Showing papers in "Evolution in 1957"
TL;DR: August Weismann's theory is subject to a number of criticisms, the most forceful of which are: 1) The fallacy of identifying senescence with mechanical wear, 2) the extreme rarity, in natural populations, of individuals that would be old enough to die of the postulated death-mechanism, 3) the failure of several decades of gerontological research to uncover any deathmechanisms, and 4) the difficulties involved in visualizing how such a feature could be produced
Abstract: A new individual entering a population may be said to have a reproductive probability distribution. The reproductive probability is zero from zygote to reproductive maturity. Later, perhaps shortly...
3,981 citations
TL;DR: The objectives of the study were to investigate numerous characters simultaneously in a considerable group of species; to quantify the relations shown among the species, using objective methods; and to indicate these relationships.
Abstract: The purpose of the study reported in this paper was to determine whether certain statistical procedures might aid persons interested in the relationships among organisms. The objectives of our study were to investigate numerous characters simultaneously in a considerable group of species; to quantify the relations shown among the species, using objective methods; and to indicate these relationships. The organisms selected as an example for use in this study are solitary bees in the family Megachilidae. This choice was made because one of us (C. D. M.) has made recent systematic studies of these insects, so that conclusions as to the relationships obtained by usual systematic procedures could be compared
558 citations
TL;DR: It is easy to demonstrate that there are too few natural tree-holes for the demands of the hole-nesting birds.
Abstract: A considerable number of birds nest in holes of some kind. If we restrict ourselves to Passerine species only, we arrive at the following figures for the percentages of hole-nesters (table 1). The essential thing is not so much the number of species as the number of pairs. As there are fairly good estimations of the numbers of land birds nesting in Finland (Merikallio), I have included the percentages in question. Both in Palearctic and Nearctic woods the numbers of hole-nesters are quite large, if we take into consideration that suitable nesting-holes are far from abundant. The premium on nesting in holes was first studied by Mrs. Nice in her classical work on the Song-Sparrow. In a number of hole-nesting species she found about 65% of the eggs resulting in fledglings, whereas the corresponding value for open nesters was only 43%. This difference has since been confirmed by large bodies of data. The drawback is the severe interand intraspecific competition for nesting-holes. It is easy to demonstrate that there are too few natural tree-holes for the demands of the hole-nesting birds. (1) In the beginning of my Pied Flycatcher investigation (v. Haartman, 1949) after catching the males I used to bring them home to ring them. This repeatedly allowed other males to take over the territory during the short absence of its former owner. Thus, at one nest-box six males succeeded each other within a few days. (2) By putting up nest-boxes one is usually able to increase enormously the number of hole-nesting birds. This has been proved in many study-areas in Finland, Germany, Holland, and England (cf. for instance v. Haartman, 1956; Creutz, Campbell). Before nest-boxes were put up in my study area in S.W. Finland there were hardly 10 pairs of Pied Flycatchers. Now there are about 70, and I am sure the population can still be increased. An even more drastic increase was brought about by Pfeifer in a small protected area in Germany. A corresponding population increase was found in the Tits.
229 citations
TL;DR: The adaptive nature of most of the normal relationships between members of one species is usually apparent as mentioned in this paper, and active participants seem to derive benefits from these relationships, but sometimes, active participation in a social activity places an individual at a personal disadvantage, for instance, the mother in the foetal-maternal relationship.
Abstract: The adaptive nature of most of the normal relationships between members of one species is usually apparent. Active participants seem to derive benefits from these relationships. Several individuals working cooperatively, for instance, might accomplish what would be impossible for the same individuals working independently. Pack-forming behavior of wolves may be an example. Presumably it was developed because of increased reproductive success of individuals that had greater than average inclinations to form cooperative groups. The development of a placental attachment by a foetus, a very different sort of "social" phenomenon, also has patent survival value to the foetus. Sometimes, however, active participation in a social activity places an individual at a personal disadvantage, for instance, the mother in the foetal-maternal relationship. At best, the mother must sacrifice some food energy, and there may be other disadvantages, such as increased predator liability. The sacrifices made by the mother may sometimes result in her death, but they cannot be regarded as deleterious in an evolutionary sense, because they play an essential part in reproduction. The immediate sacrifices involved in any type of parental care may be regarded as a price paid for attendant reproductive advantages, and no special explanation is required. Parental care probably accounts for most of the examples of social activities in which one individual sacrifices or endangers its own well-being for the benefit
202 citations
TL;DR: A group of ten related North American species, sharply set off from all other amaranths of the world by their dioecious habit are considered, more open to reconstruction than most of the genus because its distribution and heredity were less radically reshaped by ancient man.
Abstract: The genus Amaranthus is notable mainly because of the success of many of its members as fellow-travelers of mankind. Sometimes deliberately cultivated as grain crops, green vegetables, dye plants, or ornamentals, more often unintentionally encouraged weeds, many amaranth species have spread and diversified with the advance of artificial habitats on every continent. The part of the genus considered here is a group of ten related North American species, sharply set off from all other amaranths of the world by their dioecious habit. Descriptions of the morphology and geography of each species, documented by specimen citations, with other information appropriate to a conventional taxonomic revision, are given elsewhere (Sauer, 1955). The present paper is an attempt to reconstruct some of their history. This group is more open to such reconstruction than most of the genus because its distribution and heredity were less radically reshaped by ancient man. None of the dioecious amaranths have become domesticated plants or pandemic weeds. Yet, they have also been increasing in geographic and genetic ranges in response to civilization. Tracing their comparatively plain case histories may be a fair approach to understanding the behavior of the whole genus.
165 citations
TL;DR: The form of a bird's wing is so basically important to the successful exploitation of an ecological niche that it inevitably yields many instructive examples of adaptive evolution and it may be profitable to examine the principal categories of wing type and to see how they correlate with special requirements.
Abstract: The form of a bird's wing is so basically important to the successful exploitation of an ecological niche that it inevitably yields many instructive examples of adaptive evolution. It also provides interesting examples of convergence, as is to be expected of a structure that contributes materially to such important functions as locomotion and the obtaining of food. It may therefore be profitable to examine the principal categories of wing type (using the word aerodynamically rather than anatomically) and to see how they correlate with special requirements. Space does not warrant a full discussion of the function of an airfoil, which is readily obtainable in adequate detail from elementary treatments of aircraft aerodynamics, such as those issued for pilot training; but attention must be drawn to some points that are vital to an appreciation of the various adaptions with which we are concerned.
165 citations
TL;DR: The role of random genetic drift in the evolutionary process has, for about two decades, been one of the controversial issues in population genetics and should not be used as a loophole; to be accepted it requires a firmer basis than suspicion.
Abstract: The role of random genetic drift in the evolutionary process has, for about two decades, been one of the controversial issues in population genetics. Some authors have appealed to "drift" as a convenient explanation of the origin of differences among organisms for which no other explanations seemed to be available. But one's inability to discover the adaptive significance of a trait does not mean that it has none (cf. Dobzhansky, 1956). The hypothesis of random genetic drift should not be used as a loophole; to be accepted it requires a firmer basis than suspicion. Other authors seem to think that drift and natural selection are alternatives. As soon as a gene is shown to have any effect whatever on fitness, the conclusion is drawn that its distribution in populations must be determined solely by selection and cannot be influenced by random drift. But this is a logical non-sequitur. The important work of Aird et al. (1954) and of Clarke et al. (1956) disclosed that the incidence of certain types of gastrointestinal ulceration is significantly different in persons with different blood groups. This is, however, far from a convincing demonstration that the observed diversity in the frequencies of the blood group genes in human populations is governed wholly, or even partially, by selection for resistance to ulcers. To make such a conclusion tenable it would have to be demonstrated that the environments in which human racial differences have evolved actually favored greater resistance in certain parts of the
136 citations
TL;DR: The greatest diversity of species of ants is found in tropical rain-forests, and the relationship between diversity and latitude stands out perfectly clearly despite various disturbing factors.
Abstract: The greatest diversity of species of ants is found in tropical rain-forests. It decreases with increasing latitude, with increasing elevation above sea level, and with increasing aridity. Obviously, for meaningful comparisons the territories in which the diversities of the ants are estimated should be of at least approximately equal magnitude. Data culled out of the literature, even from works of authors of unquestionable competence, may suffer from some subjectiveness in the evaluation of species and subspecies. Different local faunae have, of course, not been investigated equally thoroughly. Despite all these sources of errors, some general relationships stand out reasonably clearly. A summary of latitudinal data for the Western hemisphere is shown in table 1. The relationship between diversity and latitude stands out perfectly clearly despite various disturbing factors. For example, the area of the isle of Trinidad is only 4800 KiM2, and yet 134 species of ants are known to occur there, more than on Cuba which is an island of much greater area. This is probably related to Trinidad being a continental island, with a fauna derived from the neighboring continent of Soutih America. The fauna of Cuba is rich in endemic species (and also an endemic genus-Macromischa). The ants of Europe are quite well known. The increase of the number of
115 citations
TL;DR: A second record from the New World be made of bats visiting flowers, and once again the flowers of an unknown "umbelliferous" species visited belong to the Bignoniaceae.
Abstract: INTRODUCTION naceae). At Buitenzorg (now Bogor) in Cheiropterophilous plants are pollinated Java, Burck (1892) reported that the bat by bats which visit their flowers. This Pteropus vampyrus (Linn.) Brisson paid process is peculiar to species growing in attention to the flowers of a liane which tropical regions where suitable vegetarian was finally identified by van der Pijl bats occur. Relatively few systematic and (1956) as Freycinetia insignis Bl. (Pansustained investigations of the process danaceae) . Confusion has arisen regardhave been made and it is the aim of this ing this work by Burck because other paper to provide first-hand observations species of Freycinetia are bird-pollinated. upon the bat-pollination of a species of Again, at Buitenzorg, Heide (1927) Parkia (Mimosaceae) and to discuss the was the first to observe Eonycteris spelaea evolutionary problems which they raise. Dobson, a small fruit bat, visiting the flowThe first suggestion that bats might ers of planted specimens of Kigelia aethiact as pollinating agents for flowering opica Decne. (Bignoniaceae) and Markplants was made by Moseley (1879) who hamia (Dolichandrone) stipulata Seem. observed bats attacking and eating the red (of the same family). In India, McCann flowers of a tree, probably a species of (1931) described the behavior of the bat Erythrina (Papilionaceae), during the Cynopterus sphinx Vahl. which visited the hours of daylight. These observations flowers of Kigelia pinnata DC. and Orowere made in the Pacific islands of Tonga xylon indicum Vent. (again of the Bignoduring the cruise of H.M.S. Challenger. niaceae). This record was not, however, the first to A second record from the New World be made of bats visiting flowers, the honor was made by Porsch (1931) who obfor which probably belongs to De La Nux served visits in Costa Rico by Glossophwho, in a letter dated 1772, wrote to the aga soricina Pall. to two species of CalaFrench botanist Buffon that he had seen bash tree, Crescentic cujete L. and Parbats of the species Pteropus niger visiting mentiero alata Miers. Once again the flowers of an unknown \"umbelliferous\" species visited belong to the Bignoniaceae. plant at Reunion in the Mascarene Islands In 1936, Altmann informed van der (Jaeger, 1954b). Subsequently, Gould Pijl (1936) that he had observed small (1863) in Australia, saw flowers of bats visiting the flowers of the Baobab Eucalyptus attacked and eaten by Ptero(Adansonia digitata L., of the Bombacapus alecto gouldi. ceae) planted in Java, but it was not until After Moseley's publication, further ob1943 that Jaeger (1945) confirmed this servations of flower-visits by bats were from French West Africa where the spemade in Trinidad by Hart (1897) who cies is native. Jaeger observed visits by recorded visits to Bauhinia megalandra the large fruit bat Eidolon helvum Kerr to Griseb. (Caesalpiniaceae). Hart, in a this tree. Subsequently, Jaeger (1954a) letter to Knuth (cited by Knuth, 1908), published his description of the visits of also recorded visits by the bat now known an unidentified bat to the Silk Cotton as Anourageoffroyi (Peters) Gray to the Tree (Ceiba pentandra Gaertn., also of flowers of Eperua falcata Aubl. (Papillothe Bombacaceae) in the same region.
107 citations
TL;DR: Drawing significant conclusions indicating that certain of the concepts of species ranges and ecological occupancy have been unnatural are found.
Abstract: The generalization that no two species of organisms can occupy the same ecological niche at the same time has been expressed as Gause's Law (Lack, 1949), although there appears to be some doubt as to such an exact application of Gause's work (Gilbert, Reynoldson, and Hobart, 1952). In apparent contradiction to this generalization, we have at times found different insect species living in what appear to the collector to be identical situations. This has led us to seek sets of observations which would elucidate the problem. In particular, certain leafhoppers which feed on the eastern sycamore (Platanus occidentalis) seemed to offer evidence pertaining to this matter of ecological occupancy. A series of collections of these insects was made, and the data are here summarized. I believe that they permit significant conclusions indicating that certain of our concepts of species ranges and ecological occupancy have been unnatural.
82 citations
TL;DR: The ecological requirements of contemporary fishes and amphibians indicate that the continuously humid climate is the more favorable for invasion of the land, and to advocate this climate as the one in which tetrapods arose violates the principle of parsimony.
Abstract: they had inherited. Solutions to these problems appear incompatible since the scales offer protection from desiccation. Here, again, an apparent problem depends on semi-arid conditions. In the wet tropics today, animals that are notably stenohygric-Qnychophora, leeches, and amphibians-move about olfer land as though they were independent of water. Similarly, if the tetrapods arose in a continuously humid climate, desiccation would have been at most a minor problem. Under these circumstances evolution of the exoskeleton would not have been restrained by the needs of water regulation. The position advanced in this brief essay is simple. The geochemical analysis of the Upper Devonian red beds points to their deposition in the tropics under conditions either of periodic drought or of evenly distributed rainfall. The ecological requirements of contemporary fishes and amphibians indicate that the continuously humid climate is the more favorable for invasion of the land. Furthermore the behavior and distribution of contemporary air-breathing, terrestrial fishes demonstrate that terrestrial habits are adopted in a continuously humid climate. On the contrary, the alternative climate is very unfavorable for amphibious animals and, in effect, raises more problems than it solvesas witness the papers of Orton, Colbert, and Goin and Goin. To advocate this climate as the one in which tetrapods arose violates the principle of parsimony.
TL;DR: Results are presented of fornian serpentine soils, and other ashybridizations involving thirty-two differpeets of this striking form of endemism ent population samples of Streptanthus glandulosus that have been applied to a taxonomic interpreta.
Abstract: The outcrops of serpentine and other crops). Several of these local populaferromagnesian rocks in California are tions throughout the range of the complex well known for the array of distinctive have been considered distinct enough to endemic species that their derived soils merit taxonomic recognition as species. support (Mason, 1946; Stebbins, 1942). Such a network of edaphically isolated The causal aspects of restriction to serand morphologically distinct populations pentine, the chemical basis of the edaphic poses problems in evolution and taxonendemism, the tolerance of certain plant omy that are amenable to experimental species to the low nutrient status of Caliattack. This paper presents results of fornian serpentine soils, and other ashybridizations involving thirty-two differpeets of this striking form of endemism ent population samples. Plants grown are discussed in Kruckeberg, 1951, 1954; from seed collected in the wild served as Walker, 1954, 1955; and Whittaker, 1954. the pollen and seed parents of over 300 The restriction of a number of species artificial hybrid combinations. The major of the cruciferous genus Streptanthus to effort has been to determine and evaluate serpentine soils of California has been of any correlation between the extent of spaparticular interest to students of plant tial isolation of the various populations geography and evolution (Kruckeberg, and the degree of fertility of their hybrids. 1951, 1954; Mason, 1946; Morrison, In addition, study of meiosis in many of 1941; Stebbins, 1942; Walker, 1954). the hybrids has been pursued in an atSome species of Streptanthus are found tempt to establish a cytological basis for on but one or two serpentine outcrops of the variation found in the fertility of only a few miles in extent. Others may interpopulational hybrids. show wider distribution but remain obliThis analysis of hybrid fertility thus gate to the serpentine habitat. Still others has led to an assessment of the magnimay be restricted chiefly to serpentine tudes of genetic isolation that may exist but in addition possess populations intolbetween spatially isolated populations. erant of serpentine (Kruckeberg, 1951). On the premise that degree of genetic Such facultative endemism to serpentine isolation is correlated with degree of is exhibited by Streptanthus glandulosus taxonomic relationship, the results have Hook. been applied to a taxonomic interpretaStreptanthus glandulosus, a species complex of many phenotypically distintion of the complex. Intrinsically associguishable strains, is widely distributed ated with the taxonomic objective is an throughout the Coast Ranges of central evolutionary one: To achieve an underand northern California. However most standing of the kind of genetic isolation populations are spatially isolated from that has developed during the elaboration one another due to the discontinuity of of the polymorphism exhibited by the suitable habitats (mainly serpentine outgroup.
TL;DR: Drosophila willistoni has the greatest number of chromosomal inversions found within populations of any species so far investigated, and on the continent of South America, the number of heterozygous inversions per female fly varies from about 1 to more than 9 in different regions.
Abstract: Drosophila willistoni is one of the commonest, and often the commonest, species of its genus in a territory extending from the West Indies to La Plata, and from the Atlantic to the Pacific or to the eastern slope of the Andes. In this enormous distribution region, many populations carry great stores of polymorphs, the most obvious of which are the variant gene arrangements in every one of the three chromosome pairs which the species has. In fact, D. willistoni has the greatest number of chromosomal inversions found within populations of any species so far investigated-47 kinds of inversions, up to 9.4 heterozygous inversions per individual in a breeding population, and up to 16 heterozygous inversions in a single individual (Dobzhansky, Burla, and da Cunha, 1950; da Cunha and Dobzhansky, 1954, and unpublished data). The populations of different geographic regions show however some diversity, both with respect to the quality and especially with respect to the quanltity of the polymorphs present. Thus, on the continent of South America, the number of heterozygous inversions per female fly varies from about 1 to more than 9 in different regions. Owing to the generosity of Drs. H. L. Carson, W. B. Heed, W. S. Stone, and M. R. Wheeler, the writer has been privileged to examine population samples of D. willistoni collected by these colleagues
TL;DR: It is urgently important to explore the expected parallelism between the development of flowers and of insects, and to establish its evolutionary significance.
Abstract: Most students of floral ecology and insect behavior agree today that bees and flowers are closely and mutually interrelated in evolution as reciprocal selective factors (Frisch, 1950, 1954; Grant, 1949; Schneirla, 1951; Butler, 1954, p. 6). But neither the evolution of flower types to their present perfection of colors and symmetry, nor the sensory development of insect pollinators, which might have caused the gradual floral differentiation, are yet satisfactorily explained. So far, no attempt has been made to present theories or speculations on how the flowering plants, which form the main part of the vegetation on earth, have come to be as we see them today. Almost all recent writers hold the view that the evolution of the flowering plants is still as great a mystery as ever (Just, 1952; Good, 1956; Thomas, 1956). It is urgently important, therefore, to explore the expected parallelism between the development of flowers and of insects, and to establish its evolutionary significance.
TL;DR: Investigation showed that the question involved was not whether members of the family Leporidae existed, but whether rabbit-hare hybrids did, and the author was reluctantly forced to accept the existence of rabbits and hares.
Abstract: The title of this paper is slightly modified from that of an article I encountered some years ago, which appeared to be approaching the problem of the relationships of the Lagomorpha, or rabbits and their relatives, from the most basic point of view. This paper, entitled "Gibt es Leporiden ?", seemed to be questioning the very existence of such animals. Investigation showed, however, that the question involved was not whether members of the family Leporidae existed, but whether rabbit-hare hybrids did (E.B.C., 1908). Since then, I have met no one who questions the existence of rabbits and hares, and I have been reluctantly forced to accept them. Furthermore, there seems to be no question but that they are mammals. But just where, among the mammals, they belong is still unsettled. Unfortunately, there is no good popular name for the order, "rabbit" being also used for those genera of leporids that are not hares. Perhaps "bunny" is the best vernacular name for the lagomorphs, for which it is already used at times. This group of animals are currently referred to an order, the Lagomorpha, containing only two living families, the Leporidae or rabbits and hares, andthe Ochotonidae or pikas. The lagomorphs are a rather distinctive group, and there rarely seems to be any question as to whether any given animal is or is not a lagomorph. Both families have been traced back to the Oligocene, and both seem to have had a basic Holarctic distribution then
TL;DR: I agree with Scholander that there is no reason for sustaining the climatic rules and comment upon some recently developed information about adaptation to climate which has been prepared by the use of the propositions whichScholander enunciates.
Abstract: Scholander's (1955) exposition of the usefulness of adaptive insulation in considering the evolution of homoiothermous animals necessarily included denial of significance to the climatic rules attributed to Bergmann (1847) and Allen (1906). Vigorous replies from Newman (1956) and Mayr (1956) insist that the climatic rules can be useful along with Scholander's physiological observations. I hope that the clarifying influence of this enlightening controversy among my admired colleagues will be sustained by my comments. It is with pleasurable anticipation of the value of debate that I enter reasons which deny significance to some observations by which Newman (1956) and Mayr (1956) would support the use of the climatic rules as indicators of the progress of evolution in homoiothermous animals. I agree with Scholander that there is no reason for sustaining the climatic rules. On the positive side of the argument I will comment upon some recently developed information about adaptation to climate which has been prepared by the use of the propositions which Scholander enunciates. Scholander has pointed out essential errors in the thermal bases upon which Bergmann's and Allen's rules rest. I am in a position to point out a fault of evidence in a widely used report which states that climate has had an adaptive influence upon the morphology of Eskimos. I refer to Newman's (1956) quotation of Coon, Garn and Birdsell (1950) as to the commonness of amputations of Eskimos' fingers from freezing. During ten years I have often worked with Alaskan Eskimos without noticing that amputations for cold were common. Stimulated by Coon's statement, Dr. A. B. Colyar, Dr. E. M. Scott 1 and I discussed the importance of obtaining statistics upon the extent and effects of cold injury among arctic people. Dr. Colyar has kindly informed me of the indications from his preliminary inquiries. Replies from physicians in charge of hospitals in northern Alaska indicate that 2 or 3 admissions for frostbite occur annually from each of several population groups of about 1000 Eskimos. I
TL;DR: While compiling distributional data on the boring sponges, the report by Volz (1939) of nine sympatric species in the vicinity of the Adriatic town of Rovigno seemed of particular interest because of the problems raised in regard to ecological niche differentiation.
Abstract: While compiling distributional data on the boring sponges, the report by Volz (1939) of nine sympatric species in the vicinity of the Adriatic town of Rovigno seemed of particular interest because of the problems raised in regard to ecological niche differentiation. There is an abundance of calcareous substratum at Rovigno, the littoral terrace consisting of limestone bedrock extending to a depth of 2S meters. Below this is a region of sand and shells. The clionids excavate their burrows in the bedrock as well as in loose limestone rocks, in mollusc shells, and in coralline algae. The vertical distribution and relative abundance of the clionids at Rovigno are shown schematically in figure 1. In the shallow waters of the littoral terrace from a level just below low tide springs to a depth of eight meters, all nine species coexist. Three species show a greater vertical range. The optimum habitats of the dominant species show some differentiation. Thus Cliona celata Grant is found in tide pools, apparently gaining a foothold there when rocks from deeper water are thrown up into the tidal zone by waves. This species alone seems capable of withstanding the environmental extremes of this narrow zone. Cliona celata is common also in shallow, subtidal waters and is moderately common in deep water burrowing in shells and coralline algae. Cliona vastifica Hancock is the dominant species in the lowest intertidal and shallow subtidal regions, inhabiting chiefly limestone rocks. Below one meter in depth it is largely restricted to mollusc shells (principally mussels). but it is uncommon in the terrace, only to regain a
TL;DR: This paper is an attempt to illustrate that a combination of old and new data is needed to illustrate the gap between large-scale non-biological organic synthesis and the emergence of the first living organism is a vast one.
Abstract: Recent results on the radioactive dating of rocks (Patterson, Tilton, and Inghram, 1955; Russell and Allan, 1955) have placed the age of the earth at roughly 4.5 x 109 years. More precisely, this represents the time of stabilization of the earth's upper mantle, but it may also be taken as the approximate age of the crust. Subsequent local melting would have occurred, due to the concentration of radioactive materials near the surface, but at any given time after 4.5 x 109 years ago, the greater part of the earth's surface must have been non-molten and below the boiling point of water. Consequently, the formation of bodies of water on an increasingly extensive scale may also be dated from this period. Both opposing geochemical points of view agree that the terrestrial atmosphere of this time was at least weakly reducing (Urey, 1952; Rubey, 1955; Kuiper, 1957), a conclusion in general agreement with biological evidence. The large-scale production of organic matter under such conditions is very likely, and a number of suitable mechanisms have been proposed (Haldane, 1929; Oparin, 1938; Dauvillier and Desguin, 1942; Urey, 1952; Miller, 1953, 1955; Calvin, 1956; Fox, 1956; Abelson, 1956), the most promising of these involving ultravioletinduced organic synthesis in the atmosphere, and pyrosynthesis on the land. However, the gap between large-scale non-biological organic synthesis and the emergence of the first living organism is a vast one. This paper is an attempt to illustrate that a combination of old and
TL;DR: The present article reports the results of a study of the evolutionary status of a cluster of related species, which may be called the 1esophragmatica species group from the oldest described species Drosophila mnesophragrnatica Duda.
Abstract: In their monograph published in 1952, Patterson and Stone knew of 613 described species of Drosophila. The number of known species has beeen growing rapidly in recent years. This growth is due to two causes. First, the Drosophila fauna of somlle previously unexplored regions is being investigated. Secondly, some of the old "species" are being ana. lyzed with the aid of genetic, cytological, and ecological techniques. fn several instances, such arnalysis has disclosed the existence of extremely interesting groups of very closely related, and yet biologically quite clearly independent, sibling species which were previously confused under one species name. The obscura species group (Dobzhansky and Epling, 1944; Dobzhansky, 1951; Buzzati-Traverso and Scossirolli, 1952), the virilis group (Patterson and Stone, 1952), and the willistoni group (Burla et al., 1949) are examples. The neotropical faunal region contains apparently the greatest diversity of species of Drosophila. The study of Drosophila of this region is still in an early exploration stage. Many territories have never been studied for Drosophila, and the nature of most of the described species is inadequately understood. The present article reports the results of a study of the evolutionary status of a cluster of related species, which may be called the 1esophragmatica species group from the oldest described species Drosophila mnesophragrnatica Duda. Some species of this group are quite common in parts of Peru,
TL;DR: Two species of North American iguanid lizards have been used, Sceloporus olivaceus and Sceleporus undulatus hyacinthinus, to distinguish closely related species and with the determination of the adaptive significance of the differences.
Abstract: The species population is generally acknowledged to be a fundamental unit of evolution. The recognition of these groups and the adaptive significance of their differences are basic to the study of evolution on this level. This is a comparatively easy task in living forms but is often extremely difficult in fossil assemblages in which only the skeletal system is available for study. The study of living populations has shown that, in most instances, populations of closely related animals can be distinguished by statistical methods, even on the basis of skeletal material. The application of these techniques to fossil assemblages should enable one to separate groups that can be studied by the methods applicable to living populations. The present study is concerned with the use of regression lines to distinguish closely related species and with the determination of the adaptive significance of the differences. Two species of North American iguanid lizards, Sceloporus olivaceus and Sceleporus undulatus hyacinthinus, have been used because of the availability of information concerning the ecology and habits. This makes it possible to correlate morphology with function and ecology, and thus provide a basis for the interpretation of fossil samples. Quantitative methods useful in distinguishing species having a well defined adult size, are not adequate for the study
TL;DR: The results confirmed the necessity for progesterone with estrogen for the induction of recurrent estrus in the ovariectomized ewe and suggested a suggested mechanism for estrogenprogesterone interactions.
Abstract: tivity in the plasma of ovoviviparous snakes. Proc. Soc. Exp. BioI. & Mel!., 86: 477-480. EDGREN, R A., AND D. W. CALHOUN. 1957. Estrogen antagonisms: The inhibition of estrone-induced uterine growth by testosterone propionate, progesterone and 17-ethyl-19-nortestosterone. Ibid., 94: 537-539. A suggested mechanism for estrogenprogesterone interactions. In preparation. HUGGINS, C. 1956. Augmentation and depression of estriol-induced growth of the uterus by progesterone. Proc. Soc. Exp. BioI. & Med., 92: 304-305. HUGGINS, c., AND E. V. JENSEN. 1955. The depression of growth of the uterus, adrenals and ovaries by fluorinated steroids in the pregnane series. J. Exp. Med., 102: 347-360. MASON, R C. 1952. Synergistic and antagonistic effects of progesterone in combination with estrogens on oviduct weight. Endocrinology, 51: 570-572. PORTO, A. 1941. Sobre a presenca de progesterona no corpo amarelo de serpentes ovoviviparas. Mem. Inst. Butantan, 15: 27-30. ROBINSON, T. J. 1954. The necessity for progesterone with estrogen for the induction of recurrent estrus in the ovariectomized ewe. Endocrinology, 55: 403--408. 1956. Quantitative studies on the hormonal induction of oestrus in spayed ewes. J. Endocrinol., 12: 163-173. SELVE, H. 1947. Textbook of Endocrinology. Montreal: Acta Endocrinologica. SDlPSON, G. G. 1944. Tempo and Mode in Evolution. New York: Columbia Univ. Press. TURNER, C. D. 1949. General Endocrinology. Philadelphia: Saunders.
TL;DR: F 1 hybrids between two minnows, The frequency and degree of natural N otropis lepidus and N. uenustus, have hybridization between fishes recently has been shown to be much more variable than their controls, reviewed by Carl L. Hubbs (1955).
Abstract: INTRODUCTION on great variability of wild fishes. Moreover, F 1 hybrids between two minnows, The frequency and degree of natural N otropis lepidus and N. uenustus, have hybridization between fishes recently has also been shown to be much more variable been reviewed by Carl L. Hubbs (1955). than their controls (Clark Hubbs, 1956). Although many hybrids between species The hybrid swarms reported in the lit(and genera) have been reported, relaerature may still involve hybrid fertility tively few have been reported as fertile. as many valid fish species have been Most of the reported hybrid fertility is shown to produce fertile hybrids. Conbased, at least in part, on the relatively siderable work has been done on fertility increased degree of variability of the wild of hybrids between Turkish cyprinodonts. hybrids. These include those between Four species, Kosswigichthys asquamaN otropis rubellus and N. cornutus (Ibid.: tus, Anatolichthys splendens, Anato10), Hesperoleucas symmetricus and Lalichthys transgrediens, and Aphanius vinia exilicauda (Ibid. : 10), Lepomis chanteri, are considered to be of hybrid macrochirus and L. cyanellus (Ibid. : origin by Aksiray (1952), and both 2), N otropis lutrensis and N. venustus species of Anatolichthys by Kosswig (Clark Hubbs, Kuehne, and Ball, 1953: (1953). These authors have demon226), Siphoteles mohavensis and Gila strated experimentally that many of the orcutti (Carl L. Hubbs and Miller, female hybrids between these forms and 1943). With the exception of the N 0their near relatives (parental types?) are tropis lutrensis and N. venustus hybrids occasionally fertile, but they have only reported on by Clark Hubbs and Strawn produced fertile males from the cross be(1956), the fertility of the above hytween A. splendens and A. transgrediens. brids has not been confirmed experimenIn addition many partially fertile hybrids tally. As one of the F 1 hybrid samples have been produced experimentally behere reported is much more variable than tween poeciliids of the genera Xiphoits controls, doubt is cast upon the validphorus by Gordon and other workers and ity of assuming hybrid fertility based only M ollienesia by Carl L. Hubbs, although
TL;DR: It has been shown that a well adapted Drosophila gene pool responds rapidly with precision of determination when confronted with any laboratory environmental complex differing in not too great degree from its native complex.
Abstract: Chromosomal polymorphism exists in many populations of Drosophila to assist the species in making adaptive responses to environmental diversity (da Cunha, 1955; Dobzhansky, 1955). Each chromosomal arrangement possesses groups of genes organized by selective forces to produce an adaptive phenotype either by itself or in combination with other arrangements of the same chromosome "coadaptation"). A well adapted Drosophila population may respond to fluctuations in environmental conditions by altering its net gene pool, that is either by changing the frequencies of chromosomal arrangements or by redistributing the genic contents of any chromosomal unit. Apparently chromosomal frequency responses assist the species in exploitation of seasonal changes as well as geographic variation. It has been shown that such a gene pool responds rapidly with precision of determination when confronted with any laboratory environmental complex differing in not too great degree from its native complex. On the contrary an artificial population contrived by mixing individuals descended from diverse populations is not predictable as the outcome of its responsive changes (Dobzhansky and Pavlovsky, 1953; Dobzhansky, 1954). In this latter population the gene pool is unique with no recent selective history; in some cases chromosomal arrangements may become coadapted, in other cases they may not,
TL;DR: Congregans and dissocians nymphs form two separate categories of this transiens phase, illustrating at once the dynamic conception of phase polymorphism and the existence of hysteresis in cycles of densitydependent changes of shape in locusts.
Abstract: According to the Phase Theory formulated by Uvarov (1921, 1928), locusts exhibit a graduated type of densitydependent dimorphism. So marked is this dimorphism that the phases of most common locusts were once accorded specific rank. Phase polymorphism is characterized by two limiting forms linked by a whole range of intermediates; the form found in bands or swarms is known as phase gregaria, and the sedentary isolated form as phase solitaria: intermediate or transiens forms are designated by the terms congregans and dissocians, according to the direction of the phase-change. The ideas presented in this essay stem from different kinds of morphometric analysis of the locusts. First, the occurrence of an extra moult in some individuals is found to be part of a twin homeostatic growth-regulating process during ontogeny. The polymorphism that ensues is stochastically related to the density of the parental population. This density-dependent quality, though inherited, is not genically determined. Careful study of the wing-pads of the developing nymphs distinguishes insects whose innately determined phase status is not in equilibrium with the density of the larval population of which they are part. Congregans and dissocians nymphs form two separate categories of this transiens phase, illustrating at once the dynamic conception of phase polymorphism and the existence of hysteresis in cycles of densitydependent changes of shape in locusts. New methods for the quantitative study of form in locusts show that the generic differences between Red and Desert Locusts are independent of their phase polymorphism and of their normal growth. Finally, a necessarily speculative discussion of the role of polymorphism in the life-cycle of locusts is attempted.
TL;DR: The inversions of Drosophila pseudoobscura, which are proposed to discuss, are confined chiefly to two chromosomes, the acrocentric third and the metacentric X and, in the latter, to its right arm.
Abstract: A chromosome inversion results in an alteration of the original gene order. The alteration produced by each inversion is readily recognizable in the salivary gland chromosomes of Drosophila because of the constant differences in appearance and arrangement of the bands that characterize them. This genus is accordingly a facile subject for a study of the geographical distributions and frequencies of different arrangements in wild populations. The number, kinds and frequencies of arrangements vary from species to species (Patterson and Stone. 1952; da Cunha, 1955). The inversions of Drosophila pseudoobscura, which we propose to discuss, are confined chiefly to two chromosomes, the acrocentric third and the metacentric X and, in the latter, to its right arm. Nineteen arrangements have been recorded in the third chromosome and another is inferred to have existed at one time, if it does not now. They generally overlap each other and are only rarely included, and their heterozygotes are correspondingly complex. Twelve arrangements of this chromosome are known in the populations we shall discuss. Only three inversions have been recorded in the right arm of the X. They are structurally independent of each other, but are not apparently separable by crossing over in nature, and thus form only one effective arrangement. It is associated as a unit to some genetic factor that causes an alteration of the sex ratio and produces mostly females in matings of males that carry it. Three inversions have been found in the second chromosome and one in the fourth. They occur only in low frequencies in the area we shall discuss, if at all, and can have but little effect on the operation of the inversion system. Five types of the Y chromosome are associated with these inversions btut their relation to the system is uinknown. They may need be taken into account ultimately. As far as known. only one type occurs in this area. Thus, the inversion system of D. pseudoobscura is more or less equally divided between two parts of the genome. The basic data for the whole system have been presented lby Dobzhansky (Dobzhansky and Epling, 1944). More recently discovered arrangements are discussed by Epling and Lower (1957). Dobzhansky, Holz and Spassky (1942) have estimated the relative lengths of the five chromosome arms. The third chromosome constitutes approximately 18 per cent of the total and the right arm of the X approximately 23.5 per cent. Thuis, when arrangements are heterozygous simultaneously in both chromosomes, crossing over will be greatly reduced in about 40 per cent of the euchromatin of the cell concerned. The arrangements of the third chromosome have been given names suggested by the places where they were first detected, such as Arrowhead (AR), Chiricahua (CH), Treeline (TL), Pikes Peak (PP) and Standard (ST). Those of the X chromosome are known as Standard (STX) and sex ratio (SR). The term Standard in both instances means only that these arrangements were taken as a base for comparisons. 1 Supported in part by the Board of Research of the University of California; Office of Naval Research, Contr. Nonr. 233 (11); The National Science Foundation Project C1028; and the U. S. Public Health Service, Grant C-3032 M and G.
TL;DR: A review of the taxonomic status of anoplocephaline cestodes from microtine rodents and a discussion of some of the evolutionary and zoogeographic implications of distribution and host-occurrence of these and other helminths are included.
Abstract: Among those genera of microtine rodents having holarctic distribution, the parasitic helminths of North American representatives of Dicrostonyx, LLemmus, Clethrionomys, and Microtus are relatively well known. These helminths demonstrate a highly developed phylogenetic specificity, being restricted essentially to the Microtinae, but few show any evidence of host-specificity at the generic level. Both nematodes and cestodes are prevalent endoparasites of these rodents in boreal North America. For the purposes of the present work, emphasis is placed upon the cestodes, most of which are members of the subfamily Anoplocephalinae. Some of the latter are unusually interesting in that they occur in a variety of host-species over extensive geographic ranges. With the exception of Paranoplocephala omphalodes (Hermann, 1783), it has not been determined whether these cestodes are holarctic. It is evident, however, that some described from microtine rodents in Eurasia correspond morphologically to species in North America. It appears in Alaska that significant relationships between the distribution of certain cestodes and the distribution of their hosts may be recognized. Any attempt to evaluate these apparent relationships is contingent upon determining whether or not these cestodes are holarctic. The study of this problem has now been undertaken in light of work published recently by Eurasian helminthologists and the acquisition of additional comparative material. This paper contains a review of the taxonomic status of anoplocephaline cestodes from microtine rodents and a discussion of some of the evolutionary and zoogeographic implications of distribution and host-occurrence of these and other helminths. I. The genus Andrya. Five species of Andrya parasitic in microtine rodents may be considered valid at the present time. 1. Andrya macrocephala Douthitt, 1915, is the most common cestode observed in species of Microtus in North America. Its unusually wide range of normal morphological variation (Rausch and Schiller, 1949a; Rausch, 1952) has led to the description of some of its variants as distinct species. A. macrocephala has been well characterized from North American material. Two species closely resembling A. mwacrocephala have been described in Eurasia; however, their validity is questionable. One of these, A. bialozuizensis Soltys, 1949, has been reported only from Poland. A. caucasica Kirshenblat, 1938, was described fronm Transcaucasia. It was suggested by Rausch and Schiller (1949a) that A. caucasica might be conspecific with A. macrocephala. This possibility was not considered by Spasskii (1951), in his monograph of anoplocephalid cestodes. Later, Spasskii, Romanova, and Naidenova (1951) made a survey of the helminth parasites of mnuskrats (an introduced species) in Russia, and from this host collected specimens of Andrya in the Kurgansk and Archangel'sk Oblasti. They also had cestodes of this genus from voles in Pribaikal'. These workers noted the lack of significant morphological differences between these specimens and the description of A. macrocephala. It was also observed that the cestodes from the voles of Pribaikal' did not differ in any essential way from A. caucasica and A.
TL;DR: Hybrids were produced and raised to sexual maturity in the laboratory so that their fertility could be tested and methods on artificial fertilization, induction of ovulation, and raising offspring will be discussed in a separate paper.
Abstract: Field trips were made on the nights immediately following or during rains, if it was judged that approximately onehalf inch or more of rain had fallen. In nearly every instance, a \"circuit\" trip was made. A circuit trip included both hurteri and couchi localities within a 40 mile radius of Austin. Ecological observations pertinent to reproductive isolation were made in the field. Hybrids were produced and raised to sexual maturity in the laboratory so that their fertility could be tested. Methods on artificial fertilization, induction of ovulation, and raising offspring will be discussed in a separate paper (Wasserman, in manuscript).
TL;DR: An almost continuous record has been made since 1939 of the frequencies of different gene arrangements in populations of Drosophila pseudoobscura in the San Jacinto Mountains near Los Angeles and three other arrangements are being described in this paper.
Abstract: An almost continuous record has been made since 1939 of the frequencies of different gene arrangements in populations of Drosophila pseudoobscura in the San Jacinto Mountains near Los Angeles (Dobzhansky, 1943, 1947; Epling, Mitchell and Mattoni, 1953, 1957). If we assume that a generation of this species has an average life span of about a month, this period of observation covers not less than 100 generations. More than 40,000 third chromosomes have been examined and a comparable number of X chromosomes, these being the two chromosomes in which inversions occur in detectable frequencies. The samples have been made at monthly intervals as far as possible and the record reflects the changes that have occurred each year for a number of years. The basic analysis of each gene arrangement has been published by Dobzhansky (Dobzhansky and Epling, 1944). Three other arrangements are being described in this paper. They bring the number known in the third chromosome to twenty, of which twelve occur in the populations referred to. Two arrangements are known in the X chromosome.
TL;DR: Application of a modification of Makino and Nishimura's (1952) squash technique to all major groups of the Amniotca, except for the Rhynchocephalia, has led to the following conclusions.
Abstract: During the past 25 years the chromnosomal conditions in Vertebrates have been the subject of a great many investigations. With some justification it has been hoped that such work might add to our present knowledge of the evolutionary relation between the different classes of Vertebrates and, in this connection, special attention has been given to the sex chromosomes. Unfortunately the findings of various cytologists are by no means in agreement and the present note represents an effort to reach a final conclusion, at least so far as the Amniota are concerned. The case of the Anamnia is much clearer: with the only exception of the fish Mogrunda obscura where Nogusa (1955) has described in the male a heteromorphic bivalent of the X-Y type, we may assert that, as a rule, there is no cytological expression of the digamety in Fishes and Amphibians (Matthey, 1949). Application of a modification of Makino and Nishimura's (1952) squash technique to all major groups of the Amniotca, except for the Rhynchocephalia, has led us to the following conclusions:
TL;DR: The study of the phylogeny of the malalittle doubt remains about its real existcostracous Crustacea, and a review of others makes it possible thonic descendants of the Marellidae or now to give an outline of genetic relations of a group closely resembling the Marel between them and of their interpretation.
Abstract: The study of the phylogeny of the malalittle doubt remains about its real existcostracous Crustacea was based originally ence. Instead of the recent Mysidacea, almost entirely on comparative morpholStomatopoda, Euphausiacea, Tanaidacea, ogy of living forms (Claus, Grobben, Calwe find Pygocephalomorpha, Perimectuman), with important later contributions ridae, Anthracocaris, and other less well based on highly refined methods of funcpreserved forms, with a considerable tional analysis (Cannon, Dennell, Mannumber of common characters. It can be ton). Beurlen and Glaessner commenced assumed that, but for our knowledge of some 25-30 years ago to confront the actheir further differentiation into their recumulated zoological evidence with palaecent descendants revealing the significance ontological data. The evidence derived of their distinguishing characters, they from fossils can be highly significant in would have been placed in a single Order this group, firstly because the Arthropod of the Malacostraca. exoskeleton shows many important deThe following genera should be intails of internal organisation, and seceluded in the Order Pygocephalomorpha ondly because the entire evolution of the Beurlen (1930, p. 444) which was origiEumalacostraca proceeds in post-Camnally established for the genera Pygocebrian time, before the eyes of the palaephalus and Crangopsis only: 1. Anthraontologist. In modern compendia and cophausia Peach 1908, Crangopsis Salter textbooks there is little evidence of the 1863 (= Palaeocrangon Salter 1861 non impact of the knowledge of fossil higher Schauroth 1853), Palaeopalaemon WhitCrustacea on the reconstruction of their field 1880. 2. Pygocephalus Huxley 1857 phylogeny. The classification used in (Syn.: Anthrapalaemon Salter 1861, Netreatises of palaeontology is mostly that croscylla Woodward 1879), Paulo caris established for living forms and many Clarke 1920, Liocaris Beurlen 1931, Pysignificant fossils are within the limitagaspis Beurlen 1934. 3. Tealliocaris tions of this system necessarily regarded Peach 1908, Pseudogalathea Peach 1882. as obscure and \"incertae sedis:\" While These three groups differ mainly in adapsome Palaeozoic Crustacea still deserve tive characters and should be considered this designation until more is known as families. Beurlen (1934, 1935) estababout them, either from more detailed lished for the genus Pygaspis a new Submodern descriptions or additional discovorder Pygaspida, considering it as \"beneries, a review of others makes it possible thonic descendants of the Marellidae or now to give an outline of genetic relations of a group closely resembling the Marelbetween them and of their interpretation. lidae\" (1934, p. 131, translated). His All Eumalacostraca are considered to figures of Pygaspis resemble Pygocephabe derived from an ancestor possessing Ius very closely and I believe that the the morphological characters described by Brazilian Permian fossils described under Calrnan (1909, p. 144) as \"caridoid fathis name represent the ventral structures cies.\" In Carboniferous time the repreof Malacostraca of the family Pygocesentatives of different groups of Malaphalidae. They resemble closely the costraca, although to some extent dissimilarly preserved N otocaris tapscotti tinguishable, were so close to each other Broom, most of which have the abdomen and to a generalised ancestral type that \"folded round so that the telson lies under