Maximum Population Size Research Articles

People of the Sea, or of the Soil? How the Balance of Marine and Terrestrial Resource Availability Informs Maximum Population on Four Polynesian Islands

AbstractMost studies of the food resource potential of early Polynesian populations focus exclusively on agricultural potential, and specifically starchy staples, despite the importance of marine resources to the Polynesians. To more accurately estimate total precontact food resource availability, we characterized the terrestrial and near-shore marine environments of four Polynesian islands: Moʻorea, Maupiti, Mangareva and Taravai. We estimate the agricultural potential of each island after a consideration of the ecological factors related to productivity. We also estimate the productivity of the near-shore marine environment as a function of surface area. Using a range of fish yield scenarios from Pacific subsistence systems we scale relative measures of faunal food biomass derived from local archaeological excavations to generate absolute biomass estimates. We convert our estimates of agricultural and fished/foraged food potential into a maximum population size based on calorie availability. Moʻorea’s fertile valleys and wetlands would potentially generate sufficient food energy, mostly from starchy staples, to support a considerable population, many times larger than the other islands. In the most likely fish yield scenario Moʻorea gets only 0.4% of its calories from marine sources, while the others range from 7–18%. These relative inputs reflect the vast superiority in productivity (in terms of calories per km2) of agricultural vs near-shore marine zones. We also find that population size on islands with smaller fringing reefs, such as Moʻorea, may have been limited by a lack of fish protein. Moʻorea’s maximum population is approximately halved when diet breadth is considered.

An empirical study on sample size for the central limit theorem using Japanese firm data

AbstractIn statistics classes, the central limit theorem has been demonstrated using simulation‐based illustrations. Known population distributions such as a uniform or exponential distribution are often used to consider the behavior of the sample mean in simulated samples. Unlike such simulations, a number of real‐data‐based simulations are here implemented in which the populations are empirical distributions of data selected from Japanese firms. The dataset chosen contains 38 variables familiar to business students, such as sales and assets. The maximum population size of the variables is 2243. One thousand samples with replacement are selected for specific variable–sample size combinations. Hypothesis testing results indicate that the normality hypothesis for the sample mean is rejected for 31 variables at the 0.1% level even with a sample size of 500. It is emphasized that the data for these variables indicate that this should not be a surprise, and emphasize the importance of looking at data.

Demographic insights for the endangered Apennine yellow-bellied toad in the Pollino National Park (Southern Italy). A five-year Capture-Mark-Recapture study

Investigating population structure, parameters, and growth over time is vital for conserving endangered taxa like the Apennine yellow-bellied toad (Bombina variegata pachypus) in Italy. The Apennine yellow-bellied toad faces habitat loss or degradation, disease, and climate change threats. Our study delves into the population dynamics of this endemic amphibian by monitoring populations in two breeding sites within the Pollino National Park (Southern Italy) using a five-year Capture-Mark-Recapture (CMR) approach. With a particular emphasis on demographic parameters such as population size, detectability, survival, temporary emigration probability, and body condition index, the research aims to contribute to understanding population dynamics and inform conservation efforts. We used two CMR models to estimate these parameters: Jolly-Seber with POPAN parametrisation and Pollock's robust design with Huggins' estimator. Results showed variation in body size between males and females, challenging previous findings in south-central Italy. For both populations, demographic data indicate high annual adult survival, fidelity to the breeding areas, support for no movement, and minimal trap response. Abundance over the years reveals a slight decline in one site and a gradual increase in the other. The estimated maximum population size indicated ∼ 92 animals in one population and ∼ 70 in the other one. Despite the high conservation concern for the Apennine yellow-bellied toad, there remains a dearth of quantitative information on demographic aspects in Southern Italy. The findings underscore the importance of protected areas in biodiversity conservation and contribute to understanding the B. v. pachypus conservation status, suggesting that small, isolated populations may be vulnerable to unpredictable fluctuations, inbreeding depression, and extinction risks. Additionally, the research emphasises the importance of long-term CMR studies to gain insights into population dynamics and develop effective conservation strategies and management practices, particularly in the face of climate changes that may impact both the endemic taxon and its habitat.

The quality and complexity of pairwise maximum entropy models for large cortical populations.

We investigate the ability of the pairwise maximum entropy (PME) model to describe the spiking activity of large populations of neurons recorded from the visual, auditory, motor, and somatosensory cortices. To quantify this performance, we use (1) Kullback-Leibler (KL) divergences, (2) the extent to which the pairwise model predicts third-order correlations, and (3) its ability to predict the probability that multiple neurons are simultaneously active. We compare these with the performance of a model with independent neurons and study the relationship between the different performance measures, while varying the population size, mean firing rate of the chosen population, and the bin size used for binarizing the data. We confirm the previously reported excellent performance of the PME model for small population sizes N < 20. But we also find that larger mean firing rates and bin sizes generally decreases performance. The performance for larger populations were generally not as good. For large populations, pairwise models may be good in terms of predicting third-order correlations and the probability of multiple neurons being active, but still significantly worse than small populations in terms of their improvement over the independent model in KL-divergence. We show that these results are independent of the cortical area and of whether approximate methods or Boltzmann learning are used for inferring the pairwise couplings. We compared the scaling of the inferred couplings with N and find it to be well explained by the Sherrington-Kirkpatrick (SK) model, whose strong coupling regime shows a complex phase with many metastable states. We find that, up to the maximum population size studied here, the fitted PME model remains outside its complex phase. However, the standard deviation of the couplings compared to their mean increases, and the model gets closer to the boundary of the complex phase as the population size grows.

تقدير اعداد المجاميع السكانية لترسة الفرات ملساء الصدفة Rafetus euphraticus في الاهوار الوسطى ( موقع تراث عالمي)

تم تصنيف ترسة الفرات ملساء الصدفة Rafetus euphraticus على أنها مهددة بخطر الانقراض ضمن القائمة الحمراء للاتحاد الدولي لحفظ الطبيعة، ويُعتقد أنها تعرضت لانخفاض كبير في أعدادها مؤخرًا. تقتصر معلومات الأنواع في العراق على عدد قليل من المسوحات السريعة مع القليل من المعلومات التفصيلية عن التربية والتوزيع. هدفت الدراسة الى تقدير اعداد سلاحف الفرات ملساء الصدفة في الأهوار الوسطى باستخدام استقراء بسيط للعدد. تم استخدام طريقة المربع (بحجم 5 كم2 لكل منهما) لتسجيل توزيع سلحفاة الفرات ملساء الصدفة داخل موقع الدراسة وتم إجراء عشرة مسوحات ابتداءا من شهر تشرين الاول 2021 إلى ايلول 2022 باستثناء موسم السبات (كانون الاول وكانون الثانيو شباط). تم تسجيلها داخل المياه عن طريق وضع الشباك في مناطق معينة بالأهوار الوسطى. اقترح الاستقراء البسيط لتعداداتنا لكامل الأهوار الوسطى أن يبلغ الحد الأقصى لحجم المجاميع السكانية 2526.55 فردًا /المساحة الكلية) 219.700 هكتار.( تعتبر الأهوار الوسطى موقعًا مهمًا لـ R. euphraticus حيث تم تسجيل إجمالي 46 فردًا.

Dashing Growth Curves: a web application for rapid and interactive analysis of microbial growth curves

BackgroundRecording and analyzing microbial growth is a routine task in the life sciences. Microplate readers that record dozens to hundreds of growth curves simultaneously are increasingly used for this task raising the demand for their rapid and reliable analysis.ResultsHere, we present Dashing Growth Curves, an interactive web application (http://dashing-growth-curves.ethz.ch/) that enables researchers to quickly visualize and analyze growth curves without the requirement for coding knowledge and independent of operating system. Growth curves can be fitted with parametric and non-parametric models or manually. The application extracts maximum growth rates as well as other features such as lag time, length of exponential growth phase and maximum population size among others. Furthermore, Dashing Growth Curves automatically groups replicate samples and generates downloadable summary plots for of all growth parameters.ConclusionsDashing Growth Curves is an open-source web application that reduces the time required to analyze microbial growth curves from hours to minutes.

Quantifying the variation of Scaly-sided merganser’ population and their divergent response to changes in hydrological connectivity of rivers in a high-latitude water tower

The Scaly-sided Merganser (SSME) is a globally endangered waterbird species, primarily inhabiting rivers. In recognition of its precarious status, it was added to the International Union for Conservation of Nature’s (IUCN) Red List of Threatened Species in 2002. The SSME is highly sensitive to ecological environmental changes driven by changes in hydrological connectivity, particularly within riverine habitats. Changbai Mountain, a high-latitude water tower in the Northeast Asia, is considered one of the most optimal breeding grounds for the SSME worldwide. Its extensive water system and dense primary forest create an environment particularly well-suited for this species. Over the past 40 years, rivers within Changbai Mountain have experienced phases of hydropower development and ecological restoration. These activities have dramatically altered the hydrological connectivity of the area. However, the response of SSME to these changes in aquatic ecology, driven by shifts in hydrological connectivity, remains uncertain. We employed the AutoRegressive Integrated Moving Average (ARIMA) model to analyze changes in the population size of the SSME. Furthermore, the GeoDetector model was used to understand the impact of ecological changes on the maximum population size (MPS) and distribution of SSME in the context of alterations in hydrological connectivity. Our findings reveal that the restoration of hydrological connectivity, a method of ecological restoration, exerts a bidirectional influence on both the distribution and the MPS of SSME. Our findings can be summarized as follows. Firstly, there was a general trend of increase in both the distribution points and population size of the SSME. Secondly, the contribution of driving factors to the MPS of SSME was ranked in the following order: temperature > Connectivity Status Index (CSI) > river width > fish abundance > river depth > velocity > altitude > forest type. Thirdly, the impacts on the distribution and MPS of SSME were not due to a single factor, but rather a complex interplay of multiple factors. Finally, the construction of small hydropower stations significantly disrupted the hydrological connectivity of rivers, thereby altering the natural habitat of the SSME. The reduction in fish population, resulting from the loss of hydrological connectivity, adversely affected the MPS. Conversely, an increase in water temperature due to loss of hydrological connectivity positively impacted the MPS. However, these effects displayed heterogeneity across different rivers. Our study suggests that the construction of gravel dams may be a suitable approach in certain sections of the river, with a recommended height limit of 1.5 m. This research provides valuable insights for managers, offering a sustainable foundation for future energy planning and ecological restoration efforts.

Receptive field sizes and neuronal encoding bandwidth are constrained by axonal conduction delays.

Studies on population coding implicitly assume that spikes from the presynaptic cells arrive simultaneously at the integrating neuron. In natural neuronal populations, this is usually not the case-neuronal signaling takes time and populations cover a certain space. The spread of spike arrival times depends on population size, cell density and axonal conduction velocity. Here we analyze the consequences of population size and axonal conduction delays on the stimulus encoding performance in the electrosensory system of the electric fish Apteronotus leptorhynchus. We experimentally locate p-type electroreceptor afferents along the rostro-caudal body axis and relate locations to neurophysiological response properties. In an information-theoretical approach we analyze the coding performance in homogeneous and heterogeneous populations. As expected, the amount of information increases with population size and, on average, heterogeneous populations encode better than the average same-size homogeneous population, if conduction delays are compensated for. The spread of neuronal conduction delays within a receptive field strongly degrades encoding of high-frequency stimulus components. Receptive field sizes typically found in the electrosensory lateral line lobe of A. leptorhynchus appear to be a good compromise between the spread of conduction delays and encoding performance. The limitations imposed by finite axonal conduction velocity are relevant for any converging network as is shown by model populations of LIF neurons. The bandwidth of natural stimuli and the maximum meaningful population sizes are constrained by conduction delays and may thus impact the optimal design of nervous systems.

Population status of Oriental Darter Anhinga melanogaster Pennant, 1769 (Aves: Suliformes: Anhingidae) in Keoladeo National Park, India

Oriental Darter Anhinga melanogaster belonging to the family Anhingidae is a globally ‘Near Threatened’ species occurring in southern and southeastern Asia. The Keoladeo National Park (KNP), Bharatpur, Rajasthan is also known to harbour some population of this species where this study was carried out to assess the population status. Eight wetland blocks were surveyed in different seasons from January 2021 to December 2021 in KNP. The average population of Oriental Darter was found to be maximum (112.8 ±43.8 SE, n = 8) in the winter season, whereas the least (1.8±1.1 SE, n = 8) in the summer season. The maximum population size of darters among the eight wetland blocks was witnessed in Block D of KNP harbouring a mean population of 84.3±20.2 SE (n = 12), whereas the minimum population occurred in Block F (0.3±0.16 SE, n = 12). However, seasonally the total number of darters recorded in all eight wetland blocks during winter, summer and monsoon was 287, 83, and 212, respectively. The findings of the current study reveal that the KNP sustains a viable resident population of Oriental Darters. Further studies are therefore recommended for understanding the seasonal movement pattern and other ecological aspects for its long-term conservation planning.

Effects of culture conditions on the growth rate and population size of Apocyclops dengizicus (Arthropoda: Copepoda)

The study aimed to investigate the growth rate and the population size of the copepod Apocyclops dengizicus under different culture conditions of salinity, temperature, and diet. Five salinities, four levels of temperature, and four diet ratios of baker’s yeast and the microalgae were employed for a 20-day experiment. The results showed that A. dengizicus could survive in every experimental concentration of salinity after 20 days of culture, of which the highest growth rate and the largest population size were recorded at a salinity of 15 ppt with values of 0.26 ± 0.01d-1 and 1221 ± 270 individuals, respectively. As for temperature, the A. dengizicus population thrived best at 34°C, with a growth rate reaching 0.29 ± 0.01d-1 and a maximum population size of 2097.0 ± 193.29 individuals obtained at the end of the experiment. Moreover, a diet with 25% Saccharomyces cerevisiae and 75% Chlorella vulgaris showed the best population development (0.25 ± 0.01d-1, 997.5 ± 1 92.09 individuals).

Extracting accurate parameters of photovoltaic cell models via elite learning adaptive differential evolution

Photovoltaic power generation is becoming increasingly vital as the global call for environmental protection rises. Establishing an equivalent model for a photovoltaic cell and extracting accurate parameters of the model have a crucial role in supporting the fault diagnosis, performance analysis, and maximum power point tracking of the photovoltaic system. To better tackle this problem, an improved algorithm, i.e., Elite Learning Adaptive Differential Evolution (ELADE) is proposed. Four strategies, including the parameters adaptive strategy, elite learning strategy, chaotic last-place elimination strategy, and population size reduction strategy are combined to boost the exploitation process of differential evolution to effectively balance the ability to avoid local optimum and accelerate convergence speed. The suggested ELADE is applied to five photovoltaic cell models. Experimental results show that the maximum population size affects the performance of ELADE, and a recommended value 50 can promote it to achieve the most accurate and reliable parameters in comparison with other peer algorithms. Its superiority is further confirmed by two statistical test methods, including the Friedman for mean root mean square error (RMSE) values and Wilcoxon’s rank-sum of RMSE values for each independent run. Besides, the influence of different strategies on ELADE is also empirically investigated, showing that the parameters adaptive strategy contributes the most.

New Blind Image Moments Watermarking Method Based on Evolutionary Optimization of Embedding Parameters

In image watermarking, the locations where the watermark is embedded in the frequency domain and the embedding strength influence the overall performance of the blind watermarking procedure. The present paper aims to propose a new blind watermarking method based on the dither modulation by developing an automatic selection of the optimum embedding parameters that guarantee high-quality watermarked images and low bit error rates during the extraction process. The proposed automatic search method for the best discrete moments subsets is based on an evolutionary algorithm and adopts a specific coding strategy with a group of genes representing the embedding positions. The second part of the chromosome is reserved for the embedding strength coding, followed by the application of different evolutionary operators on the evolution pool. Our study explores the impact of maximum generation, population size, and cutting-point positions with different crossover and mutation rates. The performances under different attack conditions are evaluated, and a comparative study is established with other conventional selection methods and other discrete transforms. Results show that our proposed optimization algorithm baptized EWIMps achieves the best trade-off between robustness and imperceptibility with a peak signal-to-noise ratio varying from 28.33 dB to 59.87 dB and a normalized cross-correlation value from 0.707 to 1.

Research on Coal Dust Wettability Identification Based on GA-BP Model.

Aiming at the problems of the influencing factors of coal mine dust wettability not being clear and the identification process being complicated, this study proposed a coal mine dust wettability identification method based on a back propagation (BP) neural network optimized by a genetic algorithm (GA). Firstly, 13 parameters of the physical and chemical properties of coal dust, which affect the wettability of coal dust, were determined, and on this basis, the initial weight and threshold of the BP neural network were optimized by combining the parallelism and robustness of the genetic algorithm, etc., and an adaptive GA−BP model, which could reasonably identify the wettability of coal dust was constructed. The extreme learning machine (ELM) algorithm is a single hidden layer neural network, and the training speed is faster than traditional neural networks. The particle swarm optimization (PSO) algorithm optimizes the weight and threshold of the ELM, so PSO−ELM could also realize the identification of coal dust wettability. The results showed that by comparing the four different models, the accuracy of coal dust wettability identification was ranked as GA−BP > PSO−ELM > ELM > BP. When the maximum iteration times and population size of the PSO algorithm and the GA algorithm were the same, the running time of the different models was also different, and the time consumption was ranked as ELM < BP < PSO−ELM < GA−BP. The GA−BP model had the highest discrimination accuracy for coal mine dust wettability with an accuracy of 96.6%. This study enriched the theory and method of coal mine dust wettability identification and has important significance for the efficient prevention and control of coal mine dust as well as occupational safety and health development.

Microevolution of CG23-I Hypervirulent Klebsiella pneumoniae during Recurrent Infections in a Single Patient.

ABSTRACTCG23-I lineage constitutes the majority of hypervirulent Klebsiella pneumoniae. A diabetic patient suffered six episodes of infections caused by CG23-I K. pneumoniae. A total of nine isolates were collected in 2020. We performed whole-genome sequencing to elucidate the within-patient evolution of CG23-I K. pneumoniae. The maximum pairwise difference among the nine longitudinally collected isolates was five single nucleotide polymorphisms. One of the mutations was at the Asp87 position of GyrA. Four indels were identified, including an initiator tRNAfMet duplication, a tRNAArg deletion, a 7-bp insertion, and a 22-bp deletion. All 9 isolates had the genomic features of CG23-I K. pneumoniae, a chromosome-borne ICEKp10, and a large virulence plasmid. The carriage of a complete set of genes for the biosynthesis of colibactin by ICEKp10 gave the nine isolates an ability to cause DNA damage to RAW264.7 cells. Compared with the initial isolate, the last isolate with an additional copy of initiator tRNAfMet grew faster in a nutrient-limiting condition and exhibited enhanced virulence in BALB/c mice. Collectively, we characterized the within-patient microevolution of CG23-I K. pneumoniae through an in-depth comparison of genome sequences. Using the in vitro experiments and mouse models, we also demonstrated that these genomic alterations endowed the isolates with advantages to pass through in vivo selection.IMPORTANCE CG23-I is a significant lineage of hypervirulent Klebsiella pneumoniae. This study characterizes the within-patient microevolution of CG23-I K. pneumoniae. Selective pressures from continuous use of antibiotics favored point mutations contributing to bacterial resistance to antibiotics. The duplication of an initiator tRNAfMet gene helped CG23-I K. pneumoniae proliferate to reach a maximal population size during infections. For longer persistence inside a human host, the large virulence plasmid evolved with more flexible control of replication through duplication of the iteron-1 region. With the genomic alterations, the last isolate had a growth advantage over the initial isolate and exhibited enhanced virulence in BALB/c mice. This study gives us a deeper understanding of the genome evolution during the within-patient pathoadaptation of CG23-I K. pneumoniae.

A Local Approach to Better Understand the Spread and Population Growth of the Monk Parakeet as an Invasive Species

Invasive exotic species are currently a topic of interest for environmental management agencies and the media. This is due to the socio-economic and environmental problems that they are causing or may cause. The Monk Parakeet is a clear example of this, especially in some large cities, where populations are growing quickly, and their distribution continues to expand. In our study, we focused on a population that has been closely monitored during the last 25 years to understand its growth and change on a local scale to determine the maximum sustainable population size in the invaded area and to check when this population began to act as a source of new breeding colonies to adjacent areas. The first breeding of the species occurred in 2002, and from then, the average growth rate (r) of the population was 0.191 until 2016, when it stabilized and declined slightly (r = −0.043). The maximum growth rate occurred during the years 2002 and 2007 and was 0.314. The results obtained give us information about the carrying capacity of the study area, allowing us to explain the dispersal process of the species to neighbouring areas, with populations that have reached maximum size serving as sources of individuals dispersing to suitable areas. In our study area, the species shows a strong preference for building its nests in palm trees and electric utility structures. Our study’s local focus on studying the population dynamics of an invasive species may allow us to understand the increased range of the species on a larger scale, which is necessary in order to be able to design appropriate and effective management strategies.

Modeling total predation to avoid perverse outcomes from cat control in a data-poor island ecosystem.

Data hungry, complex ecosystem models are often used to predict the consequences of threatened species management, including perverse outcomes. Unfortunately, this approach is impractical in many systems, which have insufficient data to parameterize ecosystem interactions or reliably calibrate or validate such models. Here we demonstrate a different approach, using a minimum realistic model to guide decisions in data- and resource-scarce systems. We illustrate our approach with a case-study in an invaded ecosystem from Christmas Island, Australia, where there are concerns that cat eradication to protect native species, including the red-tailed tropicbird, could release meso-predation by invasive rats. We use biophysical constraints (metabolic demand) and observable parameters (e.g. prey preferences) to assess the combined cat and rat abundances which would threaten the tropicbird population. We find that the population of tropicbirds cannot be sustained if predated by 1607 rats (95% credible interval (CI) [103, 5910]) in the absence of cats, or 21 cats (95% CI [2, 82]) in the absence of rats. For every cat removed from the island, the bird's net population growth rate improves, provided that the rats do not increase by more than 77 individuals (95% CI [30, 174]). Thus, in this context, one cat is equivalent to 30-174 rats. Our methods are especially useful for on-the-ground predator control in the absence of knowledge of predator-predator interactions, to assess whether 1) the current abundance of predators threatens the prey population of interest, 2) managing one predator species alone is sufficient to protect the prey species given potential release of another predator, and 3) control of multiple predator species is needed to meet the conservation goal. Our approach demonstrates how to use limited information for maximum value in data-poor systems, by shifting the focus from predicting future trajectories, to identifying conditions which threaten the conservation goal. This article is protected by copyright. All rights reserved.

A fluid approach to total-progeny-dependent birth-and-death processes

We introduce a class of branching processes in which the reproduction or lifetime distribution at a given time depends on the total cumulative number of individuals who have been born in the population until that time. We focus on a continuous-time version of these processes, called total-progeny-dependent birth-and-death processes, and study some of their properties through the analysis of their deterministic (fluid) approximation. These properties include the maximum population size, the total progeny size at extinction, the time to reach the maximum population size, and the time until extinction. As the fluid approximation does not allow us to determine the time until extinction directly, we propose several methods to complement this approach. We also use the deterministic approach to study the behavior of the processes as we increase the magnitude of the individual’s birth rate.

Revisiting the Evolutionary History of Pigs via De Novo Mutation Rate Estimation in A Three-generation Pedigree

The mutation rate used in the previous analyses of pig evolution and demographics was cursory and hence invited potential bias in inferring evolutionary history. Herein, we estimated the de novo mutation rate of pigs as 3.6 × 10−9 per base per generation using high-quality whole-genome sequencing data from nine individuals in a three-generation pedigree through stringent filtering and validation. Using this mutation rate, we re-investigated the evolutionary history of pigs. The estimated divergence time of ∼ 10 kiloyears ago (KYA) between European wild and domesticated pigs was consistent with the domestication time of European pigs based on archaeological evidence. However, other divergence events inferred here were not as ancient as previously described. Our estimates suggest that Sus speciation occurred ∼ 1.36 million years ago (MYA); European wild pigs split from Asian wild pigs only ∼ 219 KYA; and south and north Chinese wild pigs split ∼ 25 KYA. Meanwhile, our results showed that the most recent divergence event between Chinese wild and domesticated pigs occurred in the Hetao Plain, northern China, approximately 20 KYA, supporting the possibly independent domestication in northern China along the middle Yellow River. We also found that the maximum effective population size of pigs was ∼ 6 times larger than estimated before. An archaic migration from other Sus species originating ∼ 2 MYA to European pigs was detected during western colonization of pigs, which may affect the accuracy of previous demographic inference. Our de novo mutation rate estimation and its consequences for demographic history inference reasonably provide a new vision regarding the evolutionary history of pigs.

Optimisation of the total population size for logistic diffusive equations: bang-bang property and fragmentation rate

In this article, we give an in-depth analysis of the problem of optimising the total population size for a standard logistic-diffusive model. This optimisation problem stems from the study of spatial ecology and amounts to the following question: assuming a species evolves in a domain, what is the best way to spread resources in order to ensure a maximal population size at equilibrium? In recent years, many authors contributed to this topic. We settle here the proof of two fundamental properties of optimisers: the bang-bang one, which had so far only been proved under several strong assumptions, and the other one is the fragmentation of maximisers. We prove the bang-bang property in all generality using a new spectral method. The technique introduced to demonstrate the bang-bang character of optimisers can be adapted and generalised to many optimisation problems with other classes of bilinear optimal control problems where the state equation is semilinear and elliptic. We comment on it in a conclusion section. Regarding the geometry of maximisers, we exhibit a blow-up rate for the BV-norm of maximisers as the diffusivity gets smaller: if is an orthotope and if is an optimal control, then The proof of this results relies on a very fine energy argument.

Aggressiveness of Spanish Isolates of Xylella fastidiosa to Almond Plants of Different Cultivars Under Greenhouse Conditions.

The aggressiveness of Spanish isolates of Xylella fastidiosa, representing different sequence types, were studied in almond plants of several cultivars by means of the dynamics of the population levels and symptoms, colonization and spread, and dose-effect relationships. Pathogen dynamics in almond plants under greenhouse conditions showed doubling times of 2.1 to 2.5 days during the exponential growth phase, with a maximum population size of about 35 days postinoculation (dpi). Differences in patterns in population dynamics were observed between sap and xylem tissue after the exponential growth, as population levels in the xylem tissue remained stable while viable cells in sap decreased. Population levels were higher in two upward zones than in the downward zone with respect to the inoculation area. The first symptoms were observed between 20 and 60 dpi, and disease severity increased over time at doubling times of 30 days, with a maximum observed at 120 dpi. Strains tested showed differences in population levels in the cultivars studied and were able to spread with different intensity from contaminated plant parts to new growing shoots after pruning. Two almond isolates showed different performance in dose-effect relationships when inoculated in cultivar Avijor. Whereas IVIA 5387.2 reached high population levels but showed high median effective dose (ED50) and minimal infective dose (MID) values, IVIA 5901.2 showed low population levels and low ED50 and MID values. This study has implications for the epidemiology of X. fastidiosa in almond crops, estimating doubling times of the pathogen in planta and of symptom development and showing differences in aggressiveness between strains.