摘要:

The bioenergetics of the southern harvester ant were studied on the Savannah River Project, Aiken, South Carolina. Excavation of hills revealed that density of ants ranged from 4,000 to 6,000 per hill. Labeling ants with P32 indicated that only 10% of the ants in a colony were active above ground during any 2—week period (the limit of recognition of the label); thus, short—term marking recapture estimates based on above—ground individuals greatly underestimate the size of the colony. There were 27 hills per hectare on the study area. The consumption of oxygen of workers at various temperatures was determined in a simple respirometer, and the temperature at which the ants were living in the field was determined during a year's observation at mounds. The energy expense of heat production was calculated from the oxygen consumption and activity temperature records. Total energy flow (heat production plus tissue growth) was highest in summer and lowest in winter. The annual range was from 14 to 48 kgcal/m2/yr. Tissue growth was estimated to amount to only 0.09 kgcal/m2/yr. Energy flow in this species was higher than that of 2 vertebrate granivores studies in the same field, the old—field mouse and the savannah sparrow.

ISSN:0012-9658    

DOI:10.2307/1933834

出版商:Ecological Society of America    

年代:1964

数据来源: WILEY

摘要:

Definitions of shallow—water marine climatic zones that equate the northern limit of climatic zones with minimum temperatures are shown to be not critical. The critical factor that probably determines the limits of marine shallow—water climates is the number of consecutive days or months that shallow sea water is at temperatures required for reproduction and early growth. The relations that appear to exist between duration of marine water temperature or climate and molluscan provinces are: (1) Inner tropical includes molluscan species that live in water that is 20 C or nearly 20 C for 6 or more months, and with no months cooler than 18 C. (2) Outer tropical includes those species that live in water 20 C. For only 4 months, in water that is 18 C for approximately 6 months, and for no months cooler than 10 C. (3) Warm temperate includes species that live in water approximately 15 or 18 C for almost 4 continuous and in water no colder than 10 C. (4) Mild temperate contains species living in marine water that is near or slightly below 15 C. for 3 or 4 months, and cooler than 10 C for nearly 6 months. (5) Cool temperate includes species that live in water that is 10 C for only 3 or 4 months of the year. (6) The Southern boundary of cold climate is near the southern limit of winter ice, and the distribution of cold water molluscan species may result from the distribution of polar ice.

ISSN:0012-9658    

DOI:10.2307/1933835

出版商:Ecological Society of America    

年代:1964

数据来源: WILEY

摘要:

Nest height for rufous hummingbirds differs significantly between spring and summer nests in southern British Columbia. Though spring and summer microclimates are different, the microclimate of nest sites is similar in the spring nest sites and summer nest site. Hummingbirds build their nests at low levels in conifers in spring, but higher and in deciduous trees in the summer. The effect of the stand in reducing the ambient temperature is greater at this low nest site in conifers than at the higher sites in deciduous trees. The low nest sites are more protected from climatic extremes than the high nest sites, and thus the seasonal effects of the microclimate are moderated. Radiation is higher in summer than in spring, which results in extreme climatic amplitudes near the ground; this makes the low nest sites less favorable for the birds in summer. The summer nest sites are located mainly in the crown of deciduous trees and experience the temperature reducing effect of the intensive evapo—transpiration of these trees. This means an effective protection against heat, which would not be provided at the level of spring nest sites.

ISSN:0012-9658    

DOI:10.2307/1933836

出版商:Ecological Society of America    

年代:1964

数据来源: WILEY

摘要:

The food habits of rodents inhabiting shrub grass and perennial forb ranges in western Colorado were investigated to determine the kinds and proportions of foods eaten, the effects of range treatment with 2,4—D on food habits, and the degree of competition for food among rodents inhabiting these ranges. Treated and control areas at each site were trapped periodically and estimates were made of plant coverage. A part of the stomach contents of each rodent was mounted on a slide and was examined with microscopes. The volume in percent of each food item was estimated and recorded. Deer mice exhibited a seasonal variation in diet. Their winter food was primarily seeds whereas arthropods made up a large part of the diet during the summer months. Cutworms comprised almost one—half of the food ingested during June. Male and female deer mice showed no difference in diet, but the diet of deer mice varied with age group. fugi were found in the stomachs of rodents, particularly during the fall months. Deer mice occasionally ingested parts of small mammals. Grass seeds comprised a larger proportion and forb and shrub seeds a smaller proportion of the diet of deer mice inhabiting areas treated with 2,4—D than that for untreated areas. The availability of these food items appeared to be responsible for these observed differences in diet. Least chipmunks ate a variety of arthropods, seeds, and leaves, and, like the deer mouse, exhibited seasonal variation in diet. Although there was no significant difference in diets on treated and control areas, the influence of the availability of certain seeds was evident. Range treatment with 2,4—D had no effect on the diet of montane voles. Leaves and stems of forbs and shrubs comprised a large part of the summer diet on both treated and control areas on Grand Mesa. Differences in diet with sex and age were observed. The greater abundance of montane voles on treated areas appears to be due to an increase in grass cover and not to an increase in available food. No competition for food was observed among deer mice, least chipmunks, and montane voles at the population levels sampled in this study.

ISSN:0012-9658    

DOI:10.2307/1933837

出版商:Ecological Society of America    

年代:1964

数据来源: WILEY

摘要:

A study of the influence of weather factors on the migrations of a herd of blacktailed deer showed that periods of migration as indicated by night spotlight samples were closely correlated with seasonal changes in minimal relative humidity. Both spring and fall migrations, and possibly an atypical summer movement, occurred during ranges of 40 to 60% minimal relative humidity. Snowstorms, rainfall, absolute humidity, and temperature were not so closely correlated. The migrations could not be attributed to habitat factors such as food, water, or escape cover.

ISSN:0012-9658    

DOI:10.2307/1933838

出版商:Ecological Society of America    

年代:1964

数据来源: WILEY

摘要:

The general distribution of the family geomyidae in North America is limited only by suitable soils, although a particular species may be also be limited by climatic or other factors associated with altitude and latitude and by interspecies competition. A study was made of the factors affecting the distributions of the pocket gophers Thomomys bottae, T. talpoides, Geomys bursarius, and Cratogeomys castanops in Colorado. The most critical factors in the relationships among pocket gophers are soil tolerance and competition. All four species in Colorado prefer deep light soils,but their ranges of tolerance vary, with the result that interspecies competition consists of the fundamental niche of one species being a proper subset of another. In each combination of competitive and is able to displace the other speices to less favorable habitats. The relationship among the four species in competitive ability is G. bursarius>C. castanops>T. bottae>T. talpoides. Possible mechanisms of competition are discussed in relation to body size, territory, aggression, and dispersal.

ISSN:0012-9658    

DOI:10.2307/1933839

出版商:Ecological Society of America    

年代:1964

数据来源: WILEY

摘要:

Between 300 and 400 described species of macroscopic animals (including 22 fishes) were encountered on 1,385 m 2 of a silt—stone, submarine hogback and adjacent mixed bottom located in the shallow sublittoral (9.5 to 18 m depth) about 500 m off the coast of Corona del Mar, California. The components of the epifauna are not distributed uniformly over the reef. Both the numbers of species and individuals per unit area of reef surface vary inversely with depth. Although more species achieve maximum population densities at the top of the reef than elsewhere, some species are most abundant on the reef's mid—section, on the base, or on the rock—sediment bottom. Delineations among these major groups are sufficiently marked to warrant recognition of 3 vertical epifaunal zones on the reef itself and a 4th on the surrounding bottom within a meter of the reef base. Although changing conditions associated with the highly irregular rocky surface create a high degree of patchiness in the epifauna, within any of the zones some aggregations of species are sufficiently uniform and widespread to permit recognition of communities. In general the predominant species in the upper 2 zones are sessile suspension feeders, which form thick incrustations that form biotopes for large numbers of small sessile and motile species. In the lower zones, on the other hand, the predominant species tend to be motile scavengers and deposit feedes, and the incrustations that are present are thin and formed by single species. The degree of water movement on the reef, which results primarily from the propagation of surface waves, also varies inversely with depth. It is suggested that this pattern of water movement determines the distribution of the major units of the epifauna through its effects upon the availability of food of different types at particular points on the reef. Suspended organic matter is not only more abundant on the upper levels of the reef, but its rate of delivery to crustforming organisms is enhanced by turbulence. Deposition of organic materials removed from the upper part of the reef is facilitated by the sharp reduction in degree of water movement along the lower sides and bottom of the reef.

ISSN:0012-9658    

DOI:10.2307/1933840

出版商:Ecological Society of America    

年代:1964

数据来源: WILEY

摘要:

A series of experiments was undertaken to determine (1) suitable methods for spawning and rearing Mya arenaria in the laboratory, and (2) some of the basic environmental requirements of Mya eggs and larvae. Adult Mya did not respond readily to stimuli commonly used to induce laboratory spawning of marine invertebrates and a new technique was developed to provide viable gametes. This technique consisted of cyclic fluctuations in the temperature of the running water in which the ripe clams were held. Larvae were reared through metamorphosis and their tolerance to various levels of temperature and salinity were determined. The optimum temperature range was between about 177deg;and 23°C, although slow development took place as low as 10°C. Optimum salinity was from about 16% to 32% (the highest value tested). Some differences in response to temperature and salinity between larvae from parents of different origins were observed. Several species of unicellular algae were tested as larval food. Although Cyclotella nana produced the best growth, the larvae grew nearly as well on Dicrateria inornata and Phaeodacytylum tricornutum. The last named species was considered most satisfactory, because in addition to promoting good growth, it was most easily raised in culture.

ISSN:0012-9658    

DOI:10.2307/1933841

出版商:Ecological Society of America    

年代:1964

数据来源: WILEY

摘要:

Communities in depressions, occurring as islands surrounded by naturally exposed granitic rock, were classified by the correlated of maximum soil depth and characteristic vegetation cover into: diamorpha communities, 2—6 cm; lichen—annual herb communities 16—39 cm; and herb—shrub communities, 40—50 cm. The total flora of the 40 island communities, included 76 species, but only 39 of these occurred in five or more communities and were considered characteristic. The extreme environmental conditions of high light intensity and low soil moisture content were indicated by the fact that of the 20 plants present in over 50% of the communities, 18 were lichens, mosses, and flowering annuals and only two were perennial flowering plants. The flora of the island communities is distinct from that of border vegetation. Only three endemics are among the 39 characteristics plants. Seasonal aspects of the outcrop vegetation are striking. During the winter months, November through February, mosses and lichens are most conspicuous, but seedlings of spring—blooming annuals are also present. From late February to May there is a continuous succession of plants in flower, the majority of which complete their life cycles before the hot dry months from May to August. In September the outcrops are covered with the orange—yellow flowers of Viguiera Porteri. Spring—flowering annuals germinate in October at the time summer—flowering annuals are dying. The four types of island communities described appear to represent stages in plant succession directly related to edaphic conditions. Apparently the island communities have existed long enough in geologic time for an endemic flora to have evolved. The life of any one community, however, is measured in hundreds rather than in thousands of years.

ISSN:0012-9658    

DOI:10.2307/1933842

出版商:Ecological Society of America    

年代:1964

数据来源: WILEY

摘要:

The relations between dissolved solids, water exchange, and productivity were studied in a lake—stream system. Detached epilithic algae composed the plankton of the upper stream, but all other stations displayed a lentic plankton. Turbidity and unsuitable substrate prevented the development of sessile algae on the bottom of the slow—flowing river sections (lakes), but the macrophytes provided a surface for the development of these communities. The concentrations of total dissolved solids and those ions essential for photosynthesis and phyto— and zooplankton numbers. The different rates of the decrease of these nutrients in the upper stream and lake—stream section and probably related to the greater populations of the upper stream and lake—steam section are probably related to the greater populations of autotrophic biota in the latter section. Assuming that nutrients are being added to the system through its course, then the downstream decrease indicates that the increasingly large autotrophic populations are assimilating these nutrients at a rate greater than they are being added. Thus, the deciding factor regulating the accumulation or removal of dissolved nutrients in a lake—stream system appears to be the degree of autotrophic enrichment of the system.

ISSN:0012-9658    

DOI:10.2307/1933843

出版商:Ecological Society of America    

年代:1964

数据来源: WILEY