The dynamics of the abundance, age, and sex structure of the Solovetsky reproductive gathering of the Beluga whale Delphinapterus leucas (Onega Bay, White Sea)

Based on the data from long-term research in 1999?C2009 we studied the population dynamics of Beluga whales in the Solovetsky reproductive gathering (RG) in the White Sea. This aggregation of Beluga whales is formed each year in the second half of May after the break-up of fast ice and persists to September inclusive. The aggregation numbers about 100 individuals from visual observations, with long-term variations of 20?C30 individuals. The percentage of whales of different age groups also varied in the gathering depending on year, but typically one half was formed by mature animals and the other half consisted of immature whales and yearlings. There are two pronounced peaks in numbers for the summer season in the Solovetsky Beluga RG. The number of Belugas increased with the appearance of males and females that were ready to breed and females that were ready to bear calves. The daily dynamics of Belugas in the gathering largely depended on the time of day and tidal regime. In the summer season, the state of the sea and human impacts were key factors in number fluctuations of the Belugas of the Solovetsky RG. The revealed negative correlation of the long-term population of Belugas in the gathering on air temperature is considered as a special instance of general laws of the migration activities of Beluga whales in the White Sea.     

千岛湖岛屿社鼠的种群年龄结构和性比

2009年7月至11月以及2010年3月至11月在千岛湖地区2个岛屿上对社鼠(Niviventer confucianus)种群进行标志重捕,通过对社鼠种群年龄结构和性比的研究,探讨陆桥岛屿环境下生境片段化对社鼠种群结构的影响。结果显示:社鼠种群年龄结构整体上均表现为由上半年幼年组和亚成年组占优势逐渐过渡到下半年成年组和老年组占绝对优势,岛屿环境对社鼠年龄结构变化的影响与陆地环境有所不同;两岛社鼠种群数量与性比(♀:♂)之间均存在显著的负相关性(B岛2010年7-11月除外),当种群数量处于高峰期时,雌性少于雄性,而种群数量处于低潮期时,雌性多于雄性,这可能是社鼠种群数量变动内部调节机制的一种表现;由于9-10月和2-3月的繁殖高峰以及高的胎仔数,翌年上半年种群数量就能恢复并达到全年最高峰。     

Prediction of weed density: the increase of error with prediction interval, and the use of long-term prediction for weed management

1. This paper addresses the errors that are associated with the long-term prediction of weed densities, and the effect of these errors on the performance of weed management decisions based on those long-term predictions.
2. A model of weed population dynamics was constructed and its parameters were estimated from experimental observations of population dynamics of the weed species Stellaria media in a crop rotation.
3. The observations showed that estimates of weed population growth rate differed between two locations.
4. The model was used to analyse error propagation for predicted weed densities in an enlarged prediction interval. It is concluded that errors due to an uncertain population growth rate increase linearly with the length of the prediction interval, and thus pose an upper limit to the horizon for long-term predictions.
5. It is shown that a limited ability to predict weed densities does not necessarily impair the practical use of weed population dynamic models in planning for long-term weed control programmes.     

A separation-of-timescales approach to the coalescent in a continuous population

This article presents an analysis of a model of isolation by distance in a continuous, two-dimensional habitat. An approximate expression is derived for the distribution of coalescence times for a pair of sequences sampled from specific locations in a rectangular habitat. Results are qualitatively similar to previous analyses of isolation by distance, but account explicitly for the location of samples relative to the habitat boundaries. A separation-of-timescales approach takes advantage of the fact that the sampling locations affect only the recent coalescent behavior. When the population size is larger than the number of generations required for a lineage to cross the habitat range, the long-term genealogical process is reasonably well described by Kingman's coalescent with time rescaled by the effective population size. This long-term effective population size is affected by the local dispersal behavior as well as the geometry of the habitat. When the population size is smaller than the time required to cross the habitat, deep branches in the genealogy are longer than would be expected under the standard neutral coalescent, similar to the pattern expected for a panmictic population whose population size was larger in the past.     

The process of bacterial population splitting into dissociants and long-term batch cultivation of bacteria

The growth and composition of a population were studied during long-term (up to 50 days) batch cultivation of mono and mixed cultures of Pseudomonas aeruginosa S- and M-dissociants and Rhodobacter sphaeroides R- and M-dissociants without the addition of nutrients. During the cultivation of P. aeruginosa on a glucose-containing mineral medium, periodic lysis followed by polyculture growth resumption in the late stationary phase occurred on account of the M-dissociant: the change in its cell number corresponded to the change in the total cell number of the association. It was shown that the periodic occurrence of reducing sugars in the medium preceded the resumption of polyculture growth. Periodic secondary growth of the mixed culture of R. sphaeroides photosynthesizing bacteria occurred because of fast growing R-cells after the lysis of some part of the R-dissociant population. In the monoculture of the R. sphaeroides M-dissociant, R-cells were found during the whole period of cultivation, making up to 1–10% of the population irrespective of its size, which probably corresponded to the frequency of occurrence of this dissociant. In the R-dissociant monoculture, M-cells were found only after 26 days, and their number gradually decreased to half of population by the end of cultivation period. The joint growth of dissociants was characterized by the biomass increment and bacterial growth acceleration compared to monocultures, which is important for the fast development of new habitats under natural conditions. The cells of both bacterial species were lysed during long-term cultivation by exoproteinases secreted by the thin-wall cells of M-dissociants.     

Postcatastrophe Population Dynamics and Density Dependence of an Endemic Island Duck

ABSTRACT Laysan ducks (Anas laysanensis) are restricted to approximately 9 km² in the Northwestern Hawaiian Islands, USA. To evaluate the importance of density dependence for Laysan ducks, we conducted a Bayesian analysis to estimate the parameters of a Gompertz model and the magnitude of process variation and observation error based on the fluctuations in Laysan duck abundance on Laysan Island from 1994 to 2007. This model described a stationary distribution for the population at carrying capacity that fluctuates around a long-term mean of 456 ducks and is between 316 to 636 ducks 95% of the time. This range of expected variability can be used to identify changes in population size that warn of catastrophic events. Density-dependent population dynamics may explain the recovery of Laysan duck from catastrophic declines and allow managers to identify population monitoring thresholds.     

gamma-Aminobutyric acid (GABA) mediated transmembrane chloride flux with membrane vesicles from rat brain measured by quench flow technique: kinetic homogeneity of ion flux and receptor desensitization

Transmembrane chloride flux mediated by the GABAA receptor and the desensitization of the receptor were followed using quench flow technique with 36Cl- and a membrane preparation from rat cerebral cortex. Measurements in short times allowed these two processes to be resolved. In general the ion-flux activity was desensitized in two phases. A fast phase took place in circa 200 ms (100 microM GABA) followed by a slower phase in several seconds. A minority (10%) of the membrane preparations did not display the fast phase. It is desirable to be able to separate these two phases of desensitization to facilitate analysis of the responses of the receptor. A short preincubation with GABA removed the fast phase from a subsequent measurement. In the absence of the fast phase the whole ion-flux equilibration was seen as a single phase. The measurements presented covering a time range of 0.01 seconds to 10 seconds show a single phase of ion flux which can be described by a first order ion influx process and a single first order desensitization process with a half time of circa 1 s (100 microM GABA). The results imply a single kinetically homogeneous population of vesicles containing a single population of GABA receptor (remaining active) with a single phase of desensitization. An understanding of this homogeneity, and how to ensure it, gives a basis for quantitatively testing the effects of drugs on these responses. Ion flux measurements with quench flow technique are a suitable tool for investigation of the mechanism of action of neurotransmitter receptors from brain.     

Subandrodioecy and male fitness in Sagittaria lancifolia subsp. lancifolia (Alismataceae)

Sagittaria lancifolia subsp. lancifolia is described as cosexual (monoecious), but the study population consisted of 84% cosexuals that typically had 35% pistillate buds and 16% predominant males that typically had 0-2% pistillate buds. Hand-pollinations showed that pistillate flowers required pollination to set seed, and pollen from both male and cosexual plants was potent. No gender switching was seen in the field or greenhouse. From 24 experimental crosses, 890 offspring were grown to maturity. Among these, all offspring of cosexual sires were cosexual, but approximately half the offspring of male sires were male, implying that maleness was inherited as a single, dominant allele. These results indicate that S. lancifolia is subandrodioecious, a very rare breeding system. It is rare, in part because its maintenance requires a large male-fitness differential between male and cosexual plants. In the study population, this condition was met by the differential survival of staminate buds on male racemes. Larvae of the weevil Listronotus appendiculatus killed many staminate buds. They did so in a vertical gradient, with buds lower on racemes safer. Male plants have replaced pistillate with staminate buds at these safer positions and thereby enjoy disproportionally higher male fitness.     

Identifying causes for N2O accumulation in a lab-scale sequencing batch reactor performing simultaneous nitrification, denitrification and phosphorus removal

The recently described process of simultaneous nitrification, denitrification and phosphorus removal (SNDPR) has a great potential to save capital and operating costs for wastewater treatment plants. However, the presence of glycogen-accumulating organisms (GAOs) and the accumulation of nitrous oxide (N(2)O) can severely compromise the advantages of this process. In this study, these two issues were investigated using a lab-scale sequencing batch reactor performing SNDPR over a 5-month period. The reactor was highly enriched in polyphosphate-accumulating organisms (PAOs) and GAOs representing around 70% of the total microbial community. PAOs were the dominant population at all times and their abundance increased, while GAOs population decreased over the study period. Anoxic batch tests demonstrated that GAOs rather than denitrifying PAOs were responsible for denitrification. N(2)O accumulated from denitrification and more than half of the nitrogen supplied in a reactor cycle was released into the atmosphere as N(2)O. After mixing SNDPR sludge with other denitrifying sludge, N(2)O present in the bulk liquid was reduced immediately if external carbon was added. We therefore suggest that the N(2)O accumulation observed in the SNDPR reactor is an artefact of the low microbial diversity facilitated by the use of synthetic wastewater with only a single carbon source.     

Optimization and Phenotype Allocation

We study the phenotype allocation problem for the stochastic evolution of a multitype population in a random environment. Our underlying model is a multitype Galton–Watson branching process in a random environment. In the multitype branching model, different types denote different phenotypes of offspring, and offspring distributions denote the allocation strategies. Two possible optimization targets are considered: the long-term growth rate of the population conditioned on nonextinction, and the extinction probability of the lineage. In a simple and biologically motivated case, we derive an explicit formula for the long-term growth rate using the random Perron–Frobenius theorem, and we give an approximation to the extinction probability by a method similar to that developed by Wilkinson. Then we obtain the optimal strategies that maximize the long-term growth rate or minimize the approximate extinction probability, respectively, in a numerical example. It turns out that different optimality criteria can lead to different strategies.     

Avian flu in Altay territory

The avian flu epizootia among wild waterfowl and poultry in personal farmsteads is described. In 38.9% of tests from a sectioning material from bird's mass destruction the genetic materials of a influenza virus type A (H5N1), and in 24% of tests of serum antibodies to a influenza virus type A (H5N1) in diagnostic titers are revealed. It is carried out serological monitoring among workers of integrated poultry farms and the population. Activation of epizootic process in second half of summer and is predicted by Autumn, 2006. For the prevention of distribution of disease among birds and infection of the person carrying out of a complex of the actions directed on creation of quarantine for a wild waterfowl and restriction of contacts to a poultry, and on vaccine prevention from annual 100% immunization of workers of integrated poultry farms is necessary.     

Coexistence of trichome variation in a natural plant population: a combined study using ecological and candidate gene approaches

The coexistence of distinct phenotypes within populations has long been investigated in evolutionary ecology. Recent studies have identified the genetic basis of distinct phenotypes, but it is poorly understood how the variation in candidate loci is maintained in natural environments. In this study, we examined fitness consequences and genetic basis of variation in trichome production in a natural population of Arabidopsis halleri subsp. gemmifera. Half of the individuals in the study population produced trichomes while the other half were glabrous, and the leaf beetle Phaedon brassicae imposed intensive damage to both phenotypes. The fitness of hairy and glabrous plants showed no significant differences in the field during two years. A similar result was obtained when sibling hairy and glabrous plants were transplanted at the same field site, whereas a fitness cost of trichome production was detected under a weak herbivory condition. Thus, equivalent fitness of hairy and glabrous plants under natural herbivory allows their coexistence in the contemporary population. The pattern of polymorphism of the candidate trichome gene GLABROUS1 (GL1) showed no evidence of long-term maintenance of trichome variation within the population. Although balancing selection under fluctuating biotic environments is often proposed to explain the maintenance of defense variation, the lack of clear evidence of balancing selection in the study population suggests that other factors such as gene flow and neutral process may have played relatively large roles in shaping trichome variation at least for the single population level.     

The process of continuous production and isolation of coproporphyrin

Summary The production of coproporphyrin from glucose and urea has been achieved by semi-aerobic culture ofSaccharomyces cerevisiae. The cells were entrapped in alginate gel and packed into a column reactor for continuous long-term process. The porphyrins were isolated and simultaneously concentrated from the effluent by liquid-solid phase extraction, purified by liquid chromatography and finally crystallized. Using the process described the final product of high purity was obtained.     

Hand-preference training in the mouse reveals key elements of its learning and memory process and resolves the phenotypic complexity in the behaviour.

Handedness in the mouse comprises 2 different behaviours. Some strains have a conditional behaviour, in that the mice learn a direction of hand preference in response to reaching for food, whereas other strains have an innate or constitutive behaviour, and prior experience has no measurable effect on their hand preference. However, hybrids from different strains have revealed both recessive and dominant forms of constitutive hand preference. We proposed that kinetic parameters of the learning process would resolve this genetic heterogeneity as well as the phenotypic complexity in the behaviour. We conducted and report here a detailed kinetic analysis of hand-preference training in the C57BL/6J strain. It revealed elements of the fundamental process of learning and long-term memory that underlies the behaviour by documenting consolidation of memory, blocking of this consolidation by an inhibitor of protein synthesis, retention of memory, and speed of learning in response to training reaches. Furthermore, speed of learning is clearly described by 2 parameters that we call "capacity" (or maximum amount of learned preference) and "ability" (or number of training reaches to achieve half the capacity). These 2 kinetic parameters can vary independently among genetically different strains that learn a preference, and we used them to demonstrate that the respective recessive and dominant forms of constitutive hand-preference may be the consequence of a true null or loss of function and a gain of function, possibly a memory regulator, in the learning process. The quantitative measures provide a sensitive and selective method to establish the fundamental learning process underlying mouse hand preference and to demonstrate empirically how genes and contextual environment shape its phenotypic complexity.     

The effect of a mega-fragmentation process on large mammal assemblages in the highly-threatened Pernambuco Endemism Centre,north-eastern Brazil

We documented an example of the mass extinction in a medium-sized and large mammal assemblage in the Pernambuco Endemism Centre, one of the most important hotspots of the world. During 12 months we carried out diurnal and nocturnal surveys through the line transect method, in forest fragments measuring from 10 to 500 ha. About half of the species have gone locally extinct, including all large mammals. The largest number of species and sighting rates was recorded in the largest fragment. No fragment held the entire remaining mammal community and not all species sighted in the smaller fragments were present in the largest. Only two species were sighted in the very small fragment, the commonest fragment size in the entire Pernambuco Endemism Centre. The mammalian assemblage is highly simplified, and characterized by an unprecedented local extinction process. The abundance of the remaining population is far below the minimum viable population needed for long-term survival which needs to be taken into account by decision makers. The scenario here presented suggests that the 21st century fauna of this important hotspot will be dominated by small, generalist species, which can survive in close association with humans.     

Population cycles and changes in body size of the lynx in Alaska

The lynx Lynx canadensis is a common predator in the boreal forests of North America. Its population fluctuates during a 9- to 11-year cycle in synchrony with the population size of its main prey, the snowshoe hare Lepus americanus. Using adult museum specimens, we studied changes in skull (and hence body) size of the lynx in Alaska during the second half of the 20th century. The population cycle in Alaska averaged 9 years, similar to that reported in the neighbouring Yukon. Using harvest data of lynx as an estimate of population size, we found that skull size was negatively related to population size. This relationship was strongest not for the population density in the year of death (X), but for year X-3, a carry-over effect from the first year (or years) of life, indicating that conditions during the fast-growth years are determining body size. We suggest that the density-dependent effect is probably due to changes in food supply, either resulting from the adverse effects of competition or a possible diminished availability of food. Two skull parameters decreased significantly during the second half of the 20th century. We do not know the cause for the year effect and suggest that it might be due to a long-term change in the availability of prey. Canine size did not change during the study period, probably an indication that snowshoe hares maintained their status as the main prey of the lynx throughout the study period. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Genetic evidence for larger African population size during recent human evolution

Genetic evidence suggests that the long-term average effective size of sub-Saharan Africa is larger than other geographic regions. A method is described that allows estimation of relative long-term regional population sizes. This method is applied to 60 microsatellite DNA loci from a sample of 72 sub-Saharan Africans, 63 East Asians, and 120 Europeans. Average heterozygosity is significantly higher in the sub-Saharan African sample. Expected heterozygosity was computed for each region and locus using a population genetic model based on the null hypothesis of equal long-term population sizes. Average residual heterozygosity is significantly higher in the sub-Saharan African sample, indicating that African population size was larger than other regions during recent human evolution. The best fit of the model is with relative population weights of 0.73 for sub-Saharan Africa, 0.09 for East Asia, and 0.18 for Europe. These results are similar to those obtained using craniometric variation for these three geographic regions. These results, combined with inferences from other genetic studies, support a major role of Africa in the origin of modern humans. It is less clear, however, whether complete African replacement is the most appropriate model. An alternative is an African origin with non-African gene flow. While Africa is an important region in recent human evolution, it is not clear whether the gene pool of our species is completely out of Africa or predominately out of Africa.