bluuebunny/crossref_metadata_2025 huggingface dataset:
Role of Moss in Slope Formation
Authors: Marsh William M. , Koerner John M.
Published: May 2006

Measurement of slope geometry, moss—lobe characteristics, soil creep, and sand deposition were made over a 2—year period at four sites along the southeastern shore of Lake Superior in Michigan. Woody vegetation was mapped at two of the sites. Moss lobes originate from the dislodgement of moss clumps from the sand slope crest, their stabilization on the slope face, and their subsequent revegetating by buried moss rhizoids. Moss lobes grow from sand deposition, measured at an average rate of 0.78 cm per year. Soil creep, which averaged 2.1 cm per year at one site, causes convoluting of the lobe snouts. These processes induce slope profiles which have straight or convex instead of concave midslopes as are usually found on sand slopes. The moss lobes also diversify the plant habitat as indicated by highly patterned distributions of woody stems.
Factors Affecting Host Plant Selection in Desert‐Adapted Cactiphilic Drosophila
Authors: Fellows David P. , Heed William B.
Published: May 2006

Three types of tests were conducted to determine the causal factors for the narrow larval niche breadth and the low amount of larval niche overlap observed among common species of Drosophila breeding in rotting cereus cacti in the Sonoran Desert. (1) Field test and observations show that host plant discrimination for feeding adults is very high but not absolute. (2) Substrate substitution experiments conducted individually with four species of cactiphilic Drosophila on six kinds of artificially rotted cacti show that every species except D. mojavensis reproduces bests on the cactus (or cacti) on which it is resident in nature. Even so D. mojavensis and D. arizonensis, both of which are polyphagic, emerge in large numbers from five kinds of cacti. (3) Laboratory competition tests with mixed species established in three cases that the resident species was unaffected, as compared with monoculture controls, while the alien species usually emerged in significantly fewer numbers. In two other competition situations neither the alien nor resident species was significantly affected. Inability of the polyphagic species to invade certain non—host cacti in nature could be due to competition in the first three cases. In the latter two cases either the physical characteristics of the substrate or the climate affecting distribution (and/or density) appears to be the principal restricting factor. Narrow host plant specificity is accompanied by specialized nutritional requirements and more continuously available rot pockets in the host plants.
Some Ecological Relationships of the Invertebrate Drift in Praters Creek, Pickens County, South Carolina
Authors: Reisen William K. , Prins Rudolph
Published: May 2006

The role of organic drift in the ecology of a southern, upper Piedmont stream was evaluated from September 1967 to August 1968. By sampling for a 24—hr period each month, data on the diel and monthly fluctuations of the drift were obtained. Chemical physical analyses of the water were made to evaluate the role of selected abiotic variables in the ecology of the drifters. Community biomass could not be estimated by drift because fluctuations in the standing crop were not significantly correlated with fluctuations in the drift rate. With the exception of Ephemerella sp. the drifters did not respond in a density—dependent fashion to benthic population increases. Drift seemed to be initiated by pupation or emergence activity. The diel drift for the majority of the benthos examined was decidedly negatively phototactic. Pronounced crepuscular activity was observed for most of the hemimetabolous forms with a consistent midnight depression of activity.
Protection of Barteria (Passifloraceae) By Pachysima Ants (Pseudomyrmecinae) in a Nigerian Rain Forest
Authors: Janzen Daniel H.
Published: May 2006

In a Nigerian rain forest, occupation of Barteria fistulosa saplings by Pachysima aethiops ants results in the plants having more leaves, more branches, more leaves per branch, and less damage to the shoot tips than do unoccupied Barteria. At present this difference is the result of insect damage to unprotected Barteria, but several traits of the ant colony suggest that in the recent past, large browsing mammals may also have been a threat to Barteria. These traits include a few large workers per colony, a deeply painful sting, and the habit of frequently dropping from the Barteria crown. Pachysima workers attack plants adjacent to their Barteria and clean the large Barteria leaves of debris and epiphyllae.
Optimum Mean Temperature for a Plant Growth Calculated by a New Method of Summation
Authors: Abrami Giovanni
Published: May 2006

The relationship between temperature and stem elongation has been investigated for representative herbaceous plants sampled from populations of seven species which were growing under semi—natural conditions in the Botanical Garden of the University of Padua (Italy). The growth of the floral stem was measured for the following species: Galanthus nivalis L., Corydalis cava Schw. et Krt., Anemone nemorosa l., Symphytum tuberosum L., Symphytum tuberosum L., Allium ursinum L., Aegopodium podagraria L., and Campanula rapunculoides L. Official records of daily maximum and minimum air temperatures have been elaborated by means of a new method of temperature summation. This method takes into consideration the concept that plants possess a range of sensitivity to temperature between maximum and minimum thresholds and that there is an optimal temperature for each stage of development. Data for stem elongation have been optimized (using the technique of best fit) as a function of a logistic curve which may represent growth under ideal conditions. Differences between the logistic curve and the real curve of growth may be related to the amount of deviation of values for environmental factors form optimal values. The temperature ranges between 0° C and 30° C which gave the best correlations with stem elongation have been calculated for the entire period of this process of growth. The average between the two thresholds on each day has been considered as the optimum mean temperature for that day. The optimum mean temperature increases from the start of the process to ripening, with the exception of a period just before flowering when all plants seem to require lower daily temperatures. The results of this analysis have also indicated that unknown factors other than temperature are affecting stem elongation.
Ecological Observations on the Emergence of Cercariae from Goniobasis Floridensis Reeve from the Wekiva River, Florida
Authors: Hunter George W. , Wigington E. E.
Published: May 2006

An 18—month study of the infection of Goniobasis floridensis from the Wekiva River in south—central Florida revealed that overall infection peaks appear to occur in December and then again in the spring (February—May). A total of 3,149 specimens, of G. floridensis were examined for emerging with an overall prevalence rate of 5.1%; 9% of 789 snails from station 1 and 3.8% of 2,369 snails from station 2 were positive. At Station 1 xiphidiocercariae were present in all six of the collections, strigeids in five, pleurolophocercous in four, and cysticercariae in two. At station 2 the pleurolophocercous cercariae occurred in nine collections, xiphidio in eight, strigeid in seven, and echinostome and cysticercariae in one each. When totals are considered, xiphidiocercariae were the most abundant, occurring in 14 collections compared with the pleurolophocercous in 13, strigeids in 12, cysticercariae in one. Multiple infections occurred only twice: one snail shed two species of xiphidiocercariae and the other, xiphidiocercariae and pleurolophocercous cercariae. Such items as pH, dissolved oxygen, temperature of the water, and so forth showed no particular correlation with the overall cercarial shedding pattern.
Integrated Calibrations of Plant Gas Exchange Systems
Authors: Tranquillini Walter , Caldwell Martyn M.
Published: May 2006

Calibration procedures are described to test the accuracy of plant gas exchange systems. These calibrations evaluate the contributions of all possible component errors in the determination of absolute gas exchange rates. These procedures are suitable for all gas exchange systems.
Dispersion, Dispersal, and Persistence of the Annual Intertidal Alga, Postelsia Palmaeformis Ruprecht
Authors: Dayton Paul K.
Published: May 2006

Postelsia palmaeformis is an annual brown alga that occurs on the Washington coast at upper intertidal sites subjected to extreme wave exposure. The alga occurs in patches within beds of Mytilus californianus, the competitive dominant in this region. Postelsia sporophytes are shown to colonize experimentally cleared spaces in beds of Mytilus with no concurrent colonization of adjacent uncleared controls. However, unlike many annual algae which have high spore dispersal abilities, Postelsia seems to have an effective distance of sporophyte colonization of only about 3 m from the edge of existing Postelsia patch. This limited spore dispersal is the mechanism postulated to explain the observed within—patch aggregated distribution also. Postelsia patches are maintained through time by settlement of Postelsia on other algal and animal species. By increasing the probability of both being ripped from the substraturm, and by overgrowing and smothering barnacles, Postelsia sporophytes clear primary substratum for the eventual use of sporophytes of their own species.
Habitat Selection Experiments with a Pair of Coexisting Heteromyid Rodent Species
Authors: Rosenzweig Michael L.
Published: May 2006

The kangaroo rat, Dipodomys merriami, occurs with the pocket mouse, Perognathus penicillatus, in stands of mesquite with little herbaceous cover. The dipo avoids areas that have thick cover between 8 cm and 45 cm. The pocket mouse prefers areas that have considerable cover over 45 cm. Those facts have been established both by previous studies and those reported here. This paper reports the results of altering the vegetation in small patches of land and observing concomitant changes in the land—use patterns of the rodents. The difference between the species appears to be crucial to their coexistence.
Freezing Resistance of Trees in North America with Reference to Tree Regions
Authors: Sakai A. , Weiser C. J.
Published: May 2006

Dormant one—year—old twigs of about 70 tree species were collected during mid—winter from five tree regions in North America (Rocky and Western Mountain, Northern, Pacific Coast, Southeastern Coast, and Central and Eastern Lowlands). The twigs were artificially hardened in a regime of sub—freezing temperatures between —3 degrees C and —10 degrees C for 24 days to induce maximum freezing resistance. Four Northern species, Populus tremuloides, Populus balsamifera, Betula papyrifera and Larix laricina had the greatest freezing resistance of the species tested. They resisted freezing to —80 degrees C and even immersion in liquid nitrogen (—196 degrees C) following prefreezing to —15 degrees C. Most of the Northern and Rocky and Western Mountain conifers survived freezing between —60 degrees and —80 degrees C while several species from the Pacific and SoutheasternCoast regions, which have relatively mild humid winter climates, were hardy to only among —15 degrees C. The ranges of some Pacific Coast species such as Pseudotsuga menziesii, Thuja plicata and Tsuga heterophylla extend into the mountainous inland. Samples collected from inland sites were found to be much hardier than those from the coast. A similar trend was observed in the various collections of Tsuga heterophylla from northern, central and southern areas along the Pacific Coast. Winter minimal temperatures are among the important factors setting the northern boundaries of the natural ranges of many forest tree species. However, Populus deltoides and Salix nigra from locations with temperate or moderate winter climates survived freezing to at least —50 degrees C irrespective to their native habitats. In these species, winter minimal temperatures do not appear to be the principal factor governing geographic distribution.
Growth in Artificial Climates‐‐An Indication of Mimulus' Ability to Invade New Habitats
Authors: Vickery Robert K.
Published: May 2006

Minulus guttatus and its related species have adaptable genotypes that enabled each plant to grow in a wide range of climates. The growth of the clone members of the plants differed significantly from group to partially—overlapping group of climates. The group of optimal climates had moderate day temperatures with cool nights, high illumination, and long day photoperiods of 16 hr. Overall the plants grow optimally in a wide range of moderate climates, suboptimally in both cooler and warmer climates, and least well or not at all in the most extreme climates. A few variant plants (some 12%) flourished in the more extreme climates. Thus, at least some of the populations have enough variability as to the climates producing optimal or near—optimal growth that some of their members could invade new areas. Secondary peaks of optimal growth were produced by one—third of the plants. These optima occurred in climates significantly different from the ones in which the plants produced their primary peaks. In effect, some of the populations have members that are preadapted to invade new habitats. Interpopulation hybridization produced a high proportion of vigorous even heterotic F2 recombinants, of which many (25%) reproduced in more climates than either parent. Thus, interpopulation hybridization, were it to occur in nature, could substantially increase the amount of variability useful to the plants in invading regons with different climates. Many individual Minulus plants not only are variable but have, intrinsic to their genotype, wide climatic tolerance, often with additional growth optima that endow them with the capability of growing in new habitats already. The estimates of the ability to invade new habitats for populations made up of such individuals must be high. This evaluation is borne out by their success in invading three continents in the last century or so.
Growth Rings: Annual Periodicity in Two Gorgonian Corals
Authors: Grigg Richard W.
Published: May 2006

Comparison of the number of growth rings present in the skeletons of colonies of two gorgonian corals, Muricea californica and M. fruticosa, with estimates of their age based on observed growth rates indicates that the periodicity of ring formation is annual. Data from two other methods used to determine periodicity support this conclusion. The results indicate that the observed growth of these gorgonians decreases constantly as a function of height. Height—age equations are derived for both species. Because the growth rate of both species was found to be variable, counting the rings to estimate age is more accurate than methods based on growth rates.
Loss of Prey Body Contents during Feeding by an Aquatic Predator
Authors: Dagg Michael J.
Published: May 2006

During the feeding process of the grasping and chewing amphipod Calliopius laeviusculus, a significant portion of the prey body contents is lost to the surrounding water. The amount of material lost decreases as the size of the predator increases. If this loss is ignored in ingestion studies, the result is a substantial overestimation of assimilation and assimilation efficiency, as determined by the gravimetric method.
Energetics of the Rusty Lizard Sceloporus Olivaceus
Authors: Dutton Ronald H. , Fitzpatrick Lloyd C. , Hughes John L.
Published: May 2006

Rates and energy equivalents of consumption (C), egestion + excretion (FU), assimilation (A), respiration (R) and production (P) were measured in two groups of Sceloporus olivaceus: (1) a laboratory group acclimated at five seasonally encountered temperatures (15°, 20°, 25°, 30° and 35°C); and (2) four acclimatization groups collected at different seasons when ambient temperatures corresponded to 15°, 20°, 25°, and 30°. Weight—specific rates and energy equivalents of C, FU, A, R and P were significantly influenced by temperature, and in general, showed inverse exponential relationships with body weight. Although there were no significant differences in R between ♂ ♂ and nongravid ♀ ♀, gravid ♀ ♀ had rates that were 17.4% higher. Weight—specific rates of C, FU, A, R, and P were adjusted for patterns of metabolic compensation to seasonally encountered ambient temperatures, body temperatures, weather conditions, and number of hours lizards were active during the year, and were used to calculate the annual energy budget of a typical 16.49—g, 1—yr—old lizard; C = 262.3 kcal (1,098 kJ), FU = 43.3 kcal (181.2 kJ), A = 218.0 kcal (912.5 kJ), R = 98.5 kcal (412.3 kJ), and P = 119.5 kcal (500.2 kJ). The annual apportionment of A between R and P was also calculated by assuming that rates of active lizards are 2, 2.5 and 3 x their laboratory metabolic rates.
Photosynthetically Elevated pH as a Factor in Zooplankton Mortality in Nutrient Enriched Ponds
Authors: O'Brien W. John , deNoyelles Frank
Published: May 2006

During a nutrient enrichment study of eight small ponds, the mortality of crustacean zooplankton species was investigated using a life table technique. There was close agreement between high pH values and the disappearance of crustacean zooplankton in four of the highly fertilized ponds. Pond water containing phytoplankton was toxic to the dominant Ceriodaphnia reticulata, yet pond phytoplankton isolated from pond water and resuspended in chlorinated tap water supported excellent growth of C. reticulata. Millipore—filtered pond water was not toxic. Analysis of chemical changes occurring in pond water with filtration showed a slight decrease in pH as the only significant alteration that is directly related to zooplankton mortality. The existence of such a pH mortality factor was demonstrated by testing the survivorship of newborn. C. reticulata in artificially adjusted pH treatments. A change from pH 10.8 to 11.2 radically altered the survivorship. Other hypothesis to explain the disappearance of C. reticulata–predation, starvation, allelophathic chemicals–are discounted. It is suggested that the one reported case of allelopathy between a green alga and a cladoceran, that reported by Ryther (1954), may instead have been partly a pH mortality factor. It is further suggested that in culturally enriched waters of low buffering capacity such a pH mortality factor may be common. In such lakes and ponds the quality of the water deteriorate due to the loss of the zooplankton.
Competition for Food between Two Intertidal Starfish Species and its Effect on Body Size and Feeding
Authors: Menge Bruce A.
Published: May 2006

Two predaceous intertidal starfish that overlap broadly with respect to food, space, and time were found to compete for a limited food supply in the San Juan Islands, Washington State. The experiment involved complete removal of a larger (up to 600 g average wet weight) starfish (Pisaster ochraceus) from a small island—reef and addition of them to a second island—reef while a third reef served as a control. In response to Pisaster removal, the mean individual wet weight of the smaller (maximum size = 45 g wet weight) asteroid (Leptasterias hexactis) increased significantly in 15 months. Addition of Pisaster resulted in a significant decrease in Leptasterias size; no change in average Leptasterias size was observed on the control reef. A highly significant inverse correlation between the estimated biomass densities (wet weight/m2) of the two species at 10 areas suggests that competition is widespread and that the species are generally in competitive equilibrium. A major consequence of the small size of Leptasterias is an apparent inability to capture larger prey. Coexistence seems based upon "specialization" by each predator on different—sized prey. Evidently, reduced competition stress results in an increase in Leptsterias's community role as a predator. Conversely, when competition is severe, the community role of Leptasterias appears unimportant.
African Ungulate Life Tables
Authors: Spinage C. A.
Published: May 2006

The survival curves of four species of African ungulate–impala, buffalo, zebra, and warthog–derived from skulls found in the Akagera National Park, Rwanda, are compared. Three of the species are shown to have the typical logarithmic negatively—skewed adult curve shown by undisturbed large mammal populations, but warthogs apparently have a heavy age—constant number of deaths to middle—age. Attention is drawn to the limitations of time—specific data in the study of population dynamics.
Water Potential in Red Pine: Soil Moisture, Evapotranspiration, Crown Position
Authors: Sucoff Edward
Published: May 2006

Diurnal patterns in leaf water potential were examined on eight red pine trees throughout one summer in northern Minnesota. The daily high in leaf water potential was plotted against total soil moisture to produce a soil—moisture release curve characterizing the plant—soil—atmosphere system. Diurnal patterns in leaf water potential at various soil moistures were compared. Also compared were patterns in leaf water potential under high and low evaporational demand and constant soil moisture. Results were generally consistent with previously constructed models. Very little variation in leaf water potential was observed among whorls or needle ages. Laboratory studies of the effects of leaf water potential when synthesized with data from the forest on occurrence of leaf water potentials suggest that growth was limited by water deficit every day of the 1969 summer.
Age‐Specific Energetics of the Pea Aphid, Acrythosiphon pisum
Authors: Randolph Polley Ann , Randolph J. C. , Barlow C. A.
Published: May 2006

A laboratory study of energy flow in different—aged pea aphids was accomplished by the balance sheet method. Growth, reproduction, molted exoskeletons, oxygen consumption, and honeydew production were monitored daily. Absolute amounts of energy expended on reproduction, growth, maintenance, and rejecta all varied with age of the aphid. Efficiencies of production and respiration also varied with the life history stage. Assimilation efficiency did not vary with age. Gross productions efficiency (° = 49%) and assimilation efficiency (°=83%) are higher in this insect than in most other insects reported. The reason for such high efficiency may be the unusually high amino acid content of pea phloem sap. Rates of exudation of amino acids and sugars from pea phloem through severed aphid stylets and greater than twice the total daily energy requirement of continuously feeding aphids. This would be true even for passively feedings aphids. Under the study conditions the daily ingestions of one average adult aphid is approximately 8% of the daily net primary production of a 0.15 a (dry wt) pea seedling.
On the Evolution of Energy Balance in Some Exploiter‐Victim Systems
Authors: Pimentel David , Levin Simon A. , Soans A. Benedict
Published: May 2006

By means of mathematical models and an experimental system we argue that density—dependent genetic feedback has the potential to regulate the amount of energy taken by a predator (parasite and herbivore) population from the prey or host population. The experimental system was a simulation using the housefly, Musca domestica, with artificial reproduction and prey, thereby restricting predator population feeding and adjusting it to surplus energy of the prey or host population. The experimental predator population, controlled by genetic feedback, was adjusted to a mean density of about 53 animals and in turn was removing less than the total amount of energy available from the prey population. The control predator population, regulated only by competition, fluctuated wildly about a mean density of about 147 animals, and consumed about 78% of the energy available from its prey population. Fluctuations existed in the experimental predator population, but were significantly damped compared with those in the control. These results generally complement those of earlier mathematical models, and support the idea that prey evolution can enhance predator stability and lead to a balanced supply—demand economy between predator and prey. In nature, the genetic feedback mechanism must function interdependently with other population control mechanisms, but the attempt here is to isolate the mechanism and assess its effect.
The Interface between Slugs and Wild Ginger: Some Evolutionary Aspects
Authors: Cates Rex G.
Published: May 2006

Data collected on natural populations of Asarum caudatum in western Washington indicated that populations were polymorphic for growth rate, seed production, and palatability to a native slug. However, in habitats where slugs were not as abundant, populations of wild ginger were dominated by individuals allocating more energy to growth rate and seed production, and less to the production of an antiherbivore mechanism. On the basis of these data, I postulated that in the absence of grazing pressure, palatable, faster growing individuals would be at a competitive advantage over slower growing individuals that devote more energy to an antiherbivore mechanism. Under grazing pressure, however, fitness of the unpalatable individuals would be increased since smaller amounts of photosynthetic tissue would be consumed.
The Nature of Prey Selection by Planktivorous Fish
Authors: Eggers Douglas M.
Published: May 2006

The nature of prey selection by planktivorous fish is presented as a model. The model conceptualization is based on the predation cycle, and the effects of prey distribution, encounter rate, handling time, capture success, and optimal foraging on food selection are explicit. The model as presented assumes a multiple species prey assemblage admitting within—species size variation. Conditions are given so that the optimal strategy of prey utilization can be expressed as a breadth of diet, and the specific components of the predator—prey interaction of fish and zoo plankton are discussed in detail. A reduced form of model is applied to two experimental situations. Specific factors which influence prey selection are also discussed.
A Laboratory Study of the Population Dynamics and Productivity of Dugesia Polychroa (Turbellaria: Tricladida)
Authors: Boddington M. J. , Mettrick D. F.
Published: May 2006

Populations of the flatworm Dugesia polychroa were studied in the laboratory over 42 mo under constant regimes of temperature, food, and space. Three populations completed four reproductive cycles, a fourth achieved an equilibrium size in its third cycle, while a fifth became extinct after its second reproductive period. The populations fluctuated in numbers and biomass during each cycle. As the populations matured, the mean population size (in terms of numbers and biomass) increased, as did the mean number of adults present. There were also increases in the length of the cycles, the reproductive periods, and total number of cocoons laid; there were decreases in the rate of cocoon production, adult fecundity, viability of cocoons, amplitude of the fluctuations in, and the average of the biomass turnover rate. In general, mortality balanced recruitment with the majority of mortality occurring at the time of recruitment. Only the absolute amount of food presented was found to be of importance in influencing the above parameters. The relationship between food availability and average biomass standing stock gave a value of 0.76, which was used to obtain good comparative abundance estimates for a field situation. Modifications of the above parameters were what might be expected from a density dependent organism and the results support field observations on triclads in general, and on D. polychroa in particular, showing that their populations are regulated by intraspecific competition for food.
Functional Analysis of Space‐Related Behavior in the Seaside Sparrow
Authors: Post William
Published: May 2006

This paper compares Seaside Sparrow (Ammospiza miritima) populations nesting in two dispersion patterns: territories and grounded territories. Territories, found in altered (ditched) salt marshes, were large, all—purpose activity spaces. Grouped territories, found in unaltered salt marshes, were small activity spaces from which birds made distant foraging flights. Among the factors influencing the grouped territory spatial pattern the most important were nest site, availability and lack of predation. A scarcity of nest sites in the unaltered habitat appeared to require the birds to nest close together, while such aggregation was made possible by scarcity of ground predators. The territorial pattern was thought to be influenced by low population density, low food availability, and sufficiency of nest sites. The amount of time that birds spent foraging, singing, and resting did not differ between spatial patterns, nor did the diurnal pattern of these activities. Birds on grouped territories spent more time in aggression than did birds on territories. The breeding success of birds found in the two dispersion patterns did not differ. The rate of delivery of food to the nest was also the same, although birds on territories flew twice as far to gather food for their nests. The results suggest that both spatial patterns are equally successful for the given conditions. Because of its variability it is doubtful that the space—related behavior of the Seaside Sparrow acts to limit population size.
Balancing Predation and Competition in Cladocerans
Authors: Allan J. David
Published: May 2006

A graphic model is proposed relating the balance between predation and competition to size strategies and species richness in zooplankton communities. As decreasing survivorship, due to predation, and increasing food—collecting ability are arranged along the single dimension of body size, both may be specified clearly. The model indicates that not all size strategies are equally advantageous. Rather, it reveals an adaptive peak in the smaller size ranges and, less commonly, an adaptive peak at very large sizes. Moderate size strategies are feasible only if the species are flexible in size at first reproduction or cyclomorphosis. Under certain combinations of the predation and competition functions, an increase in species richness may also be expected.
Interspecific Aggressive Behavior of Pocket Gophers Thomomys Bottae and T. Talpoides (Geomyidae: Rodentia)
Authors: Baker Ann Eileen Miller
Published: May 2006

The distributions of pocket gopher species in Colorado are contiguously allopatric. The pattern has been attributed to competitive exclusion, perhaps due to aggression toward the broad—niche species by more narrow—niche species. This study tested for differences in aggressiveness between the narrow—niche Thomomys bottae and the broader niched T. talpoides. Twenty—seven individuals of T. bottae were paired with 27 T. talpoides. Each animal was used once. Contrary to expectations the broader niched species, T. talpoides, is more aggressive than T. bottae.
Temperature Distribution and Calorimetric Determination of Heat Production in the Nest of the Wood Ant, Formica Polyctena (Hymenoptera, Formicidae)
Authors: Coenen-Stass Dieter , Schaarschmidt Bernd , Lamprecht Ingolf
Published: May 2006

This paper describes the temperature and population distribution in the nest hill of the wood ant Formica polyctena. Calorimetric and manometric data on the heat production of ants, pupae, and nest material were used to estimate their possible contribution to the heat balance of the nest hill. The pattern of isothermal lines in the nest did not fully correspond with the population distribution. Oxygen consumption and heat production of the worker ants and pupae steadily with arising ambient temperature. Investigations of the nest material showed a rapid increase in oxygen consumption in spring and a slower decrease in autumn. From spring to autumn the heat production of material from the center of the nest was higher than that of peripheral material. Heat production of the nest material originates in microbial activities and is chiefly the result of aerobic metabolism. The mass—specific heat production of ants is clearly higher than that of nest material. However, considering the total mass of the nest, the rate of heat production of the nest material is more than seven times the heat evolved by the ants. The seasonal fluctuation in the heat production of nest material coincides well with the active phase of the ants. It is conceivable that the nest materials is aerated and loosened by the building actions of the ants, and thus enough nutrient material and optimum conditions are available to the microorganisms.
The Nature and Ecological Significance of Metabolic Changes During the Life History of Copepods
Authors: Epp Robert W. , Lewis William M.
Published: May 2006

Studies of the relationship between metabolic rate and body weight through development in three species of copepods (two cyclopoids, one calanoid) showed that; (1) for each of the three species, the slope of the regression line relating metabolism to size is not uniform across all twelve developmental stages (six naupliar stages, six copepodid stages), (2) nauplii have a logarithmic metabolism—weight relationship with a slope ≈1.0, indicating little change in QQ2 (oxygen consumed per unit weight) with increasing body size, (3) copepodids have a logarithmic metabolism—weight relationships with a slope °1.0, indicating a decline in QQ2 with increasing size, and (4) there is an abrupt increase in QQ2 between the last napliar stage and the first copepoids stage. These metabolic features of copepods contribute to an explanation of retention of two very different body forms (nauplius, copepodid) through development in copepods. The smallest nauplii have a relatively low metabolic rate, considering their small size, which suggests that the naupliar from is energy efficient at small body sizes. The nauplii are locked into a steep (°1:1) increase in metabolism with size, however, which should make the energetic requirements of a mature animal unfeasible. This enforces a transition to a new body form (copepoid) partway through development. The new form has a higher energy consumption than the nauplii just at the point of transition, but shows a declining QQ2 with increasing body size. This allows for a substantial increase in size without a prohibitive increase in energy expenditure. Radical changes in locomotion, behavior, and nutritional requirements probably explain the change in metabolic characteristics with changes in body form.
Thermoregulation by the Black Swallowtail Butterfly, Papilio Polyxenes (Lepidoptera: Papilionidae)
Authors: Rawlins John Edward
Published: May 2006

Male black swallowtails, Papilio polyxenes, regulate thoracic temperatures in the field by behaviorally changing abdomen position, wing position, orientation to the sun, perching duration and perching height. At relatively low ambient temperatures (<14°C), postures with abdomens raised above the flattened wings were associated with long periods of perching relatively to the ground. Under relatively high ambient temperatures (>22°), postures with abdomens lowered in the shade of the wings were associated with shorter perch durations, greater flight frequencies, and higher perch heights. Between 14° and 22° ambient, thoracic temperatures were regulated between 28° and 32°. Shivering is not capable of elevating temperatures above ambient as much as basking alone does, and is seen only in disturbed individuals under conditions too cool for flight. Overheating due to metabolic heat production in flight is avoided by gliding or soaring with reduced wingbeat frequency. Swallowtails survive air temperatures above 50° for 30—min intervals in water—saturated air, but die above 46° at lower humidities. Swallowtails survive cooling to below 0°. Thoracic temperatures above 24° are apparently necessary for flight, and vigorous flight occurs only when thoracic temperatures exceed 28°. Thoracic—abdominal temperature differences were greatest at low ambient temperatures where thoracic temperatures necessary for flight are difficult to attain or maintain. At low ambient temperatures, decreased transfers of heat from thorax to abdomen via hemolymph circulation are associated with raised abdominal postures. At higher ambient temperatures, increased circulatory exchange between abdomen and thorax (augmented by abdominal contractions and a lowered abdomen) serves to dissipate heat from the thorax, especially when the abdomen is shaded by the wings.
Seed Selection in Dipodomys Merriami and Perognathus Penicillatus
Authors: Smigel Barbara W. , Rosenzweig Michael L.
Published: May 2006

Theories of resource allocation in sympatric heteromyids have often been based on the idea that body size is a key factor in determining the size of resource packages an animal takes. Considerable field data have supported this idea. In this study, however, two coexisting heteromyid species of different sizes are shown to be selecting the same set of seed sizes. These findings and other conflicting data show a need for a new theoretical basis for the correlation of body size with seed size in heteromyids. Both species tested take a more specialized diet at high seed densities than low. This supports the hypothesis that these seed eaters are in some sense adaptively, flexible selective. It also supports the notion that the selectivity is inversely proportional to the time required to find a seed.
Dietary Analysis in Granivores through the Use of Neutron Activation
Authors: Smigel Barbara W. , Rosenzweig Michael L.
Published: May 2006

A technique is used which permits simultaneous tracing of several foods in the field without the use of radioactive isotopes. Seeds are tagged with different stable (nonradioactive) isotopes of rare elements and then distributed in the environment. Free—living rodents that have been exposed to these seeds are then trapped and their feces are collected. The relative amounts of the several tagged foods consumed by the rodents are determined by subjecting the feces to neutron activation analysis in the laboratory. In activation analysis stable isotopes are rendered radioactive by permitting them to capture neutrons in a nuclear reactor. The elements emit characteristic wave lengths of gamma radiation, allowing not only detection but precise quantification. The technique presents many technical problems, enough of which have been solved to allow its application to the investigation of some interesting ecological questions.
Deposition of Water and Cations on Artificial Foliar Collectors in Fir Krummholz of New England Mountains
Authors: Schlesinger William H. , Reiners William A.
Published: May 2006

Atmospheric depositions of water, calcium, magnesium, sodium, potassium, and lead were measured in an Abies balsamea krummholz ecosystem in New Hampshire, U.S.A. Two types of collectors were used. Open buckets captured rainout, washout, and sedimentation (bulk precipitation), while buckets with attached artificial conifer foliage collected intercepted aerosols and cloud droplets as well as bulk precipitation. Water catchment averaged 4.5 times greater in the foliar collectors than in open buckets, and calcium, magnesium, sodium, potassium, and lead deposition averaged 8.3, 6.0, 4.9, 5.7, and 5.5 times greater, respectively, in the foliar collectors. Most of the increase in foliar collectors was due to higher volume catchment but some concentration enrichment through interception was also contributory. These data cannot be extrapolated to elemental deposition per unit area without correcting capture efficiency of collectors to that of natural vegetation. These data do strongly suggest, however, that in areas of high wind and frequent exposure to clouds or fog, such as in montane areas of New England, measurements of total elemental deposition require an evaluation of interception as well as bulk precipitation.
Predator and Prey Densities as Controls of the Rate of Capture by the Predator Didinium Nasutum
Authors: Salt George W.
Published: May 2006

An experimental investigation of the roles of predator density, prey density, and their interaction in the control of the capture rate by the predator was conducted, with Didinium nasutum as the predator and Paramecium aurelia as the prey. An analysis of variance of the results revealed that both predator densityand prey density were potential controls and that the latter was stronger than the former. The interaction effect was not significant. It is postulated that these two controls are alternates, that the capture rate is set by whichever is the more restrictive, and that the prey density control is probably a fixed internal control. The character of the predator density control remains to be determined.
Comparative Photosynthetic Capacities of Intertidal Algae under Exposed and Submerged Conditions
Authors: Johnson W. S. , Gigon Andreas , Gulmon S. L. , Mooney H. A.
Published: May 2006

Photosynthetic rates were measured for five species of intertidal marine algae, in the air and submerged. Ulva expansa and Prionitis lanceolata from the lower intertidal show reduced photosynthetic capacity air in air compared to submergedrates. In contrast, species from the middle and upper littoral (Iridaea flaccida, Porphyra perforata, Fucus distichus, and Endocladia muricata) reach maximum photosynthesis after some degree of drying. For these latter species, photosynthetic rates can be 1.6 to 6.6 times greater in air than in water at the same illumination and temperature. Desiccation rates under natural conditions are slow enough that these algae are capable of continuing a high rate of photosynthetic activity for extended periods while exposed and may fix the bulk of their carbon at this time. The capacity of these algae for sustained photosynthesis in air vary according to their intertidal zonation. It is suggested that these relationships may be partially responsible for the vertical distribution of intertidal marine algae.
Mortality in a Population of Daphnia Rosea
Authors: Dodson Stanley I.
Published: May 2006

A Daphnia rosea population was observed over a 2—year period in order to compare mortality with natural predation pressure. A technique is presented for estimating the instantaneous death rate of Daphnia from population dynamics data as derived from quantitative, serial, plankton samples. The effect of predation by a specific predator (Chaoborus larvae) on daphniid mortality is shown by the comparison between (1) the number of daphniid deaths and number of predator—prey encounters (per unit time and volume), (2) the probability of daphniid deaths and the relative probability of a Daphnia encountering a predator, and (3) the Chaoborus feeding rate implied by the daphniid mortality and independently observed Chaoborus feeding rates. The Daphnia population had six generations per year. For the last four generations, Chaoborus predation accounted for about 93% of the daphniid mortality. Daphnia mortality due to salamander larvae (Ambystoma tigrinum) averaged 3.5%, never more than 10%, that of Chaoborus larvae. These results support the hypothesis that Chaoborus larvae are significant predators of the D. rosea population, and that the rate of the Daphnia population's growth is significantly influenced by predation pressure.
Plankton Diatom Species Biomasses and the Quality of American Rivers and the Great Lakes
Authors: Williams Louis G.
Published: May 2006

Biomass (biovolume) measurements of the total phytoplankton per liter and the biomass of each species of diatoms in 5 microliters of diatom biomass per sample are presented for a number of sampling stations on the Great Lakes and several of the major rivers of the United States, compromising 54 semimonthly samples per station for 27 months. Diversity and dominance of species of diatoms for both the spring and fall population pulses are given for 128 stations. Possible relationships of various physical, chemical, and biotic parameters of water quality are suggested for immediate application to water pollution assessment and pollution abatement.
Influence of Food Distribution and Human Disturbance on the Reproductive Success of Herring Gulls
Authors: Hunt George L.
Published: May 2006

A three year study of Herring Gull (Larus argentatus) reproductive success on four islands in Maine indicated that production of young was controlled by different factors operating on the eggs and chicks. Hatching success was inversely related to the disturbance of colonies by picnickers, which apparently caused the adults to leave their eggs exposed to sufficient solar radiation to addle the eggs. The survival of chicks was lower on islands distant from sources of edible refuse (outer islands) than on islands close to sources of waste (inner islands), regardless of visits by picnickers. The nutrition and growth rates of chicks on inner and outer islands were similar. The attendance of parents on the territories was found to be less on an outer island than on an inner island. It is concluded that differences in parental behavior associated with greater foraging effort were responsible for a higher loss of chicks to predation on the outer islands.
The Role of Shell Adequacy in Behavioral Interactions Involving Hermit Crabs
Authors: Vance Richard R.
Published: May 2006

Field studies have suggested that the intertidal hermit crabs of the San Juan Islands of Washington normally occupy snail shells smaller than preferred. In this study the effects of shell size on protection from predation and on hermit crab shell fighting were studied in the laboratory. A predator (Cancer) presented with two hermit crabs (Pagurus granosimanus), identical except in size of occupied shell, preyed upon the hermit in the smaller shell first in 15 out of 16 trials. This results suggests that large shell size confers a selective advantage on the occupying crab. Shell fights involving two hermit crabs (P. hirsutiusculus) of unequal size were observed in which replicates differed only in the shell size of the larger crab. The probability of the larger crab effecting a shell exchange through fighting was shown to increase as the size of its shell decreased. However, shell size was shown to have no effect on the level of aggressiveness as measured by four criteria. The mechanism underlying the former result thus appears to involve a continual high level of general aggressiveness together with an increased tendency associated with occupancy of an inadequate shell by the dominant crab for that crab to evoke a shell exchange during an aggressive interaction.
Correlation of the Exposure and Potential Solar Radiation to Plant Frequency of Agropyron Desertorum
Authors: Mayland H. F.
Published: May 2006

The hypothesis that exposure and potential solar beam radiation are useful parameters in describing frequency response of a monoculture bunchgrass was tested. Slope, aspect [sine (azimuth angle +68°)]; and daily solar beam radiation (June 22) accounted for 18%, 8% and 13%, respectively, and 22% collectively, of the variation in Agropyron desertorum plant frequency. Maximum plant numbers occurred on south— to—west exposures, but these exposures had more steeply inclined slopes and actually received less potential solar radiation than others during the summer solstice. Aspect data alone are inadequate for interpreting plant response to soil moisture, temperature, and solar radiation, especially when a wide range in slope is involved.