Spatial foraging patterns and colony energy status in the African honey bee,Apis mellifera scutellata

The relationship between changes in foraging patterns (inferred from waggle dance activity) and colony energy status (inferred from brood rearing activity, food storage, and colony weight) was examined for the African honey bee during a period of relative resource abundance and resource dearth. When resources were more abundant mean foraging distances (about 400 m) and foraging areas (4–5 km²) were small, and colonies recruited to 12–19 different sites per day. Colony foraging ranges and sites visited increased slightly during the dearth period, yet foraging continued to be concentrated within less than 10 km². The degree to which fluctuations in foraging patterns were correlated with colony energy status varied with the availability of floral resources. During periods of relative forage abundance, increases in foraging range and number of sites visited were significantly correlated with increases in brood rearing and colony weight. In contrast, colonies examined during periods of resource dearth exhibited no correlations between foraging areas, foraging distances, and fluctuations in brood rearing, food storage, or colony weight. Thus, during dearth periods colonies may not be able to coordinate foraging patterns with changes in colony energy status.     

Anarchy in the UK: Detailed genetic analysis of worker reproduction in a naturally occurring British anarchistic honeybee,Apis mellifera,colony using DNA microsatellites

Anarchistic behaviour is a very rare phenotype of honeybee colonies. In an anarchistic colony, many workers' sons are reared in the presence of the queen. Anarchy has previously been described in only two Australian colonies. Here we report on a first detailed genetic analysis of a British anarchistic colony. Male pupae were present in great abundance above the queen excluder, which was clearly indicative of extensive worker reproduction and is the hallmark of anarchy. Seventeen microsatellite loci were used to analyse these male pupae, allowing us to address whether all the males were indeed workers' sons, and how many worker patrilines and individual workers produced them. In the sample, 95 of 96 of the males were definitely workers' sons. Given that approximately 1% of workers' sons were genetically indistinguishable from queen's sons, this suggests that workers do not move any queen-laid eggs between the part of the colony where the queen is present to the area above the queen excluder which the queen cannot enter. The colony had 16 patrilines, with an effective number of patrilines of 9.85. The 75 males that could be assigned with certainty to a patriline came from 7 patrilines, with an effective number of 4.21. They were the offspring of at least 19 workers. This is in contrast to the two previously studied Australian naturally occurring anarchist colonies, in which most of the workers' sons were offspring of one patriline. The high number of patrilines producing males leads to a low mean relatedness between laying workers and males of the colony. We discuss the importance of studying such colonies in the understanding of worker policing and its evolution.     

Benefits of recruitment in honey bees: effects of ecology and colony size in an individual-based model

Why do some social insects have sophisticated recruitment systems,while other species do not communicate about food source locationsat all? To answer this question, it is necessary to identifythe social or ecological factors that make recruitment adaptiveand thus likely to evolve. We developed an individual-basedmodel of honey bee foraging to quantify the benefits of recruitmentunder different spatial distributions of nondepleting resourcepatches and with different colony sizes. Benefits of recruitmentwere strongly dependent on resource patch quality, density,and variability. Communication was especially beneficial ifpatches were poor, few, and variable. A sensitivity analysisof the model showed that under conditions of high resource densityrecruitment could even become detrimental, especially if foragingduration was short, tendency to scout was high, or recruitsneeded a long time to find communicated locations. Colony size,a factor often suspected to influence recruitment evolution,had no significant effect. These results may explain the recentexperimental findings that in honey bees, benefits of waggledance recruitment seem to vary seasonally and with habitat.They may also explain why some, but not other, species of socialbees have evolved a strategy to communicate food locations tonest mates.     

The influence of colony population and brood rearing intensity on the activity of detoxifying enzymes in worker honey bees

Abstract. Cohorts of worker honey bees from a single parental hive, cross-fostered into colonies which differed in population and other colony parameters, were assessed for activities of enzymes involved in metabolic detoxication. Activities of glutathione S-transferase and mixed-function oxidase enzymes were negatively correlated with foster colony population, but positively correlated with the ratio of larvae (brood)/adult workers. Worker bees which had begun foraging had enzyme activity levels higher than any found in bees which were still performing in-hive duties. Elevated levels of detoxifying enzymes in colonies with low populations and high ratios of larvae/adults may be a protective mechanism to prevent poisoning of larvae by toxins brought to the colony by foragers.     

The cost of defense in social insects: insights from the honey bee

Defense is one of the most important factors affecting life history. The relationship of defense to life history traits as well as its possible costs has been reviewed extensively for many groups, including plants. However, defense in social insects, such as honey bees, has never been examined from a trade‐off perspective, although defense in honey bees, Apis mellifera L. (Hymenoptera: Apidae), has been widely studied. In this review, we discuss the life history traits of honey bees, particularly traits related to defense. We then examine trade‐offs in the context of resource availability. Lastly, we offer suggestions for future research on trade‐offs in honey bees and other social insects.     

The effects of drone age, semen storage and contamination on semen quality in the honey bee (Apis mellifera)

Abstract. The effect of semen storage time, drone age and semen contamination on honey bee semen quality was investigated using assays for motility and viability of semen in vitro. Four age groups (1, 2, 4 and 6 weeks) and five storage times (0, 1, 2, 4 and 6 weeks) were examined. As storage time increased, sperm viability and motility significantly decreased. However, motility patterns of unstored semen samples were significantly lower than those samples that were stored up to 2 weeks. Sperm viability decreased significantly with increasing drone age, but motility patterns did not change. Those semen samples that were found to be contaminated with foreign particles or microorganisms had a significantly lower mean viability than uncontaminated samples.     

On the relationship between food, reproduction and survival of two carabid beetles: Calathus melanocephalus and Pterostichus versicolor

Abstract.

• 1 The relative influences of temperature and availability of food on reproduction, survival and growth of all developmental stages of two carabid beetle species are discussed with special reference to the suggested relationship between availability of food, size of egg production and survival of adults from one breeding season to the next.
• 2 Temperature as well as food supply influence the length of larval growth and adult body size. Beetles grown at low temperatures and low amounts of food are smaller than those grown at higher temperature and with more food.
• 3 The number of eggs laid per female was correlated with the amount of food gathered. There was no inverse relationship (trade-off) between reproductive output and survival in the field until the next breeding season.
• 4 In 1980 no significant relationship was found between winter mortality and the amounts of food gathered by beetles in the period after reproduction and before winter diapause. However, in 1981 in C. melanocephalus a lower number of starved beetles survived the winter than the fed ones and‘field’beetles.
• 5 Only in the first part of the feeding activity period in autumn can enough food be gathered by C.melunocephalus for successful hibernation. In the second part of this period there is not enough food to build up the fat reserves needed to survive the winter.
• 6 Difference in population fluctuations of both species are discussed in relation to their life histories.

     

Survival of repeated frosts by the Queensland fruit fly, Dacus tryoni: experiments in laboratory simulated climates with either step or ramp fluctuations of temperature

Ability to survive exposure to single or repeated periods at a subzero temperature is related to the temperature experienced, whether it is approached quickly or slowly, the time for which it prevails and the interval between exposures.The severity of any low temperature can be expressed in terms of LE₅₀ (time required to kill 50% of individuals with one exposure). Minima enduring for 35% LE₅₀ do not cause any mortality, even when repeated daily. Minima enduring for 44% LE₅₀ cause ca 14% mortality on the first occurrence but no more if repeated at 3 day intervals, but 3% more per occasion if repeated daily. Minima enduring for 88% LE₅₀ cause ca 40% mortality on first occurrence and an equal amount at each recurrence even if each is 7 days apart. Minima enduring for 125% LE₅₀ and over 150% LE₅₀ cause respectively ca 80% and 100% mortality respectively on first occurrence.The daily maximum temperature (in the range 15°C to 25°C) appears to have little relevance to the mortality caused by a repeated minimum of -5°C. Flies of different ages have a similar ability to survive a repeated minimum of -6°C for up to six exposures, but thereafter old flies are more susceptible than young ones.These results can be related to mortality caused by frosty conditions in the field so long as the time spent at the minimum is known and the temperature on the ground can be measured or calculated.

---

Résumé L'aptitude à survivre à une ou plusieurs expositions à des températures inférieures à zéro dépend à la fois de leur sévérité et du laps de temps entre les expositions. L'effet d'une température minimale déterminée dépend de sa valeur, de sa durée et du type de refroidissement: brutal (step) ou progressif (ramp).Les effets de toute température minimale peuvent être exprimés en termes de LE₅₀ (temps nécessaire pour obtenir une mortalité de 50% avec une exposition unique). Lorsque le temps d'application de la température minimale correspond à 35% du LE₅₀, il n'y a pas de mortalité, de même dans le cas de répétitions quotidiennes. Lorsque le minimum est subi pendant 44% du LE₅₀, il provoque environ 14% de mortalité après la première exposition, avec 3% supplémentaire après chaque exposition quotidienne, mais l'augmentation est nulle si l'exposition au froid n'a lieu que tous les 3 jours. Lorsque le minimum est subi pendant 88% de LE₅₀, la mortalité après la première exposition est d'environ 40% et de même importance à chaque nouvelle exposition, même si elles sont espacées de 7 j. Lorsque la durée d'exposition au minimum correspond à 125% et à 150% de LE₅₀, les mortalités sont respectivement d'environ 80% et 100% à la première exposition.La température maximale quotidienne, entre 15 et 25°C, semble avoir peu d'influence sur la mortalité provoquée par des expositions répétées à-5°C. Les mouches d'âges différents résistent de la même façon jusqu'à 6 expositions répétées à-6°C, mais au-delà les mouches âgées sont plus sensibles que les jeunes.Dans la mesure où, dans la nature, la durée d'exposition à la température minimale est connue et où la température dans le sol peut être calculée ou mesurée, ces résultats peuvent permettre d'interpréter la mortalité provoquée par le gel.

     

Identification of a homolog of Arabidopsis DSP4 (SEX4) in chestnut: its induction and accumulation in stem amyloplasts during winter or in response to the cold

Oligosaccharide synthesis is an important cryoprotection strategy used by woody plants during winter dormancy. At the onset of autumn, starch stored in the stem and buds is broken down in response to the shorter days and lower temperatures resulting in the buildup of oligosaccharides. Given that the enzyme DSP4 is necessary for diurnal starch degradation in Arabidopsis leaves, this study was designed to address the role of DSP4 in this seasonal process in Castanea sativa Mill. The expression pattern of the CsDSP4 gene in cells of the chestnut stem was found to parallel starch catabolism. In this organ, DSP4 protein levels started to rise at the start of autumn and elevated levels persisted until the onset of spring. In addition, exposure of chestnut plantlets to 4 °C induced the expression of the CsDSP4 gene. In dormant trees or cold-stressed plantlets, the CsDSP4 protein was immunolocalized both in the amyloplast stroma and nucleus of stem cells, whereas in the conditions of vegetative growth, immunofluorescence was only detected in the nucleus. The studies indicate a potential role for DSP4 in starch degradation and cold acclimation following low temperature exposure during activity-dormancy transition.     

Gold climates and the evolution of viviparity in reptiles: cold incubation temperatures produce poor-quality offspring in the lizard, Sceloporus virgatus

Evolutionary origins of viviparity among the squamate reptiles are strongly associated with cold climates, and cold environmental temperatures are thought to be an important selective force behind the transition from egg-laying to live-bearing. In particular, the low nest temperatures associated with cold climate habitats are thought to be detrimental to the developing embryos or hatchlings of oviparous squamates, providing a selective advantage for the retention of developing eggs in utero, where the mother can provide warmer incubation temperatures for her eggs (by actively thermoregulating) than they would experience in a nest. However, it is not entirely clear what detrimental effects cold incubation temperatures may have on eggs and hatchlings, and what role these effects may play in favouring the evolution of viviparity. Previous workers have suggested that viviparity may be favoured in cold climates because cold incubation temperatures slow cmbryogenesis and delay hatching of the eggs, or because cold nest temperatures are lethal to developing eggs and reduce hatching success. However, incubation temperature has also been shown to have other, potentially long-term, effects on hatchling phcnotypcs, suggesting that cold climates may favour viviparity because cold incubation temperatures produce offspring of poor quality or low fitness. We experimentally incubated eggs of the oviparous phrynosomatid lizard, Sceloporus virgatus, at temperatures simulating nests in a warm (low elevation) habitat, as is typical for this species, and nests in a colder (high elevation) habitat, to determine the effects of cold incubation temperatures on embryonic development and hatchling phenotypes. Incubation at cold nest temperatures slowed embryonic development and reduced hatching success, but also affected many aspects of the hatchlings' phenotypes. Overall, the directions of these plastic responses indicated that cold-incubated hatchlings did indeed exhibit poorer quality phenotypes; they were smaller at hatching (in body length) and at 20 days of age (in length and mass), grew more slowly (in length and mass), had lower survival rates, and showed greater fluctuating asymmetry than their conspecifics that were incubated at warmer temperatures. Our findings suggest that cold nest temperatures are detrimental to S. virgatus, by delaying hatching of their eggs, reducing their hatching success, and by producing poorer quality offspring. These negative effects would likely provide a selective advantage for any mechanism through which these lizards could maintain warmer incubation temperatures in cold climates, including the evolution of prolonged egg retention and viviparity.     

The effect of timing and amount of leaf removal on survival,growth and reproduction in the perennial herb Sanicula europaea L.

In Sweden the deciduous forest perennial Sanicula europaea L. (Apiaceae) is frequently subjected to leaf loss due to cattle grazing and trampling. In a two-season field experiment, the effects of the extent, timing and repetition of leaf removal on survival, growth and reproduction in S. europaea were examined. Removal of vegetative tissue in S. europaea reduced future survival, growth and flowering probabilities. The magnitude of these effects depended both on the extent and the timing of the season of the leaf losses, as greater leaf losses had more negative effects than moderate and early removals had more negative consequences than late. Moreover, the probability of an individual to regrow the same season after severe losses was higher when losses occurred early in the season than when they occurred late. And, those defoliated early that did regrow, did so to a larger extent than those defoliated later. Experimental responses were more pronounced after a second year of leaf removals, indicating that repeated herbivory exhausts resources. Thus, herbivory causing losses in vegetative tissue will affect the performance of S. europaea. However, the impact depends on the extent and timing of the leaf losses. This should be considered in managing policies and cattle should, if possible, not be introduced early in the growing season.     

Demography of the Okinawan eusocial wasp Ropalidia fasciata (Hymenoptera: Vespidae) I. Survival rate of individuals and colonies, and yearly fluctuations in colony density

We conducted a series of demographic studies of the primitively eusocial wasp Ropalidia fasciata in Okinawa, a subtropical part of Japan, and found the following. The colony cycle of this wasp is annual, spanning from April to November or even December; this is longer than the colony cycles of other temperate polistine wasps so far reported. The survival rate of the marked foundresses was 40% to June, dropping to 1.4% by September. These survival rates are similar to other subtropical and tropical species. Most females that emerged in November were probably second generation adults (progeny of the original foundresses), which would participate in founding nests in the following spring. These facts indicate that R. fasciata in Okinawa is at least partially bivoltine. Survival of a nest to September was 10–20%; however, because a failed nest is often rebuilt, survival of the colony to September was as high as 50%. The mean number of new foundresses produced per foundress was 7.5, and their overwintering survival was 16%. Hence, a single foundress produced, on average, 1.2 progeny foundresses to the following year. Density dependence was shown in the rate at which the progeny foundresses were produced. These results explain the remarkable stability of nest densities from year to year in the area. The above results reveal that R. fasciata in Okinawa shares many demographic characteristics with other primitively eusocial wasps, particularly year‐to‐year stability of nest density and a long colony cycle.     

Decoupling of reproduction and growth: an unusual pattern in the life cycle of the Mediterranean geophyte Narcissus serotinus

The unpredictable seasonality of the Mediterranean climate imposes on the development of specific life‐cycle phenologies such as those seen in geophyte species that have a period of dormancy to avoid stressful abiotic conditions. To date, two life‐cycle strategies are recognized in Mediterranean geophytes. In some species, growth and reproduction occur in different seasons (hysteranthous geophytes), whereas in others these two processes occur at the same time (synanthous geophytes). A study of the life cycle of the autumnal‐flowering Narcissus serotinus in three populations over two consecutive years confirmed that neither the hysteranthy nor the synanthy strategy could be applied to this geophyte. Rather, reproduction and growth occur simultaneously, but in different plants. A strong correlation was found between bulb weight and the presence of reproductive or vegetative plants.     

Egg discrimination in the Australian reed warbler (Acrocephalus australis): rejection response toward model and conspecific eggs depending on timing and mode of artificial parasitism

In a coevolutionary arms race between an interspecific broodparasite and its host species, both are expected to evolveadaptations and counteradaptations. We studied egg discriminationin the Australian warbler (Acrocephalus australis). This speciesis currently not significantly parasitized by the seven speciesof cuckoo for which it is a suitable host. However, experimentalbrood parasitism in the warbler revealed a fine tuned egg discriminationresponse towards non-mimetic and conspecific eggs, the firstsuch evidence in an Australian passerine: (1) non-mimetic eggswere significantly more often rejected than conspecific eggs;(2) only non-mimetic dummy eggs were rejected selectively,whereas rejection of conspecific eggs entailed a rejectioncost; (3) replacement of a host's egg with a conspecific eggduring egg laying resulted in a significantly higher rejectionrate than after the day of clutch completion; (4) by contrast,rejection rate after addition of a conspecific egg was independentof nest stage; (5) conspecific eggs introduced into a clutchduring the egg laying period led to a significantly highernest desertion rate and a lower egg ejection rate than afterthe day of clutch completion; and (6) addition of a conspecificegg led to egg ejection while egg replacement with a conspecificegg led to nest desertion. The fact that this species respondsdifferentially toward different modes of artificial parasitismsuggests that its egg discrimination has evolved to minimizethe costs of rejection and parasitism. The ability to rejecthighly mimetic conspecific eggs may explain the current paucityof brood parasitism in this species. The significance of thisfor brood parasite-host coevolution is discussed.     

Survival of Escherichia coli in the environment: fundamental and public health aspects

In this review, our current understanding of the species Escherichia coli and its persistence in the open environment is examined. E. coli consists of six different subgroups, which are separable by genomic analyses. Strains within each subgroup occupy various ecological niches, and can be broadly characterized by either commensalistic or different pathogenic behaviour. In relevant cases, genomic islands can be pinpointed that underpin the behaviour. Thus, genomic islands of, on the one hand, broad environmental significance, and, on the other hand, virulence, are highlighted in the context of E. coli survival in its niches. A focus is further placed on experimental studies on the survival of the different types of E. coli in soil, manure and water. Overall, the data suggest that E. coli can persist, for varying periods of time, in such terrestrial and aquatic habitats. In particular, the considerable persistence of the pathogenic E. coli O157:H7 is of importance, as its acid tolerance may be expected to confer a fitness asset in the more acidic environments. In this context, the extent to which E. coli interacts with its human/animal host and the organism''s survivability in natural environments are compared. In addition, the effect of the diversity and community structure of the indigenous microbiota on the fate of invading E. coli populations in the open environment is discussed. Such a relationship is of importance to our knowledge of both public and environmental health.     

Parental effort of kestrels (Falco tinnunculus) in nest defense: effects of laying time, brood size, and varying survival prospects of offspring

We studied the nest defense behavior of Eurasian kestrels (Falcotinnunculus) towards a stuffed pine marten (Martes martes) througha 3-year vole cycle (1990–92) in western Finland. Survivalprobability of offspring decreases with a later start of breeding,and, therefore, early breeders should protect their offspringmore than late ones. We found this true for males during theincubation period, but not for females. In addition, we expectedthe nest defense intensity to increase with offspring number.During the incubation period, this was true for females, butnot for males. During the nestling phase, parents did not adjusttheir defense effort to natural or manipulated (by one to twoyoung) brood size. Survival prospects of kestrel offspring werehighest in the increasing vole year 1991 and lowest in the decreasingvole year 1992, and, therefore, we expected the defense activityof kestrels to follow the same trend. However, the oppositeresult appeared true for females with a similar tendency formales. Most hypotheses predicting avian nest defense behaviorwere not supported by our data. Temporally heterogeneous environmentand low degree of nest-site tenacity of migratory kestrels maymake them unfamiliar with environmental variation and survivalprospects of their offspring. Therefore, fitness benefits ofparental care are not predictable, and kestrels may thus adjusttheir parental effort to their own future reproductive potential(i.e., number of future breeding attempts), rather than to somecurrent investment indicator, like offspring age and number.     

Long‐term patterns in growth of Oneida Lake walleye: a multivariate and stage‐explicit approach for applying the von Bertalanffy growth function

Total length ( L _T) and its inter annual variation of walleye Sander vitreus from Oneida Lake, New York, based on 51 years (1950–2000) of data for ages 1 to 7 years were analysed. Growth increased over time at young ages, did not change at intermediate ages and decreased at old ages. Total length at age increased over time to age 4 or 5 years, but was stable at older ages. Principle component analysis was used to study the pattern of variations in annual L _T increments among years. More than 92 and 91% of inter annual variability in growth was described by the first three principal components for males and females, respectively. The first principal component was a general indicator of annual growth at all ages, but was dominated by annual growth at intermediate ages. The second and third principal components represented contrasts among yearling L _T, yearling growth and growth at older ages. Therefore, changes in the three stage‐specific parameters, yearling L _T, yearling growth and asymptotic L _T, explained most of the variance in observed growth. Using these three stage‐specific parameters for the von Bertalanffy growth function facilitated interpretations of growth comparisons.     

Non-structural carbohydrates and nitrogen dynamics in mediterranean sub-shrubs: an analysis of the functional role of overwintering leaves

Previous studies have led to contrasting results about the role of overwintering leaves as storage sites, which is related to leaf longevity and life-form. The aim of this study was to evaluate the functional role of the leaves of four species of Mediterranean sub-shrubs, with different leaf phenology, as sources of nitrogen (N) and non-structural carbohydrates (NSC) for shoot growth. The seasonal dynamics of the concentrations and pools of N and NSC were assessed monthly in the leaves and woody organs of each species. Overwintering and spring leaves served as N and NSC sources for shoot growth in the evergreen species analyzed, providing up to 73 % and 324 % of the N demand for spring and autumn growth, respectively. Excess autumn N was stored in woody structures which contributed to the N and NSC requirements of spring growth. In the winter deciduous species, woody organs were the main N source for spring growth, while current photosynthesis from immature brachyblasts seemed to be the main carbon (C) source. Due to their short lifespan, overwintering and spring leaves did not show several translocation processes throughout their life time, their contribution to new growth being made during senescence. The successive exchange of leaf cohorts displayed by Mediterranean sub-shrubs might serve as a mechanism to recycle N and C between consecutive cohorts as plants perform the pheno-morphological changes needed to adapt their morphology to the seasonality of their environment.     

Resource allocation among sexual,clonal reproduction and vegetative growth of two Potamogeton species and their hybrid: Adaptability of the hybrid in relation to its parents

Resource allocation, as well as the tradeoffs among different reproductive components, plays an important role in the adaptability of plants to different environments. The hybrid may exhibit a higher adaptability in life history in heterogeneous environments because of the genetic variation derived from its parents. In this study, we exploited three levels of water depths and two types of sediments to investigate the resource allocation pattern of the first generation of the natural hybrid Potamogeton ×intortifolius compared to its parents P. wrightii and P. perfoliatus. We also measured the ramet survivorship and the seed set of the hybrid P. ×intortifolius. Our results showed that P. ×intortifolius had higher ramet survival than its parents at 1.5-m water depth on clay sediment. The possible tradeoffs showed that in P. ×intortifolius the tradeoff pattern between sexual and clonal reproduction was more pronounced in limiting environments. The individuals allocated more resources to sexual reproduction when the environment was limiting, which might confer a higher ability to utilize resources, to produce offspring and to found new populations. Although the seed set of P. ×intortifolius was lower than its parents, it had a higher ability to increase its seed set when the environment was limiting (sandy sediment) than its parents, which might benefit its future survival. These results indicated that the F₁ hybrid P. ×intortifolius was more able to adapt to limiting environments than one or both of its two parental taxa.