Apparent breeding success drives long-term population dynamics of a migratory swan

The ability of a species to adapt to environmental change is ultimately reflected in its vital rates – i.e. survival and reproductive success of individuals. Together, vital rates determine trends in numbers, commonly monitored using counts of species abundance. Rapid changes in abundance can give rise to concern, leading to calls for research into the biological mechanisms underlying variations in demography. For the northwest European population of Bewick's swan Cygnus columbianus bewickii, there have been major changes in the population trends recorded during nearly five decades of monitoring (1970–2016). The total number of birds increased to a maximum of ca 30 000 in 1995 and subsequently decreased to about 18 000 individuals in 2010. Such large fluctuation in population numbers is rare in long-lived species and understanding the drivers of this population change is crucial for species management and conservation. Using the integrated population model (IPM) framework, we analysed three demographic datasets in combination: population counts, capture–mark–resightings (CMR) and the proportion of juveniles in winter over a period of ~50 years. We found higher apparent breeding success in the years when the population had a positive growth rate compared to years with a negative growth rate. Moreover, no consistent trend in adult and yearling survival, and an increasing trend in juvenile survival was found. A transient life-table response experiment showed that apparent breeding success and adult survival contributed most to the variation in population trend. We explored possible explanatory variables for the different demographic rates and found a significant association between juvenile survival both with the water level in lakes during autumn migration, which affects food accessibility for the swans, and with summer temperatures. Such associations are important for understanding the dynamics of species with fluctuating population sizes, and thus for informing management and conservation decisions.     

Climatic drivers of pinyon mouse Peromyscus truei population dynamics in a resource-restricted environment

Highly variable patterns in temperature and rainfall events can have pronounced consequences for small mammals in resource-restricted environments. Climatic factors can therefore play a crucial role in determining the fates of small mammal populations. We applied Pradel's temporal symmetry model to a 21-year capture–recapture dataset to study population dynamics of the pinyon mouse (Peromyscus truei) in a semi-arid mixed oak woodland in California, USA. We examined time-, season- and sex-specific variation in realized population growth rate (λ) and its constituent vital rates, apparent survival and recruitment. We also tested the influence of climatic factors on these rates. Overall monthly apparent survival was 0.81 ± 0.004 (estimate ± SE). Survival was generally higher during wetter months (October–May) but varied over time. Monthly recruitment rate was 0.18 ± 0.01, ranging from 0.07 ± 0.01 to 0.63 ± 0.07. Although population growth rate (λ) was highly variable, overall monthly growth rate was close to 1.0, indicating a stable population during the study period (λ ± SE = 0.99 ± 0.01). Average temperature and its variability negatively affected survival, whereas rainfall positively influenced survival and recruitment rates, and thus the population growth rate. Our results suggest that seasonal rainfall and variation in temperature at the local scale, rather than regional climatic patterns, more strongly affected vital rates in this population. Discerning such linkages between species' population dynamics and environmental variability are critical for understanding local and regional impacts of global climate change, and for gauging viability and resilience of populations in resource-restricted environments.     

格庶尺蛾种群消长规律及综合治理研究

采取室内饲养和林间调查相结合的方法,研究了格庶尺蛾〔Ｓｅｍｉｏｔｈｉｓａ ｈｅｂｅｓａｔａ （Ｗａｌｋｅｒ）〕的生活史,种群消长与环境因素的关系和综合防治试验。提出了以营林措施为基础,应用白僵菌、苏云金杆菌生物防治为主,辅以化学、物理、人工防治和保护利种天敌的综合治理策略。     

一种模拟昆虫种群动态的改进的变维矩阵模型

提出了一种模拟昆虫种群动态的改进的变维矩阵模型,该模型以发有历期为维数,采用分解与合成的方法变维,并考虑了个体间的发育差异。经模拟检验,模型模拟结果略优于徐汝梅等（1981）变维矩阵模型的结果。     

Ocean temperature and density dependence as key drivers of the population dynamics of an intertidal crab at the Brazilian oceanic islands

Understanding how climatic and density-dependent processes affect demography is crucial for predicting population responses to climate change. For marine invertebrates with complex life cycle such as decapod crustaceans, increasing temperatures might affect survival and development of early pelagic stages, whereas high density can increase competition and thus reduce growth and fecundity of older life stages. In this study, we investigate the effects of warm ocean events, body size and density on the population dynamics of the intertidal Sally lightfoot crab (Grapsus grapsus) at the Brazilian oceanic islands. Firstly, we assessed the trends of marine heatwaves (MHW) and positive temperature anomalies (ΔSST+) at the equatorial St Peter and St Paul (SPSP) Archipelago and Rocas Atoll and the subtropical Trindade Island. We then jointly analyzed short-term count, capture-recapture and fecundity data, and long-term population monitoring data (2003–2019) using an integrated population model. Warm ocean events have become more frequent and intense only at the equatorial islands. Increasing MHW frequency positively influenced recruitment in the high-density SPSP population, while MHW intensity and ΔSST+ frequency had negative impacts. Conversely, no climatic effects were observed for the low-density Rocas population, which has the largest crabs. Despite a lack of warming in Trindade, this subtropical population with intermediate density and body size was negatively affected by ΔSST+. Our findings revealed population-specific responses to climate change when accounting for local life history and ecology. Thus, environmental and density-dependent effects should be broadly considered in future conservation studies regarding ocean warming impacts on marine invertebrate populations.     

An integrated modeling approach to estimating Gunnison sage‐grouse population dynamics: combining index and demographic data

Evaluation of population dynamics for rare and declining species is often limited to data that are sparse and/or of poor quality. Frequently, the best data available for rare bird species are based on large‐scale, population count data. These data are commonly based on sampling methods that lack consistent sampling effort, do not account for detectability, and are complicated by observer bias. For some species, short‐term studies of demographic rates have been conducted as well, but the data from such studies are typically analyzed separately. To utilize the strengths and minimize the weaknesses of these two data types, we developed a novel Bayesian integrated model that links population count data and population demographic data through population growth rate (λ) for Gunnison sage‐grouse (Centrocercus minimus). The long‐term population index data available for Gunnison sage‐grouse are annual (years 1953–2012) male lek counts. An intensive demographic study was also conducted from years 2005 to 2010. We were able to reduce the variability in expected population growth rates across time, while correcting for potential small sample size bias in the demographic data. We found the population of Gunnison sage‐grouse to be variable and slightly declining over the past 16 years.     

Integrated population model reveals that kestrels breeding in nest boxes operate as a source population

The identification of the source–sink status of a population is critical for the establishment of conservation plans and enacting smart management decisions. We developed an integrated population model to formally assess the source status of a kestrel Falco tinnunculus population breeding in nest boxes in Switzerland. We estimated juvenile and adult survival, reproduction and net dispersal (emigration/immigration) by jointly analyzing capture–recapture, dead recovery, breeding monitoring and population survey data. We also investigated the role of nest boxes on kestrel demography and assessed the contributions of vital rates to realized population growth rates. The results indicate that the kestrel population breeding in nest boxes has acted as a source over the 15 years of the study duration. A quantitative approach suggests that a substantial number of individuals have emigrated annually from this population likely affecting the population dynamics outside the management area. Variation in fecundity explained 34% of the temporal variability of the population growth rate. Moreover, a literature review suggests that kestrel pairs produce on average 1.4 chicks more per breeding attempt in nest boxes compared to natural open nests. Together, these findings suggest that fecundity was an important driver for the dynamics of this population and that nest boxes have contributed to its raise. Nest boxes are regularly used as an efficient tool for conservation management. We suggest that such a conservation action can result in the establishment of a source population being beneficial for populations both inside and outside the managed area.     

数学判别模型在预测害虫种群动态上的应用

根据两个总体的Fisher判别准则,建立了预测害虫种群动态的数学判别模型,对山东省惠民县1967～1977年共11年二代棉铃虫发生程度的两类资料进行了数量分析,建立了数学模型：y＝0．0127x1－0．023X2,对历史资料的回代验证与独立样本的预测,符合率在90％以上。     

Rainfall and rats: Climatically-driven dynamics of a tropical rodent population

A five-year mark–recapture study of dusky rats (Rattus colletti) on the Adelaide River floodplain, within the Australian wet–dry tropics, revealed substantial spatial and temporal variation in demographic characteristics (abundance, condition, and rates of survival, growth, and reproduction) of the rats. Our data suggest that annual variation in the intensity and timing of monsoonal rainfall during the ‘wet-season’ is the main factor driving the demography of the rats. When total rainfall figures are modified to reflect the magnitude and duration of inundation of the floodplain each year, a link is evident between rainfall patterns and the rat population dynamics. Minor spatial variations in elevation (and hence, in the duration of inundation) across the floodplain engender large differences in rat growth rates, condition factors, survival rates, and the duration of reproductive activity each year. Because these rats have very high reproductive rates, small rain-induced differences in the duration of their reproductive season (i.e. number of litters per year) can cause massive differences in subsequent rat abundances. Hence, rat numbers can be predicted from rainfall patterns during the preceding wet-season. Similar links between rainfall, the duration of breeding, and fluctuations in abundance may typify many rodent populations in tropical and arid regions of the world.     

An approach to the nonlinear dynamics of Russian wheat aphid population growth with the cusp catastrophe model

Many insect field populations, especially aphids, often exhibit irregular and even catastrophic fluctuations. The objective of the present study is to explore whether or not the population intrinsic rates of growth ( r _m) obtained under laboratory conditions can shed some light on the irregular changes of insect field populations. We propose to use the catastrophe theory, one of the earliest nonlinear dynamics theories, to answer the question. To collect the necessary data, we conducted a laboratory experiment to investigate population growth of the Russian wheat aphid (RWA), Diuraphis noxia (Mordvilko), in growth chambers. The experiment was designed as the factorial combinations of five temperatures and five host plant-growth stages (25 treatments in total): 1800 newly born RWA nymphs arranged in the 25 treatments (each treatment with 72 repetitions) were observed for their development, reproduction and survival through their entire lifetimes. After obtaining the population intrinsic rates of growth ( r _m) from the experimental data under various environmental conditions, we built a cusp catastrophe model for RWA population growth by utilizing r _m as the system state variable, and temperature and host plant-growth stage as control variables. The cusp catastrophe model suggests that RWA population growth is intrinsically catastrophic , and dramatic jumps from one state to another might occur even if the temperature and plant-growth stage change smoothly . Other basic behaviors of the cusp catastrophe model, such as catastrophic jumps , hystersis and divergence , are also expected in RWA populations. These results suggest that the answer to the previously proposed question should be "yes".     

INSTAR,a discrete event model for simulating zooplankton population dynamics

In this paper we discuss the basic principles of discrete event, individual oriented, data based modelling in ecology, and we present an application of this modelling strategy. The strategy is contrasted with some more conventional modelling strategies with respect to its purpose, its basic units and its heuristic properties.INSTAR applies this modelling strategy to the simulation of the fluctuations of the population structure and density of microcrustaceans through the year. The model encompasses one microcrustacean species at a time, and its interface with the rest of the ecosystem; it has been applied to several Cladocera and Copepoda species in a shallow eutrophic lake in the Netherlands (Vijverberg & Richter 1982a, b). Possibilities for extending the model are discussed.     

Spatial heterogeneity in the effects of climate change on the population dynamics of a Mediterranean tortoise

Climatic shifts may increase the extinction risk of populations, especially when they are already suffering from other anthropogenic impacts. Our ability to predict the consequences of climate change on endangered species is limited by our scarce knowledge of the effects of climate variability on the population dynamics of most organisms and by the uncertainty of climate projections, which depend strongly on the region of the earth being considered. In this study, we analysed a long‐term monitoring programme (1988–2009) of Hermann's tortoise (Testudo hermanni) aimed at evaluating the consequences of the drastic changes in temperature and precipitation patterns predicted for the Mediterranean region on the demography of a long‐lived species with low dispersal capability and already suffering a large number of threats. Capture–recapture modelling of a population in the Ebro Delta (NE Spain) allowed us to assess the effect of climate variability on the survival of tortoises. Winter rainfall was found to be the major driver of juvenile and immature survival, whereas that of adults remained high and constant across the study. Furthermore, local climate series obtained ad hoc from regional climate simulations, for this and 10 additional Mediterranean locations where tortoises occurred, provided us with reliable future climate forecasts, which were used to simulate the fate of these populations under three precipitation scenarios (mean, wet and dry) using stochastic population modelling. We show that a shift to a more arid climate would have negative consequences for population persistence, enhancing juvenile mortality and increasing quasiextinction risk because of a decrease in recruitment. These processes varied depending on the population and the climate scenario we considered, but our results suggest that unless other human‐induced causes of mortality are suppressed (e.g. poaching, fire, habitat fragmentation), climate variability will increase extinction risk within most of the species’ current range.     

A simple model of a Gyrodactylus population

Experimental populations of 20 Gyrodactylus alexanderi Mizelle &; Kritsky, 1967, on 19 isolated Gasterosteus aculeatus at 15°C increased for 2 weeks to a mean of 61, then decreased in 2 further weeks to a mean of 9. Fish that lost their fluke infestations were refractory to further infestation for about 3 weeks.The chief factors affecting fluke abundance were measured, including reproduction and mortality rates of flukes on fish, rate of shedding by the fish, mortality rates of flukes while off fish, and the rate of reattachment of the flukes. Data on these individual factors were combined to form a simple deterministic model which simulated the population changes on isolated fish. This was later made more realistic by the introduction of a random variable. When the model was tested in a multiple-host situation it predicted results close to those observed experimentally.