Showing papers in "The American Naturalist in 1959"

A Theoretical Ecological Model of Size Distributions Among Species of Animals

Abstract: Even within a given level of the food web there appear to be fewer species of large than of small animals. A model can be constructed in which the properties of the niches of different species are defined by the numbers of kinds of interface between a limited number of sorts of randomly distributed environmental mosaic elements. This model implies few very small species, rapid increase in number of species up to a modal size and a slow decline in number, ideally asymptotic to unity, as the size increases. Structurally uniform groups of animals such as the Odonata do not show this distribution, but in mammal faunas it is approached. It is suggested that if a really complete faunistic list for a given biotope could be constructed the size distribution by species would approximate the form given by the model.

A Line of Maize with High Haploid Frequency

Abstract: Chase (1949) has reported considerable variation in monoploid frequencies among different lines of maize, dependent upon both the maternal and paternal parents. The highest frequency found (0.688 per cent haploids from a particular single-cross hybrid crossed by a particular inbred pollen parent) is well above the average frequency of 0.111 per cent for all crosses used in the study. It is generally accepted that a haploid frequency of 0.1 per cent is usual. A genetic inbred with an unusually high frequency of haploids has been found. Data accumulated over several years on self-pollinated progenies of an inbred designated as \"stock 6\" show 343 haploids in 10,616 observed plants, giving an over-all frequency of 3.23 per cent. Relatively few of these haploids have been verified by chromosome counts on root tips, as they are field-grown plants; however, the uniformity of stock 6 and the striking features of its haploids permit clear classification within the line without difficulty. The haploids are invariably small, with narrow, erect leaves; tassels and ears are usually completely sterile; the anthers are much smaller than normal; zebra-striping is usually present on the leaves, and linear sectors of white tissue (presumably through chromatin loss) are common. Complete verification of other haploids by root-tip chromosome counts confirms the presence of a potential for high haploid frequency. Preliminary tests indicated that the high frequency could be attributed largely to the pollen of stock 6, as if the pollen were inducing an increased proportion of haploids in maternal parents. This affords the opportunity to study the inheritance of induction by testing individual plants of outcross progenies involving stock 6 for their haploid-inducing potential. By using individual plants as pollen parents large enough progenies can be obtained for statistically adequate tests. Stock 6 is A C R9 Pr b pl. As the usual dominant markers for the pollen parent in haploid tests (RT B P1, conferring purple root and color) are absent, a maternal parent with a differentiating recessive seedling marker is needed. In the following inheritance tests a maternal parent carrying a glossy seedling marker (gl) is employed. Table 1 gives frequencies of maternal haploids in the gl parent pollinated by the following: Stock 6, line 2698, the F1 hybrid, the backcross to stock 6, and the backcross selfed. Line 2698, the low-frequency parent, is an a2 tester, carrying Rr B P1 for concurrent incorporation into an eventual

Environmental Determinants of Faunal Diversity

Abstract: It should be possible to test the hypothesis that tropical faunas are more diversified as a result of selection for smaller niches, by assembling complete censuses for periglacial and southern areas of similar topography during different intervals of Pleistocene time.

A Cichlid Fish, Symphysodon discus, with Unique Nurture Habits

Abstract: The amazing parent-offspring relationship in Symphysodon discus is probably unique among fishes studied to date. Normally the newly-hatched fry feed exclusively off the skin of the parents. This first food was observed to be an abundant mucous secretion with a granular composition produced by both parents over the entire body including the fins. Histological sections revealed that this food is secreted by numerous, large mucous cells in the epidermis of the hypertrophied parental skin.

A Speculative Consideration of Certain Possible Forms of Sexual Selection in Man

Abstract: There appears to be sufficient evidence that paraphilia, or the tendency to substitute reproductively non-significant sexual goals for a mate of the opposite sex, is sufficiently widespread in human populations, involves sufficiently lowered fertility and is under enough genetic control to affect the distribution of genotypes in such human populations as have been well studied. Psychoanalytic theory suggests that the most probable mode of operation of the genetic determinants is on the rates of development of neuro-psychological mechanisms involved in identification processes and other aspects of object relationship in infancy. As such, they may have pleiotropic effects of importance. A consideration of fetichism suggests that certain aspects of sexual selection in man may involve mechanisms neutralizing castration fear, and so may ultimately influence such maturation rates. The type of display involved, which seems different from ordinary epigamic display in the lower animals, is designated cryptandric.

The Contribution of Autecological and Genecological Studies to Our Knowledge of the Past Migrations of Plants

Abstract: PROLOGUE Although the success or failure of a plant depends upon all of its relations with its environment taken together, sometimes a single aspect of this relationship, applying perhaps to a single stage in its life-cycle, may be crucial. This is not a new suggestion. It has been tacitly assumed by many botanists, and is a central plank in Good's Theory of Tolerance (Good, 1931, 1947). However, by seeking out these crucial stages, and discovering how the environmental factors controlling them have varied in the past, we may be provided with valuable information concerning the history of the taxa involved and, possibly, of the floristic elements which include them. It is the purpose of this paper to show that some of these data are available already and to indicate the manner in which further data may be sought. Four stages may be distinguished in the life-cycle of a higher plant species and each of these could be further subdivided: 1) Vegetative growth;

Parthenogenesis in Drosophila mangabeirai Malog.

Abstract: Meiosis and autogamous fusion has been described for a thelytokous strain of Drosophila mangabeirai in which meiotic spindle orientation differs from the type reported for other species of Drosophila. As a result of this orientation, there is an increased probability for the type of fusion to occur which will produce structurally heterozygous, diploid females. It is suggested that the type of spindle orientation favoring the formation of such individuals is adaptive in nature, since all flies examined are structurally heterozygous diploids, having a relatively high per cent hatchability.

On the Anomalous Response of Drosophila pseudoobscura to Light

Abstract: Under usual conditions of handling in the laboratory, D. pseudoobscura shows a number of evidences of positive phototaxis. In an experiment to determine the reaction of this species to light, Pittendrigh (1958) found them to be negatively phototactic in contrast to general observation. The experiments reported in the present paper show that D. pseudoobscura is indeed negatively phototactic under conditions of low excitement, but that if the flies are forced to walk rapidly or to fly, they lose their negative phototaxis and become strongly attracted to light.

Integration of Plant Growth Processes

Abstract: Studies of the temperature relations of cell division and cell elongation in the root of Zea, of the correlation of cytological and growth processes in the anther of Lilium, and of the vegetative shoot growth in Xanthium are cited as evidence of the existence of precise integrative mechanisms in the growth and development of plants. The existence of such integrative mechanisms allows one to devise precise developmental indices which should have great utility in developmental studies.

Competition between Sunbird and Honeyeater Species in the Moluccan Islands

Abstract: Observations of unrelated but ecologically comparable species of sunbirds, Nectariniidae, derived from Malaysia, and honeyeaters, Meliphagidae, derived from Australia in the interstitial region of the eastern Indonesian islands, indicate that these birds of identical size and similar food habits, are at least in partial competition. A study of the behavior of these birds in the territory of one of the species indicates an unequal numerical ratio between the species and dominant, aggressive behavior by the scarcer species (honeyeater). It is suggested that the behavioral activity of aggressiveness may in itself serve to limit successful reproduction in addition to other phenomena such as clutch size or nesting success of which so far nothing is known. Any activities of a social or behavioral nature which may serve to limit the reproductive rate of the species may, therefore, have a considerable absolute survival value.

Cytology, Homology and Phylogeny-A Note on "Organic Design"

Abstract: The origins of the resemblances between living organisms are discussed. It is suggested that at the lower levels of organization, exemplified by biochemical characters, cell organelles, and early embryonic forms, similarities do not necessarily imply common ancestry; independent origin is equally probable. The reasons for advocating this view are given and the problems which it raises in attempting to define the term `homology' are examined. The relevance of the idea to discussions of the phylogeny of the lower organisms is briefly considered.

Temperature Effects on Maternally Inherited "Sex-Ratio" Conditions in Drosophila willistoni and Drosophila equinoxialis

Abstract: A strain of Drosophila equinoxialis producing unisexual female progenies was isolated from flies collected in Puerto Rico. As in D. willistoni and in several other Drosophila species, the condition is inherited through the female line only, being due presumably to transmission of virus-like particles through the egg cytoplasm. This "sex-ratio" condition in D. equinoxialis can be "cured" by heat treatment of the embryos. Males appear in the F1 and F2 progenies of the treated female zygotes. The loss of the "sex-ratio" condition is irreversible. Identical heat treatments failed to disrupt the "sex-ratio" condition in D. willistoni.

One-Sided Reproductive Isolation between Geographically Remote Populations of a Planorbid Snail

Abstract: Crossing experiments were made between remote populations of the planorbid snail, Taphius glabratus, using albinism as a genetic marker. Each couple consisted of a recessive albino from Santa Luzia, Brazil, and a homozygous pigmented specimen from either Capanema, Brazil (2,100 kms. from Santa Luzia), or Caracas, Venezuela (4,100 kms. from Santa Luzia). After copulation, egg production by the albinos decreased until abnormal masses without eggs were eventually deposited. These abnormalities were most intense in the matings between the most remote populations. Cross-fertilized eggs from albinos were much less numerous in the matings Capanema x Santa Luzia than in those between populations from less remote localities. They were even less numerous in the matings Caracas x Santa Luzia, in which some albinos produced no cross-fertilized eggs at all. Egg production by the pigmented specimens remained unaffected after copulation. Moreover, cross-fertilized eggs were laid by them in much greater numbers than by t...

Some Ecological Factors Bearing on the Origin and Evolution of Pigment in the Human Skin

Abstract: The putative physiological values of skin melanization of many tropical peoples do not withstand critical examination. If these supposed physiological benefits cannot be supported, then it is desirable to investigate the possibility that the distribution of low albedo skin color may be explained on some other basis. Because we perceive objects only in terms of visible wavelengths of light, and because the visible range includes some 50 per cent of the incoming radiation, interpretation of the role of differing albedo is more logically limited to functions associated with light that can be seen than to the invisible infrared and ultraviolet that cannot. On this basis it is proposed that the concealment factor innate in differing albedos in areas of differing light intensities and environmental illumination proffers a reasonable hypothesis by which to explain some of the variations in human melanization, especially as observed in "black"-skinned people.

An Electrophoretic Study of Egg-White Proteins in Twenty-Three Breeds of the Domestic Fowl

Abstract: Fresh albumen samples from a total of 244 eggs from 23 breeds of Domestic Fowl (Gallus gallus) were analyzed electrophoretically. These breeds include the wild-type Red Jungle Fowl, as well as a wide variety of bantam, laying, and exhibition breeds which provide a large amount of morphological and physiological diversity. No variation in the egg-white proteins among these breeds could be detected that was greater than normal sampling and measuring errors inherent in the technique. It is concluded that the structure of the egg-white proteins is phylogenetically conservative.

New Species and Forms of Cereals Derived from Hybridization between Wheat and Couch Grass

Abstract: Remote interspecific and intergeneric hybridization is one of the most important factors in the natural evolution of the organic world and a powerful method in creating new varieties and species of cultivated plants and breeds of domestic animals. Hybridization between cultivated cereals and wild grass species is one of the leading ways in which this method is elaborated and used. Our studies have established that all species of wheat cross relatively well with four species of genus Agropyron: A. glaucum Desf. (A. intermedium (Host) P.B., (2n = 42), A. elongatum (Host) P.B., (2n = 70), A. ftmceum (L.) P.B., (2n = 42), A. trichophorum (Link) Right (2n = 32) and one of the varieties (Siberian) of A. repens (L.) P.B., (2n = 42). But not all of the foregoing species of couch-grass yield valuable hybrids. The hybrids with the greatest practical value are produced by crossing Tr. vulgare and Tr. durum with A. glaucum and A. elongatum. Both these species of couch-grass are quite polymorphic, especially A. glaucum. Special studies of a large collection of couch-grass gathered from different habitats have shown that many forms yield hybrids differing sharply in biological and morphological characters. Consequently, the couch-grass parent had to be selected according to its degree of perennial growth, winter or spring development, the biochemical composition of the grain, especially its protein content, and a number of other characters.

Metabolic Polymorphisms in Mammals and Their Bearing on Problems of Biochemical Genetics

Abstract: Examples of chemical differences between different members of a single mammalian species are reviewed. The commonest situation seems to be that in which allelic genes control the formation of closely related but distinct proteins, two of which are present in heterozygotes. The proteins can differ by as little as single amino-acid substitutions in each molecule or part of a molecule. The synthetic mechanisms set in train by the allelic genes often operate at unequal rates, and may be differentially modified. In the case of blood group genes, the products in heterozygotes can be "hybrid" in character and different from those in either homozygotes; but there is no evidence that this is true of protein products. In another group of polymorphisms, different amounts of the same product (usually enzymes) are present in the several phenotypes. In some metabolic polymorphisms, notably the human hemoglobins, selective agencies are known to operate unequally on the different genotypes, maintaining the polymorphism t...

Information Theory of Biological Integration

Abstract: Two phenomena are commonly observed in complex systems: integration, or the restriction of possible configurations of the system through strong coherence between its parts; and feature sampling, or the restriction of functional significance to a fraction of the aspects (the "signature") of a complex configuration. The two effects complement each other: integration means over-determination of systems configurations, and feature sampling, under-evaluation. The stability of a system depends on degree and kind of both effects. Assuming the specification of admissible configurations, and of signatures, to be random, the degree of both effects alone determines the stability. This hypothesis leads to a mathematical relation between probability of systems failure and dose of some injurious agent. The relation found fits a wide variety of experimental data.

Possible genetic difference between the head louse and the body louse (pediculus humanus l.)

Abstract: The head louse and the body louse are human parasites which are distinguishable by their morphological traits, as well as by their preferred location on the host. The nature of the differences between them is, however, by no means clear. Many investigators regarded them as full-fledged species (Pediculus capitis and P. vestimenti), and even alleged that the hybrids between them were sterile intersexes. Other investigators united them in a single species (Pediculus hum anus), and treated the differences between the head and the body forms as mere environmental modifications. New evidence has been obtained in the careful experiments of Alpatov and his collaborators, conducted in 1942-1946, and published in concise but most workmanlike papers by Alpatov, Nastjukova, and Khartulari (1945) and by Alpatov and Nastjukova (1955).

A Study of an Experimental Drosophila Population in Equilibrium

Abstract: An experimental population of D. pseudoobscura was maintained for four and one half years in order to study the stability of its initial chromosomal polymorphism. It was found that it took some 17 months (20 generations) for the population to achieve its final equilibrium frequencies and that the chromosomal polymorphism was then maintained for the remainder of the experiment which was a period of three years (46 generations). It was also found that the different karyotypes of the population did not exhibit any preferences for different parts of the food cups as egg laying sites. The significance of these observations in view of recent findings is discussed.

Studies of the Relative Fitnesses of Experimental Populations of Drosophila melanogaster

Abstract: This paper deals with an attempt to estimate the relative fitnesses of several experimental populations of D. melanogaster. The measure of fitness used was the number of offspring produced by single pairs of individuals. Each experiment consisted of a study of two "competing" populations. Fifty males and 50 virgin females from each of two populations were mated as single pairs in vials. The number of sterile matings was recorded; the offspring produced by fertile pairs were counted fourteen days after mating. Males and virgin females were collected from these vials to establish a second generation of 50 single pairs in vials. The experiments were continued in this way for ten generations. All possible pairs of eight populations (see table 1) were studied. Among the flies representing populations 1 and 3, frequencies of sterile matings increased in successive generations to a high level; this increase must be ascribed to selection of sterility genes in heterozygous condition. In contrast with the increase ...

Study of Fertilization and Embryogenesis in Certain Angiosperms Using Living Material

Abstract: Recently in vivo studies have made considerable progress (P. Maheshwari, 1950). In the U.S.S.R., K. J. Kostriukova, G. K. Benetskaya, M. V. Tschernoyarov, M. S. Yakovlev, M. D. Yoffe and the writer have used the in vivo method for studying pollen grains, pollen tubes, embryo sacs, endosperm and embryos. This has led to some new and interesting findings. Macrosporogenesis, various developmental stages of the embryo sac, fertilization and early embryo development have usually been followed on fixed material. Hence, our investigations have been focussed on the in vivo -studies of precisely these phases of development. Unsectioned total preparations of live pollen grains, pollen tubes, ovules and seeds have been used, Since Strasburger (1900) and Shibata (1902) no data from living material have been available on fertilization in angiosperms. Strasburger studied Monotropa hypopitys, and Shibata, Monotropa uniflora. Physiological studies of fertilization as well as other embryonic processes necessitate the use of living material. In the orchids Cypripedium insigne, Calanthe Veitchii and Dendrobium mobile, we have studied in vivo not only spermiogenesis, gametogenesis and embryogenesis, but also cytogenesis. In all the above three species the penetration of the pollen tube and fusion of the gametes have frequently been followed up. Our method was extremely simple. The ovules separated from the placenta were placed on a slide in a drop of water or of a ten per cent sugar solution, covered with a coverslip, and examined under water or oil immersion. In this way it was possible to examine promptly numerous diverse objects. The pictures were so distinct and clear that there was no necessity to use the phase contrast or the anoptral microscope. The orchids provide extremely favorable material for studying embryonic processes in vivo, as their ovules are minute and the integuments thin and transparent. This is a long-known fact which has made the orchids favorite objects of embryological study. A comparison of the patterns of gametophyte and gamete formation, of fertilization and embryogenesis, on living and fixed material, discloses a great similarity. However, in vivo studies reveal some details which escape observation on fixed material, since in vivo the plasma and its inclusions, such as plastids, chondriosomes, fat globules, etc., are better preserved. Moreover, since the in vivo method is simpler it allows more extensive study. It has thus proved possible to follow the behavior of plastids and chondriosomes at different stages of development of the reproductive organs.

Cytology and Sex Ratios of an African Species of Armored Scale Insect (Coccoidea-Diaspididae)

Abstract: The armored scale insect, Aspidiotus simulans DeLotto, has been reported only for the central highlands of Kenya, in and near Nairobi, where it apparently replaces the closely allied, cosmopolitan species, A. destructor Sign., of the warmer coastal and inland areas. In most regards A. simulans is cytologically a typical armored scale. The females have eight chromosomes, and four bivalents appear at oogenesis. The males become haploid, with four chromosomes, by eliminating chromosome sets during early embryonic mitoses. The eliminated chromosomes are, however, considerably more active on the spindle, and much less contracted than is usual during this process in the armored scales. Although accurate counts were not possible, the number of symbionts in the embryos at very late cleavage was roughly the same for the four-chromosome (male) and the eight-chromosome (female) embryos. The females of collection No. 1 contained either all four-chromosome or all eight-chromosome embryos at postcleavage stages. In the...

High Frequency of Chromatid Breaks in Two In vitro Cell Populations

Abstract: Spontaneous chromosome or chromatid breakages and reunions have been found in both in situ and in vitro cell populations, but the frequency is exceedingly low. McCoy and his associates claimed that cells of Jensen rat sarcoma (McCoy et al., in press), like those of the Walker carcinosarcoma 256, require asparagine in the medium to grow in tissue culture. However, using his medium formula 5 a (McCoy et al., 1959) without asparagine, McCoy succeeded in establishing two mutant cell lines, JA-1 and JA-2, which did not require asparagine. At the tenth and eighth subculture in medium without asparagine, Strains JA-1 and JA-2 were shipped to this laboratory for cytological checkup. Two sets of colchicine-hypotonic-squash preparations were made. The modal chromosome numbers for both lines were registered at low 60's. However, like the populations of the Novikoff hepatoma cell lines (Hsu and Klatt, 1959), most cells in JA-1 and JA-2 displayed various combinations of their marker chromosomes so that the populations were highly polymorphic (detailed cytological data for Jensen sarcoma and its derivatives will be presented elsewhere).

Differences between populations in embryonic developmental rates

Abstract: In an effort to find common ground between the fields of population and developmental genetics, techniques have been worked out for observing and measuring some embryonic characters in Drosophila melanogaster. Measurements made on developmental rates in three strains show that each has its own developmental pattern. These characteristic patterns of development are evidence of the way in which the genetic system of a population produces the array of adult phenotypes characteristic of the population by effecting its own set of biochemical and embryonic events.

A Partial Dominant for Suppression of Color in the Syrian Hamster, Cricetus Mesocricetus auratus

Abstract: In the last few years there have been several reports of a blind, pinkeared albino hamster, recently described by Knapp and Polivanov (1958). In contrast to the dark eared albino (designated cdcd by Robinson) in which faint grey pigmentation of the ears appears at about four weeks and develops fully to a deep grey or black by maturity, pigmentation is completely suppressed in the blind albino. In addition these animals demonstrate an incomplete optic development, while the dark-eared albino's eyes function normally. Knapp and Polivanov noted anophthalmia in all their animals, but microphthalmic albinos have been reported by other breeders. Albert Marsh reported (unpublished observations, 1955) that blind whites had appeared several years previously in Wisconsin, and had been bred to several hundred specimens. Bred to normal goldens, a golden F1 resulted, and the F2 consisted of golden and blind whites. Bred to the dark-eared albino, a golden F, was again produced, and the F2 was made up of golden, dark-eared, albino, and blind whites. Marsh, as well as Knapp and Polivanov, came to the conclusion that the factors for complete albinism and blindness could not be separated. Recently we obtained an extremely white panda, or piebald, (ss) male hamster with ruby eyes. (This dilution of eye color is often produced in the panda when the pattern of white spotting passes over the eye.) This male, bred to a normal female carrying a panda factor, produced an F1 of 16, of which nine survived. Of these three were normals, while the other six were distinguished by distinct ruby eyes and a white ventrum (WV) (in contrast to the usual ventral coloring of light grey underfur with pale cream tips). At maturity a few small clumps of white hair were discernible in the dorsal area of some WV. None exhibited the white blaze normally associated with panda. The lack of pandas may be attributed to their typical lower viability and inability to cope with competition of hardier littermates. A pair of WV were bred, resulting in the appearance of two blind pinkeared albinos (BA), along with five WV and two normals. At least one BA has occurred in all subsequent F2 (WV x WV) litters. These albinos differ from those of Knapp and Polivanov only in the matter of eye development, being characterized by microphthalmia rather than anophthalmia. Size of the eyeball at 19 days is one-half to one-third that of a normal littermate. In addition, the eyeball may be either opaque or clear. It is of interest to note