ISSN:0012-9658    

DOI:10.2307/1935373

出版商:Ecological Society of America    

年代:1970

数据来源: WILEY

摘要:

There is a high degree of concordance among the patterns of geographic size variation in birds in the eastern and central United States. This is demonstrated for 12 species by assuming that wing length measurements are an indicator of body size on the intraspecific level, and by arranging the data in the form of a grid of means of wing lengths for sample areas. Maps giving isophenetic lines for wing length indicate gradually increasing size clines northward and westward from Florida in the Hairy Woodpecker (Dendrocopos villosus), Dowy Woodpecker (Dendrocopos pubescens), Blue Jay (Cyanocitta cristata), Carolina Chickadee (Parus carolinensis), White—breasted Nuthatch (Sitta carolinensis), and Eastern Meadowlark (Sturnella Magna). In each case there is a trend for larger (or longer—winged) birds to extend southward in the Appalachian Mountains and for smaller (or shorter—winged) birds to extend northward in the Mississippi River valley. Maps made by a computer and automatic plotter using contour intervals of 0.5 mm of mean wing length for the Downy Woodpecker, for male White—breasted Nuthatches, and for female Blue Jays show that, in addition to the patter just mentioned, relatively longer—winged birds extend southward in the interior highlands of Arkansas, and relatively shorter—winged birds extend northward up other river valleys. These subtle relationships between intraspecific size variation and topographic features suggest that the link between the two phenomena may be precise adaptations to even minor climatic gradients. The relationship between these findings and the subspecies concept is discussed. Correlation coefficients for the patter of variation in the Downy Woodpecker with seasonal and annual wet—bulb temperature, vapor pressure, and absolute humidity were all either equal to or higher than correlations with dry—bulb temperature. Since these variables reflect the combined effects of temperature and humidity, the obvious indication is that size variation is more closely related to this combination than to temperature alone. Additional correlations using the mean wing length data for seven other species confirmed that wet—bulb temperature patterms are more closely related to bird size than either dry—bulb temperature patters or latitude. These relationship can be expressed numerically as regressions of mean wing length on either annual wet—bulb temperature or mean annual total heat per pound of air. Since increased evaporation at high altitudes and in arid areas accentuates the depression of a wet—bulb thermometer, my hypothesis may partially account for several cases of size variation in birds cited by others as disturbing exceptions to Bergmann's ecogeographic rule. Sections of a translation of Bergmann's paper published in 1847 are given. The biological mechanisms by which these relationships are maintainted are unknown, and the wide range of tolerance by birds to diurnal and seasonal temperature variations tends to mask them. If the well—established inverse relationship between weight and metabolic rate per gram of homeotherms is operative on the intraspecific level, the relationships can be discussed in terms of avenues of heat loss and of energy budget equations.

ISSN:0012-9658    

DOI:10.2307/1935374

出版商:Ecological Society of America    

年代:1970

数据来源: WILEY

摘要:

Sites on different strata of Bearpaw shale and on alluvium derived from the shale in a small basin in northeastern Montana supported strikingly different plant communities, including three Nuttall saltbush, three big sagebrush, two greasewood, one western wheatgrass, one blue grama, one silver sagebrush, one foxtail, one buckwheat, and a community of mixed shrubs. Several soil factos were measured, but only total soil—moisture stress and soil—moisture volume gave rational ordinations of the communities studied. Total soil—moisture stress at the average root depth ranged from a high of 96 bars for a Nuttall saltbush community to only 19 bars for a mixed shrub community. The Nuttall saltbush community was found on soils having a high soluble salt content, high soluble sodium percentages, high total soil—moisture stress, and low infiltration rates. Soils at the big sagebrush site had low soluble salt content, relatively high soluble sodium, and intermediate total soil—moisture stress values. The wettest site, subject to spring flooding, was occupied by western wheatgrass. Quantities of water evapotranspired from each habitat (calculated as maximum soil moisture minus minimum plus increments added to soils by summer storms) when related to precipitation provided approximations of runoff from, or run—in moisture for, each habitat.

ISSN:0012-9658    

DOI:10.2307/1935375

出版商:Ecological Society of America    

年代:1970

数据来源: WILEY

摘要:

Sympatric native Anolis species with similar structural habitats but contrasting climatic habitats are closer in head and body size on species—rich than on depauperate islands. In two localities, sympatric Anolis species with differential occurrences in sun or shade sought lower, more shaded perches during midday, resulting in partly nonsynchronous utilization of the vegetation by the two species. The second observation may be related to the first in the following way: nonsynchronous spatial overlap could dictate relatively great resource overlap for species coinhabiting patchy or edge areas, requiring great differences between the species in prey size in addition to those in climatic habitat. The extent of such overlap on small depauperate islands could be greater if these contained a greater proportion of patchy or edge habitats (with respect to insolation), or if climatic preferences were broader and more overlapping than on large, species—rich islands. In each locality, the relatively more shade—inhabiting species occurred more often on larger perches and on lower perches than did the other species. In both species of the Bermudan pair, adult males occupied higher and larger perches, and in grahami, shadier perches, than did female—sized individuals. The statistical significance of these and other differences was evaluated using several unweighted g2procedures, Cochran's weighted g2test and a partitioning technique for analyzing interactions among variables in complex contingency tables. The last method is described in detail in the papaer by Fienberg, immediately following this one.

ISSN:0012-9658    

DOI:10.2307/1935376

出版商:Ecological Society of America    

年代:1970

数据来源: WILEY

摘要:

Ecological data often come in the form of multidimensional tables of counts, referred to as contingency tables. During the last decade several new methods of analyzing such tables have been proposed. Here, a class of models analogous to those used in the analysis of variance is discussed, and a method for computing the expected cell counts for the different models is presented. Two differenet tests for checking the goodness—of—fit of a particular model are then examined. The first is the simple generalization of the Pearson chi—square test statistic, while the second is referred to as the likelihood—ratio chi—square test statistic. Both have the same asympototic g2distribution. The likelihood—ratio statistic can be used in the selection of a suitable model, via the technique of partitioning. All of the methods presented are illustrated using data collected by Schoener on lizards from the West Indies.

ISSN:0012-9658    

DOI:10.2307/1935377

出版商:Ecological Society of America    

年代:1970

数据来源: WILEY

摘要:

Incoming solar, net, and reflected radiation, wind velocity, relative humidity, and temperatures at various levels above and below an open desert surface were recorded simultaneously at 30—minute intervals for a 3—day period. Concurrent measurements were also made of arthropod burrow temperatures and relative humidities, scorpion body temperatures, and body and subelytral temperatures of tenebrionid beetles. The burrowing habit enabled arthropods to escape the hot, desiccating conditions recorded on the desert surface during the day. Temperatures and humidities to which scorpions were subjected while in their subterranean retreats depended upon the burrow's depth and subsequent movements in the burrow. Vertical movements between the surface and maximum burrow depths during a 24—hour period provided arthropods with a wide choice of micro— environments. Tenebrionid beetles on the surface were able to achieve a temperature equilibrium only under low temperature and radiation loads. Subelytral cavity temperatures in black Eleodes armata were generally 2—7°C warmer than body temperatures after exposure to direct sunlight. Temperature differences between subelytral cavities of black beetles and beetles with their elytra painted white were small, but suggested that a white dorsal surface was, at least, paritally effective in reducing absorption of solar radiation. The subelytral cavity, in addition to reducing transpiratory water loss, apparently provides a mechanism for increasing convective cooling, and may serve as a temperature “buffer zone” against heat conduction resulting from high intensity solar radiation. A heat exchange budget was estimated for E. armata on the desrt surface. Major contributing factors were heat gained from incoming radiation versus heat lost from convection and reradiation. Contributions from evaporation and metabolism, as determined by laboratory experiments, were very small in comparison, while the role of conduction in energy exchange was assumed to be negligible. Inherent problems in the estimation of contributing factors to net energy exchange, and comparison of similar budgets for mesic arthropods are discussed.

ISSN:0012-9658    

DOI:10.2307/1935378

出版商:Ecological Society of America    

年代:1970

数据来源: WILEY

摘要:

–Six poarasitoid species (Hymenoptera: 5 Ichneumonidae, 1 Eulophidae) coexist on cocoon populations of the Swaine jack pine sawfly, Neodiprion swainei Midd. in Quebec. Their distribution between plant communities was related to host availability except for Gelis urbanus (Brues) which has alternative hosts. Pleolophus basizonus (Grav.) was dominant at high host densities, tending to displace Pleolophus indistinctus (Prov.) which was dominant at low host densities. Mastrus aciclatus (Prov.) occupied dry open sites at high host densities, where other species were less numerous. The highest species diversity of cocoon parasitoids occurred at the ecotone around jack pine stands and at moderate host densities in increasing host populations. Furthermore, parasitoids attacking larvae were well represented in moderately dense host populations. As the host density increased, P. basizonus became so dominant that it reduced species diversity, particularly among the parasitoids attacking the host larvae. Species diversity can be predicted from the proportion of P. basizonus present. This parasitoid acts as an organizer species within the parasitoid complex because of its superior coimpetitive ability. Parasitoids of larvae have a conservative strategy for host exploitation that appears adapted for utilizing low host populations. In contrast, the parasitoids attacking cocoons gain dominance only when host—finding is easy in high host populations.

ISSN:0012-9658    

DOI:10.2307/1935379

出版商:Ecological Society of America    

年代:1970

数据来源: WILEY

摘要:

The results of bird censuses from 13 Chilean habitats are presented. Any one habitat supports a slighly higher bird species diversity than structurally similar habitats in North America and Australia. The bird species turnover between habitats in the same locale, in contrast to other temperate areas, is very low–an island characteristic. Turnover between geographically distinct habitats within Chile is comparable to that between adjacent habitats in North America. Chilean birds exhibit wide habitat tolerance in narrow geographic areas, whcih is attributed to a slow development rate of this bird fauna. Character convergence, where similarities in appearance have evolved to faciliate interspecific aggression and aggregation, is a byproduct of this type of distribution.

ISSN:0012-9658    

DOI:10.2307/1935380

出版商:Ecological Society of America    

年代:1970

数据来源: WILEY

摘要:

Microcosms containing leaf litter, sand, and three, six, or nine millipedes were incubated for 14 weeks at either 5°, 15°, or 25°C under three rates of simulated rainfall. Effects of temperature, rate of leaching, and millipede density on transfer of(137)Cs, K, Mg, and mass and on evolution of CO2were analyzed statistically and by analog computer simulation. Loss rates from litter increased in the order: Mg

ISSN:0012-9658    

DOI:10.2307/1935381

出版商:Ecological Society of America    

年代:1970

数据来源: WILEY

摘要:

Fluctuations in the densities of marine phytoplankton species in the open and coastal ocean follow a sequence wherein one or several species may increase in abundance very much without causing a reduction in abundance of other forms. Theoretical calculations of the maximum size of nutrient—depleted zones about the plankton cells show that overlapping of these zones cannot occur at cell densities less than 3 x 108/liter. Since densities rarely exceed 106/liter in the open and coastal ocean, there is no possibility of an abundant species monopolizing the nutrient supply and forcing a less abundant form to extinction. The change from a coccolithophore—dominated plankton in the Sargasso Sea to the diatom—dominated plankton in the coastal water off New York cannot, therefore, be attributed to competition for nutrients by the two types of cells. But in some very shallow estuaries, Great South Bay and Moriches Bay near New York and Salt Pond at Woods Hole, the dominant forms sink considerably more slowly than the coastal and oceanic species and would thus be at an advantage over the latter. Plankton concentrations in the estuaries may come close to or exceed 109/litter, and monopolization of the nutrient supply should aid in the continued dominance of the abundant forms, eventually bringing about the extinction of many of the residual forms. This sequence is considered to be a real possibility in these estuaries and to be the reason for the reduced diversity of species observed there.

ISSN:0012-9658    

DOI:10.2307/1935382

出版商:Ecological Society of America    

年代:1970

数据来源: WILEY