in some remote places were unable to access modern meteorological information. Long-term accurate rain forecasting is needed for better agricultural planning and to secure crop production. Rain forecasting can be improved by blending modern meteorological information with traditional proven indications. Farmers who have considerable traditional knowledge along with modern technological updates are capable of using both sources of information in suitable and successful farm planning for better crop production. Significance Statement The purpose of this study is to examine red-wattled lapwing behavior as rain measurements and compare its reliability with modern rain forecasting methods. We also develop a theoretical framework for understanding traditional and modern rain forecasting methods for disaster management in remote and accessible areas, to assist resource management and to minimize costs of cultivation. Our results provide a guideline for blending both types of knowledge and for providing relevant information to remote tribal areas at appropriate times for better farm planning and crop production.

Assessment of the Entomopathogenic Potential of Fungal and Bacterial Isolates from Fall Armyworm Cadavers Against Spodoptera frugiperda Caterpillars and the Adult Boll Weevil, Anthonomus grandis

Increased attention is being focused on the biological control of agricultural pests using microorganisms, owing to their potential as a viable substitute for chemical control methods. Insect cadavers constitute a potential source of entomopathogenic microorganisms. We tested whether bacteria and fungi isolated from Spodoptera frugiperda (JE Smith) cadavers could affect its survival, development, egg-laying pattern, and hatchability, as well as induce mortality in Anthonomus grandis Boheman adults. We isolated the bacteria Enterobacter hormaechei and Serratia marcescens and the fungi Scopulariopsis sp. and Aspergillus nomiae from fall armyworm cadavers and the pest insects were subjected to an artificial diet enriched with bacteria cells or fungal spores to be tested, in the case of S. frugiperda, and only fungal spores in the case of A. grandis. Enterobacter hormaechei and A. nomiae were pathogenic to S. frugiperda, affecting the survival of adults and pupae. The fungus Scopulariopsis sp. does not affect the survival of S. frugiperda caterpillars and pupae; however, due to late action, moths and eggs may be affected. Aspergillus nomiae also increased mortality of A. grandis adults, as well as the development of S. frugiperda in the early stages of exposure to the diet, as indicated by the vertical spore transfer to offspring and low hatchability. Enterobacter hormaechei and A. nomiae are potential biocontrol agents for these pests, and warrant further investigation from a toxicological point of view and subsequently in field tests involving formulations that could improve agricultural sustainability practices.

Phylogenetic analysis of viviparity, matrotrophy, and other reproductive patterns in chondrichthyan fishes.

The reproductive diversity of extant cartilaginous fishes (class Chondrichthyes) is extraordinarily broad, reflecting more than 400 million years of evolutionary history. Among their many notable reproductive specialisations are viviparity (live-bearing reproduction) and matrotrophy (maternal provision of nutrients during gestation). However, attempts to understand the evolution of these traits have yielded highly discrepant conclusions. Here, we compile and analyse the current knowledge on the evolution of reproductive diversity in Chondrichthyes with particular foci on the frequency, phylogenetic distribution, and directionality of evolutionary changes in their modes of reproduction. To characterise the evolutionary transformations, we amassed the largest empirical data set of reproductive parameters to date covering nearly 800 extant species and analysed it via a comprehensive molecular-based phylogeny. Our phylogenetic reconstructions indicated that the ancestral pattern for Chondrichthyes is 'short single oviparity' (as found in extant holocephalans) in which females lay successive clutches (broods) of one or two eggs. Viviparity has originated at least 12 times, with 10 origins among sharks, one in batoids, and (based on published evidence) another potential origin in a fossil holocephalan. Substantial matrotrophy has evolved at least six times, including one origin of placentotrophy, three separate origins of oophagy (egg ingestion), and two origins of histotrophy (uptake of uterine secretions). In two clades, placentation was replaced by histotrophy. Unlike past reconstructions, our analysis reveals no evidence that viviparity has ever reverted to oviparity in this group. Both viviparity and matrotrophy have arisen by a variety of evolutionary sequences. In addition, the ancestral pattern of oviparity has given rise to three distinct egg-laying patterns that increased clutch (brood) size and/or involved deposition of eggs at advanced stages of development. Geologically, the ancestral oviparous pattern arose in the Paleozoic. Most origins of viviparity and matrotrophy date to the Mesozoic, while a few that are represented at low taxonomic levels are of Cenozoic origin. Coupled with other recent work, this review points the way towards an emerging consensus on reproductive evolution in chondrichthyans while offering a basis for future functional and evolutionary analyses. This review also contributes to conservation efforts by highlighting taxa whose reproductive specialisations reflect distinctive evolutionary trajectories and that deserve special protection and further investigation.

How competition between overlapping generations can influence optimal egg-laying strategies in annual social insects.

Annual social insects are an integral functional group of organisms, particularly in temperate environments. An emblematic part of their annual cycle is the social phase, during which the colony-founding queen rears workers that later assist her in rearing sexual progeny (gynes and drones). In many annual social insects, such as species of bees, wasps, and other groups, developing larvae are provisioned gradually as they develop (progressive provisioning) leading to multiple larval generations being reared simultaneously. We present a model for how the queen in such cases should optimize her egg-laying rate throughout the social phase depending on number-size trade-offs, colony age-structure, and energy balance. Complementing previous theory on optimal allocation between workers vs. sexuals in annual social insects and on temporal egg-laying patterns in solitary insects, we elucidate how resource competition among overlapping larval generations can influence optimal egg-laying strategies. With model parameters informed by knowledge of a common bumblebee species, the optimal egg-laying schedule consists of two temporally separated early broods followed by a more continuous rearing phase, matching empirical observations. However, eggs should initiallybe laid continuously at a gradually increasing rate when resources are scarce or mortality risks high and in cases where larvae are fully supplied with resources at the egg-laying stage (mass-provisioning). These factors, alongside sexual:worker body size ratios, further determine the overall trend in egg-laying rates over the colony cycle. Our analysis provides an inroad to study and mechanistically understand variation in colony development strategies within andacross species of annual social insects.

Influence of Increased Freedom of Movement on Welfare and Egg Laying Pattern of Hens Kept in Aviaries

Simple SummaryThe laying hen industry is shifting from cages to alternative housing systems (such as aviaries) to address societal concerns regarding animal welfare. However, it is important to understand the hens’ needs in these systems, in terms of space use and behaviour, to promote their welfare and avoid drawbacks. Therefore, we examined the effects of three different structural modifications (addition of ramps and/or removal of internal partitions) to increase the hens’ freedom of movement in a commercial aviary system. Higher freedom of movement resulted in positive effects on feather conditions and the possibility of choosing between the aviary tiers according to the hens’ preferences. Laying hen producers may therefore adopt some of these structural modifications in aviary systems to enhance the welfare of hens.This work investigates the effects of structural modifications on the welfare level and laying patterns of hens in a three-tier commercial aviary system. Four experimental groups were used: C (control, housed in a traditional aviary); LM (longitudinal movement, in which internal partitions were removed); VM (vertical movement, in which ramps were installed); and FM (freedom of movement, both LM and VM modifications). Hens showed worse body condition scores (p < 0.05) in all the modified aviaries, while plumage condition was improved in FM but worsened in VM (p < 0.05). No significant effect was observed on egg deposition patterns, egg quality or keel bone damage. When ramps were available (VM and FM groups), hens reduced the number of flights and increased the number of walks from 0.52 to 7.7% of the displacements on average (p < 0.05). Apart from some feather pecking concerns in VM (likely due to overcrowding in some favourite aviary areas), LM and FM seemed to facilitate animal movement and promote species–specific behaviour. It is concluded that hen welfare in aviary systems can be improved by means of tailored structural modifications. Producers may therefore adopt some of these modifications (providing ramps and/or removing vertical barriers) to enhance the welfare of hens.

Effects of Female and Male Density on their Mating Performance and Female Post-Mating Reproductive Fitness in Plagiodera versicolora (Laicharting) (Coleoptera: Chrysomelidae)

In insects, mating performance and female post-mating reproductive fitness is closely related to female and male density. In nature, females and males of the willow leaf beetle, Plagiodera versicolora (Laicharting), exhibit the phenomenon of swarming damage. This study investigated the effects of female and male density on their mating performance and on female post-mating fecundity, egg hatching rates, and egg-laying patterns. Female and male density had a significant positive effect on the time from pairing to successful mating and on female fecundity, the duration of the egg-laying period, and the number of egg clutches, but it had a significant negative effect on the egg hatching rate. Female and male density had no significant effect on female post-mating longevity and the number of eggs per clutch. Our study shows that variation in female fecundity and egg-laying patterns is an adaptive strategy for P. versicolora at relatively high population densities. This strategy helps to expand the distribution of offspring and lower the competition for food resources among offspring, which, in turn, helps to maintain or increase population abundance.

Honey bee queen health is unaffected by contact exposure to pesticides commonly found in beeswax

Honey bee queen health is crucial for colony health and productivity, and pesticides have been previously associated with queen loss and premature supersedure. Prior research has investigated the effects of indirect pesticide exposure on queens via workers, as well as direct effects on queens during development. However, as adults, queens are in constant contact with wax as they walk on comb and lay eggs; therefore, direct pesticide contact with adult queens is a relevant but seldom investigated exposure route. Here, we conducted laboratory and field experiments to investigate the impacts of topical pesticide exposure on adult queens. We tested six pesticides commonly found in wax: coumaphos, tau-fluvalinate, atrazine, 2,4-DMPF, chlorpyriphos, chlorothalonil, and a cocktail of all six, each administered at 1, 4, 8, 16, and 32 times the concentrations typically found in wax. We found no effect of any treatment on queen mass, sperm viability, or fat body protein expression. In a field trial testing queen topical exposure of a pesticide cocktail, we found no impact on egg-laying pattern, queen mass, emergence mass of daughter workers, and no proteins in the spermathecal fluid were differentially expressed. These experiments consistently show that pesticides commonly found in wax have no direct impact on queen performance, reproduction, or quality metrics at the doses tested. We suggest that previously reported associations between high levels of pesticide residues in wax and queen failure are most likely driven by indirect effects of worker exposure (either through wax or other hive products) on queen care or queen perception.

Biological features of egg productivity of black African ostriches under a semi-intensive keeping

The study of egg-laying patterns and defining ways of increasing egg-laying productivity is a necessary condition for the development and increased efficiency of ostrich breeding. Therefore, some studies deal with egg productivity of ostriches of different age groups (group 1 - age 8-9 years, group 2 - age 4-5 years) for their long-term keeping under a semi-intensive system forest-steppe zone of Ukraine. The sex ratio in the families was 1: 2-3. Behavioral patterns of poultry during the breeding season are close to natural ones. Older individuals are characterized with a longer productive period (January-October) than younger ones (March-September). According to the most extended daylight hours at this time of year, the higher level of egg-laying performance is established in May and summer months. The females’ egg-laying performance analysis shows their significant individual features - 9-42 eggs were obtained from one female. It is worth mentioning that the productivity period’s duration does not continuously regulate the number of eggs. There is a high positive correlation between the duration of the egg-laying process and total egglaying performance in group 1 (r = 0.7981); in group 2 � there is no relation between these features (r = -0.0843). The variability of egg-laying cycles of ostrich females has been confirmed, and it requires further studies. According to the intensity of lying during the breeding season, there are differences between younger and older poultry groups. The first two months and the last month of egg-laying are the least productive for all. It was established that the egg weight of older females is higher compared to young ones, with a potential difference between the groups (P&gt; 0.999) and a significant level of individual variability (Cv = 1.78-8.06%). This indicates the necessity of successive work with the herd to optimize egg weight, as a significant variation in egg weight affects the duration of incubation and embryonic development of ostriches. It also leads to the elongation of the “hatch window” that causes heterogeneity of ostrich weight. New data allow characterizing the peculiarities of ostrich physiology, their ability to adapt to industrial conditions of breeding at farms located in the northern part of the forest-steppe zone of Ukrai.

The Grey-backed Shrike parents adopt brood survival strategy in both the egg and nestling phases

BackgroundGreat diversity exists in the parenting pattern of altricial birds, which has long been considered as an adaptive response to specific environmental conditions but not to their life-history style.MethodsWe examined the egg-laying and nestling-raising pattern of the Grey-backed Shrike (Lanius tephronotus) that breeds only once a year on the Tibetan Plateau. We compared the dietary composition to that of its sympatric competitor, the Brown-cheeked Laughing Thrush (Trochalopteron henrici) that breeds twice a year.ResultsFemale Grey-backed Shrikes produced a fixed clutch size of five, with increasing egg size by their laying sequence. The last offspring in the brood is disadvantageous in the size hierarchy because it hatches later. However, they had the largest fledgling body mass. These findings indicate that Grey-backed Shrikes adopt the brood survival strategy in both the egg and nestling phases. Moreover, males and females exhibit no sexual division in providing parental care as they made an equal contribution to the total amount of food delivered to their brood. This parenting pattern of Grey-backed Shrikes, as well as their dietary items, differ significantly from those of the Brown-cheeked Laughing Thrush.ConclusionsWe suggest that the differentiation in life-history style between sympatric competitors, rather than a behavioral response to specific environmental conditions, plays a decisive role in driving avian parenting strategy diversification.

EVALUATION OF FOUR NONLINEAR MODELS DESCRIBING EGG PRODUCTION CURVE OF FAYOUMI LAYERS

Egg production data used in this work were obtained from records of Fayoumi chickens flock belongs to El-Takamoly poultry project at Al-Azab, Fayoum Governorate. Egg production records over a 52-wk egg laying period related to 1900 hens. All data was summarized on a weekly basis as eggs per hen per week on hen-day (survivor) basis. Regarding Wood and McNally models, (a) stands for initial egg production, (a) parameter value was very low (0.001) for both models. The increasing rate to the egg production peak (parameter b) was 2.90 for the Wood model and 2.19 for the McNally model. Similarly, parameter c, the decreasing rate of egg production from the peak, was estimated to be 0.08 for the Wood model and 0.06 for the McNally model. Depending on compartmental function m, n, p and q represent scale parameter, measure of persistency of egg production, sexual maturity rate, and age at first egg, respectively and estimated values for these parameters were 86.47, 0.01, 0.23 and 21.61 wks of age, respectively, Concerning the modified compartmental model the parameters A, B, C and D represent a scale parameter, the rate of decrease in laying ability, the reciprocal indicator of the variation in sexual maturity and the mean age of sexual maturity of the hens, respectively. In this work the estimated values of the abovementioned parameters were 75.26, 0.006, 1.14 wks and 24.96 wks of age for A, B, C and D respectively. According to goodness of fit criteria, modified compartmental model was the best model for describing the egg-laying pattern of Fayoumi layers which had the lowest Akaike information criterion and Bayesian information criterion values and the highest coefficient of determination. Moreover, the modified compartmental model showed correspondence with the actual hen day of egg production (age and percentage at peak were 29.44 weeks of age and 64.16%, respectively).

Distinctive egg-laying patterns in terminal versus non-terminal periods in three fruit fly species.

The specific objective of this study was to use a logistic regression model for determining the degree to which egg laying patterns of individual females at the end of life (i.e., terminal segments) in each of three different fruit fly species could be distinguished from the egg-laying patterns over a similar period in midlife (i.e., non-terminal segments). Extracting data from large-scale databases for 11-day terminal and 11-day non-terminal segments in the vinegar fly (Drosophila melanogaster), the Mexican fruit fly (Anastrepha ludens) and the Mediterranean fruit fly (Ceratitis capitata) and organizing the model's results in a 2×2 contingency table, we found that: (1) daily egg-laying patterns in fruit flies can be used to distinguish terminal from non-terminal periods; (2) the overall performance metrics such as precision, accuracy, false positives and true negatives depended heavily on species; (3) differentiating between terminal and non-terminal segments is more difficult when flies die at younger ages; and (4) among the three species the best performing metrics including accuracy and precision were those produced using data on D. melanogaster. We conclude that, although the reliability of the prediction of whether a segment occurred at the end of life is relatively high for most species, it does not follow precisely predicting remaining life will also be highly reliable since classifying an end of life period is a fundamentally different challenge than is predicting an exact day of death.

Correlated evolution of nest and egg characteristics in birds

Correlational selection is defined as selection for adaptive character combinations, and it therefore favours combinations of coevolved traits via phenotypic integration. Whereas the evolution of avian nest-building and egg-laying characteristics are well understood, their correlated dynamics remain overlooked. Here, we examined patterns of correlated evolution between nest, egg and clutch characteristics in 855 species of birds from 90 families, representing nearly 9% and 33% of avian species- and family-level diversity. We show that the ancestral state of birds’ nests was semi-open with nest sites having since become progressively more open over time. Furthermore, nest characteristics appear to have influenced egg-laying patterns in that while semi-open nests with variable clutch sizes were probably ancestral, clutch sizes have declined over evolutionary time in both open and closed nests. Ancestrally, avian eggs were also large, heavy and either elliptic or round, and there have been high transition rates from elliptic to round eggs in open nests and vice versa in closed nests. Ancestrally, both unpigmented (white) and pigmented (blue–brown) eggs were laid in open nests, although blue–brown eggs have transitioned more to white over time in open and closed nests, independently. We conclude that there has been a remarkable level of correlated evolution between the nest and egg characteristics of birds, which supports scenarios of correlational selection on both of these extended avian phenotypes.

Egg-Laying Pattern of Helicoverpa zea1 in Sweet Corn: A New Pest Management Prospect

The corn earworm, Helicoverpa zea (Boddie), is a major insect pest of maize (Zea mays L.), cotton (Gossypium hirsutum L.), and vegetable crops. Maize silk is a favorite egg-laying site of H. zea. However, other parts of the maize plant might be even more attractive for oviposition by H. zea. Under field conditions and in insect-proof cages in a greenhouse, egg-laying distribution patterns were assessed on a late and an early sweet corn cultivar, i.e., Java (Technisem) and Garrison (Syngenta), respectively. Maize tassels on both cultivars were the main egg-laying sites of the pest. In insect-proof cages, at the maize silking stage, more than 60% of the total number of eggs collected were on tassels. In the field, oviposition by H. zea began at tassel emergence, and more than 80% of the total number of eggs were collected from tassels. Egg distribution on leaves and silk varied according to the sweet corn cultivar. The findings offer new prospects to control H. zea. The tassel emergence stage is the best period for controlling H. zea in maize fields and the best phenological stage to use maize as a trap crop for the pest.

Analyses of mathematical models for Yangzhou geese egg-laying curves

Mathematical models of the egg-laying curves for Yangzhou geese exposed to both natural and artificial photoperiods were established to optimise the parameters for maximising geese reproductive performance and for the development of precision feeding methods. With the natural photoperiod, egg-laying starts in autumn when daily photoperiod decreases, but accelerates after the winter solstice, and reaches the peak in spring when photoperiod increases. An accumulating model was constructed based on the hypothesis that the egg-laying capacity of geese was determined by two components of the photoperiod: photo-stimulation and photo-inhibition. In addition, a second segmented model was constructed based on the hypothesis that the photo-stimulation only occurred with lengthening photoperiods after the winter solstice, and the lesser laying rate in autumn could be attributed to the non-photo-dependent animal-husbandry technologies. This model consists of a logistic model before the winter solstice, and an accumulating model after this solstice. The use of the logistic and accumulating resulted in more precise predictions that occurred with use of Model 1 with a greater R2 and lesser RMSE, AIC and BIC. Likewise, the egg-laying curves when there was consideration of artificial photoperiods could also be constructed with consideration of stimulatory and inhibitory photoperiodic effects. The model consists of an initial logistic and subsequently a quadratic polynomial model. With use of this model, there is consideration of changes in egg-laying patterns when there is a fixed photoperiod, with the model parameters reflecting the effects by photoperiod control-programs and age of the geese. In conclusion, new mathematical models have been developed to best fit egg-laying curves when there are both natural and artificial photoperiods. These models can contribute to development of precision-feeding technologies for breeding geese in future.

Investigating the genetic determination of clutch traits in laying hens

Clutch traits were proposed as a more detailed description of egg-laying patterns than simple total egg production. In this study, egg production of 23,809 Rhode Island Red (RIR) and 22,210 White Leghorn (WL) hens was described in terms of number of clutches, average and maximum clutch size, age at first egg, total saleable egg production, and percentage of egg defects. Genetic parameters were estimated using a six-trait animal model. Of the phenotyped birds, 1433 RIR hens and 1515 WL hens were genotyped with line specific 50K Affymetrix Axiom single nucleotide polymorphism chips to perform genome-wide association analyses. Moderate heritabilities were estimated for clutch traits of 0.20 to 0.42 in the RIR line and 0.29 to 0.41 in the WL line. Average and maximum clutch size was positively genetically correlated with total saleable egg number in both lines. Genome-wide association analysis identified seven regions that were associated with egg production in the RIR line and 12 regions in the WL line. The regions identified were line and trait specific, except for one region on chromosome 6 from 28 to 29 Mb that influenced number of clutches and maximum and average clutch size in WL hens. Regions associated with egg production identified here overlapped with 260 genes, with some strong positional candidates based on gene ontology including WASH1, which is involved in oocyte maturation, NPVF, involved in regulation of follicle-stimulating hormone secretion, and FOXO3, involved in oocyte maturation and ovulation from the ovarian follicle. Confirmation of the role of these genes in regulation of egg production pattern will require further studies.

Factors affecting the egg-laying pattern of Forficula auricularia (Dermaptera: Forficulidae) in three climatologically different zones of North America

AbstractEgg-laying patterns of the European earwig, Forficula auricularia Linnaeus (Dermaptera: Forficulidae), from three climatologically different areas; Montréal, Québec, Canada, Vancouver, British Columbia, Canada, and San Francisco, California, United States of America; were compared in laboratory. Three different egg-laying patterns were observed. Among the biotic parameters studied; previtellogenic follicular atresia, number of oocytes per ovariole at imaginal moult, female life expectancy, and ovarian activity explained female successful responses to local weather conditions. Follicular atresia, combined with a low number of oocytes, impeded oviposition in a low percentage of females from Montréal. It also impedes the production of a third brood in the Vancouver population, and of a fourth brood in the San Francisco population. Both female life expectancy and length of ovarian activity also had a significant impact on the oviposition pattern in the three climatic regions. Under the cold temperate climate of the Montréal area, only one brood was produced due to the short period of female fertility. Longer period of fertility and life expectancy enabled females to produce two broods in the milder temperate climate of Vancouver, and three broods in the San Francisco climate. Our results strongly suggest an exaptation enabling the native European populations of F. auricularia to adapt successfully in North America.

Resistance changes in Salmonella enterica serovar Typhimurium treated by High Hydrostatic Pressure and Pulsed Electric Fields and assessment of virulence changes by using Caenorhabditis elegans as a test organism

Abstract The goal of this study was to evaluate the development of Salmonella enterica subsp. enterica serovar Typhimurium resistance against Pulsed Electric Fields (PEF) and High Hydrostatic Pressure (HHP), and to study the possible virulence changes of the resistant subpopulations using Caenorhabditis elegans. Results showed that S. Typhimurium became resistant to both non-thermal technologies after four consecutive treatments. Survival probability of the worms (C. elegans) increased significantly when they were fed with S. Typhimurium treated by PEF four consecutive times in comparison with the other two subpopulations, untreated and treated once. For HHP, results indicated that up to percentile 50%, the survival probability of worms fed with treated microorganisms (once and four times) was greater than that of worms fed with untreated ones. Also, the C. elegans egg-laying pattern was modified and there were significant differences in the number of eggs laid in the first two days among the three subpopulations studied. Consequently, although S. Typhimurium develops microbial resistance against PEF or HHP treatments, when it is applied repeatedly, its virulence against C. elegans appears to decrease. Industrial relevance Among the non-thermal technologies, Pulsed Electric Fields and High Hydrostatic Pressure have a great potential. Nevertheless, it is necessary to validate them from a safety point of view because of the huge amount of damaged cells that can be obtained if sublethal treatments are applied. These studies have industrial relevance in food safety ensuring proper processing when using these non-thermal technologies.

Common kestrel (Falco tinnunculus, Falconiformes, Falconidae) in colonial settlements of rook (Corvus frugilegus, Passeriformes, Corvidae) in steppe ecosystems of the Manych valley

Relationships between the state of common kestrel (Falco tinnunculus) population and the structure of rook (Corvus frugilegus) colonies located in the steppe ecosystems of the Manych valley (Rostov region, Russia) were studied. A brief description of the biology and ecology of the satellite species is given. A relation between the egg-laying date and patterns of common kestrel and the structure of the rook colony was revealed: the larger the area of the rookery and the density of nesting rooks in it, the more compressed is the formation timing of its clutches. The breeding success of common kestrel was found to be the highest for the slot on side branches (71.1%) and at a height of 6.0–7.0 m above the ground (83.0%). It was shown that the a small falcon females nesting in the biological center of the rook colonies to have a smaller span of ages and more synchronous breeding compared with the females nesting on the periphery. The species forming a mixed colony have different spatial and ethological structures. The biological center of the common kestrel colony is located on the periphery (both geometric and biological) of the rook colony, and the biological edge of the colony is in the center of the rookery.

Spatial patterns at host and forest stand scale and population regulation of the pine processionary mothThaumetopoea pityocampa

Different spatial processes are likely to generate variability at different scales. Thus, the explanation of patterns may be facilitated by knowledge about the spatial scales where variation in patterns occurs. In the present study, the link between spatial patterns of the pine processionary moth Thaumetopoea pityocampa Den. & Schiff. (Lepidoptera, Notodontidae) at two different scales, as well as its population dynamics, was assessed. First, the spatial patterns of T. pityocampa population were assessed at the forest stand scale by surveying the distribution of larval colonies within the pine forest, indicative of adult dispersion. Second, egg-laying patterns across individual host-plants, indicative of female oviposition choices, were assessed, as well as their impact on the survival of immature stages. It was found that T. pityocampa presents a gregarious distribution in homogeneous pine forests, over distances of a few dozen metres. At the pine tree scale, females tend to aggregate their egg batches, whereas aggregation increases with population density. Natural enemies such as parasitoids do not appear to play an important role in regulating the population dynamics of the species. At the same time, aggregation in individual hosts leads to increased mortality in the period from hatching to the third instar, which is notable at high population densities. A patchy distribution in the landscape over short distances has a potentially positive effect on population dynamics of the species, avoiding the Allee effect, and allowing for a rapid increase in population, even where initial numbers are low, leading to localized outbreaks. At the same time, increased mortality as a result of egg-batch clumping at high population densities is a potential density-dependent mechanism of population regulation.