Self-optimization, community stability, and fluctuations in two individual-based models of biological coevolution

We compare and contrast the long-time dynamical properties of two individual-based models of biological coevolution. Selection occurs via multispecies, stochastic population dynamics with reproduction probabilities that depend nonlinearly on the population densities of all species resident in the community. New species are introduced through mutation. Both models are amenable to exact linear stability analysis, and we compare the analytic results with large-scale kinetic Monte Carlo simulations, obtaining the population size as a function of an average interspecies interaction strength. Over time, the models self-optimize through mutation and selection to approximately maximize a community fitness function, subject only to constraints internal to the particular model. If the interspecies interactions are randomly distributed on an interval including positive values, the system evolves toward self-sustaining, mutualistic communities. In contrast, for the predator-prey case the matrix of interactions is antisymmetric, and a nonzero population size must be sustained by an external resource. Time series of the diversity and population size for both models show approximate 1/f noise and power-law distributions for the lifetimes of communities and species. For the mutualistic model, these two lifetime distributions have the same exponent, while their exponents are different for the predator-prey model. The difference is probably due to greater resilience toward mass extinctions in the food-web like communities produced by the predator-prey model.Comment: 26 pages, 12 figures. Discussion of early-time dynamics added. J. Math. Biol., in pres

Comparison of Fixed and Variable Pitch Actuators for Agile Quadrotors

This paper presents the design, analysis and experimental testing of a variable- pitch quadrotor. A custom in-lab built quadrotor with on-board attitude stabi- lization is developed and tested. An analysis of the dynamic di erences in thrust output between a xed-pitch and variable-pitch propeller is given and validated with simulation and experimental results. It is shown that variable-pitch actuation has signi cant advantages over the conventional xed-pitch con guration, includ- ing increased thrust rate of change, decreased control saturation, and the ability to quickly and e ciently reverse thrust. These advantages result in improved quadro-tor tracking of linear and angular acceleration command inputs in both simulation and hardware testing. The bene ts should enable more aggressive and aerobatic ying with the variable-pitch quadrotor than with standard xed-pitch actuation, while retaining much of the mechanical simplicity and robustness of the xed-pitch quadrotor.Aurora Flight Sciences Corp.National Science Foundation (U.S.) (Graduate Research Fellowship Grant 0645960

Predicting evolution and visualizing high-dimensional fitness landscapes

The tempo and mode of an adaptive process is strongly determined by the structure of the fitness landscape that underlies it. In order to be able to predict evolutionary outcomes (even on the short term), we must know more about the nature of realistic fitness landscapes than we do today. For example, in order to know whether evolution is predominantly taking paths that move upwards in fitness and along neutral ridges, or else entails a significant number of valley crossings, we need to be able to visualize these landscapes: we must determine whether there are peaks in the landscape, where these peaks are located with respect to one another, and whether evolutionary paths can connect them. This is a difficult task because genetic fitness landscapes (as opposed to those based on traits) are high-dimensional, and tools for visualizing such landscapes are lacking. In this contribution, we focus on the predictability of evolution on rugged genetic fitness landscapes, and determine that peaks in such landscapes are highly clustered: high peaks are predominantly close to other high peaks. As a consequence, the valleys separating such peaks are shallow and narrow, such that evolutionary trajectories towards the highest peak in the landscape can be achieved via a series of valley crossingsComment: 12 pages, 7 figures. To appear in "Recent Advances in the Theory and Application of Fitness Landscapes" (A. Engelbrecht and H. Richter, eds.). Springer Series in Emergence, Complexity, and Computation, 201

Isolation-by-Distance and Outbreeding Depression Are Sufficient to Drive Parapatric Speciation in the Absence of Environmental Influences

A commonly held view in evolutionary biology is that speciation (the emergence of genetically distinct and reproductively incompatible subpopulations) is driven by external environmental constraints, such as localized barriers to dispersal or habitat-based variation in selection pressures. We have developed a spatially explicit model of a biological population to study the emergence of spatial and temporal patterns of genetic diversity in the absence of predetermined subpopulation boundaries. We propose a 2-D cellular automata model showing that an initially homogeneous population might spontaneously subdivide into reproductively incompatible species through sheer isolation-by-distance when the viability of offspring decreases as the genomes of parental gametes become increasingly different. This simple implementation of the Dobzhansky-Muller model provides the basis for assessing the process and completion of speciation, which is deemed to occur when there is complete postzygotic isolation between two subpopulations. The model shows an inherent tendency toward spatial self-organization, as has been the case with other spatially explicit models of evolution. A well-mixed version of the model exhibits a relatively stable and unimodal distribution of genetic differences as has been shown with previous models. A much more interesting pattern of temporal waves, however, emerges when the dispersal of individuals is limited to short distances. Each wave represents a subset of comparisons between members of emergent subpopulations diverging from one another, and a subset of these divergences proceeds to the point of speciation. The long-term persistence of diverging subpopulations is the essence of speciation in biological populations, so the rhythmic diversity waves that we have observed suggest an inherent disposition for a population experiencing isolation-by-distance to generate new species

Реакция посевов сои и гороха в Приобье на гуминовый антистрессант к гербицидам в лесостепи Западной Сибири

In the article, the authors presented those enticing actual herbicidal treatments (the active ingredient is cloquintocet-mexyl, fenoxaprop-P-ethyl), spring-summer and summer droughts, are stress factors for the development of early-ripening soybean varieties and zoned pea varieties in the forest-steppe of the Priobye region. They limit the realization of the biological yield potential of soybeans and reduce the coarseness of pea grains and their total protein. Use with the herbicide of humic preparation from leonardite Cytogumat at a rate of 0.4 l/ha relieves physiological stress on soybean plants, providing a rapid increase in biomass and grain yield of 4.2-5.5 c/ ha, or 19%. Furthermore, the humic product in a single year can increase the duration of soybean vegetation by 3-4 days and the height of lower bean attachment by 24%. The authors analyze the stress resistance to the anti-cereal herbicide of 5 varieties of peas. They also found that the varieties Altaysky Usatiy and Novosibirets mediumresistant, Yamal, and Astronaut are sensitive to the herbicide. The application of Cytogumat in susceptible varieties increased green mass by 30.1% and 24.0%, grain yield by 10.5-12.0%, weight of 1000 grains by 7.1-7.4%, and total protein. In moderately resistant varieties, the reaction to Cytogumat was less pronounced and was accompanied by an increase in yield by 8–10%, grain size by 5–5.4%, and protein content by 1.9%. The Yamalsky pea variety in the Ob River region proved to be tolerant to stress, and it is inexpedient to use Cytogumat on it.Показано, что стрессовыми факторами для развития раннеспелых сортов сои и районированных сортов гороха посевного в лесостепи Приобья служат противозлаковые гербицидные обработки (действующее вещество – клоквинтосет-мексил, феноксапроп-П-этил), весенне-летняя и летняя засухи. Они ограничивают реализацию биологического потенциала урожайности сои, снижают крупность зерна гороха и содержание в нем протеина. Использование совместно с гербицидом гуминового препарата из леонардита Цитогумата в норме 0,4 л/га снимает физиологический стресс растений сои, обеспечивая быстрый прирост биомассы и прибавку урожайности зерна 4,2–5,5 ц/га, или 19%. Гуминовый препарат в отдельный год может увеличить продолжительность вегетации сои на 3–4 дня и высоту прикрепления нижних бобов на 24%. Проанализирована стрессоустойчивость к противозлаковому гербициду 5 сортов гороха посевного. Установлено, что сорта Алтайский усатый и Новосибирец среднеустойчивы, Ямал и Астронавт – чувствительны к гербициду. Применение Цитогумата на чувствительных сортах давало прирост зеленой массы на 30,1 и 24,0%, повышало урожайность зерна на 10,5–12,0%, массу 1000 зерен на 7,1–7,4% и увеличивало содержание протеина. У среднеустойчивых сортов реакция на Цитогумат была выражена меньше и сопровождалась повышением урожайности на 8–10%, крупности зерна – на 5–5,4 и возрастанием его белковости на 1,9%. Сорт гороха Ямальский в Приобье показал себя толерантным к стрессу, и использовать Цитогумат на нем нецелесообразно

Rapid Transition towards the Division of Labor via Evolution of Developmental Plasticity

A crucial step in several major evolutionary transitions is the division of labor between components of the emerging higher-level evolutionary unit. Examples include the separation of germ and soma in simple multicellular organisms, appearance of multiple cell types and organs in more complex organisms, and emergence of casts in eusocial insects. How the division of labor was achieved in the face of selfishness of lower-level units is controversial. I present a simple mathematical model describing the evolutionary emergence of the division of labor via developmental plasticity starting with a colony of undifferentiated cells and ending with completely differentiated multicellular organisms. I explore how the plausibility and the dynamics of the division of labor depend on its fitness advantage, mutation rate, costs of developmental plasticity, and the colony size. The model shows that the transition to differentiated multicellularity, which has happened many times in the history of life, can be achieved relatively easily. My approach is expandable in a number of directions including the emergence of multiple cell types, complex organs, or casts of eusocial insects

Влияние органических удобрений на основе птичьего помёта на продуктивность кормовых культур и микробиологические показатели почвы

The creation of optimum plant nutrition plays a significant role in increasing farming efficiency. Fertilisers are one of the fastest ways to intensify the cultivation technology of all crops. The application of organic fertilisers derived from chicken manure changes the soil’s nutrient regime and nitrification capacity, its biological activity and improves physical properties. The study aims to identify the comparative evaluation of organic fertilisers based on chicken manure and establish their effect on the productivity of fodder crops (soybean and oats) and soil biological activity. The authors also determined the effectiveness of using poultry manure as an organic fertiliser to preserve soil bioresources. New organic fertilisers based on chicken manure were tested in work, obtained using a cavitation-vortex heat generator by processing semi-dry manure. Their influence on growth, development and biometric indicators of oat and soybean plants, phytosanitary state of crops, yield and grain quality has been revealed. The effect of organic fertilisers from chicken manure on microbiological indicators of soil has been determined. The increase of the oat grain yield was from 0.4 to 0.63 tons/ hectare, or 17% of the control. The output of soybean grain increased significantly by 0.18 to 0.22 t/ha. There was a slight increase in the protein content of seeds (by 1.2-2.6%). It was found that the fertilisers improved the structural indicators of oat and soybean plants. Thus, the weight of grains in oats increased by 18-23%; the number of grains in the panicle also increased by 13%. As for soybean, the number of beans on a plant grown by 14-23%; the weight of grains per plant increased by 16-19%; safety of plants for harvesting increased by 5-7%. Fertilisers based on chicken manure help improve the soil’s microbiological characteristics, which grows the availability of nutrients to plants.Ведущая роль в повышении эффективности земледелия принадлежит созданию оптимального уровня питания растений. Удобрения являются одним из быстродействующих средств интенсификации технологии возделывания всех культур. Внесение органических удобрений, полученных на основе куриного помета, изменяет пищевой режим и нитрификационную способность почвы, ее биологическую активность, улучшает физические свойства. Цель исследований – дать сравнительную оценку органических удобрений на основе куриного помёта и установить их влияние на продуктивность кормовых культур (соя и овес) и биологическую активность почвы; определить эффективность использования птичьего помета в качестве органического удобрения для сохранения биоресурсов почвы. В процессе выполнения работы были испытаны новые органические удобрения на основе куриного помета, полученные при использовании кавитационно-вихревого теплогенератора методом переработки полусухого помета. Выявлено их влияние на рост, развитие и биометрические показатели растений овса и сои, фитосанитарное состояние посевов, урожайность и качество зерна. Определено влияние органических удобрений из куриного помета на микробиологические показатели почвы. Прибавка урожайности зерна овса составила 0,4–0,63 т/га, или 17% к контролю. Достоверно увеличилась – на 0,18–0,22 т/га урожайность зерна сои, отмечено небольшое (на 1,2–2,6%) повышение содержания белка в семенах. Установлено, что удобрения улучшают структурные показатели растений овса и сои: у овса на 18– 23% увеличивается масса зерна и на 13% количество зерен в метелке, у сои на 14–23% возрастает количество бобов на растении и на 16–19% – масса зерен с одного растения, на 5–7% повышается сохранность растений к уборке. Удобрения, полученные на основе куриного помета, способствуют улучшению микробиологических характеристик почвы, что повышает доступность элементов питания для растений

Отзывчивость сои на внесение органических удобрений на основе птичьего помета

Organic fertilizers based on chicken manure have a diverse composition of basic nutrients and microelements, which is their advantage over mineral fertilizers. The introduction of organic fertilizers obtained based on chicken manure improves the biological activity of the soil. The study aims to determine the effectiveness of using bird droppings as an organic fertilizer to conserve soil bioresources and increase soybean productivity. In the course of the work, the authors tested new organic fertilizers based on chicken manure obtained using a cavitationvortex heat generator by processing semi-dry manure. Their influence on soil microbiological indicators, growth, development, and biometric characteristics of soybean plants, phytosanitary condition of crops, productivity, and product quality was revealed. The authors also found that fertilizers based on chicken manure help to improve the microbiological characteristics of the soil, which increases the availability of nutrients for plants. The authors note a change in the number of mycomycetes at the beginning of the growing season: a decrease of 68% with the use of Preparation 1 and an increase of 35.6% with the use of nitrogen fertilizers. Pre-sowing introduction of preparations into the soil and processing during the growing season activate the vegetative development of plants and contribute to an increase in the yield of green mass and grain. The greatest effect was obtained when preparation 2 was applied under soybean. The increase in soybean grain yield was 0.2–0.3 t/ha or 8–14% of the control. The authors also found that treatment with drugs improves the structural parameters of soybean plants: the number of beans per plant increases by 6–8%; by 18–23% - the mass of grains from one plant; the safety of plants for harvesting increases by 2–4%.Органические удобрения на основе куриного помета имеют разнообразный состав основных элементов питания и микроэлементов, в этом их преимущество над минеральными удобрениями. Внесение органических удобрений, полученных на основе куриного помета, улучшает биологическую активность почвы. Цель исследований – определить эффективность использования птичьего помета в качестве органического удобрения для сохранения биоресурсов почвы и повышения продуктивности сои. В процессе выполнения работы были испытаны новые органические удобрения на основе куриного помета, полученные при использовании кавитационно-вихревого теплогенератора методом переработки полусухого помета. Выявлено их влияние на микробиологические показатели почвы, рост, развитие и биометрические характеристики растений сои, фитосанитарное состояние посевов, урожайность и качество продукции. Установлено, что удобрения, полученные на основе куриного помета, способствуют улучшению микробиологических характеристик почвы, что повышает доступность элементов питания для растений. Отмечено изменение численности микомицетов в начале вегетации: снижение на 68 % при использовании Препарата 1 и увеличение на 35,6 % при применении азотных удобрений. Предпосевное внесение препаратов в почву и обработка по вегетации активизируют вегетативное развитие растений и способствуют повышению урожайности зеленой массы и зерна. Наибольший эффект получен при внесении под сою Препарата 2. Прибавка урожайности зерна сои составила 0,2–0,3 т/га, или 8–14 % к контролю. Установлено, что обработка препаратами улучшает структурные показатели растений сои: на 6–8 % увеличивается количество бобов на растении и на 18–23 % – масса зерен с одного растения. На 2–4 % возрастает сохранность растений к уборке

Evolution of Blind Beetles in Isolated Aquifers: A Test of Alternative Modes of Speciation

Evidence is growing that not only allopatric but also sympatric speciation can be important in the evolution of species. Sympatric speciation has most convincingly been demonstrated in laboratory experiments with bacteria, but field-based evidence is limited to a few cases. The recently discovered plethora of subterranean diving beetle species in isolated aquifers in the arid interior of Australia offers a unique opportunity to evaluate alternative modes of speciation. This naturally replicated evolutionary experiment started 10-5 million years ago, when climate change forced the surface species to occupy geographically isolated subterranean aquifers. Using phylogenetic analysis, we determine the frequency of aquifers containing closely related sister species. By comparing observed frequencies with predictions from different statistical models, we show that it is very unlikely that the high number of sympatrically occurring sister species can be explained by a combination of allopatric evolution and repeated colonisations alone. Thus, diversification has occurred within the aquifers and likely involved sympatric, parapatric and/or microallopatric speciation

The evolution of postpollination reproductive isolation in Costus

Reproductive isolation is critical to the diversification of species. Postpollination barriers may be important in limiting gene flow between closely related species, but they are relatively cryptic and their evolution is poorly understood. Here, we review the role of postpollination reproductive isolation in plants, including the various stages at which it operates and the hypotheses for how it may evolve. We then review empirical studies in the plant genus Costus, evaluating documented postpollination barriers in light of these hypotheses. We summarize isolation due to parental style length differences and present evidence supporting the hypothesis that the differences are in part a by-product of selection on floral morphology. Additionally, we show that reduced pollen adhesion, germination, and tube growth contribute to reproductive isolation between two closely related sympatric species of Costus. Geographic variation in the strength of these crossing barriers supports the hypothesis that they evolved under reinforcement, or direct natural selection to strengthen isolation