Population Dynamics Of Colonies Research Articles

Warmer autumns and winters could reduce honey bee overwintering survival with potential risks for pollination services

Honey bees and other pollinators are critical for food production and nutritional security but face multiple survival challenges. The effect of climate change on honey bee colony losses is only recently being explored. While correlations between higher winter temperatures and greater colony losses have been noted, the impacts of warmer autumn and winter temperatures on colony population dynamics and age structure as an underlying cause of reduced colony survival have not been examined. Focusing on the Pacific Northwest US, our objectives were to (a) quantify the effect of warmer autumns and winters on honey bee foraging activity, the age structure of the overwintering cluster, and spring colony losses, and (b) evaluate indoor cold storage as a management strategy to mitigate the negative impacts of climate change. We perform simulations using the VARROAPOP population dynamics model driven by future climate projections to address these objectives. Results indicate that expanding geographic areas will have warmer autumns and winters extending honey bee flight times. Our simulations support the hypothesis that late-season flight alters the overwintering colony age structure, skews the population towards older bees, and leads to greater risks of colony failure in the spring. Management intervention by moving colonies to cold storage facilities for overwintering has the potential to reduce honey bee colony losses. However, critical gaps remain in how to optimize winter management strategies to improve the survival of overwintering colonies in different locations and conditions. It is imperative that we bridge the gaps to sustain honey bees and the beekeeping industry and ensure food and nutritional security.

The Effects of Sugar Syrup Enriched with Amino Acid Mixtures at Different Concentrations on Colony Population Dynamics and Development Characteristics of Bumble bee (Bombus terrestris)

In this study, we tested the effects of amino acid-supplemented diets on colony development performances in Bombus terrestris. A total of 75 queens artificially hibernated were randomly separated into three groups. These groups were fed with different diets: normal sugar syrups and normal pollen (Control), sugar syrup which contains recommended dose (for honey bees: 10 mL/L, Sucrose syrup) of amino acid supplement and normal pollen (10 mL/L), sugar syrup which contains twice higher recommended dose of amino acid supplement and normal pollen (20 mL/L). Some developmental traits of queens and their colonies were determined. According to our findings, there were no significant differences in any of the traits of colony development except the number of total individuals among the groups (P<0.05). Results showed that feeding with an amino acid-supplemented diet is not influencial on colony development traits in B. terrestris.

Oviposition, Life Cycle, and Longevity of the Leaf-Cutting Ant Acromyrmex rugosus rugosus.

Studies related to the demography of individual members from ant colonies have received little attention, although they are the basis to understanding the population dynamics of colonies. Thus, the objective of this work was to study the queen oviposition rate and the duration of the life cycle and longevity of Acromyrmex rugosus rugosus workers. To determine the oviposition rate, queens from three colonies were individually placed in plastic containers, and the eggs laid were quantified over a 96 h period. The development of the immature forms was observed every 24 h, with which the duration of each stage of development was determined. To verify the longevity of workers, the newly emerged adults were marked and daily observations were made. According to the results, there is variation in the development time of immature forms within the colony itself and between colonies. In addition, the number of eggs deposited was also inconstant in the three colonies, ranging from 5 to 119 eggs per day, while the longevity of workers varied from 3 to 7 months. Occasionally, it was found that the workers feed on the eggs produced by the queen; besides, there was a disappearance of larvae and pupae during the research, indicating a possibility of the practice of cannibalism in this species.

On the Effects of Artificial Feeding on Bee Colony Dynamics: A Mathematical Model.

This paper proposes a new mathematical model to evaluate the effects of artificial feeding on bee colony population dynamics. The proposed model is based on a classical framework and contains differential equations that describe the changes in the number of hive bees, forager bees, and brood cells, as a function of amounts of natural and artificial food. The model includes the following elements to characterize the artificial feeding scenario: a function to model the preference of the bees for natural food over artificial food; parameters to quantify the quality and palatability of artificial diets; a function to account for the efficiency of the foragers in gathering food under different environmental conditions; and a function to represent different approaches used by the beekeeper to feed the hive with artificial food. Simulated results are presented to illustrate the main characteristics of the model and its behavior under different scenarios. The model results are validated with experimental data from the literature involving four different artificial diets. A good match between simulated and experimental results was achieved.

Prey size and scramble vs. contest competition in a social spider: implications for population dynamics.

There are many benefits of group living, but also substantial costs, one of which is competition for resources. How scarce food resources are distributed among different members of a population or social group - whether via scramble or contest competition - can influence not only the variance in individual fitness, but also the stability and therefore survival of the group or population. Attributes of the food resources themselves, such as their size, may influence the typeof intraspecific competition that occurs and therefore the intrinsic stability of a group or population. By experimentally manipulating the size of prey fed to artificial colonies of the social spider Anelosimus eximius, we investigated whether prey size could alter the degree of scramble vs. contest competition that takes place and, thus, potentially influence colony population dynamics. We found that large prey were shared more evenly than small prey and that individuals in poor condition were more likely to feed when prey were large than when prey were small. Additionally, we show that individuals participating in prey capture are also more likely to feed on the captured prey. We developed a simple mathematical model to explore the prey sizes that would be energetically worth defending, i.e. prey that are 'economically defendable'. The model shows that neither very small prey, nor prey above a certain size is worth monopolizing, with only intermediate size prey being 'economically defendable'. We therefore suggest the small and large prey in our experiment corresponds to our model's intermediate and large prey categories, respectively. As the size of prey captured by social spider colonies increases with colony size, our findings suggest that scramble competition may predominate in large colonies. Scramble competition, combined with the fact that prey biomass per capita declines as colonies grow beyond a certain size, would then explain why extremely large colonies of this social spider may suddenly go extinct. Our project thus illustrates the potential triple link between characteristics of the resources, individual behaviour and population dynamics, a link rarely considered in an empirical setting.

Increased tolerance and resistance to virus infections: a possible factor in the survival of Varroa destructor-resistant honey bees (Apis mellifera).

The honey bee ectoparasitic mite, Varroa destructor, has a world-wide distribution and inflicts more damage than all other known apicultural diseases. However, Varroa-induced colony mortality is more accurately a result of secondary virus infections vectored by the mite. This means that honey bee resistance to Varroa may include resistance or tolerance to virus infections. The aim of this study was to see if this is the case for a unique population of mite-resistant (MR) European honey bees on the island of Gotland, Sweden. This population has survived uncontrolled mite infestation for over a decade, developing specific mite-related resistance traits to do so. Using RT-qPCR techniques, we monitored late season virus infections, Varroa mite infestation and honey bee colony population dynamics in the Gotland MR population and compared this to mite-susceptible (MS) colonies in a close by apiary. From summer to autumn the deformed wing virus (DWV) titres increased similarly between the MR and MS populations, while the black queen cell virus (BQCV) and sacbrood virus (SBV) titres decreased substantially in the MR population compared to the MS population by several orders of magnitude. The MR colonies all survived the following winter with high mite infestation, high DWV infection, small colony size and low proportions of autumn brood, while the MS colonies all perished. Possible explanations for these changes in virus titres and their relevance to Varroa resistance and colony winter survival are discussed.

Individual Cell Fate as a Factor of Colony Population Dynamics in Oncogenesis

Cells in multicellular organisms may have distinct cell fates, such as proliferation or differentiation into specializied cell types. The individual cell fate is determined by a range of factors, such as genetic predisposition or epigenetic factors. However, for a substantial number of cells in the organism statistic homogeneity and ballance of the system may be achieved; though the fate of an individual cell may vary. For most cell types these random individual events do not [ influence the final outcome due to a large number of cells of this type. Nevertheless, the switch between cell fate plays a far more important role if we consider stemm cells (SC) or colony-forming units (CFU) as well as cancer stem cells (CSC) because individual cell events determine further development of a colony (metastase) or its elimination. The report presents a mathematical model of the initial stage of cell colony development (for hematopoetic tissue). In order to establish the role of an individual event in the process of oncogenesis and its consequences, as well as to understand the mechanism of population dynamics, it is important to study in detail the interaction of probability distribution of cell events, and feedback regulation. This paper is part of a larger research aimed at elaborating a model of a competing clonal hematopoesis in terms of oncogenesis and oncohematological diseases.

ECOBEE: a tool for long-term honey bee colony monitoring at the landscape scale in West European intensive agroecosystems

SummaryIn Central Western France, as in many other areas, traditional apiculture has been replaced by more intensive practices to compensate for colony losses and current decreasing honey yields. One neglected aspect concerns the choice by professional beekeepers of apiary sites in intensive agrosystems, with regard to landscape features, a choice which appears to be largely empirical. ECOBEE is a colony monitoring scheme specifically intended to provide beekeepers and researchers with basic ecological data on honeybees in intensive agrosystems, as well as colony population dynamics. ECOBEE was launched in 2008 as a long-term ecological project with three specific aims: 1. to monitor seasonal and inter-annual population dynamic parameters of honeybee colonies in a heterogeneous farming system; 2. to provide relevant and robust datasets to test specific hypotheses about bees such as the influence of landscape planning, agricultural inputs or human pressure; and 3. to offer opportunities for assessing the effectiveness of agro-environmental schemes or the effects of changes in agricultural policies on honey bee wellbeing. Here we present an overview of ECOBEE, the type of datasets collected over the first four years of monitoring, and their possible application and use. We found that colony dynamics were largely influenced by the phenology of the main mass-flowering crops foraged by bees, namely oilseed rape and sunflowers. Furthermore, we detected a sharp food shortage period in late spring between the flowering of oilseed rape and sunflowers, possibly temporarily constraining colony sustainability. We further discuss the research perspectives offered by ECOBEE, especially with regard to spatial ecotoxicology.

Outcome of the First Round of Public Consultation on the draft Guidance Document on the Risk Assessment of Plant Protection Products on Bees (Apis mellifera, Bombus spp. and Solitary Bees)

Outcome of the First Round of Public Consultation on the draft Guidance Document on the Risk Assessment of Plant Protection Products on Bees (Apis mellifera, Bombus spp. and Solitary Bees)

An Evolutionary Dynamics Model Adapted to Eusocial Insects

This study aims to better understand the evolutionary processes allowing species coexistence in eusocial insect communities. We develop a mathematical model that applies adaptive dynamics theory to the evolutionary dynamics of eusocial insects, focusing on the colony as the unit of selection. The model links long-term evolutionary processes to ecological interactions among colonies and seasonal worker production within the colony. Colony population dynamics is defined by both worker production and colony reproduction. Random mutations occur in strategies, and mutant colonies enter the community. The interactions of colonies at the ecological timescale drive the evolution of strategies at the evolutionary timescale by natural selection. This model is used to study two specific traits in ants: worker body size and the degree of collective foraging. For both traits, trade-offs in competitive ability and other fitness components allows to determine conditions in which selection becomes disruptive. Our results illustrate that asymmetric competition underpins diversity in ant communities.

A quantitative model of honey bee colony population dynamics.

Since 2006 the rate of honey bee colony failure has increased significantly. As an aid to testing hypotheses for the causes of colony failure we have developed a compartment model of honey bee colony population dynamics to explore the impact of different death rates of forager bees on colony growth and development. The model predicts a critical threshold forager death rate beneath which colonies regulate a stable population size. If death rates are sustained higher than this threshold rapid population decline is predicted and colony failure is inevitable. The model also predicts that high forager death rates draw hive bees into the foraging population at much younger ages than normal, which acts to accelerate colony failure. The model suggests that colony failure can be understood in terms of observed principles of honey bee population dynamics, and provides a theoretical framework for experimental investigation of the problem.

Population dynamics of natural colonies of Aurelia sp. scyphistomae in Tasmania, Australia

The aim of this study was to identify potential environmental controls of the asexual phases of reproduction by measuring the rates of asexual reproduction (budding and strobilation) and mortality in naturally occurring populations of Aurelia sp. scyphistomae at different spatial and temporal scales. The percentage cover, density of colonies of Aurelia sp. scyphistomae, and density of the population of two naturally occurring colonies of Aurelia sp. scyphistomae were examined over 2 years in southern Tasmania. Artificial substrates were also deployed to investigate colony dynamics when density dependent effects were reduced. Clear spatial and temporal differences in the population dynamics of the colonies were observed. Density dependent effects controlled budding and recruitment of new scyphistomae to the substrate when populations were dense and space limiting. In contrast, environmental controls of budding and strobilation were more apparent in a colony with significantly greater area of bare substrate and hence room for expansion. Water temperature and rainfall (as a proxy for salinity) were linked to changes in population size. Annual and seasonal differences in population dynamics were not observed in a colony limited by space but were apparent in a colony where space was not limited. When space was removed as a limiting factor by deploying artificial substrates, a seasonal environmental effect on the rate of growth of the colony was observed. These studies suggest that the growth, survival and reproduction of the sessile colonial phase of Aurelia sp. is regulated by a combination of density dependent factors and environmental conditions, which are consequently important to the formation of jellyfish blooms.

Colony Size Selection Determines Adult Survival and Dispersal Preferences: Allee Effects in a Colonial Bird

Avian coloniality traditionally has been investigated by examining how breeding success varies with colony size, but other crucial fitness components rarely have been examined. This may lead to wrong conclusions because unmeasured parameters may change the final fitness balance. We used multistate capture-recapture models to investigate adult survival and dispersal in relation to colony size within a long-term monitored population of lesser kestrels (Falco naumanni). Nest predation probability decreases with colony size, and adult survival is predicted to show the same trend because adults are exposed to the same suite of predators. As expected, survival probability was higher in large colonies (0.72+/-0.015; mean+/-SE) than in medium or small colonies (0.65+/-0.02). Additionally, dispersal probabilities were higher going from small to large colonies (0.20+/-0.01) than from large to small (0.08+/-0.01), as predicted by theory of habitat selection shaped by fitness maximization. These asymmetries are likely to generate size-specific colony population dynamics, so they should be taken into account in studies of colonial birds and other metapopulation-like systems. Allee effects, that is, positive density dependence, appear to be the cause of the evolution of dispersal behavior and may explain the maintenance of coloniality in this species.

Tritrophic interactions in the context of climate change: a model of grasses, cereal Aphids and their parasitoids

AbstractBiologists have been challenged to envisage the likely consequences of increases in atmospheric carbon dioxide concentrations, and the suite of accompanying environmental changes (e.g. rising temperature, changing rainfall patterns, etc.) on our biotic systems. Research to date on plant responses has been extensive, but work on herbivore responses has been less complete, and work on higher trophic levels nearly nonexistent. One group of herbivores that has been reasonably well studied is aphids, and at least for this group, researchers have even begun to investigate responses at higher trophic levels, to include parasitoids. In this paper, we develop a mechanistic mathematical model of the general interaction between grasses, cereal aphids and their parasitoids. We used this model to investigate the interacting effects of rising CO2and temperature. The model suggests that, while parasitoids do have an impact on the aphid colony population dynamics, they do not fundamentally alter the aphid response to climate change. The model predicts that for both aphids and their parasitoids, the population responses to combined effects of elevated CO2and temperature will be more similar to current ambient conditions than we might expect from the individual effects of CO2or temperature increases. This interaction has important consequences for the interpretation of results from experiments that study only the effect of rising CO2.

The response of Acropora hyacinthus and Montipora tuberculosa to three different types of colony damage: scraping injury, tissue mortality and breakage

Three types of injuries commonly generated by biotic and abiotic agents on the periphery of coral colonies are tissue mortality, scraping injuries and breakage. To determine if recovery (amount of regeneration) was affected by injury type, colonies of Acropora hyacinthus and Montipora tuberculosa were inflicted with tissue, scraping and breakage injuries and their recovery monitored over 24 days. The influence of the tissue available for regeneration (i.e. the zone of tissue of bordering or partially injured polyps from which regeneration can occur) and the amount of settlement of algae on recovery was also measured for the different injury types and species. Overall, the amount of regeneration was up to four times greater for a scraping injury than tissue mortality and breakage. Furthermore, the amount of regeneration of the breakage injuries was approximately two-times greater for M. tuberculosa than for A. hyacinthus colonies. The regeneration rate of all injury types declined over time for both species. Recovery of injuries was influenced by the amount of algae that colonised the lesion and the zone of tissue available for regeneration. In general, the amount of regeneration of injuries was lower for injuries with a small zone of basal tissue available for regeneration, and the amount of regeneration was negatively correlated with the amount of algal settlement. The results of this study are important for understanding the role of partial mortality in the demography of scleractinian corals. Injuries impact on the population dynamics of colonies because regenerative processes require resources usually available for other processes (e.g. growth and reproduction), and slow recovery rates potentially increase the chance of whole colony mortality.

Tending Ants (Hymenoptera: Formicidae) RegulateDalbulus quinquenotatus(Homoptera: Cicadellidae) Population Dynamics

Population dynamics of colonies of the mymecophilous leafhopper Dalbulus quin- quenotatus DeLong & Nault were recorded in the laboratory in the presence and absence of the tending ant, Formica fusca (L.). These experiments used colonies of leafhoppers started with five male and five female adults on a single Tripsacum dactyloides L. plant. The first experiment consisted of eight leafhopper colonies, four with tending ants and four without. The second experiment used 16 leafhopper colonies, eight with tending ants and eight without, with four of each of these ant treatments also with Nabis americoferus Carayon predators. The numbers of young nymphs, older nymphs, and adult leafhoppers, along with host plant condition were recorded every 2—3 d for 62 d for both experiments. Nontended leafhopper colonies exploded and overwhelmed their host plants, killing them in an average of 39.0 d, resulting in the extirpation of those leafhopper colonies. Ants maintained leafhopper colonies by regulating population dynamics, with colonies of leafhoppers tended by ants being significantly smaller (P , 0.02) and developing from egg to adult significantly slower (P , 0.001) than colonies of nontended leafhoppers. Ant-tended leafhopper colonies did not overwhelm their host plants during either experiment, as the ants removed excess honeydew and leafhopper exuvia, thus maintaining a constant supply of honeydew. Ants were observed protecting leafhoppers from nabid predators, although this protection did not significantly influence leafhopper population size or length of egg to adult development.

Short‐term effects of culling on the ecology and population dynamics of the yellow‐legged gull

Summary1. Culls are being performed in many yellow‐legged gullLarus cachinnanscolonies in the Mediterranean region, but little is known of their effects on this species. Between 1992 and 1996, 25 000 breeding yellow‐legged gulls were culled in the colony of the Medes Islands, north‐western Mediterranean, because of the possible role of gulls in the transmission of pathogens and as predators on other bird species. In the present study the effect of the culls on several ecological parameters and on the population dynamics of the colony were analysed.2. Some breeding parameters (nest density, clutch and egg sizes, chick growth and breeding success, intraspecific predation, size and body condition of adults), diet (importance of the different prey categories and width of the trophic niche) and population dynamics of the colony were analysed during the years of cull. The annual culls did not include the entire colony, so culled and unculled areas were distinguished.3. Nests density decreased significantly both in the culled and the unculled areas. No significant difference in clutch size was detected between culled and unculled areas in any year, but clutch size decreased significantly through time within the culled areas. In three‐egg clutches the mean egg volume was significantly larger in unculled than in culled plots, whereas no significant year effect was found. No differences were detected in the mass or in the body condition of chicks throughout the study, whereas both fledging success and breeding success increased significantly over the period of the study. Intraspecific predation had decreased significantly by 40% two years after the beginning of the study. Size and body condition of adults varied between years but no trend was observed.4. Despite the large decrease in breeding gull numbers and an expected reduction in intraspecific food competition, no changes in diet were detected during the study. The dietary niche width was very similar between years, and gulls continued to exploit the same foraging resources.5. Annual censuses showed that from 1960 to 1992, colony size increased at a rate of 5% per year. During the culling period, between 21% and 29% of the breeding adults were killed, and colony size decreased progressively at an estimated rate of 19% per year. The estimated annual adult survival according to ring recoveries during the culling period was 74%. A demographic model was developed to assess the observed changes in numbers of yellow‐legged gulls. This suggested that gulls born in the Medes Islands were emigrating during the years of culling, with a particularly high estimated emigration rate of 25% per year since 1994.6. The planning of culling programmes by wildlife agencies has not always taken into account the multiple factors responsible for the population dynamics of colonies and the effects of culls. Culling at the Medes Islands probably failed to reduce the breeding numbers of yellow‐legged gulls at the metapopulation level, due to the emigration of birds to neighbouring colonies that had recently increased in numbers. Thus, the potential problems linked to large numbers of gulls in a colony may simply have been transferred to other sites.

Apparent Competition between Two Aphid Species

1. The population dynamics of colonies of nettle aphids (Microlophium carnosum Buckton) were studied on potted nettle plants placed beside plots of grass on some of which outbreaks of grass aphids (Rhopalosiphum padi L.) had been induced by fertilizer application. 2. Nettle aphid colonies adjacent to grass aphid concentration suffered an earlier population decline, and produced fewer alate dispersers, than control colonies. 3. The reduced performance of nettle aphids in the vicinity of grass aphid was due to increased predation by Coccinellidae, attracted into the area by the large concentrations of grass aphids. The indirect interaction between the two species of aphids is an example of apparent competition. 4. Because predators pre-emptively exploited nettle aphids on plants in the grass aphid treatment, the numbers of nettle aphids attacked by parasitoid wasps was greatly reduced in these sites compared to the controls.

PC BEEPOP, an ecotoxicological simulation model for honey bee populations

AbstractPC BEEPOP is a computer model that simulates honey bee (Apis mellifera L.) colony population dynamics. The model consists of a feedback system of interdependent elements, including colony condition (e.g., initial size, reproductive potential of the queen and forager longevity), environmental variability (e.g., weather) and contaminant exposures. It includes a mortality module (BEEKILL) and a chemical‐toxicity data base and probit analysis program (BEETOX). PC BEEPOP is a modified version of an cxisting colony dynamics model, BEEPOP, and can be used as a tool for environmental risk assessments. Results of sensitivity analysis and simulations of various climatic and toxic scenarios are discussed and compared to observed changes in the size and composition of honey bee colony populations.

BEEPOP: A honeybee population dynamics simulation model

BEEPOP is a computer model that simulates honey bee colony population dynamics. Estimates of population size and composition (i.e., proportions of workers and drones) at time ( t) are based upon initial colony population size, weather conditions, reproductive potential of the queen, and forager longevity. Results of a sensitivity analysis indicate that the queen's egg-laying potential has the greatest effect on colony population size. Yearly trends in population growth and age structure generated from simulations are also discussed.