bluuebunny/crossref_metadata_2025 huggingface dataset:
Modification of Fitness in Species and Strains of Flour Beetles due to X‐Ray and DDT
Authors: Erdman Howard E.
Published: May 2006

Insecticides and ionizing radiations can induce population changes which under selection are beneficial or harmful. Such changes are known in some cases to have a genetic basis. Studies were designed to determine the early effects of DDT and x—radiation, singly and in combination, on mortality and productivity of flour beetle species and strains (Tribolium confusum Duval "Chicago standard" and T. castaneum Herbst "Brazil cI" an "Sooty"). Five replicate populations each containing ten pairs of virgin beetles x—rayed with 0, 1, 2 or 4 kR of x—rays (250 kvp, 30 ma, 0.25 mm Cu + 1.0 mm A1 filtration, 0.86 mm Cu HVL and 2.5 inches between target and subjects produced 1 kR/min) were cultured under standard conditions in food containing 0, 5, 10, 20 or 50 ppm DDT. Every two weeks for six weeks parental mortality was recorded and living adults were placed on fresh comparable food. The old food was reincubated and F1 adult biomass and numbers were the measures of productivity. Parental mortality was 1) unaffected by x—rays, 2) increased for "Brazil cI" at 50 ppm DDT, and 3) greater for females than males but unrelated to radiation or insecticide. Productivity measurements decreased with increasing x—ray or DDT. Productivity of T. confusum was, in general, more radiation—sensitive than that of T. castaneum strains, whereas, both T. castaneum strains were mor DDT—sensitive than was T. confusum. Radiation of 4 kR was almost sterilizing to T. confusum; of T. castaneum strain "Brazil cI" left no F1 at 50 ppm DDT. Proportions of lethals due to x—ray or DDT were considered genetic dominants and used to quantify the relationship between radiation and insecticide in combination. Observed lethality simulated that expected for genetic dominant lethal effects when "Chicago standard" and "Brazil cI" were stressed with x—ray plus DDT. In "sooty," observed lethality was consistently lower than that predicted on the assumption of dominant lethal effects; i.e., productivity was less adversely affected when both stresses were applied than that expected by multiplying the effects of singly stressed populations. Within a specie "sooty" populations showed more lethality due to x—rays than did "Brazil cI" populations; DDT had the opposite effect.
Oyster Mortality Studies in Virginia V. Epizootiology of MSX, A Protistan Pathogen of Oysters
Authors: Andrews Jay D.
Published: May 2006

MSX, a pathogen of oysters (Crassostrea virginica), produced a drastic epizootic in high—salinity areas of Chesapeake Bay from 1959 to 1963. The patterns of infection and mortality were determined by imports from disease—free seed—oyster areas. Winter and spring imports became infected in early summer and began dying in late summer. Late—summer imports apparently became infected promptly but infections remained subclinical until the following May. Death rates were highest during warm months but losses occurred throughout the year. MSX was assigned as the cause of a high percentage of deaths by sampling live and dead oysters. Mortality for the first and second years after import was usually 50 to 60% annually. A fungus disease caused by Dermocystidium marinum was also prevalent in some areas. Prevalence of MSX did not decline as oyster populations were decimated; hence nearly half of Virginia's private beds have been forced out of production.
Forest, "Prairie," and Soils in the Black Belt of Sumter County, Alabama, in 1832
Authors: Jones Alice Simms , Patton E. Gibbes
Published: May 2006

Field notes and plats of the original land survey of Sumter County, Alabama (1832), are used to reconstruct the vegetation of the 278,093 acres of Black Belt in the county. Calculation from map sampling at all the 424 section corners shows that 65,074 acres (23.4%) supported no trees or less than 10 trees per acre and thus can be considered open land. When section corners are located on a modern soil map, a strong correlation exists between the 99 points which had low tree density (10 trees or less per acre) and the 167 points which have alkaline clay soils: 70.7% of these open—land points lay on what is now alkaline clay. By contrast, 72.5% of the dense forest of 1832 represented by 62 points of high tree density–120 trees or more per acre) is associated with the 257 acid—soil points (mostly loams, some clays). The association of open land (prairie) in Sumter County which alkaline clay soils made for a distinctive, and probably natural, Black Belt vegetation. Tree densities in this part of the county unmistakably represented dense forest (120 or more trees 2 inches dbh or greater, per acre) at only 14.5% of the sampling points. The commonest trees were oaks (Quercus) and hickories (Carya); pine (Pinus) made up less than 5% of the trees sampled and red cedars (Juniperus) made up less than 0.3%.
Soil‐Vegetation Relationships within the Ponderosa Pine Type in the Central Oregon Pumice Region
Authors: Dyrness C. T. , Youngberg C. T.
Published: May 2006

Six plant communities occurring within the ponderosa pine (Pinus ponderosa) and white fir (Abies concolor) zones were identified east of the Cascade Mountains in south—central Oregon. These units, listed in order of increasing effective moisture and increasing elevation, are as follows: (1) Pinus ponderosa/Purshia tridentata, (2) Pinus ponderosa/Purshia tridentat/Festuca idahoensis, (3) Pinus ponderosa/Purshia tridentata—Arctostaphylos parryana var. pinetorum, (4) Pinus ponderosa/Ceanothus velutinus—Purshia tridentata, (5) Pinus ponderosa/Ceanothus velutinus, and (6) Abies concolor/Ceanothus velutinus. The Pinus/Purshia/Festuca association is restricted to areas of Shanahan coarse study loam, while the remaining five units all occur on Lapine loamy coarse sand. Both series are Regosols developed on aeolian pumice deposits. Lapine profile characteristics influencing plant root distribution, such as thickness of the gravelly C1 horizon and amount of mixing of C2 material with the buried soil, showed some apparent correlations with plant communities. The Lapine soil under the Pinus/Purshia and Pinus/Ceanothus—Purshia communities had thickest C1 horizons and the smallest amounts of mixing in the C2. The soil associated with the Pinus/Ceanothus community had the thinnest C1 and a well—mixed C2 horizon. Roots were generally well distributed throughout the C2 horizon in the latter community, whereas in soils possessing a thick C1 and little mixing in the C2 roots are restricted largely to the A1, AC, and D horizons. Soil—moisture measurements indicated that depth and time of onset of soil drought are important factors in controlling the distribution of plant communities in the study area. The A1 horizon under Pinus/Ceanothus and Abies/Ceanothus communities contained appreciably greater quantities of available P, exchangeable Ca, and total N. Organic matter content of the Lapine A1 horizon was considerably higher under the more mesic communities. Carbon—nitrogen ratios of Lapine and Shanahan A1 and AC horizons were not correlated with plant groupings. C/N values were found to be very much higher than those encountered in surface horizons of zonal forested soils, probably due to slow rates of organic matter decomposition.
Fecundity, Fertility, and Longevity of DDT‐Resistant and Susceptible Populations of Drosophila Melanogaster
Authors: Underhill James C. , Merrell David J.
Published: May 2006

The fecundity, fertility, and longevity of three DDT—resistant populations have been compared with these traits in their corresponding controls. The controls usually showed higher fecundity and fertility, but the resistant flies had a longer life span. These differences are interpreted in terms of the differing selection pressures that have existed in the two kinds of populations.
Moisture Measurements in Glacial Soils from Airphotos
Authors: Winkler Erhard M.
Published: May 2006

Photographs with two commercial aerial films of soil samples from glacial drift established a relation between the tone of airphotos and water content of soils. Optical densities of film negatives, measured with a Weston photographic analyzer, decreased proportionally with added moisture nearly to the Atterberg plastic limit of the soil, but then sharply increased as the Atterberg liquid limit was approached. Although these results do not exactly match moisture amounts inferred from densities of actual airphotos, further studies may yield empirical values useful in some areas.
Behavioral Aspects of Population Dynamics in Unisexual‐Bisexual Poeciliopsis (Pisces: Poeciliidae)
Authors: McKay Francis E.
Published: May 2006

Unisexual forms of Poeciliopsis require sperm from males of gonochoristic species. Selection pressures dictate that males discriminate against unisexuals until the latter become extinct. Most Poeciliopsis unisexual—bisexual populations have a unisexual—bisexual female ratio that favors unisexuals, indicating that selection for conspecific mating by males has either not been operative, not persisted for a sufficient period of time, or been disrupted by unknown factors. In mate selection and insemination tests single males show almost absolute preference for conspecific females, but social interactions among males result in unisexual inseminations. Mate selection reduces unisexual fecundity in natural populations, but the all—female forms receive sufficient sperm to sustain themselves.
Coexistence in Unisexual‐Bisexual Species Complexes of Poeciliopsis (Pisces: Poeciliidae)
Authors: Moore William S. , McKay Francis E.
Published: May 2006

All—female forms of Poeciliopsis rely on males of closely related bisexual species for sperm. The natural habitat of Poeciliopsis in Sonora Mexico, consists of a variety of small ponds connected by intermittent watercourses. Optimal areas, containing mixed female aggregates, are defended by territorial males. Social structure in natural populations very closely resembles that of laboratory experiments, wherein subordinant males show reduced mate discrimination and inseminate unisexuals. An equation relating male density to unisexual inseminations is used in a computer simulation model of a population. A stable equilibrium is inherent in unisexual—bisexual species complexes but the level of equilibrium is affected by the environment. Coexistence does not require niche separation. The simulations predict the percentage of unisexuals pregnant in natural populations and explain their distribution pattern. The strength of the mechanism is demonstrated by a natural population in which the percentage of unisexuals pregnant responded strongly to a modest change in unisexual—bisexual composition.
Competition and Thermoregulatory Behavior of the Namib Desert Tenebrionid Bettle Genus Cardiosis
Authors: Hamilton William J.
Published: May 2006

Tenebrinonid beetles of the genus Cardiosis are confined to sand dunes and other sandby substrates of the Namib Desert in South West Africa and Angola. In the northern Namib the breadth of environments occupied by each species is considerably greater in the southern Namib. This may be due to competition resulting in ecological divergence, since there is sympatry in this genus only in the southern Namib. All species of the genus Cardiosis, including the sympatric C. fairmairei and C. hamiltonuli are diurnal. The daily activity rhythm of these species responds to ambient thermal conditions, and fluctuations in ambient conditions result in differing patterns of activity. Substrate and ambient temperatures are the important microclimatic variables influencing the actual timing of activity. This usually results in a concentration of activity in the least humid hours of the day. On cool days or when winds cool the sand surface, activity may extend through the middle hours of the day. On hot or calm days activity becomes bimodal, with activity limited to intervals when body temperatures can be maintained at levels well above 30 degrees C and substantially below lethal limits. The interval of morning activity is less pronounced than the afternoon activity period and on especially hot days morning activity may be omitted altogether. Unconfined populations of Cardiosis extend their activity over considerably greater intervals than confined populations exposed to identical macroclimatic conditions. This is due to the ability of the unconfined population to utilized a broad spectrum of environments, thus locating favorable thermal conditions as they develop in the course of a daily cycle.
Social Facilitation in Weaverbirds: Importance of Colony Size
Authors: Collias N. E. , Victoria J. K. , Shallenberger R. J.
Published: May 2006

During the height of the breeding season there was relatively little or no social facilitation of nest—building when Africa Village Weaverbirds (Ploceus cucullatus cucullatus) kept in large outdoor aviaries in very small and in larger experimental colonies were compared. The sex ratio was kept the same (1:1) irrespective of size of colony. Social stimulation by crowding of the birds early or late in the breeding season led to the earlier onset and later cessation of nest—building, and so extended the breeding season over a longer period of time. The implications of this findings are discussed.
A Pollen Profile from Woden Bog in North‐Central Iowa
Authors: Durkee L. H.
Published: May 2006

Vegetational and environmental changes are deduced from a pollen diagram at a site located in present—day prairie grassland. Three pollen assemblage zones were delineated by analysis of the 10—m core starting with a spruce—fir assemblage which began about 12,000 years ago and was replaced by a deciduous forest assemblage about 10,500 years ago. During the period 9,000—7,500 years ago there was a progressive increase in nonarboreal pollens. At the end of this time, the prairie flora is believed to have been well established.
Diversity in Tree Species in Oklahoma Upland Forests
Authors: Risser Paul G. , Rice Elroy L.
Published: May 2006

Tree—species diversity was measured in 61 Oklahoma upland forest stands. Most stands were dominated by Quercus stellata and Quercus marilandica, but the stands with the greatest diversity were those dominated by other species. There was an inverse relation of dominance concentration (Simpson and McNaughton indexes) to species diversity and the Shannon—Wiener index. The Shannon—Wiener index was positively related to stand basal area and inversely related to stand density. Diversity decreased and concentration of dominance increased along the precipitation gradient from seat to west. Species diversity of Oklahoma forests is generally low to medium compared to southern Appalachian forests.
Population Ecology of Desert Rodent Communities: Habitats and Environmental Complexity
Authors: Rosenzweig Michael L. , Winakur Jerald
Published: May 2006

We investigated the relative densities of granivorous, nocturnal desert rodents in small plots within two arid regions of Arizona to study how sympatric species avoid competitive extinction. The most common rodents were kangaroo rats, Dipodomys spp., and pocket mice, Perognathus spp. We attempted correlating the density of each species with several environmental measurements, derived from the soil's i) depth; ii) texture or iii) resistance to sheer stress; or from the plant's i) species diversity; ii) growth forms or iii) foliage density. Successful variables were derived from plant growth form and foliage density. The soil's resistance to sheer stress also seemed important for a few species. In general, kangaroo rats were associated with sparseness of vegetation; pocket mice with denseness. One group of mice, which we term bush mice, seemed to require bushes and included two Perognathus spp., three Peromyscus spp., and probably a harvest mouse (Reithrodontomys fulvescens). Two other Perognathus spp. were taken in grassy habitats. Some suitable habitats tended to be complementary to others, suggesting that species associated with them are competitors. Comparisons of the density and distribution of D. merriami, present in both regions but under different biotic circumstances, reinforces the opinion that competition is responsible for the complementariness of habitats. In some cases the evidence suggests that competitive coexistence is accounted for by the fact that different specializations are needed to escape predation in different environments. We use variables which correlate with the relative density of various species to construct a model of habitat complexity. The rodent species diversities obtained in our plots can be approximately accounted for by this model. The model is based on the premises that the rodents collectively discriminate four qualities of soil surface, and three heights and two densities of vegetation. In general, specializations based on biotic variables appear most important.
Cuvette Temperatures and Transpiration Rates
Authors: Ritchie Gary A.
Published: May 2006

A cuvette which automatically opens between sampling periods and thus reduces internal temperature buildups was developed for use in measuring transpiration rates of intact plants in the field. In a closed cuvette air—temperature buildups of 5°—7°C and needle—temperature buildups of 17°C above ambient air temperatures are not uncommon, and these temperature alterations are reflected in the transpiration of the enclosed foliage. The open—closed cuvette reduced the buildups by 50% or more.
Age and Space Distribution of the Desert Shrub Larrea Div Aricata
Authors: Barbour Michael G.
Published: May 2006

Field observations of Larrea divaricata Cav. throughout its United States range were used to determine: (1) the age distribution of stand members; (2) the spatial distribution of stand members; and (3) the magnitude of certain soil changes across abrupt community boundaries. Significant non—central tendencies in age distribution of most stands indicated that germination and survival are rare events, contributing to one—age or several—age stands. Shrubs were distributed at random, in clumps, or at regular intervals depending on the environment. Soil pH and salinity changes across ecotones were neither predictable nor usually great enough to affect germination and early growth of Larrea.
Periodicity and Energetics of Torpor in the Kangaroo Mouse, Microdipodops Pallidus
Authors: Brown James H. , Bartholomew George A.
Published: May 2006

The effects of three environmental temperatures and four food rations on the duration and periodicity of torpor were examined, the oxygen consumption of torpid and normothermic kangaroo mice was measured, and temperature profiles in their habitat were obtained during all seasons. Because of their fossorial and nocturnal habits, kangaroo mice need not face environmental temperature above 30°C or much below 0°C although temperatures in their Great Basin habitat normally fluctuate far outside this range. Torpidity affords a reduction in energy expenditure which increases as temperature decreases. At 5°C the oxygen consumption of torpid mice was less than one—sixtieth that of normothermic mice. When the animals were given seeds in excess each day, none became torpid at either 17° or 6°C, but when the daily ration was reduced to 1.5 g all individuals become torpid. The per cent time torpid and the duration of torpor cycles varied inversely with temperature. At 6°C the time in torpor increased when he daily food ration was reduced from 1.5 to 0.5 g but decreased slightly when food in excess was made available at longer intervals. Periods of torpor varied from a few hours to several days. The time in torpor was related to environmental temperature and food supply in such a way that the mice maintained body weight and accumulated food stores under all conditions tested. This suggests that in nature Microdipodops can regulate periods of torpor so as to conserve its stored seeds during both chronic and acute shortages of food.
Avian Predation on the Larch Sawfly, Pristiphora Erichsonii (HTG.), (Hymenoptera: Tenthredinidae)
Authors: Buckner C. H. , Turnock W. J.
Published: May 2006

Forty—three of the 54 species of birds collected in or near tamarack bogs were predators of the larch sawfly. Birds feeding in the tree crowns utilized sawflies to a greater degree than birds feeding in the shrub layer or those that captured their prey while in flight. Predation varied within and between taxonomic groups of birds and important predators were found in every group collected. Some species popularly regarded as vegetarian (viz. sparrows) proved to prey heavily upon sawflies. The warblers, popularly regarded as important insect predators, were clearly of less importance as predators of the larch sawfly than the fringillids. A preference was indicated by many bird species for adult sawflies, even when they were relatively rarer than larvae. Larger and then smaller larvae followed in order of preference. Some species decapitated larvae and ate the body and either rejected or swallowed the head capsule. Positive functional responses were indicated at low and high prey densities for 22 predators, negative for four, and no response for two. The remaining predators were collected only at one of the two prey densities encountered. Population censuses provided data on 34 of the predator species in two plots. Numerical responses were suggested for all except those of sporadic occurrence. Nonresident species were prominent in the plot with a high prey density. Birds are likely to influence sawfly population trends at low insect densities, and perhaps at higher densities as well. The importance of predation on adult sawflies is stressed.
Grazing Effect on Sea Grasses by Herbivorous Reef Fishes in the West Indies
Authors: Randall John E.
Published: May 2006

A conspicuous band of bare sand averaging about 30 ft in width often separates reefs and beds of sea grasses (Thalassia and Cymodocea) in the Virgin Islands and other islands of the West Indies. This zone of sand appears to be the result of heavy grazing by parrotfishes (Scarus and Sparisoma) and surgeonfishes (Acanthurus) that stay close to reefs for shelter from predaceous fishes. Floating sea grass fragments are eaten by the halfbreak Hemiramphus brasiliensis and occasionally by the Bermuda chub Kyphosus sectatrix and the triggerfish Melichthys radula. Within the beds, the sea grasses are fed upon by the small resident parrotfish Sparisoma radians, the echinoids Lytechinus, Tripneustes, and Diadema, the green turtle Chelonia mydas, and in part by the queen conch Strombus gigas, and manatee Trichechus manatus. It is the author's opinion that if the pre—Columbian population of the green turtle could be restored and its fishery properly regulated, the enormous production of the sea grasses in the Caribbean region could be realized more fully for the benefit of man.
Influence of Photosynthetic Crown Structure on Potential Productivity of Vegetation, Based Primarily on Mathematical Models
Authors: Jahnke Leland S. , Lawrence Donald B.
Published: May 2006

Productivity studies have shown that plants with marked vertical extension of photosynthetic crown can be more productive per unit area of land or water occupied than plants whose photosynthetic surface is spread in a thin horizontal sheet on the earth's surface if environmental factors are not otherwise limiting. Geometric models including a flat disc and cones of several heights but constant base radius show that heightening cones intercept progressively more light. Amount of chlorophyll displayed per unit area of earth's surface can also increase greatly with vertical extension of aerial crown. These observations suggest that thickness, geometric configuration, and chlorophyll content of the photosynthetic portion of the vegetation per unit area of earth's surface, and light intensity incident on surfaces at right angles to sun's rays should be measured and described as basic data in primary productivity studies.
Hand‐Operated Piston Corers for Lake Sediments
Authors: Cushing Edward J. , Wright H. E.
Published: May 2006

A modification of the Livingstone sampler, a thin—wall core sampler with stationary piston, will obtain long and undeformed cores of sediment from shallow lakes, with core diameters of 1 to 2 inches. Cores of 4—inch diameter up to 1½ m long can be taken with a piston sampler of slightly different design. The utility of both samplers is greatly extended by their use in combination with a drive frame and two lightweight chain hoists, which can provide up to 2 tons of force for driving and withdrawing the samplers.
Refining Correlations of Water Deficits and Radial Growth in Young Red Pine
Authors: Zahner Robert , Donnelly John R.
Published: May 2006

Two sources of variation, one in the pattern of growth, the other in the pattern of rainfall, were reduced by utilizing vertical sequences rather than horizontal sequences of ring width, and utilizing calculated water deficits rather than rainfall per se. Results from two 21—year—old plantations of Pinus resinosa Ait. on a sand soil in Lower Michigan showed a high correlation between ring width over a 10—year period and moisture variables. Moisture dificits alone for the current growing season had a simple correlation of–.83 with ring width, while rainfall alone for the current year had a correlation of .69. Multiple regression analysis accounted for over 80% of the annual variation in ring width (R = .91) by water deficits and rainfall together, for both the previous and the current growing seasons. Fourteen per cent of the variation was associated with moisture conditions of the previous season (July through September), and 68% was associated with moisture conditions of the current season (May through September). It is concluded that these correlation coefficients of .80 to .90 are approaching the upper limit for relating single environmental factors, such as moisture, to tree growth.
Clinal Variation in the Surface‐Volume Relationships of the Columnar Cactus Lophocereus Schottii in Northwestern Mexico
Authors: Felger Richard S. , Lowe Charles H.
Published: May 2006

Regression analysis of clines in the surface—volume ratios of stems of the columnar cactus Lophocereus schottii in Sonora, Mexico, reveals similar relationships for clinal interpopulation variation and ontogenetic intrapopulation variation. Smaller surface—volume ratios (larger, thicker stems) occur in the northern parts of the distributions of Lophocereus and the othe large columnar species; the younger (sterile) growths of all populations also have smaller surface—volume ratios. Evolution of the surface—volume ratios of the columnar Cactaceae is discussed in relation to complex environmental gradients of temperature and moisture that characterize their effective environments in northwestern Mexico and southwestern United States.
Influence of Naturally Occurring Compounds on Germination and Growth of Jack Pine
Authors: Brown Robert Thorson
Published: May 2006

Water extracts of 56 plants common in jack pine forests were used as moistening media for jack pine (Pinus banksiana Lamb.) seed germination tests. Nine of these extracts consistently inhibited germination. Five extracts often stimulated germination. Greenhouse tests indicated rapid denaturing of biologically active substances and stimulation of growth by Cornus canadensis. Field tests showed definite inhibition of Pinus banksiana germination in the presence of Prunus pumila, Gaultheria procumbens, and Solidago juncca. Best germination was observed in the presence of Pinus resinosa, Pteridium aquilinum, and Cornus canadensis. It is concluded that biologically active chemicals influence plant succession and distribution.
Spatial Relationships of Mesic Forest Herbs in Southern Wisconsin
Authors: Smith Bryce E. , Cottam Grant
Published: May 2006

Species distributions and their interrelationships within the herbaceous stratum of 10 southern Wisconsin maple—basswood (Acer saccharum—Tilia americana) stands were studied. Frequency data were collected in each stand within a belt transect which consisted of 500 contiguous square—foot quadrats. Aggregation and association characteristics of individual species in these stands were compared. A D/d index was calculated by dividing the actual density (D) (each occupied quadrat as considered to be an individual) by expected density (d). Run—gap index values were determined by obtaining the average frequency within the 5—ft segments considered to be within aggregates and dividing by the average frequency within those 5—ft segments considered to be within gaps between aggregates. The larger the D/d and run—gap values, the greater the intensity of aggregation within the stand. Generally, these two indices were found to be higly correlated. All species examined were aggregated at the level tested. Cole's index of association values were calculated from the 1—square—foot quadrat data. Those species combinations with significant association value as determined by a chi—square test were used for further analysis. The highly negative associations indicate either dissimilar habitat requirements or a high degree of competition which leads to the exclusion of one species. The highly positive associations indicate which species require a similar habitat, but do not compete directly.
The Vertical Distribution of the Infauna of a Sand Flat
Authors: Johnson Ralph Gordon
Published: May 2006

This study is concerned with the vertical distribution of macroscopic invertebrates at two sites in Tomales Bay, California. Four sampling procedures were used to obtain data on more than 20,000 individuals. The infauna does not react to tidal fluctuations in water level by appreciable vertical movements in the areas studied. There is no evidence that the depth of the infauna varies with elevation in the range from 0 to 1 m above sea level. The average median depth of all species (except Phoronopsis harmeri) was found to be 8 cm in samples taken at low tide during daylight hours. Most species of the infauna and about 80% of the individuals occur in the upper 15 cm.
2,4‐D Herbicide, Vegetation, and Pocket Gopher Relationships Black Mesa, Colorado
Authors: Tietjen Howard P. , Halvorson Curtis H. , Hegdal Paul L. , Johnson Ancel M.
Published: May 2006

In a 7—year study on Black Mesa, Colorado, elevation 10,000 ft 2,4—D herbicide treatment initially reduced forb abundance and northern pocket gopher (Thomomys talpoides) populations 80% to 90%. Both forbs and pocket gophers remained at low levels on one area but returned to pretreatment levels on the other area. The decline in pocket gopher numbers was caused by an inability to survive where their preferred food (forbs) was eliminated by herbicide treatment. The decline was not caused by movements of the animals from sprayed areas, or by direct or indirect toxicity of 2,4—D. The common grasses offer, at best, only a marginal diet for northern pocket gophers; only succulent grasses or those bearing corms or rhizomes yield a subsistence diet. Limited sampling did not indicate that the spray treatment affected the numbers of other small mammals.
Cohabitation and Relative Abundance of Two Species of Wild Oats
Authors: Marshall D. R. , Jain S. K.
Published: May 2006

Data on the relative abundance of Avena fatua and A. barbata in a number of mixed populations during the seed, seedling, and adult stages were analyzed in terms of a simple model. The results indicated that natural selection favoring A. fatua through better seedling establishment and A. barbata in terms of higher fecundity primarily determines the extent and pattern of cohabitation. Other ecogenetic factors such as the degree of genetic polymorphism in the two species are briefly discussed.
Temperature Control of Germination of Helenium Amarum Seeds
Authors: Caplenor Donald
Published: May 2006

Germination of seeds of the common bitterweed was tested under several temperature regimes. The effect of constant temperatures depended upon duration of storage. Fresh seeds germinated well without statistically significant differences at 11°, 15°, and 19°C. Extended storage at room temperature resulted in general loss of viability, increase in optimum temperature for germination, and decreased temperature sensitivity, especially decreased inhibition by higher temperatures. Alternating temperatures did not generally increase germination. The temperature—sensitive reactions are interpreted as ecologic adaptations rendering the plants highly successful in disturbed areas throughout the southeastern United States. The adaptation specially allows establishment of seedlings in the autumn and growth through the winter without competition.
Dispersal of Aquatic Organisms: Viability of Disseminules Recovered From the Intestinal Tract of Captive Killdeer
Authors: Proctor Vernon W. , Malone Charles R. , DeVlaming Victor L.
Published: May 2006

Earlier studies have shown that viable disseminules of a variety of aquatic, organisms my be recovered from the feces of birds. The present report is concerned primarily with the maximum length of time that vegetative cells and spores of algae, various crustacean eggs, and living adult ostracods can be retained within the divestive tracts of Killdeer (Charadrius vociferus) and, to a lesser extent, Mallard Ducks (Anas platyrhynchos). Some disseminules survived only rapid passage while others were still viable after being retained within the intestional tract for 12—24 hr. Eggs of Artemia salina and oospores of Chara zeylanica were retained for the longest periods. Viable disseminules were retained for much longer periods by Killdeer than by ducks. The results suggest that Killdeer and similar shore birds may be important agents of transport for many kinds of aquatic organisms. Smaller numbers of disseminules area carried by individual shore birds than by ducks, but they can be retained for longer periods, and hence carried across greater intervening distances.
Forest Succession in the Glacier Park Cedar‐Hemlock Forests
Authors: Habeck James R.
Published: May 2006

A gradient analysis and description was made of forest succession among the Thuja plicata—Tsuga heterophylla communities in the vicinity of Lake McDonald in Glacier National Park Montana. Thirty—three pioneer, seral, and climax communities located on well—drained slopes at elevations between 3,200 and 3,500 ft (1,050—1,150 m) were sampled. Through the calculation of indices of community similarity and dissimilarity, the stands were objectively arranged along a unidimensional gradient. The data summarized along the resulting ordination gradient provide a quantitative description of the basic successional pattern existing among these cedar—hemlock communities. Typically, following burning Pinus contorta communities become established, and these in turn are gradually replaced by Pinus monticola and Pseudotsuga menziesii in various proportions. Climax communities on the upland sites become dominated by Tsuga heterophylla, with smaller, but self—reproducing populations of Thuja plicata also persisting.
Germiantion Requirements of the Desert Shrub Larrea Divaricata
Authors: Barbour Michael G.
Published: May 2006

Germination requirements of Larrea divaricata Cav. were studied in the laboratory using seed collected at 34 United States sites. Collection sites were grouped into three desert regions (Chihuahuan, Sonoran, Mojave) of increasing aridity from east to west. Optimum laboratory conditions for germination were: darkness, 23°C, leaching the mericarps with running water, wetting and drying cycles, exposure to cold temperatures prior to sowing, and maintaining the medium about the seeds near—zero in osmotic pressure and low in NaC1. Exposure of dry seeds to warm temperatures (37—71°C) prior to sowing resulted in marked reduction of germination. Maximum root growth was obtained at 29°C in a slightly acidic medium low in NaC1 and near—zero in osmotic pressure. There were no regional differences in germination behavior. Due to seed abortion, non—germination, and mortality over 6 months' growth, only 20 seedlings survive for every 100 mericarps sown under optimum conditions in the greenhouse. It is unlikely that large—scale germination and survival occur often in nature.
Competition for Nutrients and Light between the Annual Grassland Species Bromus Mollis and Erodium Botrys
Authors: McCown Robert L. , Williams William A.
Published: May 2006

Experiments showed that when competition between the common grass resident, Bromus mollis, and an associated forb, Erodium botrys, was primarily for sulfur and crowding was not intense, Erodium growth was much greater than in pure stands, and Bromus growth was markedly less. With competition under a low sulfur regime, Erodium acquired a disproportionate share of the available sulfur because of its more rapid root extension. At high sulfur levels, Bromus became increasingly competitive as its population density was increased, and wide ratios of Bromus to Erodium virtually eliminated Erodium. Leaf area and illumination profiles revealed that Bromus became the superior competitor for light because of its greater stature and more erect leaf habit when exposed to favorable nutrition and population density, and that Erodium supremacy at low sulfur levels and sparse population densities was closely associated with reduced leaf—area production by Bromus.
A Consideration of Insecticide Effects on Hypothetical Avian Populations
Authors: Young Howard
Published: May 2006

Models are constructed which indicate that species respond in variable fashion to insecticide exposure, dependent upon their breeding patterns and longevity. Direct mortality has the most drastic effect on long—lived slow breeding forms, and the least effect on short—lived rapidly breeding forms. The reverse would be true if sterility resulted from insecticide exposure. Species intermediate in respect to breeding rate and longevity are intermediate in their responses to insecticide—caused mortality or sterility.
A Comparative Study of Feeding Rates of Tentaculate Ctenophores
Authors: Bishop John W.
Published: May 2006

Measurements were made of the rates at which the ctenophores Pleurobrachia bachei and Bolinopsis microptera feed on copepods. The data were used to ascertain selectivity and rates of procurement of food in the natural habitat. Both ctenophores selected smaller prey (Pseudocalanus minutus) over larger prey (Ephilabidocera amphitrites). P. bachei selected, whereas B. microptera did not appear to select older over younger stages of development of P. minutus. B. microptera fed on smaller prey at a greater rate than did P. bachei.
Relation of Cladoceran Remains in Lake Sediments to Primary Productivity of Lakes
Authors: Harmsworth Rodney V. , Whiteside Melbourne C.
Published: May 2006

Cladoceran microfossil remains from the surficial sediments of 19 Danish and 14 Indiana lakes were analyzed quantitatively. An attempt was made to correlate the numbers of remains with C14 primary productivity measurements by previous authors. The Spearman rank correlation method gave no correlation for lakes in different drainage basins. It is suggested that under special circumstances there may be a correlation when only lakes of the same drainage basin are considered.
Preliminary Models for Growth Rates in Altricial Birds
Authors: Ricklefs Robert E.
Published: May 2006

The rate of growth in body weight of birds is not correlated with nestling mortality, but rather is a function of the adult body size of the species and the mode of development of the young. To examine the adaptive basis of growth rates, models are formulated which incorporate the mortality of the young, their energy requirement and their rate of growth into a function which determines the productivity of offspring. This function is maximized when growth rate occurs as rapidly as possible, at the expense of brood size. Optimally, one young should be raised which grows as rapidly as the parents are able to supply food. Because this is not observed in nature, and because of other inefficiencies due to the form of the growth curve, it is postulated that physiological constraints, based on the functional organization of the body plan, limit growth rate. This may occur either through bottlenecks placed on the rate at which food can be processed and utilized, or by problems of allocation of energy and tissues among mature and embryonic functions.
Zooplankton Grazing Rates Estimated under Field Conditions
Authors: Enright J. T.
Published: May 2006

An analysis of unpublished phytoplankton data collected in 1919—1920 suggests that certain chain—forming diatoms, under field conditions, undergo synchronized cell division at night and suffer extensive daytime grazing mortality. If this interpretation of the data is correct, the average total daily grazing represents at least 40%, and possibly as much or more than 50% of the standing crop. Such rates would imply that turnover of phytoplankton is extremely rapid in the nearshore area studied.
Factors Influencing the Growth and Relative Growth of Acmaea Digitalis, A Limpet
Authors: Giesel J. T.
Published: May 2006

Two forms of Acmaea digitalis, a limpet, one found on sandstone faces of the marine littoral zone, the other found associated with the gooseneck barnacle, Pollicipes polymerus, differ in their relative length—height growth rates. The limpets characteristic of the barnacle beds increased in height faster than did the rock—dwelling forms. Growth rate of the barnacle—associated limpets showed correlation with the growth rate of the Pollicipes. Both relative and absolute growth rates of these limpets may be functions of the selective action of intertidal physical factors, as affected by the relationship of the limpets to their homesites.
Selection in Density‐Regulated Populations
Authors: Charlesworth Brian
Published: May 2006

This paper examines the effect of natural selection on the composition of a population when the expected numbers of offspring of the different genotypes are decreasing functions of population size. It is shown that the eventual outcome of selection (whether there is a stable polymorphism or fixation of one or other allele) is determined by the genotypic K—values, but that the r—values influence the composition of equilibrium populations. With certain r—values there may be permanent oscillations in population size and gene frequency. A different model of selection, where selective differences are unrelated to differences in r and K in a regulated population, is also described and its relevance to the problem of genetic load is discussed.
Food Competition Among the Cellular Slime Molds (Acrasieae)
Authors: Horn Edward G.
Published: May 2006

Four species of Acrasieae (Dictyostelium mucoroides, D. purpureum, Polysphondylium pallidum, and P. violaceum) coexist in forest soils. All are capable of feeding and reproducing on a wide variety of bacteria than exist in their habitat. The four Acrasieae and four strains of food bacteria were isolated from the soil. When the four slime molds were forced to compete on a single strain of bacteria, one species always outcompeted the others. For any particular food the same species of Acrasieae is the consistent winter. Each species uses a different strategy to outcompete its competitors. The consistency of competitive success and the coarse—grained nature of the food distribution allow the coexistence of these four species of Acrasieae in nature.
Seasonal Changes in the Body Composition of the Garter Snake (Thamnophis Sirtalis Parietalis) at Northern Lattitudes
Authors: Aleksiuk Michael , Stewart Kenneth W.
Published: May 2006

At northern latitudes the garter snake (Thamnophis sirtalis parietalis) undergoes a prolonged period of hibernation and has access to food only from mid—May to mid—September. An examination of seasonal changes in the body composition of this organism revealed that protein and ash, expressed as percentage of total body weight, remain essentially constant throughout the year. Lipids are low in the spring, increase during the summer, and decrease during the autumn and winter. Percentage water content exhibits a pattern which is the reverse of that of lipids, with the exceptions of a dehydration in the autumn and a rehydration in the spring. Expressed in absolute terms, for an animal of fixed body length, ash remains relatively constant throughout the year, while all other components show a seasonal pattern similar to that of lipids. The data suggest that the animals are near starvation in May, at the end of an 8—month aphagic period. The period of aphagia and low winter temperatures appear to be the most important factors causing seasonal changes in body composition.
Mineral Equilibria in Ecosystem Geochemistry
Authors: Johnson Noye M.
Published: May 2006

In terrestrial ecosystems the composition of runoff water may not reflect chemical equilibrium conditions, but rather chemical flux conditions through an open system. The irreversible flow of chemicals through the boundaries of an ecosystem, as exemplified by chemical weathering, may assume a time—invariant mode (steady—state) which resembles a state of equilibrium in a closed system.
Analysis of single nucleotide polymorphisms in genes in the chromosome 12Q24.31 region points to P2RX7 as a susceptibility gene to bipolar affective disorder
Authors: Barden Nicholas , Harvey Mario , Gagné Bernard , Shink Eric , Tremblay Monique , Raymond Catherine , Labbé Michel , Villeneuve André , Rochette Denis , Bordeleau Lise , Stadler Herbert , Holsboer Florian , Müller‐Myhsok Bertram
Published: May 2006

Previous results from our genetic analyses using pedigrees from a French Canadian population suggested that the interval delimited by markers on chromosome 12, D12S86 and D12S378, was the most probable genomic region to contain a susceptibility gene for affective disorders. Association studies with microsatellite markers using a case/control sample from the same population (n = 427) revealed significant allelic associations between the bipolar phenotype and marker NBG6. Since this marker is located in intron 9 of the P2RX7 gene, we analyzed the surrounding genomic region for the presence of polymorphisms in regulatory, coding and intron/exon junction sequences. Twenty four (24) SNPs were genotyped in a case/control sample and 12 SNPs in all pedigrees used for linkage analysis. Allelic, genotypic or family‐based association studies suggest the presence of two susceptibility loci, the P2RX7 and CaMKK2 genes. The strongest association was observed in bipolar families at the non‐synonymous SNP P2RX7‐E13A (rs2230912, P‐value = 0.000708), which results from an over‐transmission of the mutant G‐allele to affected offspring. This Gln460Arg polymorphism occurs at an amino acid that is conserved between humans and rodents and is located in the C‐terminal domain of the P2X7 receptor, known to be essential for normal P2RX7 function. © 2006 Wiley‐Liss, Inc.
Cross‐Coupling Reactions on Azoles with Two and More Heteroatoms
Authors: Schnürch Michael , Flasik Radoslav , Khan Ather Farooq , Spina Markus , Mihovilovic Marko D. , Stanetty Peter
Published: May 2006

Recent progress in the field of transition‐metal‐catalyzed cross‐coupling reactions on various azole systems is summarized. Most important C–C‐ and C–X‐bond formation methodologies (Negishi, Suzuki–Miyaura, Stille, Kumada–Corriu–Tamao, Hiyama, Sonogashira, Heck, C–H activation) are reviewed and discussed for the imidazole, oxazole, thiazole, pyrazole, isoxazole, and isothiazole system, as well as for azoles with more than two heteroatoms. This review covers the literature that appeared in the past ten years up to the end of 2005 with corresponding azoles used either as metal organyl or halide (including triflates and some other less frequently applied leaving groups); literature describing azole structures only as ligands was not included.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)