Number Of Descendants Research Articles

On the Notion of Fitness, or: The Selfish Ancestor

We introduce a concept of fitness of a lineage as the number of descendents weighted by their degree of relatedness with the ancestor of the lineage and propose this as a scheme for analyzing altruistic behavior.

The Biological Basis of Aging and Death

A Means to an End: The Biological Basis of Aging and Death William Clark Oxford University Press A Means to an End: The Biological Basis of Aging and Death by William Clark deals with senescence, the process by which our vulnerability to disease and death increases steadily with age. One chapter discusses the evolutionary basis for differences in lifespan. We may be tempted to say that naturally living organisms wear out, as do machines, and we should not be surprised when tissues grow old and fail to function. However, this process for similar tissues occurs at quite different rates. At the microscopic and biochemical level, the cellular processes in a mouse and a human are quite similar. Yet the maximum lifespan of a mouse is only 3.5 years while for a human it is 122 years. Clearly, the tissues of some species are engineered to function longer than those of other animals. Why do different species have such different lifespans? Clark points out that part of it seems related to the age of reproduction. Animals whose function declines before reproduction would be out reproduced by animals whose bodies lasted longer. What has prevented human bodies from evolving to last longer is that most of us have finished rearing our young by the time really serious deterioration has set in (say age 65). While we would like to live longer, living into retirement age contributes little to the number of descendants we leave. Thus, if the price of this living longer is fewer children born at younger ages, there is likely to be selection against the genes for body maintenance. While Clark argues that we have genes for senescence (as well as genes that retard it), he never is quite clear on why those that delay senescence (and hence have a longer reproductive life) do not out reproduce those experiencing earlier senescence. The missing detail is that delaying senescence probably has costs (possibly from diverting energy to cell maintenance and repair). Individuals that divert resources from bodily maintenance can use these resources to avoid being eaten, to fight parasites, or to find mates. The individuals that leave the most descendants accept a shorter lifetime in exchange for other benefits that contribute to leaving descendants. Arking (1998) provides a better discussion of theories of aging. That an organism's length of life can evolve in response to selection for early or late reproduction has been shown in several experiments. When each succeeding generation of fruit flies was grown from eggs laid late in the life of the fly, the lifespan of fruit flies was increased. In Trinidad, it was found that guppies from the lower pools reproduced earlier and had a shorter lifespan than those from the upper pools. In the lower (further down the river) pools the main predator ate guppies of reproductive age. In the upper pools the main predator ate immature guppies. In the later case, once a guppy had survived to reproductive age it would leave more offspring if its body survived longer. Thus, the guppies had evolved to live longer. When breeding stock from the pools where lifetime was short were introduced into pools where the predators neglected the older fish, the guppies evolved towards an older lifespan. Finally, when predators that went after the older fish were introduced into the pools with the originally short lived upper pool stock, these guppies evolved shorter lifespans. Thus, it appears that in these two species at least, and probably in other species, including humans, the gene pool contains genes for a longer life span. In human populations (races) evolving in different circumstances, lifespans could be different. Miller (1994) has argued that in climates where male provisioning of the young is necessary for children to survive, selection for a long life has been stronger than in tropical areas. The evolutionary mechanism that produces the correlation between lifespan and age of reproduction could also operate within humans. …

Interspecific Competition in the Laboratory between Drosophila subobscura and D. azteca

Abstract Drosophila subobscura and D. azteca are closely related species that have coexisted on the west coast of North America since that area was colonized by D. subobscura in the late 1970s. We have studied competition between the two species by the serial transfer technique at different initial proportions (20%, 50%, 80% and 100%) and at two densities (20 and 100 individuals). The cultures were maintained at 18 C. In the mixed cultures D. subobscura outcompeted D. azteca at both densities and all initial proportions. Survivorship was similar for both species, although the productivity of D. azteca was reduced, especially in the mixed cultures. The productivity of D. subobscura in the mixed cultures was a function only of the initial number of individuals of this species, and was completely unaffected by the number of D. azteca in the populations. Carrying capacity was attained by both species when the number of founder individuals was twenty; however, the number of descendants was much lower for D. az...

Species traits for future biomonitoring across ecoregions: patterns along a human‐impacted river

1. Current budgets for environmental management are high, tend to increase, and are used to support policy and legislation which is standardized for large geographic units. Therefore, the search for tools to monitor the effects of this investment is a major issue in applied ecology. Ideally, such a biomonitoring tool should: (1) be as general as possible with respect to its geographic application; (2) be as specific as possible by separating different types of human impact on a given ecosystem; (3) reliably indicate changes in human impact of a particular type; and (4) be derived from a sound theoretical concept in ecology.2. We developed an approach to biomonitoring which matches these ‘ideal’ characteristics by focusing on numerous, general biological species traits (e.g. size, number of descendants per reproductive cycle, parental care, mobility) and on the habitat templet concept, which relates trends in these general species traits to disturbance patterns. Using the French Rhône River and benthic macroinvertebrates as an example, we have used the data to demonstrate a general framework and the potential of our approach rather than to produce a ready‐made tool. Our data covered a large river and its major tributaries, which has a catchment that crosses ecoregions, and known gradients and discontinuities in human impact.3. We applied multivariate analyses to evaluate how the distribution of species traits in invertebrate communities could discriminate environmental differences along the Rhône in comparison to traditionally used approaches (e.g. community structure, based on species abundances, or ecological species traits, such as velocity preferences and pollution tolerance). Invertebrate community structure expressed in terms either of the abundance or the traits of species reliably indicated differences in overall human impact. The community structure based on biological traits was less confounded by natural spatial gradients and reliably indicated human impact, while community structure based on ecological traits was the most confounded by natural spatial gradients and was the poorest indicator of human impact. Community structure based on species abundances was an intermediate indicator of human impact.4. These results indicate that a revision of biomonitoring approaches which have been based on a single aspect of the biological responses may be warranted. The biological traits of species could separate the different types of human impact. Therefore, the use of these traits in biomonitoring could improve existing multi‐metric approaches. Future research has to show if the general applicability of species traits allows the development of a unique biomonitoring tool for running waters of the European Union, for running waters in temperate climates on several continents, for freshwater, marine and terrestrial systems, and/or for global biodiversity assessment.

Influência da idade dos ovos de Helicoverpa zea (Boddie) no parasitismo de Trichogramma pretiosum Riley

Entre os agentes de controle biológico, os parasitóides do gênero Trichogramma representam um dos mais importantes grupos, pois controlam diversas pragas na agricultura. Este trabalho teve por objetivo determinar a melhor idade dos ovos de Helicoverpa zea (Boddie) para que Trichogramma pretiosum Riley tenha uma melhor eficiência no controle dessa praga. Ovos com um, dois, três e quatro dias foram oferecidos para o parasitismo, por um período de 24 horas a 25 ± 1ºC, umidade relativa de 70 ± 10% e fotofase de 14 horas. Ovos de um dia de idade apresentaram a maior taxa de parasitismo, viabilidade e número de descendentes por fêmea. A mais alta eficiência de T. pretiosum será alçancada no campo, quando for observado maior densidade de ovos de H. zea com, no máximo, dois dias de desenvolvimento embrionário.

Average-Case Analysis of Priority Trees: A Structure for Priority Queue Administration

Priority trees (p-trees ) are a certain variety of binary trees of size n constructed from permutations of the numbers 1, . . ,n . In this paper we analyze several parameters depending on n (the size) and j (a number between 1 and n ), such as the length of the left path (connecting the root and the leftmost leaf), the height of node j (the distance from the root), the number of left edges on the path from the root to node j , the number of descendants of node j , the number of key comparisons when inserting an element between j and j+1 , the number of key comparisons when cutting the p-trees into two p-trees , the number of nodes with 0 , 1 , or 2 children. Methodologically, recursions are set up according to a fundamental decomposition of the family $ \cal A $ of p-trees (using auxiliary quantities $ \cal B $ and $ \cal C$ ); using generating functions, they lead to systems of differential equations that can be solved explicitly with some efforts. The quantities of interest can then be identified as coefficients in the explicit forms of the generating functions.

Phenotypic and evolutionary adaptation of a model bacterial system to stressful thermal environments.

We studied both phenotypic and evolutionary adaptation to various thermal environments using the bacterium Escherichia coli as an experimental model system. We determined that 42 degrees C was stressful to a bacterial clone adapted to 37 degrees C, based on reductions in both absolute and competitive fitness, as well as induction of a heat stress response. This clone was also used to found replicated populations that were propagated for thousands of generations under several different thermal regimes, including 42 degrees C. Evolutionary adaptation of the populations to 42 degrees C resulted in an increase in both absolute and relative fitness at that temperature, measured respectively as an increase in the number of descendants (and their biovolume) and in competitive ability relative to the ancestral clone. The replicated experimental lineages achieved their evolutionary improvement by several distinct pathways, which produced differential preadaptation to a non-stressful nutrient environment. Adaptation to this stressful temperature entailed neither a change in the ancestral thermal niche nor any pronounced trade-offs in fitness within the thermal niche, contrary to a priori predictions. This study system was several important advantages for evaluating hypotheses concerning the effects of stress on phenotypic and evolutionary adaptation, including the ability to obtain lineages that have evolved in controlled and defined environments, to make direct measurements of fitness and to quantify the degree of stress imposed by different environments.

On the number of descendants in an object DAG

In this paper we address the problem of evaluating the expected number of descendants for an object set in a directed acyclic graph. We prove an exact formula for the descendant number when the distribution of the set fanout is known. Also, we derive an approimated formula expressed in terms of the average fanout.

MOLECULAR MARKERS AS A TOOL FOR BREEDING FOR FLOWER LONGEVITY IN ASIATIC HYBRID LILIES

Segregation of flower longevity in two lily populations was studied and the genetic linkage of morphological markers and RAPD markers with loci involved in flower longevity was investigated. A large variation in flower longevity was found within the two populations tested at individual plant level. Longevity values were well correlated between experiments at the individual plant level and at clonal level. One out of 278 RAPD markers and one morphological marker (male sterility) were significantly (P<0.005) linked to flower longevity in the clonal test. Linkage studies were hampered because of the low number of descendants evaluated in both longevity and marker analysis. The possible influence of male sterility on flower longevity of Asiatic hybrid lilies is discussed.

Who's for work? The management of labour in the process of accumulation in three Adja villages, Benin

In the rural Adja region of south-west Bénin there is a labour problem. People who want to expand their businesses need cheap and reliable labour, but such labour is difficult to find and to manage. The sort of ‘big men’ known asalo-su amè dji—those mainly interested in investing in and dominating people—would like to keep up the appearance of being a ‘big man’ with many people under their control, but they cannot avoid the modern temptation of aspiring to personal wealth. Their style of management is to use mainly domestic labour, yet they face problems as the young begin to distrust the intentions of their household heads: the latter are suspected of looking after their own interests, while their followers doubt whether they will get a fair share of the assets when there are so many of them in a large family. Furthermore, sons and dependants find a long, very low-paid ‘apprenticeship’ increasingly unacceptable.There is growing awareness of the difficulties of working with domestic labour and of the splintering effect of redistributing assets between a great many people. A small but growing number want accumulation for themselves and a limited number of descendants. This new style is associated with the sort of accumulators calledeho wu amè, people who try to maximise financial gain. They work with much less family than hired labour (and prefer a much lower rate of polygyny). But hired labour at economic rates is not easy to find and there are organisational problems.

Theoretical habitat templets, species traits, and species richness: aquatic Coleoptera in the Upper Rhône River and its floodplain

SUMMARY To test predictions of the river habitat templet and the patch dynamics concept, trends in species traits and species richness of aquatic beetles were related to the spatial‐temporal variability of eighteen habitat types in the alluvial floodplain of the French Upper Rhône River. One hundred and twenty species of beetles were used in this analysis. The basic information was obtained either from the literature (for most of the species traits) or from observations made at approximately 500 sampling sites in the Brégnier‐Cordon and Jons sections over the past 19 years (for habitat utilization). This information was structured by a fuzzy coding technique and examined by ordination analyses. Analyses of the relationships among nineteen species traits revealed a clear distinction according to traits such as body form (for adults), functional feeding type and food (adults and larvae), attachment to the substrate and dissemination potential (adults and larvae), and patterns of aquatic and/or terrestrial life of adults and larvae. Species traits such as number of descendants per reproductive cycle, and number of reproductive cycles per year or per individual showed less contrast, because these traits are rather homogeneous in aquatic beetles. Analyses of the habitat utilization by the aquatic beetles revealed a vertical gradient that separates interstitial from superficial habitats, and a transverse gradient for the superficial habitats, which extends from the main channel towards permanent oxbow lakes and temporary waters. The significant relationship betweeen species traits and habitat utilization demonstrates that most beetle species use a particular set of habitat types with a particular set of species trait modalities. Species traits of aquatic beetles are homogeneous but evidently very successful and are adapted to many potential conditions of spatial–temporal variability. Because of this homogeneity, observations on aquatic beetles do not support trends of traits in the framework of spatial–temporal variability predicted from the river habitat templet. The observed species richness of aquatic beetles is low in habitat types with a low spatial–temporal variability, increases as spatial variability increases, and tends to be highest at intermediate temporal variability. This pattern matches predictions of the patch dynamics concept.

Theoretical habitat templets, species traits, and species richness: fish in the Upper Rhône River and its floodplain

SUMMARY Recent developments in ecological theory concerned with habitat templets, species assemblages, and life history traits were examined for the riverine fish communities of the Upper Rhône River, France, in the context of spatial–temporal habitat variability. Relationships among species traits, habitat utilization of species, the relationship between species traits and habitat utilization, and trends of species traits and species richness in the spatial–temporal variability of the habitat types were analysed. Relationships among twelve species traits, and utilization of eight habitats were examined for twenty‐five fish species using correspondence analysis; the relationship between species traits and habitat utilization was investigated by co‐inertia analysis. Positive relationships among species traits were observed for size, fecundity, and the number of reproductive cycles per individual. However, species were not well differentiated according to the habitat utilization, except for habitats rarely connected with the main channel (i.e. two types of oxbow lakes). No significant relationship was found between species traits and habitat utilization, nor for either species traits or species richness when examined in the framework of spatial–temporal habitat variability. Only two species traits corresponded (with slight trends) to predictions in a river habitat templet: (i) the number of descendants per reproductive cycle increased along with temporal variability; and (ii) the number of reproductive cycles per individual was either low or high at low temporal variability and intermediate at elevated temporal variability. The discrepancy between the predictions of the river habitat templet as well as of the patch dynamics concept and the results observed for the fish in the Upper Rhône was explained in terms of scale problems, the evolutionary ecology of the European fish fauna, and the history of the Rhône River.

Theoretical habitat templets, species traits, and species richness: floodplain vegetation in the Upper Rhône River

SUMMARY The floodplain vegetation at approximately 100 sites located in nine different habitat types of the Upper Rhône River, France, was surveyed three times over the past 27 years. Information on species traits of the higher plants comprising the Rhône floodplain vegetation was based on studies conducted between Geneva, Switzerland, and Lyon, France. These data were structured using a ‘fuzzy coding’ technique and then examined using ordination analyses to investigate: (i) relationships among species traits; (ii) habitat utilization; (iii) the relationship between species traits and habitat utilization; and (iv) trends of species traits and species richness in the framework of spatial–temporal habitat variability to test predictions of the river habitat templet and the patch dynamics concept. Size, number of descendants per reproductive cycle, number of reproductive cycles per individual, and the regeneration potential of an individual were positively related with each other, whereas the degree of attachment to the soil decreased, and the reproductive period shifted from autumn/late summer towards early summer/spring, as size increased. The habitat utilization by the higher plants of the floodplain revealed a double lateral gradient: the first was from the banks of the temporary waters to terrestrial flats; the second from aggrading pebble to aggrading silt habitats. These gradients were related to gradients in water saturation, oxygen conditions, nutrient loading, and nutrient retention of the soils. A significant relationship between species traits and habitat utilization was observed for the floodplain vegetation, i.e. plant communities used particular habitat types with a particular set of species trait modalities (= categories). Patterns of species trait modalities were significantly related to temporal and spatial habitat variability but only modalities of the trait ‘parental care’ conformed to trends predicted from theory. No trends were observed when species richness of different habitat types was considered in the framework of spatial–temporal habitat variability. Although the habitats of the Upper Rhône clearly act as a templet for the species traits of the floodplain vegetation, the lack of agreement between observations and predictions on trends in species traits and richness in terms of habitat variability suggest that important elements of theory should be rejected. However, human‐induced changes in these habitats are too recent when compared with the longer time periods required for floodplain vegetation to respond to such changes.

Large deviations of the height of a random tree

AbstractThe paper is devoted to the relation between random trees and branching processes for which the number of descendants of one particle has the Poisson distribution. The main result of the paper consists in finding the leading term of the asymptotics of the probabilities of large deviations for the height of a random tree. Similar problems were considered in [1-6].

Hierarchical triangulation using cartographic coherence

Triangulated Irregular Networks (TINs) approximate surfaces for many applications. For those that require different resolutions, TINs may be stored in a hierarchical structure. In the past, techniques have been emphasized where a coarse triangulation is refined by focusing on plane geometry using very little of the surface data. For example a new point is introduced where the surface deviates farthest from the plane of the triangle, and the triangle is subdivided into three new ones. Variants of Delaunay triangulations have also been used. We propose a technique where we take into account that deviations of a terrain surface from planarity do not occur at isolated points but they occur coherently along ridges, valleys, peaks and other features. If, for example, a ridge cuts across a triangle, that triangle is divided by a line along the ridge and the remaining quadrilateral gets split into the two most nearly equilateral triangles. In this way the number of very thin triangles (slivers) is significantly reduced. Such triangles produce undesirable effects in animation. In addition the number of levels of the TIN tree is reduced which speeds up searching within the data structure. Our tests on digital elevation data have confirmed the above theoretical expectations. Results show that average “sliveriness” with our new method is between 1 5 and 1 10 that of triangulations produced with DeFloriani's first method. The resulting number of levels in the hierarchy is about one third and although there is an increase in the number of descendants at each level, the total number of triangles is also lower.

Clonal analysis of epiblast fate during germ layer formation in the mouse embryo

The fate of cells in the epiblast at prestreak and early primitive streak stages has been studied by injecting horseradish peroxidase (HRP) into single cells in situ of 6.7-day mouse embryos and identifying the labelled descendants at midstreak to neural plate stages after one day of culture. Ectoderm was composed of descendants of epiblast progenitors that had been located in the embryonic axis anterior to the primitive streak. Embryonic mesoderm was derived from all areas of the epiblast except the distal tip and the adjacent region anterior to it: the most anterior mesoderm cells originated posteriorly, traversing the primitive streak early; labelled cells in the posterior part of the streak at the neural plate stage were derived from extreme anterior axial and paraxial epiblast progenitors; head process cells were derived from epiblast at or near the anterior end of the primitive streak. Endoderm descendants were most frequently derived from a region that included, but extended beyond, the region producing the head process: descendants of epiblast were present in endoderm by the midstreak stage, as well as at later stages. Yolk sac and amnion mesoderm developed from posterolateral and posterior epiblast. The resulting fate map is essentially the same as those of the chick and urodele and indicates that, despite geometrical differences, topological fate relationships are conserved among these vertebrates. Clonal descendants were not necessarily confined to a single germ layer or to extraembryonic mesoderm, indicating that these lineages are not separated at the beginning of gastrulation. The embryonic axis lengthened up to the neural plate stage by (1) elongation of the primitive streak through progressive incorporation of the expanding lateral and initially more anterior regions of epiblast and, (2) expansion of the region of epiblast immediately cranial to the anterior end of the primitive streak. The population doubling time of labelled cells was 7.5 h; a calculated 43% were in, or had completed, a 4th cell cycle, and no statistically significant regional differences in the number of descendants were found. This clonal analysis also showed that (1) growth in the epiblast was noncoherent and in most regions anisotropic and directed towards the primitive streak and (2) the midline did not act as a barrier to clonal spread, either in the epiblast in the anterior half of the axis or in the primitive streak. These results taken together with the fate map indicate that, while individual cells in the epiblast sheet behave independently with respect to their neighbours, morphogenetic movement during germ layer formation is coordinated in the population as a whole.

Solving tree problems on a mesh-connected processor array

In this paper we present techniques that result in O ( n ) time algorithms for computing many properties and functions of an n -node forest stored in an n × n mesh of processors. Our algorithms include computing simple properties like the depth, the height, the number of descendents, the preorder (resp. postorder, inorder) number of every node, and a solution to the more complex problem of computing the Minimax value of a game tree. Our algorithms are asymptotically optimal since any nontrivial computation will require Ω ( n ) time on the mesh. All of our algorithms generalize to higher dimensional meshes.

Altruism and the Economic Theory of Fertility

The economic approach to fertility emphasizes the effects of parents income and the cost of rearing children. With a few exceptions this approach has neglected the analytical links between decisions by different generations of the same family. This article develops the implications of altruism toward children where utility of parents depends on their own consumption their fertility and the utility of each of their children. Altruism toward children implies that the welfare of all generations of a family is linked through a dynastic utility function that depends on the consumption fertility and number of descendants in all generations. The head of a dynastic family acts as if he maximizes dynastic utility subject to a dynastic budget constraint which involves the wealth inherited by the head interest rates the cost of rearing children in all generations and the earnings of all descendants. The authors neglect uncertainty marriage the spacing of births and capital-market restraints over life cycles and across generations. Nevertheless even a highly simplified model of altruism toward children and the behavior of dynastic families appears to us to capture important important aspects of the dynamic behavior of fertility and consumption. If so a new approach would be warranted to the analysis of trends and long-term fluctuations in fertility population growth and consumption.

A Reformulation of the Economic Theory of Fertility

An economic analysis of the linkages in fertility rates and capital accumulation across generations is developed considering the determination of fertility and capital accumulation in each generation when wage rates and interest rates are parameters to each family and to open economies. The model is based on the assumption that parents are altruistic toward their children. The utility of parents depends on their own consumption and on the utility of each child and the number of children. By relating the utility of children to their own consumption and to the utility of their children a dynastic utility function was obtained that depends on the consumption and number of descendants in all generations. The term reformulation was used because of the emphasis on dynastic utility model of altruism toward children and deriving the budget constraint and utility function of a dynastic family the model was applied to the Great Depression and World War II. The 1st-order conditions to maximize utility imply that fertility in any generation depends positively on the real interest rate and the degree of altruism and negatively on the rate of growth in per capita consumption from 1 generation to the next. Consumption of each descendant depends positively on the net cost of rearing a desdendant. Applying the model it is shown that the analysis is consistent with baby busts during the Depression and the war and with a baby boom after the war. The effects on fertility of child mortality subsidies to (or taxes on) children and social security and other transfer payments to adults were considered. The demand for surviving children rises during the transition to low child mortality but demand for survivors return to its prior level once mortality stabilizes at a low level. Fertility falls in response to declines in international real interest rates and increases in an economys rate of technological progress. Extending the analysis to include life-cycle variations in consumption earnings and utility fertility emerges as a function of expenditures on the subsistence and human capital of children but not of expenditures that simply raise the consumption of children. The path of aggregate consumption in demographic steady states does not depend on interest rates time preference or other determinants of life-cycle variations in consumption.

Rate of Extinction and Limiting Distributions for a Geographically Structured Population

The model of a population we discuss describes a situation in which individuals alternately migrate within an infinite array of colonies and undergo random mating within each colony. The number of genes in each colony is N. In time zero a mutant gene is introduced to colony zero; $N_0 ( n )$ is the number of descendants of this gene in generation n. We find a lower bound of the rate of extinction of the mutant population and the limiting distribution for $N_0 ( n )$.