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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Evolutionary ecology 1 (1987), S. 1-3 
    ISSN: 1573-8477
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Evolutionary ecology 1 (1987), S. 5-10 
    ISSN: 1573-8477
    Keywords: Habitat matching ; ideal free theory ; spatial distribution ; input matching ; habitat quality
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary When fitness of a resource-limited animal depends only on that individual's share of the total resource in a habitat patch and individuals are free to move to the patch where their gains are highest, population density matches resource availability under the simple assumption that individual fitness increases with resource use. Previous theory on habitat matching required the stronger assumption that individual fitness was directly proportional to (rather than monotonically increasing with) resource use. The basic theory suggests conditions under which population density empirically indicates habitat quality. Extensions of this basic theory apply when individuals that are free to move among resource patches interact by interfering with each other's resource extraction or by competing unequally. Analysis of existing models of such “ideal free competition” yields conditions for a single general matching rule in which the logarithm of “crowding” is a linear function of the logarithm of resource abundance. Double logarithmic plots of empirical data on habitat use and habitat quality based on this rule furnish possible graphical indicators of the occurrence and intensity of competition in nature.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Evolutionary ecology 1 (1987), S. 30-36 
    ISSN: 1573-8477
    Keywords: Plant breeding systems ; sexual reproduction ; mixed ESS
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Sex allocation (male allocation/female allocation) as a function of selfing rate is studied in the wild riceOryza perennis. Using dry weight measures, the male/female ratio is linearly related to the selfing rate. This linear relationship may have a fairly radical interpretation in terms of current sex allocation theory. It suggests that the intermediate selfing rates are themselves maintained by a form of frequency dependence. In particular, the linearity suggests: (i) the relative fitness of a selfed versus outcrossed offspring decreases with increased selfing; (ii) in equilibrium, a selfed offspring is approximately half as fit as an outcrossed offspring; (iii) the frequency dependence, being the opposite of that proposed in most selfing models, may result from the same forces thought to be involved in the maintenance of sex itself, and (iv) the position of the fitted line contains information about the plant's use of wind pollination for male reproduction. It suggests that wind shows much less mixing of pollen than previously assumed, and/or that there are severe morphological constraints on pollen presentation. The above interpretations are clearly speculative and tentative. Possible problems in the analysis, and some alternatives for data interpretation are discussed.
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  • 4
    ISSN: 1573-8477
    Keywords: Genetic elements ; estimate ; senescence ; Drosophila
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Although many different physiological and biochemical changes characterize the process of senescence, little is understood of the genetic elements that determine its age of onset. We provide here the first estimates of the number of genetic factors that extend longevity inDrosophila melanogaster. Life span was measured in F1, F2 and backcrosses of true-breeding long and short-lived stocks ofD. melanogaster, established by selection. Estimates of the number of effective factors delaying senescence range from about 0.3 to 1.5, indicating control by a single factor. The distribution of longevity shows this to arise as selection acts on the short-lived parental stock. Life span is extended at the cost of early fecundity.
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  • 5
    ISSN: 1573-8477
    Keywords: Diversity ; β diversity ; mosaic diversity ; ecological communities ; landscape mosaics ; plant ecology ; affinity ; community analysis ; ordination ; community variation ; statistical inference ; random community arrays ; null-hypothesis communities
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Concepts and methods for use in the study of plant community variation across a single landscape, or for the comparative analysis of two or more landscapes, are presented. The method is called affinity analysis because it produces a sorting and scaling of all the communities in a data set according to degree of differentiation in composition away from an objectively identified subset of modal communities. Modal communities possess maximum affinity with the whole landscape because they contain a large number of the species common throughout the landscape. The modal communities provide a kind of central tendency for the landscape and an anchor for depicting the dispersion of all other communities in it. To accomplish affinity analysis, the Jaccard similarity coefficient and the WilcoxonT statistic are used in a two-step transformation of the primary species-by-site data matrix. From these calculations we obtain both a visual image, theS-T graph, and summary statistics for the landscape-wide diversity described by the data. One summary statistic is a high-order diversity measure for the total patchwork of communities. We refer to this measure as mosaic diversity. The analytical results are referred to collectively as the ‘metastructure’ because they provide a general, abstract, characterization of any set of community data. This abstract rendering of the data allows comparison of pattern and variation between taxonomically, geographically, and temporally different landscapes. Either presence/absence or abundance data may be used. Examples using artificial and field data are presented. All but one of the field data sets showed a significantly higher mosaic diversity than would be expected from a randomly constructed landscape. We also show how the new methods may be used with ordination to explore intralandscape patterns in more detail than was previously possible. In addition to statistical matters, ecological and evoutionary interpretations of affinity analysis are discussed. Topics included in this discussion involve reasoning about the influences on diversity arising from micro- and macroevolution, species packing and association, environmental gradients, differential fitness expression among species-populations, continuity in community variation, and the uses of both presence/absence and abundance data in community studies. Among the examples provided, mosaic diversity is independent of β diversity (Whittaker, 1972).
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  • 6
    ISSN: 1573-8477
    Keywords: Rare species ; genetic polymorphism ; allozymes ; breeding systems ; self-compatibility ; angiosperms ; biogeography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Evolutionary theory predicts low levels of genetic polymorphism and high levels of self-compatibility in plant species with small ranges and few individuals. To test these predictions, I compared published data on electrophoretically detectable genetic variation and breeding systems for geographically restricted and widespread congeners in eleven genera. The restricted species exhibit significantly fewer polymorphic loci and alleles per polymorphic locus than do their widespread congeners. Although some rare species are genetically impoverished, others are nearly as polymorphic as their widespread congeners. The restricted species and their widespread congeners do not differ consistently with respect to breeding systems.
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  • 7
    ISSN: 1573-8477
    Keywords: Lag load ; Red Queen ; ESS ; coevolution ; evolutionary rate ; predator coevolution ; competitor coevolution ; stasis ; punctuated equilibrium ; evolutionary constraints ; White Queen's Constraint ; Alice's Constraint ; bauplan ; fitness-generating function ; versatility ; guilds ; adaptive zones ; constraint surface ; genostasis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The Red Queen principle states that a set of interacting species reaches an evolutionary equilibrium at which all their rates of coevolution exactly balance each other. The lag-load model, which is one way of searching for Red Queens, has, by itself, previously predicted that they do not exist. But this model has assumed that infinite maladaptedness is possible. The lag-load model is improved by assuming that once the lag load of all but one species is determined, so is that of the final species. This assumption eliminates the possibility of infinite maladaptedness. Its result is to allow the lag-load model to yield Red Queen coevolution. It does this whether or not speciation and extinction rates are included. Thus the lag-load model is harmonized with the earlier Red Queen model derived from studies of predation. Because of the intercorrelation of phenotypic traits, the predatory model concluded that the eventual stable rate of coevolution must be zero (except for intermittent bursts after some correlation or compromise is successfully broken). Another model that predicts stable coevolutionary rates of zero is that of evolutionarily stable strategies (ESS). Red Queen assumes that the more extreme a phenotypic trait is, the better it is, and that there are no constraints on the growth of such a phenotypic trait value. Such traits are the key to the Red Queen prediction of progressive coevolution. ESS models make no such assumptions. Eliminating unbounded traits from the model of predator-victim evolution changed its prediction from progressive coevolution to stasis. Before this paper, no model had dealt simultaneously with both unbounded and constrained traits. To handle both sorts of phenotypic traits at the same time in the same model, we abandoned lag load as a measure of evolutionary rate (lag loads do not uniquely determine phenotype). Instead, we used the traditional assumption that rate is proportional to the slope of the adaptive landscape. A model, relying on continuous evolutionary game theory, was developed and simulated under various conditions in two or three species sets, with up to five independent traits coevolving simultaneously. The results were: (1) there was always a set of equilibrium densities eventually achieved by coevolution; if the population interaction represented by this stable coevolutionary state is also stable, then the system should persist whether it evolves further or not; (2) whenever traits were present which were unbounded and best at their most extreme values, then a Red Queen emerged; (3) whenever traits were present which were correlated with each other or constrained below infinity, then an ESS emerged; (4) if both types were present, both results occurred: Red Queen in the unbounded traits and ESS in the constrained ones. Because unbounded traits may not exist, the Red Queen may have no domain. But the domain of ESS is real. ESS should lead to the evolutionary pattern called punctuated equilibrium. The changes in design rules which punctuate stasis should lead to an ever-expanding independence of traits from each other, i.e. to more and more refined differentiation. A single set of design rules which governs a set of species is called a fitness-generating function. Such functions may help to define the concepts of adaptive zone and ecological guild.
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  • 8
    ISSN: 1573-8477
    Keywords: Sex allocation ; Pandalid shrimp ; ESS ; sex change
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary In many populations of protandrous shrimp, two alternative life histories coexist. One way to interpret this fact is that one age (or size) group consists of a mixture of males and females. This is a nice example of a ‘phenotype limited evolutionarily stable strategy (ESS)’, in the sense of Parker (1982, p. 187). This paper explores the ESS theory for the mixture.
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  • 9
    ISSN: 1573-8477
    Keywords: probabilistic optimization ; optimal phenotype distribution ; adaptation under uncertainty
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Explorations of optimizing selection often find discrepancies between the theoretically expected and observed phenotypes. Such discrepancies are usually attributed to a variety of potential constraints. We suggest that one common constraint, environmental uncertainty, may reduce the applicability of traditional deterministic or stochastic optimization methods and that many apparent discrepancies might be artifacts of these methods. Since natural selection is essentially a statistical process, we propose that a probabilistic optimization procedure, that includes all of the variability in phenotype distributions and associated fitness potential functions might offer better results. The traditional methods define an optimal gene or genotype as that which produces a phenotype distribution with a mean or other measure of central tendency that equals the value yielding the maximum fitness potential. Our method defines the optimal gene or genotype as that which produces the phenotype distribution that maximizes fitness summed or integrated over its associated fitness potential function. Often the central tendency of the phenotype distribution yielding the probabilistic optimum will differ from the deterministic expectation. This method is an extension of utility theory to any phenotypic character. We illustrate our method using an example based on Price and Waser's (1979) notion of optimal inbreeding via optimal pollen dispersal.
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  • 10
    ISSN: 1573-8477
    Keywords: Evolution of sex ; sexual selection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary In the present paper we distinguish between two aspects of sexual reproduction. Genetic recombination is a universal features of the sexual process. It is a primitive condition found in simple, single-celled organisms, as well as in higher plants and animals. Its function is primarily to repair genetic damage and eliminate deleterious mutations. Recombination also produces new variation, however, and this can provide the basis for adaptive evolutionary change in spatially and temporally variable environments. The other feature usually associated with sexual reproduction, differentiated male and female roles, is a derived condition, largely restricted to complex, diploid, multicellular organisms. The evolution of anisogamous gametes (small, mobile male gametes containing only genetic material, and large, relatively immobile female gametes containing both genetic material and resources for the developing offspring) not only established the fundamental basis for maleness and femaleness, it also led to an asymmetry between the sexes in the allocation of resources to mating and offspring. Whereas females allocate their resources primarily to offspring, the existence of many male gametes for each female one results in sexual selection on males to allocate their resources to traits that enhance success in competition for fertilizations. A consequence of this reproductive competition, higher variance in male than female reproductive success, results in more intense selection on males. The greater response of males to both stabilizing and directional selection constitutes an evolutionary advantage of males that partially compensates for the cost of producing them. The increased fitness contributed by sexual selection on males will complement the advantages of genetic recombination for DNA repair and elimination of deleterious mutations in any outcrossing breeding system in which males contribute only genetic material to their offspring. Higher plants and animals tend to maintain sexual reproduction in part because of the enhanced fitness of offspring resulting from sexual selection at the level of individual organisms, and in part because of the superiority of sexual populations in competition with asexual clones.
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