Emergence patterns of riverine dragonflies (Odonata: Gomphidae) in Hungary: variations between habitats and years

In this paper the results of a six-year study on riverine dragonflies (Odonata: Gomphidae) emergence based on the systematic collection of exuviae are presented. The exuviae were counted to determine variations in species composition, abundance and emergence pattern of gomphids at four different sites along the rivers Tisza and Szamos, as well as at a selected site in five different years. While the number of species decreased, the abundance of exuviae increased downstream the river Tisza. The total numbers of exuviae differed significantly between the dammed and non-dammed sites. The emergence of gomphids varied in initiation, synchronisation and also in duration between sites as well as between years. The onset of emergence was dependent mainly on the species-specific temperature sums, consequently earlier or later emergence resulted from the differences in the spring water temperature. The duration of emergence in G. flavipes and G. vulgatissimus was twice as long at the dammed site, characterised by a higher larval density, as at the other sites. In the degree of synchrony G. flavipes showed the emergence characteristics both of the spring and the summer species. Such interyear variations at the same site might have been attributed to the differences in annual fluctuations in the water temperature, indicating that rising temperatures may influence not only the onset of emergence but the synchrony as well.     

Delayed phenological timing of dragonfly emergence in Japan over five decades

Recent increases in air temperature have affected species phenology, resulting in the earlier onset of spring life-cycle events. Trends in the first appearance of adult dragonflies across Japan were analysed using a dataset consisting of observations from 1953 to 2005. Dynamic factor analysis was used to evaluate underlying common trends in a set of 48 time series. The appearance of the first adult dragonfly has significantly shifted to later in the spring in the past five decades. Generalized linear mixing models suggested that this is probably the result of increased air temperatures. Increased summer and autumn temperatures may provide longer bivoltine periods and a faster growth rate; thus, the second generation, which previously hatched in summer, can emerge in the autumn causing the size of the population of dragonflies that emerge in spring to decrease. It is also possible that reduced dragonfly populations along with human development are responsible for a delay in the first observed dragonflies in the spring. However, human population density did not appear to strongly affect the appearance date. This study provides the first evidence of a delay in insect phenological events over recent decades.     

A checklist of the dragonflies (Odonata) of Kenya

A checklist of Odonata has been compiled for Kenya. It is based on an inventory of museum material, publications and personal observations made between 1978 and 1997. Changes of scientific names and synonyms are documented. The list contains 194 valid dragonfly species recorded for Kenya.     

Temporal patterns of emergence of the riverine dragonfly Onychogomphus uncatus (Odonata: Gomphidae)

The emergence of Onychogomphus uncatus from three stretches at two adjacent canals in Southern France was compared in 1993. Whereas 50% of annual emergence from the two stretches at one canal had occurred after 25 and 36 days, respectively, it had occurred after 5 days at the second, where emergence began 14 days earlier. At the second canal most of the larvae of one generation had overwintered in the final instar but at the first canal only half did so. These differences correlate with greater annual fluctuations of temperature at the second canal which are responsible for high temporal synchronisation. Other factors that may cause differences in seasonal regulation, such as drying up and density, are discussed. Differences exist also in sex ratio and abundance of emerging individuals, particularly between the two collection sites at the first canal.     

Species composition,abundance and emergence phenology of midges (Deiptera: Chironomidae) in a brown-water stream of West-Central Alberta,Canada

Sixteen floating, box type emergence traps, each covering 0.1 m², were placed along 150 m of a third-order stretch of the Bigoray River, a slow-flowing, vegetation-choked, brown-water muskeg stream. Effects of trap design, trap shading, length of sampling interval, and stream velocity on the number of midges caught was examined. Of the 112 species of Chironomidae caught, 32 species made up 90% of the catch and their emergence phenology is described in detail. There were more rare species than expected from Preston's lognormal distribution. Percentage of Bigoray species belonging to Tanypodinae, Orthocladiinae, Chironomini and Tanytarsini was 18%, 43%, 20%, and 19%, and was compared with 27 other studies on lotic chironomids. During the 140-day emergence period an average of 19.3 × 10³ chironomids emerged per square meter of stream. Based on changes in male:female ratios throughout a species emergence period, it was postulated that 30% of the Bigoray chironomid species were univoltine, 50% were bivoltine, and 20% were trivoltine.     

A mixed strategy model for the emergence and intensification of social learning in a periodically changing natural environment

Based on a population genetic model of mixed strategies determined by alleles of small effect, we derive conditions for the evolution of social learning in an infinite-state environment that changes periodically over time. Each mixed strategy is defined by the probabilities that an organism will commit itself to individual learning, social learning, or innate behavior. We identify the convergent stable strategies (CSS) by a numerical adaptive dynamics method and then check the evolutionary stability (ESS) of these strategies. A strategy that is simultaneously a CSS and an ESS is called an attractive ESS (AESS). For certain parameter sets, a bifurcation diagram shows that the pure individual learning strategy is the unique AESS for short periods of environmental change, a mixed learning strategy is the unique AESS for intermediate periods, and a mixed learning strategy (with a relatively large social learning component) and the pure innate strategy are both AESS's for long periods. This result entails that, once social learning emerges during a transient era of intermediate environmental periodicity, a subsequent elongation of the period may result in the intensification of social learning, rather than a return to innate behavior.     

A model for the origin of life

Summary A simple statistical model is constructed, describing the transition from disorder to order in a population of mutually catalytic molecules undergoing random mutations. The consequences of the model are calculated, and its possible relevance to the problem of the origin of life is discussed. The main conclusion of the analysis is that the model allows populations of several thousand molecular units to make the transition from disorder to order with reasonable probability.     

Historical changes in the phenology of British Odonata are related to climate

Responses of biota to climate change take a number of forms including distributional shifts, behavioural changes and life history changes. This study examined an extensive set of biological records to investigate changes in the timing of life history transitions (specifically emergence) in British Odonata between 1960 and 2004. The results show that there has been a significant, consistent advance in phenology in the taxon as a whole over the period of warming that is mediated by life history traits. British odonates significantly advanced the leading edge (first quartile date) of the flight period by a mean of 1.51 ±0.060 (SEM, n=17) days per decade or 3.08±1.16 (SEM, n=17) days per degree rise in temperature when phylogeny is controlled for. This study represents the first review of changes in odonate phenology in relation to climate change. The results suggest that the damped temperature oscillations experienced by aquatic organisms compared with terrestrial organisms are sufficient to evoke phenological responses similar to those of purely terrestrial taxa.     

A comparative analysis of senescence in adult damselflies and dragonflies (Odonata)

Any population whose members are subject to extrinsic mortality should exhibit an increase in mortality with age. Nevertheless, the prevailing opinion is that populations of adult damselflies and dragonflies do not exhibit such senescence. Here, we challenge this contention by fitting a range of demographic models to the data on which these earlier conclusions were based. We show that a model with an exponential increase in age-related mortality (Gompertz) generally provides a more parsimonious fit than alternative models including age-independent mortality, indicating that many odonates do indeed senesce. Controlling for phylogeny, a comparison of the daily mortality of 35 odonate species indicates that although male and female mortalities are positively correlated, mortality tends to be higher in males of those species that exhibit territoriality. Hence, we show for the first time that territoriality may impose a survivorship cost on males, once the underlying phylogenetic relationships are accounted for.     

The anatomy of predator-prey dynamics in a changing climate

Humans are increasingly influencing global climate and regional predator assemblages, yet a mechanistic understanding of how climate and predation interact to affect fluctuations in prey populations is currently lacking. Here we develop a modelling framework to explore the effects of different predation strategies on the response of age-structured prey populations to a changing climate. We show that predation acts in opposition to temporal correlation in climatic conditions to suppress prey population fluctuations. Ambush predators such as lions are shown to be more effective at suppressing fluctuations in their prey than cursorial predators such as wolves, which chase down prey over long distances, because they are more effective predators on prime-aged adults. We model climate as a Markov process and explore the consequences of future changes in climatic autocorrelation for population dynamics. We show that the presence of healthy predator populations will be particularly important in dampening prey population fluctuations if temporal correlation in climatic conditions increases in the future.     

Germination and emergence of Ambrosia artemisiifolia L. under changing environmental conditions in China

Laboratory and greenhouse studies were conducted to determine the effects of key environmental factors on germination and seedling emergence of the invasive weed Ambrosia artemisiifolia L. (common ragweed) collected from Mudanjiang (temperate climate), Nanjing (temperate–subtropical) and Nanchang (subtropical) in China. Germination of seeds occurred at temperatures ranging from 5 to 40°C, under both a 12‐h photoperiod and continuous darkness. Germination success exceeded 48% in solutions with pH values between 4 and 12, with maximum rates occurring in distilled water at pH 5.57. Germination was greatly reduced in solutions with osmotic potentials below ?0.8 MPa. Accordingly, the final germination ratio exceeded 69% at <200 mmol/L NaCl, but only reached 8% at 400 mmol/L NaCl. Emergence was greater than 75% at burial seed depths of 1–4 cm; no seedlings emerged from a soil depth of 8 cm. Seeds collected from Mudanjiang, Nanjing and Nanchang had very similar germination traits, with the main differences occurring in relation to temperature. The great germination success of common ragweed over highly variable conditions throughout its Chinese distribution range explains its successful large‐scale invasion.     

The smaller fruit tortrix, Grapholita lobarzewskii: predicting the phenology of adult emergence

The smaller fruit tortrix, Grapholita lobarzewskii Nowicki, has become a major pest in the recent past in apple orchards north of the Alps. Nevertheless little is known about the biology and the behaviour of this species. The effect of temperature on post-diapause development and survival was studied under controlled conditions in order to establish a basis for the forecasting of adult emergence. Survival was found to be highest at 17 °C and lowest at 11.8 °C. The sex ratio did not differ significantly from 1:1. Based on a linear relationship between temperature and developmental rates, thermal thresholds of 9.6 °C and 9.8 °C were determined for females and males respectively. The thermal constants, i.e., the mean developmental times in physiological time units, were found to be 342 day-degrees for females and 317 day-degrees for males, suggesting a slight protandry. Based on the mean and the variance of the developmental times, a simple temperature-driven phenology model was built using a time-varying distributed delay. The model was validated by visually comparing the predictions with independent observations on adult emergence, and by calculating the temporal deviations of the predictions. In 4 out of 5 years the mean error was less than 3 days. The model was therefore found to give reliable forecasts of the emergence of G. lobarzewskii and can be used to determine the optimal time for the exposure of pheromone traps, the application of pheromone dispensers for mating disruption, and for the timing of insecticide applications.     

应对全球气候变化的昆虫学研究

大气二氧化碳浓度升高、温度上升、降雨分布不均、灾害性天气出现频次增加等全球气候变化,深刻改变着农林生态系统昆虫群落的组成结构、功能和演替,使昆虫分布区域扩大、发生世代增多、生态适应性变异,从而影响了原有的植物-害虫-天敌间内在联系和各营养层间的固有平衡格局,最终导致一些害虫暴发成灾,一些昆虫种群数量下降,甚至一些昆虫物...     

Simulating the impact of genetic diversity of Medicago truncatula on germination and emergence using a crop emergence model for ideotype breeding

Background and Aims

Germination and heterotrophic growth are crucial steps for stand establishment. Numerical experiments based on the modelling of these early stages in relation to major environmental factors at sowing were used as a powerful tool to browse the effects of the genetic diversity of Medicago truncatula, one of the model legume species, under a range of agronomic scenarios, and to highlight the most important plant parameters for emergence. To this end, the emergence of several genotypes of M. truncatula was simulated under a range of sowing conditions with a germination and emergence simulation model.

Methods

After testing the predictive quality of the model by comparing simulations to field observations of several genotypes of M. truncatula, numerical experiments were performed under a wide range of environmental conditions (sowing dates × years × seedbed structure). Germination and emergence was simulated for a set of five genotypes previously parameterized and for two virtual genotypes engineered to maximize the potential effects of genetic diversity.

Key Results

The simulation results gave an average value of 5–10 % difference in final emergence between genotypes, which was low, but the analysis underlined considerable inter-annual variation. The effects of parameters describing germination and emergence processes were quantified and ranked according to their contribution to the variation in emergence. Seedling non-emergence was mainly related to mechanical obstacles (40–50 %). More generally, plant parameters that accelerated the emergence time course significantly contributed to limiting the risk of soil surface crusting occurring before seedling emergence.

Conclusions

The model-assisted analysis of the effects of genetic diversity demonstrated its usefulness in helping to identify the parameters which have most influence that could be improved by breeding programmes. These results should also enable a deeper analysis of the genetic determinism of the main plant parameters influencing emergence, using the genomic tools available for this model plant.     

A generalized, bioclimatic index to predict foliar phenology in response to climate

The phenological state of vegetation significantly affects exchanges of heat, mass, and momentum between the Earth's surface and the atmosphere. Although current patterns can be estimated from satellites, we lack the ability to predict future trends in response to climate change. We searched the literature for a common set of variables that might be combined into an index to quantify the greenness of vegetation throughout the year. We selected as variables: daylength (photoperiod), evaporative demand (vapor pressure deficit), and suboptimal (minimum) temperatures. For each variable we set threshold limits, within which the relative phenological performance of the vegetation was assumed to vary from inactive (0) to unconstrained (1). A combined Growing Season Index (GSI) was derived as the product of the three indices. Ten‐day mean GSI values for nine widely dispersed ecosystems showed good agreement (r>0.8) with the satellite‐derived Normalized Difference Vegetation Index (NDVI). We also tested the model at a temperate deciduous forest by comparing model estimates with average field observations of leaf flush and leaf coloration. The mean absolute error of predictions at this site was 3 days for average leaf flush dates and 2 days for leaf coloration dates. Finally, we used this model to produce a global map that distinguishes major differences in regional phenological controls. The model appears sufficiently robust to reconstruct historical variation as well as to forecast future phenological responses to changing climatic conditions.     

Potential risks for European beech (Fagus sylvatica L.) in a changing climate

Over large areas of Europe, coniferous monocultures are being transformed into mixed forests by the re-introduction of broadleaf tree species belonging to the potential natural vegetation. One important species of interest in this changing forest policy is European beech (Fagus sylvatica). However, at present, this forest management directive has ignored potential adverse effects of global climate change on wide-spread re-introduction of beech to these areas. Average global surface temperatures have risen by approx. 0.8°C in the period between 1861 and 2005 and are expected to continue to increase until the end of this century by 1.5–5.8°C above the 1990 value. To estimate the climate change in the southern part of central Europe in future, we reviewed calculations from regional climate models. Temperature increase for the southern part of central Europe is projected to be up to 2°C within the next 40 years. In contrast, the annual precipitation will most likely remain constant over the same time period, but will experience significant changes in seasonal patterns. Rising intensities of individual precipitation events may result in increasing number and intensities of flooding events and reduced precipitation during the growing season in a higher frequency of summer droughts. Growth and competitive ability of European beech will not, necessarily, respond to increasing CO₂ concentrations but may be strongly impacted by intensive drought that occurs during the growing season. Seedlings as well as adult trees may suffer from xylem embolism, restricted nutrient uptake capacity and reduced growth under limited water availability. However, it remains uncertain to what extent other environmental factors (e.g. soil properties, competitive interactions) may modify the drought response of beech, thus either enhancing susceptibility or increasing drought tolerance and resilience potential. Water-logged soils, predicted during the spring for several regions due to higher than average precipitation, could negatively impact nutrient uptake and growth of beech. Whereas other dominant species as, e.g. oak are well adapted to that environmental stress, beech is known to be sensitive to water-logging and flooding. Thus, the competitive capacity of beech might—depending on the other environmental conditions—be reduced under the expected future climate conditions. Silvicultural practices must be aware today of the potential risks which a changing climate may impose on sustainable forest development.     

The development of dragonfly larvae (Odonata: Anisoptera) from two streams in north-eastern Victoria, Australia

Developmental stages of larvae of eight species of Anisoptera from the Kiewa River and Middle Creek, Victoria, were determined and their phenology investigated. The last six to nine instars of each species were distinguished by size frequency and scatter plots, using labium width, metafemur and wing-pad measurements, and the early instars were estimated from Dyar's Law. This suggested between 11 to 14 instars. Four species appeared to be univoltine and four species semivoltine.     

Modeling population dynamics of a tea pest with temperature-dependent development: predicting emergence timing and potential damage

The tea leaf roller, Caloptilia theivora Walsingham (Lepidoptera: Gracillariinae), is one of the serious pests of tea plants in Japan. To understand the mechanism of seasonal occurrence of this insect pest, we developed a population dynamics model that explicitly incorporates the temperature-dependent development of the pest. The model predictions were compared with observed captures in pheromone traps at the experimental site of the Kagoshima Tea Experiment Research Station in Japan. The results showed that the emergence timing of the insect pest observed in the field was determined primarily by temperature. The relationship between the timing of adult emergence and the leaf damage level was also studied using a logistic regression model. The infestation level decreased as the interval between the adult peak emergence date and the date of tea plucking increased, implying that asynchrony between plant phenology and emergence of the insect pest is a critical factor reducing damage level. We examined how the damage level changes according to global warming. Increased temperature made the timing of insect appearance forward and enhance asynchrony of plant–pest phenology. Therefore, reduction of damage level by the insect pest is expected under global warming.