Field Of Population Biology Research Articles

Population genetics meets ecology: a guide to individual-based simulations in continuous landscapes.

Individual-based simulation has become an increasingly crucial tool for many fields of population biology. However, implementing realistic and stable simulations in continuous space presents a variety of difficulties, from modeling choices to computational efficiency. This paper aims to be a practical guide to spatial simulation, helping researchers to implement realistic and efficient spatial, individual-based simulations and avoid common pitfalls. To do this, we delve into mechanisms of mating, reproduction, density-dependent feedback, and dispersal, all of which may vary across the landscape, discuss how these affect population dynamics, and describe how to parameterize simulations in convenient ways (for instance, to achieve a desired population density). We also demonstrate how to implement these models using the current version of the individual-based simulator, SLiM. Since SLiM has the capacity to simulate genomes, we also discuss natural selection - in particular, how genetic variation can affect demographic processes. Finally, we provide four short vignettes: simulations of pikas that shift their range up a mountain as temperatures rise; mosquitoes that live in rivers as juveniles and experience seasonally changing habitat; cane toads that expand across Australia, reaching 120 million individuals; and monarch butterflies whose populations are regulated by an explicitly modeled resource (milkweed).

Better trap-neuter-return for free-roaming cats: Using models and monitoring to improve population management.

Trap-neuter-return (TNR) for cat management is transitioning from an enterprise driven mainly by an urge to 'help' into an enterprise that draws useful guidance and precedent from the fields of population biology and wildlife management. This transition is in its infancy, however. At the present time many TNR programs do not produce substantial and persistent reductions in cat populations, and those that do often fail to effectively document this achievement or to publicize their success. As a result, TNR has become increasingly controversial, with TNR advocates and wildlife conservationists often staking out fundamentally incompatible positions. This may ultimately prove to be an unproductive debate, since public opinion in developed countries is unlikely to support a total abandonment of TNR in favor of widespread cat management using lethal methods, and since wildlife advocates are unlikely to support TNR as it is typically practiced. In contrast, improving the effectiveness of TNR as a population management tool can benefit both cats and wildlife, potentially on a broad scale. Making these advancements requires the diligent promotion, dissemination and adoption of tools like population modeling, population monitoring and adaptive management. By virtue of their training and exposure to the scientific method, veterinarians are uniquely well positioned to translate the more technical aspects of these approaches to TNR practitioners, and to facilitate their wider use. The purpose of this review is to describe for a veterinary audience how to facilitate more effective sterilization-based management of outdoor cats, using a combination of theoretical knowledge derived from population modeling and empirical knowledge derived from population monitoring. Using both of these information sources synergistically can offer a viable pathway to better management outcomes.

Evolution in heterogeneous populations: From migration models to fixation probabilities

Although dispersal is recognized as a key issue in several fields of population biology (such as behavioral ecology, population genetics, metapopulation dynamics or evolutionary modeling), these disciplines focus on different aspects of the concept and often make different implicit assumptions regarding migration models. Using simulations, we investigate how such assumptions translate into effective gene flow and fixation probability of selected alleles. Assumptions regarding migration type (e.g. source-sink, resident pre-emption, or balanced dispersal) and patterns (e.g. stepping-stone versus island dispersal) have large impacts when demes differ in sizes or selective pressures. The effects of fragmentation, as well as the spatial localization of newly arising mutations, also strongly depend on migration type and patterns. Migration rate also matters: depending on the migration type, fixation probabilities at an intermediate migration rate may lie outside the range defined by the low- and high-migration limits when demes differ in sizes. Given the extreme sensitivity of fixation probability to characteristics of dispersal, we underline the importance of making explicit (and documenting empirically) the crucial ecological/ behavioral assumptions underlying migration models.

Improved viability of populations with diverse life-history portfolios

A principle shared by both economists and ecologists is that a diversified portfolio spreads risk, but this idea has little empirical support in the field of population biology. We found that population growth rates (recruits per spawner) and life-history diversity as measured by variation in freshwater and ocean residency were negatively correlated across short time periods (one to two generations), but positively correlated at longer time periods, in nine Bristol Bay sockeye salmon populations. Further, the relationship between variation in growth rate and life-history diversity was consistently negative. These findings strongly suggest that life-history diversity can both increase production and buffer population fluctuations, particularly over long time periods. Our findings provide new insights into the importance of biocomplexity beyond spatio-temporal aspects of populations, and suggest that maintaining diverse life-history portfolios of populations may be crucial for their resilience to unfavourable conditions like habitat loss and climate change.

Robust Control Design for Linear Systems Using an Ecological Sign-Stability Approach

T HE fields of population biology and ecology deal with the analysis of growth and decline of populations in nature and the struggle of species to predominate over one another. Many mathematical population models were proposed over the last few decades, with the most significant contributions coming from the work of Lotka [1] and Volterra [2]. The predator–prey models of Lotka andVolterra, studied extensively by ecologists and population biologists, consists of a set of nonlinear ordinary differential equations, and stability of the equilibrium solutions of these models has been a subject of intense study for students of life sciences [3–6]. For example, many standard textbooks on mathematical models in biology, such as [7], cover these issues. These small perturbations from equilibrium can be modeled as linear state-space systems in which the state-space plant matrix is the Jacobian, and it is important to analyze the stability of these state-space (Jacobian) matrices. For communities of five or more species, the order of these matrices is high enough to cause difficulties in assessing the stability. For this reason, to circumvent these difficulties, alternative concepts of reduced computation have been proposed, and one such important concept is that of qualitative (or sign) stability. The technique of qualitative stability applies ideally to large-scale systems in which there is no quantitative information about the interrelationship of species or subsystems. Themotivation for this method actually came from economics. The paper by economists Quirk and Ruppert [8] was later followed by further research and application to ecology by May [9] and Jeffries [10]. Note that in a complex community composed of many species, numerous interactions take place. The magnitudes of the mutual effects of species on each other are seldom accurately known, but one can establish with greater certainty whether predation, competition, or other influences are present. This means that in the Jacobian matrix, one does not technically know the actualmagnitudes of the partial derivatives, but their signs are known with certainty. Thus, the qualitative information about the species is represented by the signs , , or 0. Thus, the (i,j)th entry of the statespace (Jacobian) matrix simply consists of signs , , or 0, with the positive sign indicating that species j has a positive influence on species i, the negative sign indicating a negative influence, and zero indicating no influence. An alternative visual representation of this situation can also be given by a directed graph (or, simply, a digraph), as shown in Fig. 1. For example, with respect to the digraph of Fig. 1a, the corresponding sign-pattern matrix is given by

Wildlife Damage Control

EFFECTIVE wildlife management needs to be based on the application of sound scientific principles and concepts. Both of these books provide a framework for the application of concepts and principles to wildlife management problems and attempt to bridge the gap between research and its application in management. Conservation of Wildlife Populations, by L. Scott Mills, explains theories, concepts and principles developed in the field of population biology, and their management applications. It encompasses population ecology, demography and population genetics. Wildlife Damage Control, by Jim Hone, identifies and explains the application of principles involved in assessing and controlling damage caused by wildlife.

Conservation of Wildlife Populations: Demography, Genetics and Management

Effective wildlife management needs to be based on the application of sound scientific principles and concepts. Both of these books provide a framework for the application of concepts and principles to wildlife management problems and attempt to bridge the gap between research and its application in management. Conservation of Wildlife Populations, by L. Scott Mills, explains theories, concepts and principles developed in the field of population biology, and their management applications. It encompasses population ecology, demography and population genetics. Wildlife Damage Control, by Jim Hone, identifies and explains the application of principles involved in assessing and controlling damage caused by wildlife.

THE INCREASING IMPORTANCE OF 1/f-NOISES AS MODELS OF ECOLOGICAL VARIABILITY

The features of 1/f-noise processes offer important new insights into the field of population biology, greatly helping our quest for understanding and for prediction of ecological processes. 1/f-noises account quite satisfactorily for the observed nature of ecological fluctuations. This article reviews the application of 1/f-noise processes to ecology. After a discussion of the basic problems of population ecology that makes such an innovation necessary, we review the features of 1/f-noises concentrating especially on those aspects that make these processes attractive as a solution. We also present a discussion of the analysis of real ecological data, which confirms that there are good empirical as well as good theoretical reasons to establish a leading role for pink 1/f noise. We then discuss the consequences of such a model for our understanding of ecology. The article finishes with a number of observations about some aspects of ecological data and applications that are likely to drive research in a different direction from that associated with engineering and the physical sciences.

The role of local adaptation in metapopulation restorations

AbstractWe propose an original approach to model the effect of the initial spatial distribution of a reintroduced metapopulation (one‐patch release versus multi‐patch release) on local adaptation. Genetic and demographic processes are considered to investigate how the different patterns of adaptation resulting from initial conditions affect metapopulation viability. In agreement with classical interpretations in the fields of population biology and evolutionary genetics, we observe an influence of the degree of environmental correlation among patches on demographic processes and an influence of inter‐patch connection on genetic processes. However, our results uncover some further effects of the environment, owing to positive feedback interactions among demographic and genetic processes. When considering the one‐patch release, demographic stochasticity engenders a delay in the colonization of initially empty patches. This delay enhances the genetic asymmetry among patches (in terms of local adaptation), which in turn increases demographic asymmetry. In contrast, the multi‐patch release produces similar levels of adaptation among patches. Metapopulation dynamics is strongly influenced by these differences, with contrasting effects under different environments. The pattern of adaptation produced by the one‐patch release strategy is optimal under a regime of recurrent slight perturbations or environmental stochasticity, while the multi‐release strategy is optimal in the presence of rare and severe perturbations.

Survival‐variation within and between functional categories of the African multimammate rat

1.By identifying ecological factors specific to functional categories of individuals, it may be possible to understand the mechanisms underlying life‐history evolution and population dynamics. While empirical analyses within the field of population biology have focused on changes in population size, theoretical models assuming differential sensitivities of population growth rate or fitness to demographic parameters have mostly been untested, particularly against data on small mammals.2.Statistical modelling of capture–mark–recapture data on the multimammate rat (Mastomys natalensis) from Tanzania shows that: (i) females survive slightly better than males and subadults survive much better than adults; (ii) temporal variation of survival of all individuals is similarly related to the rainfall of the month; (iii) subadults exhibit a strongly density‐dependent low persistence rate in the population immediately after their first capture; (iv) subadults survival in later months is, however, positively related to density; and (v) adult survival shows negative density‐dependence.3.Both density‐dependent and density‐independent factors simultaneously determine stage‐dependent survival variation of the multimammate rat. Whereas environmental factors in this population seem to affect survival rates of all individuals in a similar manner, density‐dependent relationships are more complex.4.The patterns of survival variation in small mammals may be different from those observed in large mammals.5.Further studies of demography in small mammals should aim at understanding how much of the variability in population growth rate is accounted for by the variability of the demographic rates resulting from limiting (density‐independent) and regulating (density‐dependent) factors, respectively. This study emphasizes the use of robust and accurate statistical methods as well as stage‐ or age‐structured population modelling.

The impact of epidemics on world population prospects for the 21st century: genetic, epidemiologic and bioethical issues

New data of recent researches on genetics and epidemiology imply the idea of rapidly evolving viruses through DNA recombination, which leads to the establishment of new virus families, eventually adapted to the environmental conditions. Consequently the framework of the epidemiological studies widens, replacing the classic aspect of the bilateral virus—host coexistence.An holistic evolutionary approach, considering all the complex interrelationship among viruses, parasites and hosts, in conjugation with the environmental changes is developing.Molecular epidemiology and updated population models renew the health strategy bringing together experts from the fields of population biology, evolution and infectious diseases.The related ethical issues, which consequently emerge should be faced accordingly.

The Distribution and Abundance of Woodland Species of British Drosophila (Diptera: Drosophilidae)

For seventy years, Drosophila has been used in genetical, cytological and evolutionary studies; in this connection fruit flies are admirable experimental animals. However, in the field of population biology it is increasingly obvious that the solution to many genetical and evolutionary problems must be found within an adequate ecological framework and this area of Drosophila study has received less attention. This paper describes some initial sampling of wild populations and forms part of a series of studies concerned with basic ecological information on the British species of Drosophila. The study was carried out at Adel Dam, an area of mixed deciduous woodland 10 km from the centre of the city of Leeds, which occupies an area of 50 ha surrounding a former mill pond, set in a shallow valley. The Leeds historian, Ralph Thoresby, refers to Adel Mill in 1715 as a corn mill so it is reasonable to suppose that the original dam was built prior to this date. Since that time the area of clear water has gradually been reduced due to extensive silting and the growth of reedmace (Typha latifolia L.). Details of the site with its vegetational zones are shown in Fig. 1.