Population Model

The Civic Theatre was created by a deconsecrated church during the period of Ligurian Republic. It was realized by the neoclassicist architect Ippolito Cremona and inaugurated the 18 July 1846. After some changes made at the end of the century, in 1933 it was demolished to be replaced by a new theatre building meeting new needs and designed by the famous architect Franco Oliva. Today it is again a cultural lighthouse and the center of performing arts in La Spezia.

Background Malaria remains one of the most significant global health challenges, particularly in tropical and subtropical regions. Despite ongoing control efforts, malaria transmission persists due to complex biological, environmental, and socioeconomic factors. Traditional malaria models have primarily focused on vector-borne transmission, overlooking the growing importance of non-vector transmission pathways, such as blood transfusions, congenital transmission, and human-to-human transmission through healthcare settings. Methods A novel mathematical model was developed to integrate both vector-borne and non-vector transmission routes. The model expands the traditional Susceptible-Exposed-Infectious-Recovered (SEIR) framework by incorporating compartments for vaccinated and non-vector exposed human populations, as well as dynamics for both human and mosquito populations. Numerical simulations were performed using MATLAB to evaluate the impact of vaccination, vector control, non-vector control, and treatment strategies. Results The results indicate that vaccination significantly reduces susceptibility to malaria, with numerical simulations showing an approximate 43% reduction in the susceptible human population. However, vector control remains critical in limiting exposure, and non-vector transmission pathways including blood transfusions, congenital transmission, and direct human-to-human transmission pose a substantial risk even in regions with effective mosquito control. This underscores the need for integrated strategies that address both vector and non-vector transmission routes. Conclusions Combining vaccination efforts with robust vector control, improved healthcare practices, and stringent non-vector transmission prevention measures is essential to effectively reduce malaria transmission. Sustained interventions, including improved blood screening and safe medical practices, are necessary to prevent malaria resurgence, particularly in high-transmission settings. This model provides valuable insights into malaria dynamics and offers a framework for designing more effective public health policies and strategies for malaria eradication.

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Olli Tahvonen is a professor of environmental economics at the Finnish Forest Research Institute, Unioninkatu 40A, 00170 Helsinki, �inl�n� �e��il� �lli������nen��e�l��� �� His ���e� ��� li��i�n is ��e �is�e�� �n� �n�i��n� �inl�n� �e��il� �lli������nen��e�l����� His ���e� ���li��i�n is ��e �is�e�� �n� �n�i��n� Fishery and Environmental Management Group, FEM, University of Helsinki, Department of Biological and Environmental Sciences. T�e s�u�� w�s been �n�nce� b� ��e Y�jö J��nns�n ��un���i�n, G��n� 5313, �n� b� ��e Ac��e�� �� �inl�n�� T�e s�u�� w�s p�esen�e� �� ���i�us se�in��s in Aus���li� �n� New Ze�l�n� �u�ing 2005�2006, �� ��e �A�R� �nnu�l �ee�ing in T�ess�l�niki �2007�, �n� �� ��e A�e�ic�n Ag�icul�u��l �c�n��ic Ass�ci��i�n �ee�ing in O�-l�n��, �L �2008�� I �� g���e�ul �� Ji� Wilen ��� �iscussi�ns� 1 T�e bi���ss ���el, ��e ���n��ic� bi���ss �pp���c�, ��e lu�pe� p����e�e� ���el, �n� ��e Sc��e�e� �1954� �pp���c� �ll �e�e� �� � speci�c��i�n w�e�e ��e �s� s��ck ��n��ics is gi�en b� B t+1 = B t + F(B t ) -h t , where B t is biomass, F is the growth function (e.g., l�gis�ic�, �n� h t is ��e ���e �� ����es�� As w�i��en b� Hilb��n �n� W�l-�e�s �2001�, ��e �e�� "bi���ss ���el" is s��ew��� c�n�using since bi���ss �� ne� p���uc�i�n is n�� � unique c����c�e�is�ic �� ��e Sc��e�e� ���el� R���e�, ��e unique c����c�e�is�ic �� ��e Sc��e�e� ���el is ��e �esc�ip�i�n �� p�pul��i�n ��n��ics in �e��s �� bi���ss ins�e�� �� nu�be�s in �ge cl�ss� T�us, ��e� use ��e �e�� "��n��ic bi���ss ���el" ��� ��e Sc��e�e� �pp���c�� T�is p�pe� uses "bi���ss ���el" ��� s�����

Apex marine predators can structure marine communities, so factors underlying their abundance are of broad interest. However, such data are almost completely lacking for large sharks. We assessed the relationship between tiger shark abundance, water temperature, and the availability of a variety of known prey over 5 years in Western Australia. Abundance of sharks in four size categories and the density of prey (cormorants, dugongs, sea snakes, sea turtles) were indexed using daily catch rates and transects, respectively. Across all sizes, thermal conditions were a determinant of abundance, with numerical peaks coinciding with periods of high water temperature. However, for sharks exceeding 300 cm total length, the inclusion of dugong density signiWcantly improved temperaturebased models, suggesting that use of particular areas by large tiger sharks is inXuenced by availability of this sirenian. We conclude that large marine predator population models may beneWt from the inclusion of measures of prey availability, but only if such measures consider prey types separately and account for ontogenetic shifts in the diet of the predator in question. Apex predators • Dugong dugon • Galeocerdo cuvier • Ontogenetic diet shifts • Tiger shark Communicated by Marc Mangel.

An ecotechnological approach to control crayfish (Procambarus clarkii ) infestation in rice fields of the Lower Mondego River Valley (Central Portugal) has recently been investigated. The application of the biodegradable non-ionic surfactant Genapol OXD-080, a fatty alcohol polyglycol ether, in rice paddies at a given concentration (50 mg/l) has been considered as a non-harmful chemical method to mitigate damage caused by crayfish digging activities to rice crops. Therefore, an important requirement regarding the ecological viability of this approach is that populations of non-target species are not significantly affected. A simple mosquitofish (Gambusia holbrooki ) population model, in which the relationships with its main food prey were considered, was developed to assess the potential risk to a non-target key species of contaminating the irrigation channels following surfactant application. The model is based on data concerning mosquitofish life cycle and population dynamics, as well as mosquitofish diet and interactions with its main prey species. Quantitative information regarding the acute and sublethal effects of Genapol OXD-080 on mosquitofish and other non-target organisms was obtained from laboratory experiments. Three concentrations of Genapol OXD-080 (0.75, 1 and 2.5 mg/l) were used to simulate a small amount of contamination in irrigation channels. If contamination occurred, the mosquitofish population would tend to decline dramatically, even when submitted to a very small concentration of Genapol OXD-080 (e.g. 0.75 mg/l, 66.7 times lower than the concentration planned to be used in rice paddies). Thus, Genapol OXD-080 could potentially cause vast damage to local mosquitofish populations, and therefore should not be used without taking all precautions to avoid contaminating important biological reservoirs, such as the rice field irrigation channels.

1. Populations of migratory birds often mix to a considerable extent in their wintering areas. Knowledge about the composition of wintering populations is highly relevant to management, not least for species such as the great cormorant Phalacrocorax carbo sinensis, prone to conflicts with human interests. However, few studies have been able to estimate long-term changes in winter population composition. 2. We use 30 years of ringing and recovery data from all major breeding populations of cormorants in continental Europe (except the Black Sea region) to estimate partitioning probabilities (i.e. the probabilities of moving to specific wintering areas) using a Bayesian capture-mark-recovery model. Combining these results with information on breeding numbers and reproductive output in a population model, we estimate the size and composition of wintering populations in Europe and North Africa. 3. Partitioning probabilities showed some variation over time, but were similar for first-winter and older birds. Cormorants from the western part of the breeding range tended to winter progressively further west over time. This may be a density-dependent response to the recent growth of more easterly breeding populations. 4. All wintering populations grew rapidly over the study period, and their composition showed pronounced changes. All wintering populations were composed of birds from many different breeding populations, but the proportion of cormorants of more easterly origin increased markedly over time in most wintering areas. of birds of different breeding origins. These mixtures are also highly variable over time. These factors reduce the chances of successfully limiting conflicts in specific wintering areas through, for example, regulation of breeding numbers in one breeding area. The dynamic nature of cormorant winter populations means that conflicts are best addressed when and where the conflict occurs, or on the scale of the entire continental population. It is unlikely that the latter will be cost-effective and politically realistic. How to cite this article: Frederiksen M, Korner-Nievergelt F, Marion L, Bregnballe T. Where do wintering cormorants come from? Long-term changes in the geographical origin of a migratory bird on a continental scale.

Populations of migratory birds often mix to a considerable extent in their wintering areas. Knowledge about the composition of wintering populations is highly relevant to management, not least for species such as the great cormorant Phalacrocorax carbo sinensis, prone to conflicts with human interests. However, few studies have been able to estimate long‐term changes in winter population composition. We use 30 years of ringing and recovery data (1983–2013) from all major breeding populations of cormorants in continental Europe (except the Black Sea region) to estimate partitioning probabilities (i.e. the probabilities of moving to specific wintering areas) using a Bayesian capture–mark–recovery model. Combining these results with information on breeding numbers and reproductive output in a population model, we estimate the size and composition of wintering populations in Europe and North Africa. Partitioning probabilities showed some variation over time, but were similar for first‐w...

We consider optimal control of a new type of non-local stochastic partial differential equations (SPDEs). The SPDEs have space interactions, in the sense that the dynamics of the system at time t and position in space x also depend on the space-mean of values at neighbouring points. This is a model with many applications, e.g. to population growth studies and epidemiology. We prove the existence and uniqueness of solutions of a class of SPDEs with space interactions, and we show that, under some conditions, the solutions are positive for all times if the initial values are. Sufficient and necessary maximum principles for the optimal control of such systems are derived. Finally, we apply the results to study an optimal vaccine strategy problem for an epidemic by modelling the population density as a space-mean stochastic reaction-diffusion equation.

Pattern dynamics of a three-trophic population model was numerically investigated in a twodimensional space. By measuring the spatial correlation function of the domain patterns, whose density was higher than 90% of the maximum density in the whole area, we found that the characteristic length scale of the ordered domain increased in time in the power law form, L(t) ∼ t for the super-predator and the predator, respectively. In the case of prey, there were two di erent growth regimes. The growth exponent changed at the crossover time t = . In order to investigate the geometrical features of the domain patterns, the evolution of the "fractal dimension" of the domain patterns was also studied. In the case of prey, fractal dimension decreased at t ¡ and increased at t ¿ . This non-equilibrium and non-steady process showed a dynamic scaling behavior in the three-trophic population model.

Current measures used to estimate the risks of toxic chemicals are not relevant to the goals of the environmental protection process, and thus ecological risk assessment (ERA) is not used as extensively as it should be as a basis for cost-effective management of environmental resources. Appropriate population models can provide a powerful basis for expressing ecological risks that better inform the environmental management process and thus that are more likely to be used by managers. Here we provide at least five reasons why population modeling should play an important role in bridging the gap between what we measure and what we want to protect. We

Previous work on resource constrained adaptive search for sparse static targets has produced two-stage allocation policies with desirable properties. For example, for large asymptotic SNR, such policies converge to the true region of interest (ROI) and attain optimal energy allocations relative to exhaustive search. This work investigates the problem of extending previous allocation policies to T >> 2 stages, with particular emphasis on cases where the SNR for any particular stage is considerably less than the asymptotic SNR. Furthermore, a new formulation is given that can account for non-static targets, including a dynamic transition model for target location and a population model to account for targets that leave or enter the scene. Under this formulation, a dynamic adaptive resource allocation policy (D-ARAP) is proposed that performs well and has low computational cost. It is shown that this policy provides significant gains over an exhaustive search policy in both static and dynamic target cases with near optimal performance as T → ∞. Moreover, D-ARAP is shown to be more robust than a greedy (myopic) policy when there are outliers or when targets may be obscured for periods of time.

Most population models assume that individuals within a given population are identical, that is, the fundamental role of variation is ignored. Here we develop a general approach to modeling heterogeneous populations with discrete evolutionary time step. The theory is applied to population dynamics of natural rotifer populations. We show that under particular conditions the behavior of the inhomogeneous model possesses complex transition regimes, which depends both on the mean and the variance of the initial parameter distribution and the final state of the population depends on the least possible value from the domain of the parameter. The question of persistence of the population is discussed.

A class of models of biological population and communities with a singular equilibrium at the origin is analyzed; it is shown that these models can possess a dynamical regime of deterministic extinction, which is crucially important from the biological standpoint. This regime corresponds to the presence of a family of homoclinics to the origin, so-called elliptic sector. The complete analysis of possible topological structures in a neighborhood of the origin, as well as asymptotics to orbits tending to this point, is given. An algorithmic approach to analyze system behavior with parameter changes is presented. The developed methods and algorithm are applied to existing mathematical models of biological systems. In particular, we analyze a model of anticancer treatment with oncolytic viruses, a parasite-host interaction model, and a model of Chagas' disease.

Most population models assume that individuals within a given population are identical, that is, the fundamental role of variation is ignored. Here we develop a general approach to modeling heterogeneous populations with discrete evolutionary time step. The theory is applied to population dynamics of natural rotifer populations. We show that under particular conditions the behavior of the inhomogeneous model possesses complex transition regimes, which depends both on the mean and the variance of the initial parameter distribution and the final state of the population depends on the least possible value from the domain of the parameter. The question of persistence of the population is discussed.

Managers of forest wildlife populations make recurring management decisions based on incomplete knowledge of system states. For example, animal population estimates may ignore spatial structure that may influence population viability. We built a spatially-explicit model for a population of birds in a forested landscape. Rates of bird population growth within forest compartments and rates of bird dispersal among compartments were functions of stand age and basal area, compartment population size, and inter-compartment distance. Stand characteristics were imbedded in a dynamic model and assumed perfectly observable and under the complete control of managers. We constructed a genetic algorithm to search for the schedule and spatial distribution of silviculture to maximize total bird abundance at the end of a fixed planning horizon, under combinations of initial habitat and population distribution. We also found policies for a smaller set of population distributions that a manager may only presume to occur (e.g. birds equally distributed among stands), as when managers are only able to observe abundance and not spatial distribution. We investigated the effect of this loss of system resolution on optimality by examining differences in projected population sizes under the two types of policies. That is, we used the set of 'presumed-state' policies to project population size from each true initial system state, then we compared these to projections under the best policy for that state. For the planning horizon that we considered, loss in optimality was highly dependent on initial habitat state and on choice of presumed population distribution. Generally, loss in optimality and species extinction rate were both greater for habitat states that were initially poor than initially favorable. For some

Summary This paper deals with the problem of software sensor (state estimation) to study the uncertain continuous age- structured model of a harvested fish population, in order to get an estimation of the biomass of fishes by age class. In our case the fishing effort is considered as a control term, the age classes as a states and the quantity of captured fish as a measured output. We formulate the observer corresponding to this system and show its asymptotic convergence. With the Lie derivative transformation, we show that the model can be transformed to a canonical observable form; then we give the explicit gain of the estimation. The considered model is nonlinear and contains an unknown function, which is supposed to be bounded. The proposed observer do not assume or require any model for this function and is very successful for accurately estimating it. The simulation results demonstrate the effectiveness of the proposed method.

Anthropogenic disturbances may alter a population's conservation status if the ability of individuals to survive and breed is affected. We used an adaptation of the Heligman-Pollard model to estimate survival at age of Cook Inlet belugas (CIB; Delphinapterus leucas), an endangered population in south-central Alaska. We developed an age-structured Leslie matrix model, based on the life history parameters survival and fecundity probability, to evaluate the sensitivity of population size and growth of CIB, to variation in estimate values of Chinook and coho salmon abundance in the Deshka River, a major tributary of the Susitna River. Birth effect (e b ) was regressed against Chinook and coho salmon levels for the year of, the year before, and two years before a beluga calf birth. The effect of a range of modifications of salmon availability was illustrated in CIB with a series of simulations. The maximum annual population growths (k) were set at 1.036 (3.6%). Ranges of CIB survival and fecundity probabilities indicated small changes in survival probabilities have a greater impact on population growth than similar changes in birth probability. As either survival (e s ) or fecundity (e b ) was reduced, the annual growth declined, with either e s = 0.961 or e b = 0.388, causing a decreased annual growth of À0.4%. Regressions of Chinook salmon for the year of, the year before, and two years before a birth were all significant at the 5% level as was coho in the year of and year prior to birth. The mechanism model with the best fit was the sum of Chinook and coho in the year of birth and year prior to birth. Simulations showed that if salmon runs remained at their current levels, the CIB population would likely continue its current slow decline and per capita births would continue to be low. The results from this study suggest reproductive success in CIB is tied to salmon abundance in the Deshka River. Current management practices should consider this when setting research priorities, designing new studies, and developing management actions to achieve CIB population recovery targets.

A length-based population model for Bristol Bay red king crab Paralithodes camtschaticus was updated and applied to abundance and catch data from 1968 to 1994. The updated model has fewer parameters and assumes constant natural mortality over length and 2 levels of natural mortality over time for males and 3 levels for females. A nonlinear least squares approach was used to estimate abundance, recruitment, and natural mortality. We added confidence intervals for the abundance estimates with a bootstrap percentile method. Natural mortality was estimated to be 4 to 5 times higher in the early 1980s than during other periods. The observed population abundances were well fitted by the updated model. Confidence intervals for legal male abundance were narrower than for mature female abundance. The stock-recruitment data estimated from the updated length-based model provided a good fit to both general and autocorrelated Ricker models. However, recruitment estimates were lower and the relationships were slightly more depensatory than in the previous model.

A simple weakly frequency dependent model for the dynamics of a population with a finite number of types is proposed, based upon an advantage of being rare. In the infinite population limit, this model gives rise to a non-smooth dynamical system that reaches its globally stable equilibrium in finite time. This dynamical system is sufficiently simple to permit an explicit solution, built piecewise from solutions of the logistic equation in continuous time. It displays an interesting tree-like structure of coalescing components.

Accommodating the needs of a large number of diverse users in the Internet of Things (IoT), notably managing how the users access the common channel, has posed unique challenges to the network designers. In this paper, we study a heterogeneous IoT network consisting of multiple classes of users who may have different service requirements. For this network, we consider the application of irregular repetition slotted ALOHA (IRSA) that is shown to offer large throughput for single-class networks. Then, we focus on finding the network performance boundaries by studying the set of feasible throughput values for each class, called the capacity region. To this end, we first introduce the concept of dual network of a multi-class network meaning a homogeneous network with the same number of users. We then prove that finding the capacity region of the assumed multi-class network boils down to finding the maximum achievable throughput of its dual network. Using this finding, we then discuss ho...

The first record of Pallas's Warbler (Phyl1oscopus proregulus) for North America was documented at Gainbell, Saint Lawrence Island, Alaska, on 25-26 September 2006. The identification and evidence supporting the record are presented here and put into context with records of other landbird vagrants found in autumn at Gainbell since the 1990s. Introduction The Aleutians and islands of the Bering Sea in western Alaska are well known to North American birders as places where Asian migrants and vagrants occur regularly Attu, Shemya, Buldir, and Adak Islands in the western and central Aleuuans, St. Paul (and to a lesser extent St. George) Island in the Pribilofs (southern Bering Sea), and the village of Gainbell at the northwestern tip of Saint Lawrence Island (northern Bering Sea) (Figure 4) are all sites that have produced many documented records of Asian waterbirds and landbirds--some of which have turned out to be regular migrants and some of which have been determined to be true ...

In a growing Saccharomyces cerevisiae population, cell size is finely modulated according to both the chronological and genealogical ages. This generates the complex heterogeneous structure typical of budding yeast populations. In recent years, there has been a growing interest in developing mathematical models capable of faithfully describing population dynamics at the single cell level. A multistaged morphologically structured model has been lately proposed based on the population balance theory. The model was able to describe the dynamics of the generation of a heterogeneous growing yeast population starting from a sub-population of daughter unbudded cells. In this work, which aims at validating the model, the simulated experiment was performed by following the release of a homogeneous population of daughter unbudded cells. A biparametric flow cytometric approach allowed us to analyse the time course joint distribution of DNA and protein contents at the single cell level; this gave insights into the coupling between growth and cell cycle progression that generated the final population structure. The comparison between experimental and simulated size distributions revealed a strong agreement for some unexpected features as well. Therefore, the model can be considered as validated and extendable to more complex situations.

It has been well recognized that many key aspects of cell cycle regulation are encoded into the size distributions of growing budding yeast populations due to the tight coupling between cell growth and cell division present in this organism. Several attempts have been made to model the cell size distribution of growing yeast populations in order to obtain insight on the underlying control mechanisms, but most were based on the age structure of asymmetrically dividing populations. Here we propose a new framework that couples a morphologically-structured representation of the population with population balance theory to formulate a dynamic model for the size distribution of growing yeast populations. An advantage of the presented framework is that it allows derivation of simpler models that are directly identifiable from experiments. We show how such models can be derived from the general framework and demonstrate their utility in analyzing yeast population data. Finally, by employing a recently proposed numerical scheme, we proceed to integrate numerically the full distributed model to provide predictions of dynamics of the cell size structure of growing yeast populations.

We investigate a partial differential equation model of a cancer cell population, which is structured with respect to age and telomere length of cells. We assume a continuous telomere length structure, which is applicable to the clonal evolution model of cancer cell growth. This model has a non-standard non-local boundary condition. We establish global existence of solutions and study their qualitative behaviour. We study the effect of telomere restoration on cancer cell dynamics. Our results indicate that without telomere restoration, the cell population extinguishes. With telomere restoration, exponential growth occurs in the linear model. We further characterise the specific growth behaviour of the cell population for special cases. We also study the effects of crowding induced mortality on the qualitative behaviour, and the existence and stability of steady states of a nonlinear model incorporating crowding effect. We present examples and extensive numerical simulations, which illustrate the rich dynamic behaviour of the linear and nonlinear models.

The Mid-continent Population of sandhill cranes (Grus canndensis) has a large geographic range. contains nearly 500,000 birds, and is hunted in much of its range. The population includes 3 subspecies; the numbers of 2 of these are uncertain, and they should be afforded protection from hunting that would be detrimental to their population. The 2 subspecies of concern tend to concentrate in the eastern part of the Great Plains during fall and spring and to winter along the Gulf Coast in Texas. This paper uses the limited information availahle ahout the Gulf Coast subpopulation in a model. We included in the model 5 input parameters: population size, annual survival rate in absence of hunting. the number of birds taken by hunters, the extent of additivity of hunting mortality, and recruitment rate, measured as the fraction of juveniles in the winter population. Using 3 widely ranging estimates of each parameter, we examined the general behavior of the simulated population. Realistic population projections occurred with medium (60,000) or large (166,000) population sizes, low (2.000) or moderate (4,000) harvests, and recruitment rates of 0.07 and 0.11. All values of survival in the absence of hunting and additivity of hunting yielded some realistic projections. Results of modeling suggest that the variables warranting closer monitoring are population size and recruitment rate.

zx The effects of bleaching and hurricanes on coral reefs in 2005 varied across the region and within countries. zx Some countries experienced intense widespread coral bleaching down to 35 m, while the effects of increased water temperatures were moderate to low in others. zx Coral mortality rates were low on average; most corals recovered quickly when water temperatures dropped. zx Greater human and financial resources are needed to monitor and effectively combat the effects of natural disasters. zx Regular monitoring and analysis of data are essential components of sound management strategies for sustainable environmental management and economic growth. Coral bleaching during the hot summer of 2005 hit the reefs of the Northern Caribbean

We study a one patch model using Ricker's equation, xn+l = xner-xn, r ~ 0. We reproduce some results that Hastings ( 1993) obtained by coupling two discrete time logistic equations. Multiple attractors could occur with dispersion where there is only one attractor without dispersion. The boundary of the basins of attraction of the attractors can be fractal in nature. This makes prediction of the asymptotic behavior of most initial conditions difficult to analyze. Furthermore, we study the same model using Ricker's equation. We show that the qualitative nature of the results for a system of difference equations with dispersion depends on the form of the local dynamics.

Long-lived marine megavertebrates (e.g. sharks, turtles, mammals, and seabirds) are inherently vulnerable to anthropogenic mortality. Although some mathematical models have been applied successfully to manage these animals, more detailed treatments are often needed to assess potential drivers of population dynamics. In particular, factors such as age-structure, density-dependent feedbacks on reproduction, and demographic stochasticity are important for understanding population trends, but are often difficult to assess. Lemon sharks (Negaprion brevirostris) have a pelagic adult phase that makes them logistically difficult to study. However, juveniles use coastal nursery areas where their densities can be high. Thus, we use a stage-structured, Markov-chain stochastic model to describe lemon shark population dynamics from a 17-year longitudinal dataset at a coastal nursery area at Bimini, Bahamas. We found that the interaction between delayed breeding and demographic stochasticity accounts for 33 to 49% of the variance. Demographic stochasticity contributed all random effects in this model, suggesting that the existence of unmodeled environmental factors may be driving the majority of interannual population fluctuations. In addition, we are able

Question: How might global climate change affect American pika (Ochotona princeps) metapopulation dynamics in the Great Basin, and how would such effects impact evolutionary dynamics of dispersal? Mathematical methods: A structured, semi-discrete, mechanistic metapopulation model in which patch age is the structuring variable. We apply adaptive dynamics for the evolutionary analysis and derive an invasion fitness proxy for this model setting. Key assumptions: Global climate change potentially alters the probability of patch extinction, dispersal costs, mortality, and fecundity. Births and immigration occur at discrete points in time. Deaths and emigration occur continuously over time. We model 'average' patch dynamics. Results: Potentially viable metapopulations nevertheless can be destined for extinction via evolutionary suicide driven by climatic forcing. Specifically, selection can drive down dispersal rates in viable metapopulations, degrading colonization rates and increasing extinction rates to the point where the metapopulation crashes. Conclusions: Exclusive reliance on ecological dynamics without this evolutionary perspective would miss the phenomenon identified here. This result arises in realistic ranges of parameters and therefore generates a testable hypothesis with potential applications to long-term metapopulation sustainability.

In this paper, a mathematical model consisting of a prey-predator involving a prey refuge and infectious disease in the predator has been proposed and analyzed. Two types of functional responses are used to describe the feeding of the predator on the available prey. The existence, uniqueness and boundedness of the solution of the system are discussed. The dynamical behavior of the system has been investigated locally as well as globally using suitable Lyapunov function. The persistence conditions of the system are established. Local bifurcation near the equilibrium points has been investigated. The Hopf bifurcation conditions around the positive equilibrium point are derived. Finally, numerical simulations are carried out to specify the control parameters and confirm the obtained results Keywords: Prey-Predator, Disease, Refuge, Stability, Bifurcation.

We present a spatially explicit population model for analysing the expansion of brown bears (Ursus arctos) after the reintroduction program in central Austria. The model is based on field investigations into brown bears in Austria and Slovenia and on current knowledge of brown bears. The landscape of the eastern Alps is represented by a GIS-derived raster map defining local habitat suitability and five major spatial barriers to dispersal. The population model follows the fate of individual bears and simulates reproduction, dispersal, home range establishment, and mortality in annual time steps. We indirectly adjust unknown or uncertain model parameters with 10-year data on the number of females with cubs in central Austria and determine key variables of population dynamics, such as population sizes and growth rates within different population nuclei, dispersal distances, or mortality rates, for model parameterisations that reproduce the data on females with cubs. We estimated a current (1996)(1997)(1998)(1999)(2000) growth rate of the population in Austria and adjacent parts of Italy of some 14%; a high proportion of this growth was due to immigration from Slovenia. Consequently, the growth rate of the subpopulation in central Austria, which probably is isolated functionally (i.e., no exchange of females) from the nuclei along the Austrian-Slovenian border, yielded some 7%. This subpopulation may comprise seven residents, and we estimated for females a 33% risk of extinction during the 1992-2000 period. Validation and confirmation of our model results with data on bear densities that were not used for model construction and parameterisation supported our findings. The high female mortality rates, together with the vulnerability of the small population to chance events (i.e., demographic stochasticity), are the most pressing threat for the population in the eastern Alps. Our approach could be widely applied for analysing dynamics of rare and endangered species in which the paucity of data precludes an appraisal of the state of the population using standard methods.

We consider an age-size structured cell population model based on the cell cycle length. The model is described by a first order partial differential equation with initial-boundary conditions. Using the theory of semigroups of positive operators we establish new criteria for an asynchronous exponential growth of solutions to such equations. We discuss the question of exponential size growth of cells. We study in detail a constant size growth model and a model with target size division. We also present versions of the model when the population is heterogeneous.

We consider a class of structured cell population models described by a first order partial differential equation perturbed by a general birth operator which describes in a unified way a wide class of birth phenomena ranging from cell division to the McKendrick model. Using the theory of positive stochastic semigroups we establish new criteria for an asynchronous exponential growth of solutions to such equations.

Shawn Crimmins); we thank them for their support. Quantifying and estimating wildlife population sizes is a foundation of wildlife management. However, many carnivore species are cryptic , leading to innate difficulties in estimating their populations . Given the difficulties in enumerating carnivore populations, wildlife managers often rely on demographic data collected from harvested animals to estimate population parameters such as survival, recruitment, and population growth (e.g., . In Wisconsin, managers at the Department of Natural Resources (WDNR) use accounting style analyses to estimate wildlife populations. The drawback of these models is their lack of scientific rigor (i.e., they provide no estimates of error or variance), and over time they can lose track of the population without independent estimates. For example, the accounting style estimate underestimated Wisconsin's black bear (Ursus americanus) population by 2/3 compared to an independent estimate from tetracycline marking (MacFarland 2009), and there are similar concerns for the current furbearer population estimates. Over the past decade there have been advances in many statistical models, including rigorous statistical models that use age-at-harvest (AAH) data and integrate auxiliary data (usually other harvest or demographic data) to accurately estimate populations. Models using AAH data are often most practical

We give a direct proof of well-posedness of solutions to general selection-mutation and structured population models with measures as initial data. This is motivated by the fact that some stationary states of these models are measures and not L 1 functions, so the measures are a more natural space to study their dynamics. Our techniques are based on distances between measures appearing in optimal transport and common arguments involving Picard iterations. These tools provide a simplification of previous approaches and are applicable or adaptable to a wide variety of models in population dynamics.

Cultivated tomato is known to be relatively low in genetic diversity. This is a result of microevolutionary processes such as founder events, genetic bottlenecks, and intense selection. For these reasons, a computational approach to predicting single nucleotide polymorphisms (SNPs) is valuable to direct laboratory efforts toward regions more likely to yield results. We have developed a method to screen an entire NCBI Unigene set for potential SNPs using SEAN (Huntley, 2003). Predictions are based on established criteria: A window on either side of the predicted SNP must be identical for all sequences in the alignment, at least two sequences agreeing on each of a minimum of two polymorphisms, etc. Polymorphisms were further examined in the context of the cultivars and clones in which they were identified. Using this method, we discovered 2,527 potential SNPs among 764 clusters from the unigene set. We are in the process of verifying these polymorphisms in the laboratory.

Coastal habitats (e.g., seagrass beds, shallow mud, and sand flats) strongly influence survival, growth, and reproduction of marine fish and invertebrate species. Many of these species have declined over the past decades, coincident with widespread degradation of coastal habitats, such that an urgent need exists to model the quantitative value of coastal habitats to their population dynamics. For exploited species, demand for habitat considerations will increase as fisheries management contends with habitat issues in stock assessments and management in general moves toward a more ecosystem-based approach. The modeling of habitat function has, to date, been done on a case-by-case basis involving diverse approaches and types of population models, which has made it difficult to generalize about methods for incorporating habitat into population models. In this review, we offer guiding concepts for how habitat effects can be incorporated in population models commonly used to simulate the population dynamics of fish and invertebrate species. Many marine species share a similar life-history strategy as long-lived adults with indeterminate growth, high fecundity, a planktonic larval form, and benthic juveniles and adults using coastal habitats. This suite of life-history traits unites the marine species across the case studies, such that the population models can be adapted for other marine species. We categorize population models based on whether they are static or dynamic representations of population status, and for dynamic, further into unstructured, age/size class structured, and individual-based. We then use examples, with an emphasis on exploited species, to illustrate how habitat has been incorporated, implicitly (correlative) and explicitly (mechanistically), into each of these categories. We describe the methods used and provide details on their implementation and utility to facilitate adaptation of the approaches for other species and systems. We anticipate that our review can serve as a stimulus for more widespread use of population models to quantify the value of coastal habitats, so that their importance can be accurately realized and to facilitate cross-species and cross-system comparisons. Lipcius et al. Quantitative evaluation of habitat effects in population dynamics will increasingly be needed for traditional stock assessments, ecosystem-based management, conservation of at-risk habitats, and recovery of overexploited stocks that rely on critical coastal habitats during their life cycle.

We examined the asymptotic rate of population extinction ; when the population experiences density-dependent population regulation, demographic stochasticity, and environmental stochasticity. We assume discrete-generation population dynamics, in which some parameters fluctuate between years. The fluctuation of parameters can be of any magnitude, including both fluctuation traditionally treated as diffusion processes and fluctuation from catastrophes within a single scheme. We develop a new approximate method of calculating the asymptotic rate of population extinction per year, ;= 0 exp(&x) u(x) dx, where u(x) is the stationary distribution of adult population size from the continuous-population model including environmental stochasticity and population-regulation but neglecting demographic stochasticity. The method can be regarded as a perturbation expansion of the transition operator for population size. For several sets of population growth functions and probability distributions of environmental fluctuation, the stationary distributions can be calculated explicitly. Using these, we compare the predictions of this approximate method with that using a full transition operator and with the results of a direct Monte Carlo simulation. The approximate formula is accurate when the intrinsic rate of population increase is relatively large, though the magnitude of environmental fluctuation is also large. This approximation is complementary to the diffusion approximation.

The field of prevention and control of wildlife damage is changing and evolving along with clientele needs, pressures from user and non-user groups, and other factors. A theoretical overview of the field may offer an action model regarding changing trends and potential responses. I propose that three things happen every time a wildlife damage problem occurs: 1) A human activity, desire, or need is interfered with, 2) the experience footers an opinion about a wild animalusually negative, and 3) a decision is made to tolerate the situation or to control it. If control is selected, availability and effectiveness of prevention and control techniques become feedback mechanisms that may affect tolerance of damage; threshold levels at which control is initiated; and opinions about damage control, wild animals, and natural systems. Wildlife damage professionals might use these concepts in responding to enhance the public understanding and professional image of the wildlife damage field.

Field studies documented increased mortality, adverse health effects, and reproductive failure in common bottlenose dolphins Tursiops truncatus following the Deepwater Horizon (DWH) oil spill. In order to determine the appropriate type and amount of restoration needed to compensate for losses, the overall extent of injuries to dolphins had to be quantified. Simply counting dead individuals does not consider long-term impacts to populations, such as the loss of future reproductive potential from mortality of females, or the chronic health effects that continue to compromise survival long after acute effects subside. Therefore, we constructed a sex-and agestructured model of population growth and included additional class structure to represent dolphins exposed and unexposed to DWH oil. The model was applied for multiple stocks to predict injured population trajectories using estimates of post-spill survival and reproductive rates. Injured trajectories were compared to baseline trajectories that were expected had the DWH incident not occurred. Two principal measures of injury were computed: (1) lost cetacean years (LCY); the difference between baseline and injured population size, summed over the modeled time period, and (2) time to recovery; the number of years for the stock to recover to within 95% of baseline. For the dolphin stock in Barataria Bay, Louisiana, the estimated LCY was substantial: 30 347 LCY (95% CI: 11 511 to 89 746). Estimated time to recovery was 39 yr (95% CI: 24 to 80).

We give a survey of partial least squares regression with one y-variable from a theoretical point of view. Some general comments are made on the motivation as seen by a statistician for this kind of studies, and the concept of soft modelling is criticized from the same angle. Various aspects of the PLS algorithm are considered, and the population PLS model is defined. Asymptotic properties of the prediction error are briefly discussed, and the relation to other regression methods are commented upon. Results indicating positive and negative properties of PLSR are mentioned, in particular the recent result of Butler, Denham and others which seem to show that PLSR can not be an optimal regression method in any reasonable way. The only possible path left towards some kind of optimality, seems then to be through first trying to find a good motivation for the population model and then possibly finding an optimal estimator under this model. Some results on this are sketched.

We evaluated the utility of combining metapopulation models with landscape-level forest-dynamics models to assess the sustainability of forest management practices. We used the Brown Creeper (Certhia americana) in the boreal forests of northern Ontario as a case study. We selected the Brown Creeper as a potential indicator of sustainability because it is relatively common in the region but is dependent on snags and old trees for nesting and foraging; hence, it may be sensitive to timber harvesting. For the modeling we used RAMAS Landscape, a software package that integrates RAMAS GIS, population-modeling software, and LAN-DIS, forest-dynamics modeling software. Predictions about the future floristic composition and structure of the landscape under a variety of management and natural disturbance scenarios were derived using LANDIS. We modeled eight alternative forest management scenarios, ranging in intensity from no timber harvesting and a natural fire regime to intensive timber harvesting with salvage logging after fire. We predicted the response of the Brown Creeper metapopulation over a 160-year period and used future population size and expected minimum population size to compare the sustainability of the various management scenarios. The modeling methods were easy to apply and model predictions were sensitive to the differences among management scenarios, indicating that these methods may be useful for assessing and ranking the sustainability of forest management options. Primary concerns about the method are the practical difficulties associated with incorporating fire stochasticity in prediction uncertainty and the number of model assumptions that must be made and tested with sensitivity analysis. We wrote new software to help quantify the contribution of landscape stochasticity to model prediction uncertainty.

Potentially adverse human and environmental effects due to hormone mimicry of environmental estrogens are a matter of current concern. Environmental estrogens belong to the so-called endocrine active compounds (EAC), which alter signalling processes of the endocrine system leading to a broad range of effects during foetal and postnatal development, puberty, adulthood, and aging. A number of synthetic chemicals as well as several plant-derived compounds, so-called phytoestrogens, are known to have weak estrogenic activity. The present study is part of the risk assessment of the weak environmental estrogens daidzein, p-tert-octylphenol, and bisphenol A. The isoflavone daidzein is an important phytoestrogen with respect to dietary exposure (soy beans and soy products). p-tert-Octylphenol and bisphenol A are industrial chemicals. The toxicokinetics and the bioavailability of these three substances in female DA/Han rats after oral and single intravenous application were investigated by the use of population models accounting for the differences in the individual metabolism. Furthermore, populations of pregnant and non-pregnant rats are compared.

This paper addresses the local and global stability of n-dimensional Lotka-Volterra systems with distributed delays and instantaneous negative feedbacks. Necessary and sufficient conditions for local stability independent of the choice of the delay functions are given, by imposing a weak nondelayed diagonal dominance which cancels the delayed competition effect. The global asymptotic stability of positive equilibria is established under conditions slightly stronger than the ones required for the linear stability. For the case of monotone interactions, however, sharper conditions are presented. This paper generalizes known results for discrete delays to systems with distributed delays. Several applications illustrate the results.