Showing papers in "The American Naturalist in 1966"

Food Web Complexity and Species Diversity

Abstract: It is suggested that local animal species diversity is related to the number of predators in the system and their efficiency in preventing single species from monopolizing some important, limiting, requisite. In the marine rocky intertidal this requisite usually is space. Where predators capable of preventing monopolies are missing, or are experimentally removed, the systems become less diverse. On a local scale, no relationship between latitude (10⚬ to 49⚬ N.) and diversity was found. On a geographic scale, an increased stability of annual production may lead to an increased capacity for systems to support higher-level carnivores. Hence tropical, or other, ecosystems are more diverse, and are characterized by disproportionately more carnivores.

On Optimal Use of a Patchy Environment

Abstract: A graphical method is discussed which allows a specification of the optimal diet of a predator in terms of the net amount of energy gained from a capture of prey as compared to the energy expended in searching for the prey. The method allows several predictions about changes in the degree of specialization of the diet as the numbers of different prey organisms change. For example, a more productive environment should lead to more restricted diet in numbers of different species eaten. In a patchy environment, however, this will not apply to predators that spend most of their time searching. Moreover, larger patches are used in a more specialized way than smaller patches.

Latitudinal gradients in species diversity: a review of concepts

Abstract: The six major hypotheses of the control of species diversity are restated, examined, and some possible tests suggested. Although several of these mechanisms could be operating simultaneously, it is instructive to consider them separately, as this can serve to clarify our thinking, as well as assist in the choice of the best test situations for future examination.

Measurement of "overlap" in comparative ecological studies

Abstract: Objective, empirical measures of overlap between samples of items distributed proportionally into various qualitative categories are presented and reviewed. These indices of overlap, derived from either probability or information theory, should prove useful to the ecologist in comparative studies of diet, habitat preference, seasonal patterns of abundance, faunal lists, or similar data.

The Role of Time and Energy in Food Preference

Abstract: A model which relates optimal food preference relationships and caloric yield per unit time of potential food sources is derived. It is suggested, on the basis of this model, that: 1) Food preferences can be adequately described only if a number of factors other than relative frequencies in the diet and relative abundances of the food types are known. 2) Animals should be more selective in their choice of foods when satiated or when food is common, more indiscriminate when starved or when food is scarce. 3) Animals may eat one food type with greater frequency, relative to its abundance, than another even if the other food is richer and more efficiently exploited. This occurs in situations of high relative abundance of the first food type. 4) The extent to which predators tend to pass by potential food items may be used to evaluate the role of food in the population limitation of a predator species. 5) Food preferences appear to change readily and appropriately to changes in the environment. preferences a ...

Shannon's Formula as a Measure of Specific Diversity: Its Use and Misuse

Abstract: Ecologists are making increasing use of \"information content\" to measure the diversity of many-species populations (Margalef, 1958; Hairston, 1959; MacArthur and MacArthur, 1961; MacArthur, 1964; Lloyd, 1964; Lloyd and Ghelardi, 1964; Pianka, 1966). Diversity is thus equated with the amount of uncertainty that exists regarding the species of an individual selected at random from a population. The more species there are and the more nearly even their representation, the greater the uncertainty and hence the greater the diversity. Information content, which is a measure of uncertainty, is therefore a reasonable measure of diversity. However, two different definitions of information content have been proposed and ecologists appear to be uncertain as to when each is appropriate. Consider first a population all of whose members have been identified and counted. Let there be N individuals in s species with Ni individuals in the ith species (i = 1, 2, . . . , s). Then, using the formula given by Brillouin (1960), the diversity (or information) per individual is

On the Relation between Habitat Selection and Species Diversity

Abstract: Breeding bird censuses were made in Puerto Rico, Panama, and temperate United States, and a profile of foliage density was made for each. Using information theory formulae both diversity indices and measurements of difference between censuses and difference between habitats can be made. Based on these, the following can be verified directly from the data: 1. Puerto Rico has nearly as many bird species per layer as Panama and the temperate regions, but the Puerto Rican species appear to recognize fewer layers and certainly subdivide habitats much less. Thus different habitats are likely to have quite similar species in Puerto Rico, unlike Panama and temperate United States.

Food and Space as Regulators of Salmonid Populations in Streams

Abstract: In an attempt o synthesize a useful general hypothesis for natural regulation of populations, Hairston, Smith, and Slobodkin (1960) concluded that plants are limited or controlled by a shortage of nutrients, light, or water, or are resource-limited. Herbivorous trophic groups, they suggested, are largely controlled by predation, while predator and decomposer groups are food-limited. In other words, all trophic groups but the herbivores are resource limited. Of course this hypothesis is a general and broad one. Looking at specific animals of a given trophic group it is difficult o find a common mechanism of population regulation. In some cases man's influence has changed the mode of control from predator to food, as has occurred in many big-game populations. For some freshwater fish populations, Larkin (1956) indicates that climatic controls seem to outweigh biological factors in controlling numbers. Possibly this could be explained by environmental stability. In unstable situations climate may prevail as more than a \"density legislative\" (Nicholson, 1954) factor. In more benign environments, intraand inter-specific competition and predation become more important as \"density governors\" in the stable framework legislated by the physical environment. Larkin suggests that in such situations inter-specific competition predisposes fish to loss from other causes, notably predation. Larkin states that freshwater environments offer comparatively little opportunity for specialization in fish (when compared with terrestrial environments). Therefore, many species have wide tolerance of habitat type and flexible feeding habits, leading to breadth at each level of the food chain rather than height of a pyramid of numbers.

"Community Structure, Population Control, and Competition"-A Critique

Abstract: The paper by Hairston et al. (1960) is examined critically with regard to its premises, logic and internal consistency, and its methodology. It is suggested that, either as conclusions or hypotheses, the major points made in the paper are not acceptable. In the present paper the importance of testability and of operational definitions in ecological hypotheses are stressed.

A Model of Growth and Cell Differentiation in Hydra

Abstract: The purpose of this paper is to present a model which analyzes certain mechanisms controlling polarity and cell differentiation in the Hydra. I am mainly interested, first, in interpreting two levels of organization (that is, polarity at the organismal level and cellular differentiation at the cellular level) through a single, fundamental hypothesis; and second, suggesting how this hypothesis may be useful if applied to developmental systems of higher organisms. No comprehensive review will be made of previous publications from our laboratory; and, for the most part, this will apply to work from other laboratories. For background information the reader is referred to the following publications (Burnett, 1961; Burnett and Diehl, 1964; Burnett, N. Diehl, and F. Diehl, 1964; Haynes and Burnett, 1963; Lesh and Burnett, 1964). I will propose that cellular differentiation in the Hydra is controlled by a single factor varying quantitatively at different levels of the body column. These quantitative differences result in qualitative differences expressed in the direction of differentiation of a given cell type located at various levels in the body column. Further, it will be suggested that although the Hydra possesses 17 cell types that may be distinguished morphologically, they all arise from two basic stem cells. The differentiation of the stem cells is regulated by two conditions, (a) the position of the cells in a chemical gradient extending apico-basally along the body column, and (b) whether they reside in the inner cell layer or outer cell layer. Finally, a mechanism through which the chemical mediators of differentiation operate will be proposed. Throughout the manuscript references will be made to an inhibitor in Hydra which specifically blocks cell divisions or certain steps in the differentiation process. It must be stressed at the outset that the concept of inhibitors being produced by coelenterates is not a novel one. Morgan (1908), Child (1935), Barth (1940), Rose and Rose (1941), Steinberg (1954), and Tardent (1960) have all referred to inhibition of hydranths along the stem of Tubularia. However, the inhibition was described in several dif-

Population Stability and Life History Phenomena

Abstract: The hypothesis was tested that, other mortality factors being of equal intensity, the survival of adult female Carabidae, from near the end of one breeding season to the start of the next, is inversely proportional to the amount of reproduction done in that first breeding season. It is suggested that this is one of the compensatory mechanisms leading to population stability in Carabidae and may be widespread in other insects. It is pointed out that the expected influence of natural selection upon life history phenomena may be quite different when actual, rather than potential, population changes are considered.

The Evolution of Morph-Ratio Clines

Abstract: 1. Simple mathematical models are suggested to represent morph-ratio clines in which the morphs are determined by pairs of alleles. 2. The models show that natural selection can bring about the spread of modifier genes influencing the slope and position of such clines. 3. If the selective effect of a modifier on the heterozygote is less than the arithmetic mean of its effects on the homozygotes, the cline will be made steeper. If its effect on the heterozygote is more than the arithmetic mean of its effects on the homozygotes, the cline will be flattened. An additive effect will leave the slope unchanged. 4. A modifier with opposite effects on different genotypes may spread in some parts of a cline but not in others. Thus it can produce one or more sharp local changes (steps) in the cline. The position of these discontinuities need not be related to any sharp changes in the environment, but will depend on the nature of the interaction between the modifier and the polymorphic locus. 5. Migration will not p...

The Adaptive Role of Winter Fattening in the White-Crowned Sparrow with Comments on its Regulation

Abstract: In White-crowned Sparrows wintering in southeastern Washington, there is an inverse correlation between the quantity of body fat and mean air temperature below about 3 C. Between 3 C and 9 C the fat reserves are independent of air temperature. Because of seasonal variation in fat-free body weight in this species, variation in total body weight is not a highly reliable index of variation in lipid reserves. A review of published data indicates that winter fattening is a common phenomenon in small birds which winter in cold habitats or high latitudes, although exceptions can be found in species that evidently in part substitute behavioral adaptations for winter fattening. It may be concluded provisionally that the magnitude of winter fattening tends to be less inwarmer habitats or at lower latitudes.It is absent in a subequatorialwintering population of Yellow Wagtails. Although it is reasonable to assume that winter fattening is an adaptation to the thermoregulatory demands of low ambient temperature, the t...

THE SELECTIVE ORIGIN OF INCOMPATIBILITY BARRIERS IN THE PLANT GENUS GILlA

Abstract: Nine species of annual Gilias in Pacific North America and South America, belonging to the same section of the genus-the Leafy-stemmed Gilias, fall into two classes with regard to geographical distribution. Five species in the California foothills and valleys are sympatric. Four maritime species on the coasts of North and South America are completely allopatric in relation to one another and either completely or mainly allopatric in relation to the foothill-and-valley species. The sympatric foothill species are isolated from one another by very strong incompatibility barriers, forming an average of 0.2 hybrid seeds per flower pollinated in interspecific crosses, whereas the allopatric maritime species can be crossed inter se with the greatest of ease, forming an average of 18.1 hybrid seeds per flower. A somewhat similar geographical distribution pattern of crossing barriers is found in another branch of the genus, the Cobwebby Gilias, which occur in western North America and are also annual herbs. The sy...

The Maintenance of Genetic Polymorphism in a Spatially Heterogeneous Environment: Variations on a Theme by Howard Levene

Abstract: 1) Levene's model of polymorphism in a patchy environment is generalized and extended to include different patch structures and inbreeding. 2) Starting with heterosis in each patch, as the fitness of the heterozygote decreases we pass through regions of average heterosis providing stable polymorphism, then one satisfying Levene's condition for polymorphism, then a region of alternative equilibria (one polymorphic, one monomorphic), and finally fixation of one allele. Variation in inbreeding, patch abundance, and patchiness can have similar effects. Any of these can result in a discontinuity in the population structure along a continuous cline in environment.

Trends in the Insular Radiation of a Lizard

Abstract: 1) An estimate of body size in Uta populations on nine deep-water islands in the Gulf of California is found to be inversely proportional to the square root of the number of sympatric species of iguanid lizards. It is tentatively concluded that (a) small size of Uta on the continent and on large islands is largely affected by interspecific interactions with other iguanid lizards; (b) the intensity of this inhibition to evolutionary increase in size is dependent (but not linearly) on the number of iguanid species interacting with Uta. Other supporting evidence for the existence of interspecific phenomena affecting the ecology and distribution of lizards is presented. 2) The relative size of scales on the dorsal surface of the body is found to be significantly correlated with the area of the island. This and other data on the geographic variation of scales of North American reptiles support the hypothesis that scales are thermoregulatory structures important in heat exchange with the environment, and that s...

A Hypothesis Concerning the Prevalence of Red Coloration in California Hummingbird Flowers

Abstract: The prevailing view that the prevalence of red colors in the hummingbird flowers of the California and western American flora is related to a preference for red, by hummingbirds is not substantiated by experimental evidence. The present paper advances an alternative hypothesis relating common red coloration to the nomadic and migratory habits of the hummingbirds in this region. It is reasoned that quick recognition of hummingbird flowers by hummingbirds which frequently enter new feeding territories is selectively advantageous for both the plants and their bird pollinators. The display of the same red floral color by the different plant species in the whole area of migration facilitates this quick recognition.

The Gene Material as the Initiator and the Organizing Basis of Life

Abstract: Outstanding nineteenth and twentieth century developments in the evidence, conceptions, and speculations concerning the origin and basis of life are considered, with special reference to whether primacy in these respects should be attributed to some form of "protoplasm" in general, or of "gene material," or whether neither of these should be considered to have primacy over the other. The author's view, of the gene material's having primacy (first expressed definitively in 1926), is defended. According to this (as it may today be stated), any living thing, stripped of all its nonessentials, must only have (or have forebears which had) the following three faculties: (1) that whereby it can form more bodies after its own pattern; (2) that whereby, in this process, changes, even indefinitely cumulative ones, can occur, which nevertheless allow the changed successors to form more bodies of these still newer types; and (3) that whereby these different kinds of successors can differently and significantly affect...

Ecological compatibility of bird species on islands

Abstract: The difficulties of coexistence on islands for ecologically similar species of birds are indicated by the paucity of homogeneric species, and by the tendency for their bill lengths, and hence their feeding characteristics, to diverge. Members of the most similar pair of homogeneric species on the Tres Marias Islands differ in bill length by 21%. This is greater than the difference between members of 12 out of a total of 14 mainland pairs which are each represented by one species only on the islands. It is suggested that in some instances both members of the mainland homogeneric pairs have reached the islands, but that one member has been eliminated due to interactions arising from mutual ecological incompatibility. It is further suggested that this process has been important in the adjustment of number of species to island area.

Plant Host Specificity Among Flower-Feeding Neotropical Drosophila (Diptera: Drosophilidae)

Abstract: A study has been made of plant host specificity of flower-feeding Drosophila collected in western, central, and eastern Panama, the west coast of Colombia, Trinidad, W. I., and Leticia, Colombia, on the headwaters of the Amazon River. Three and four species of single host flower-feeding Drosophila species were found in each of two collecting areas, respectively, in central Panama. These flies were bred only from flowers of their special hosts and never from other plants in the vicinity. A fluctuation of population numbers of the drosophilid is correlated with the period of blossoming of the plant species. Monophagous flower-feeding Drosophila occupy plants with long blossoming periods of four to nine months. Other adaptations of monophagous drosophilids to the host plant concern body color and structural details of the ovipositor and egg filaments. About 5% of flies bred from flowers of plants serving monophagous Drosophila are polyphagous drosophilids; i.e., flower-feeders, ground-feeders, or fungus feed...

Experimental Genetics and Human Evolution

Abstract: Planning based on informed foresight is the hallmark of organized human intelligence, in every theater from the personal decisions of domestic life to school bond elections to the world industrial economy. One sphere where it is hardly ever observed is the prediction and modification of human nature. The hazards of monolithic sophistocratic rationalization of fundamental human policy should not be overlooked, and medicine is wisely dedicated to the welfare of individual patients one at a time. However, though lacking machinery for global oversight, we must still find ways to cope with the population explosion, environmental pollution, clinical experimentation, the allocation of scarce resources like kidneys (transplant or artificial), even a convention on when life begins and ends, which confounds discussion of abortion and euthanasia. Concern for the biological substratum of posterity, i.e., eugenics, is divided by the same cross-purposes. Nevertheless, whether or not he dares to advocate concrete action, every student of evolution must be intrigued by what is happening to his own species (what else matters?), and especially the new evolutionary theory needed to model a self-modifying system that makes imperfect plans for its own nature. Repeated rediscovery notwithstanding, the eugenic controversy started in the infancy of genetic science. More recently, the integration of experimental genetics and biochemistry has provoked a new line of speculation about more powerful techniques than the gradual shift of gene frequencies by selective breeding for the modification of man. This article will first recapitulate a widely held skepticism about the criteria for the "good man" who is the aim of eugenic policy. The strategic impasse will not deter tactical assaults, but favors those with the most obvious, short-run payoff. I will then show how this points to an impending revision of the experimental design of human evolution, based on precedents already established in other species of animals and plants. The debate needed to ventilate these issues has started in a few conferences: Man and his future (G. Wolstenholme, ed.) Ciba Foundation Symposium, 1962; Control of human heredity and evolution (T. M. Sonneborn, ed.) MacMillan, 1965; and Biological aspects of social problems (Meade & Parkes, eds.) Plenum Press, 1965, which document many other ideas and references to primary literature. I would refer especially to Dobzhansky (1962) and Harris (1964) for outlines of the philosophical and technical foundations of the discussion. Despite every intention of generality, the outlook of this article is unavoidably culture-bound; many of my allusions pertain to academic life in

Choice of oviposition in drosophila melanogaster

Abstract: (1963) in several wild stocks and mutants of D. melanogaster and D. buskii have shown changes in the relative viabilities of coexisting genotypes in relation to density and to the proportion of each genetic constitution. An interpretation of these last results may be that the genotypic diversity and the relative frequency of the different types exhibited in some populations have a greater efficiency in exploiting the available resources compared with other populations' mutual facilitation (Beardmore, 1963). As many ecologists have pointed out, the above facts may be indicative that in nature a certain optimum density and a certain genetic diversity may be not only a function of the material resources, but may be determined also by the genetic behavior of the species. This behavior is under control of natural selection and may be responsible for the aggregation of preadult stages.

The American Naturalist in American Biology

Abstract: The birthday of The American Naturalist falls on November 22. On that day in 1866 an \"Agreement of the Editors of the American Naturalist\" was signed at the Essex Institute in Salem, Massachusetts by four young naturalists: Alpheus Hyatt, then 28 years old; Edward Sylvester Morse, 28; Alpheus S. Packard, Jr., 27; and Frederic Ward Putnam, 27. Under these and a succession of later editors and publishers, the Naturalist maintained uninterrupted publication for 100 years. It was not the first journal of its kind on this continent, as is sometimes said. The Canadian Naturalist, with similar purposes, was published from 1856 to 1883; the American Journal of Science, founded by Benjamin Silliman at Yale College in 1818 welcomed contributions from biologists but soon became primarily a journal for geology, chemistry, physics, and, recently, general natural science. Other American journals devoted to zoology, botany, and other special biological sciences are younger than the Naturalist. It is probably true that the Naturalist is the oldest continuously published American biological journal. Its beginnings and early history were recalled at its 75th anniversary by E. G. Conklin (1943). One of the circumstances affecting its character and influence during the first 40 years of its life should, however, be emphasized anew especially since information not available to Conklin has been published recently. This circumstance was its relation to the dominant figure in nineteenth century natural history in the United States-Louis Agassiz. The life and times of Agassiz have been well described by Lurie (1960). The four young men named above had been pupils of Louis Agassiz, Professor of Zoology in Harvard College from 1848 to 1873, and assistants of Agassiz in his recently (1859) established Museum of Comparative Zoology. Their relation to their teacher was probably an important, even decisive element in their later careers as productive biologists. It certainly appeared to be so to the persons who wrote the biographies of Hyatt, Morse, Packard, and Putnam in the Cyclopaedia of American Biography for each one was introduced as \"pupil of Louis Agassiz.\" Moreover, when the relationship of these four as pupils and assistants of Agassiz ended suddenly at about the same time, they all struck out on their independent careers and all played important roles in American natural history, biology, and anthropology. They had, in fact, participated in a kind of student revolt against the famous professor who had come from Switzerland to America in 1846. They were members of a \"Society for the Protection of American Students from Foreign Professors,\" (Lurie, 1960, p. 316). Together with three other student-assistants, they left the Museum after disagreement with Agassiz and his refusal to recommend tenure appointments for them. Jobs were waiting for the

On the Dispersal of Drosophila

Abstract: The data on the dispersion of Drosophila pseudoobscura reported by Dobzhansky and Wright (1943) have been reexamined; the log of the number of flies recaptured at various distances from the point of release (both for capture of individual days following release and, for practical purposes, the cumulative captures of all days) decreases linearly with the square root of distance. Crowding seems to cause an artifically rapid dispersal of the released flies. A theoretical reconstruction of the composition of a single, highly localized collection of flies reveals that as many as one-quarter of all flies in such a collection may have emerged from pupae within 25 meters of the collection site. Available data suggest that D. melanogaster, D. willisioni, and D. funebris are much more restricted in their dispersion; 60% to 80 % of individuals of these species collected at one spot may have points of origin lying within a radius of 25 meters.

The Influence of Ambient Temperature and Aridity on Modes of Reproduction and Excretion of Amniote Vertebrates

Abstract: Adaptive radiation of tetrapod vertebrates into terrestrial environments depended upon the successful emancipation of embryonic development from the aquatic "crib" of the Amphibia. The cleidoic egg of birds and the viviparous development of placental mammals are often cited by physiologists as major morphologic adaptations of the most successful terrestrial vertebrates to xeric conditions (Baldwin, 1964; Needham, 1938; Yapp, 1960). However, this interpretation of the initial adaptive significance of viviparity is not shared by ecologists (Kendeigh, 1952; Mertens, 1960). At different times in the history of a group of animals, different environmental factors have exerted major selective pressures upon the group, thereby guiding its evolution. However, major adaptation to one set of environmental factors very likely placed severe limitations on the subsequent evolution of the group, either when the environment changed or when dispersal out of that environment occurred. I contend that the amniote egg was the first stage in adaptation to terrestrial development of embryos, and that evolutionary refinements of this structure (as well as those involving nitrogen metabolism) culminated in the avian egg. Viviparity and placentation, on the other hand, most certainly were adaptive responses primarily to temperature. I hope to show that physiologic data are consistent with the hypothesis of temperature being the primary factor mediating the origin of. viviparity. In so doing, I will also examine the evidence on nitrogen excretion in amniote vertebrates, and will suggest a hypothesis on the probable evolution of enzymatic pathways concerned with nitrogen catabolism.

The Consistency of Intra- And Inter-Continental Grassland Bird Species Counts

Abstract: Evolutionary biologists (Hutchinson, 1957; MacArthur, 1965, and earlier; Patrick, 1963) have often discussed the possibility that a particular habitat contains the maximum number of species it is able to support. The question asked is, if additional (appropriate) species were available, could the habitat absorb them, with or without the elimination of species already present? If the answer to this question is negative and the habitats are saturated, we can expect to find similar numbers of species (of similar types morphologically) in habitats which are widely separated geographically but of like physical features. Little evidence can be found in the literature to verify this hypothesis, but Elton (1950, Ch. II) mentions the similarity between the numbers of species found in surveys of Greenland and southern England heaths (data from Longstaff and Roberts, respectively), and concludes that cc. . . the number of different kinds of animals that can live together in an area of uniform type rapidly reaches a saturation point.\" More extensive is the evidence presented by Patrick (1961, 1963, 1964), whose limnological studies reveal striking similarity in the numbers of species from all groups found in numerous rivers in North America and in some Amazon tributaries, in spite of a large species turnover.

Selection and Schizophrenia

Abstract: The merits of several current hypotheses regarding the maintenance of schizophrenia over time are considered on logical grounds, in the absence of empirical data. Viewing schizophrenia as a genotypically heterogeneous collection of conditions would allow a significant role to be assigned to recurrent mutation, while not excluding the possibility of favorable selective properties rooted in immunological advantages. Although the balance of selective advantages and disadvantages of the disorder in the past remains a matter for speculation, changes in reproductive fitness during recent periods are demonstrated by data from an ongoing study. Interim results show (a) the reproductive rate of schizophrenics is increasing and approaching that of the general population; (b) the reproductivity of the unaffected siblings is also increasing and surpassing that of the general population.

Studies on sexual selection in mice. Iii. Effects of the gene for albinism.

Abstract: Mice from the inbred albino strain, ST/bJ~ were crossed to mice from the inbred black-agouti strain, CBA/J. An F 1 and F 2 were obtained. From the F 2, two lines were established: one homozygous for albinism and the other homozygous for pigmentation. Twenty male mice of the derived albino line were randomly paired with 20 males of the derived pigmented line. Each pair was then placed in a cage. Into 10 of these pens, a derived albino female was placed, while into the other 10 cages an inbred albino, ST/bJ, female was placed. Ten litters were obtained from each pen giving a total of 200 litters. All males were proven fertile both at the beginning and at the end of the experiment. In the pens where derived albino females were used, the derived albino males fathered 54% of a total of 653 mice born. In the cages where inbred albino, ST/bJ, females were used, the derived albino males sired 63 % of a total of 586 mice born. These differences in reproductive success were due to the differences in composition of ...

Some Evolutionary Consequences of Pegmatypic Mating Systems (Imprinting)

Abstract: Deterministic models are employed to investigate the evolutionary consequences of selection due to imprinted mating preferences in relation to the domestic pigeon Columba livia and to sexually monomorphic and dimorphic species of ducks. It is found that in large populations with absolute imprinting, the population tends to split into two noninterbreeding groups each characterized by a different allele, whereas with relative mating preferences a stable equilibrium tends to become established. The terms pegmatype and pegmatypic mating are introduced to describe such mating preferences and such a mating system.