摘要:

Diet and external morphology of nine species of insectivorous bats from Zambia, East Africa, were compared using multivariate methods. Morphological and dietary resemblance between species were positively correlated; that is, taxa which resembled each other most strongly morphologically were also most similar in dietary intake. The degree of morphological and dietary distinctiveness of a species was positively correlated with its morphological and dietary variability. For example, species which are quite distinct from others in morphology or diet tend also to be quite variable in those two attributes. Morphology of the bats was strongly predictive of their diets; most dietary variance was accounted for by morphological variance, and the first morphological principal component predicted the presence in the diet of Lepidoptera, beetles, and Orthoptera with a high level of significance. These results led to a model of community organization for closely related species in which a relatively large number of specialists with invariant attributes are clustered near the community centroid and a smaller number of distinctive, variable species occupy niches more distant from the centroid.

ISSN:0012-9658    

DOI:10.2307/1937180

出版商:Ecological Society of America    

年代:1983

数据来源: WILEY

摘要:

We quantitatively test theoretical predictions concerning mammalian life histories, using published data on survival, reproduction, and body mass for 29 eutherian mammals. Larger mammals have a greater age at maturity, greater generation length, greater life expectancy, lower reproductive value at maturity, and smaller litters than do smaller mammals. Residual reproductive value at maturity is not correlated with adult body mass or survival. Litter size varies inversely with generation length and adult survival. Age at maturity is positively correlated with life expectancy. Twenty—seven of 29 mammals display a generation length longer than their life expectancy at birth, and the same proportion shows a greater life expectancy at maturity than at birth. A fairly high proportion (76—82%) of the variation in these dependent variables is attributable to adult mass. Many life table characteristics of mammals are interrelated, although not necessarily in the ways predicted by theory. Design constraints may preclude significant differences in life history patterns among mammals, so that the life table characteristics of only a few species may depict the pattern of life table evolution in most eutherian mammals.

ISSN:0012-9658    

DOI:10.2307/1937181

出版商:Ecological Society of America    

年代:1983

数据来源: WILEY

摘要:

Lepidopteran species richness was strongly related to sampling intensity as measured by the number of collections made by the Canadian Forest Insect Survey of insects on broad—leaved trees in Ontario. Local abundance of the host, independently estimated by Beschel et al. (1962), and ecological and geographical distribution of the host were unrelated to the local species richness of Lepidoptera when the effect of sampling intensity was accounted for. The importance of collecting effort in this analysis of an extensive sampling program suggests that the effect of sample size must be considered before it is possible to test the effects of host characteristics on herbivore species richness.

ISSN:0012-9658    

DOI:10.2307/1937182

出版商:Ecological Society of America    

年代:1983

数据来源: WILEY

摘要:

The energy budget of nestling Red—winged Blackbirds (Agelaius phoeniceus) was determined using doubly labeled water (3HH18O) to measure field metabolic rate (FMR) and body component data to measure growth energy. Sex—specific measurements permitted the evaluation of the effects of this species' substantial sexual size dimorphism on FMR and total energetics. FMR averaged CO2release of 5.12 mL°g—1°h—1, or 0.129 kJ°g—1°h—1, with no significant differences between the sexes. Daytime FMRs of CO2production (5.34 mL°g—1°h—1) were higher, but not significantly so, than nighttime FMRs (4.45 mL°g—1°h—1). Water influx averaged 0.95 mL°g—1°d—1, with daytime rates (1.22 mL°g—1°d—1) significantly higher than nighttime (0.40 mL°g—1°d—1) rates. Total assimilated energy from hatching to fledging was 1014 and 797 kJ for male and female nestlings, respectively. The sexual differences in total energetics reflected differences in body size of the nestlings and suggest that there is a greater cost to the parents in raising males than in raising females.

ISSN:0012-9658    

DOI:10.2307/1937183

出版商:Ecological Society of America    

年代:1983

数据来源: WILEY

摘要:

At Konza Prairie, Kansas, milkweeds (Asclepias viridis) were mapped and censused repeatedly to examine the influence of neighboring conspecifics on colonization of individual host plants by adults of the seed bug Lygaeus kalmii. Analysis by multiple regression suggests that the primary determinant of abundance of adult bugs on a host plant was the plant's own pod (seed) production; abundance of adult bugs also increased, however, with increasing pod production by adjacent plants. This neighborhood effect was limited to plants immediately adjacent to a host plant; pod density>3 m distant from hosts had little influence on colonization of hosts by bugs. Mark—recapture studies revealed differences in responses of the two sexes of L. kalmii to neighboring pod density: males lingered longer, while females lingered less on individual plants when these plants were surrounded by many vs. few pods. Damage from L. kalmii sustained by milkweeds thus results from a complex interplay of reproductive behaviors of individual host plants, their neighbors, and their seed predators.

ISSN:0012-9658    

DOI:10.2307/1937184

出版商:Ecological Society of America    

年代:1983

数据来源: WILEY

摘要:

Individual plants of Viola fimbriatula which germinated from buried seed in two tree blowdowns in 1975 were censused for 6 yr. Growth, seed production, and mortality were monitored at fortnightly intervals. Only seedlings of the cohort established immediately following the disturbance grew large enough to produce seed. The performance of individuals within this cohort was highly skewed, and both reproduction and survival were correlated with individual size. After 1977 the conditions in the blowdowns which initially stimulated germination, growth, and reproduction rapidly deteriorated for V. fimbriatula, and the populations declined to extinction. We conclude that individuals of V. fimbriatula, interacting with the habitat conditions of this natural disturbance, display many of the traits characteristic of species commonly associated with disturbance. In this habitat the dynamics of the entire population are determined by the relative performance of individuals immediately following the disturbance.

ISSN:0012-9658    

DOI:10.2307/1937185

出版商:Ecological Society of America    

年代:1983

数据来源: WILEY

摘要:

Major differences were found between the vegetation structure of ponderosa pine—dominanted communities on the Horse Pasture Plateau and those on the nearby but isolated Church and Greatheart Mesas in Zion National Park. The Horse Pasture Plateau was heavily grazed by livestock in the late 19th and early 20th centuries, while the mesas were never grazed. Conditions on the mesas now approximate the pre—European situation of the region as described in the earliest written accounts. Pine, oak, and juniper sapling density and cover were much higher on the formerly grazed plateau than on the relict mesas. Herbaceous species dominated the groundlayer in mesa ponderosa pine savanna stands, while grass and forb cover was low on analogous sites of the plateau. Age—class distributions of major tree species further substantiated that major physiognomic changes have occurred on the plateau since the arrival of European man. Analysis of fire scars showed that prior to 1881, the mean fire—free interval for ponderosa pine stands on the plateau was 4 to 7 yr, while the interval for Church Mesa was 69 yr. Since there were no recorded fires on Church Mesa between 1892 and 1964, and yet no corresponding increase in sapling density, the increased understory density of plateau stands should not be attributed primarily to cessation of fires. Instead, heavy grazing by livestock and associated reduction of the herbaceous groundlayer promoted the establishment of less palatable tree and shrub seedlings, Fire, however, played an important secondary role in maintaining savanna and woodland communities.

ISSN:0012-9658    

DOI:10.2307/1937186

出版商:Ecological Society of America    

年代:1983

数据来源: WILEY

摘要:

Foliage of Celtis durandii and Markhamia platycalyx are important foods of the red colobus (Colobus badius tephrosceles) and the black—and—white colobus (Colobus guereza occidentalis) at Kanyawara, Kibale Forest, Uganda. Seasonal variations in the chemical composition of this foliage were attributed to phenological changes. Moisture, crude protein, energy value, potassium, and phosphorus decreased, while acid detergent fiber, lignin, calcium, and sodium increased with advancing maturity. Intermonthly changes in plant chemistry of M. platycalyx were not so pronounced as in C. durandii; the latter also gave strong correlation among its chemical components, while similar correlations for M. platycalyx wee generally weak. The nutrient quality of leaves from C. durandii was highest during the brief period when buds (leaf and flower), flowers, and young leaves were most abundant. With increasing maturity, these leaves lost the characteristics that made them good forage. M. platycalyx, on the contrary, had foliage with varying nutrient quality. Intermonthly dietary variation of the colobus monkeys is governed by the interactions between food consumption rate and changing food quality, together with the availability of alternative food items.

ISSN:0012-9658    

DOI:10.2307/1937187

出版商:Ecological Society of America    

年代:1983

数据来源: WILEY

摘要:

Distance sampling methodology is adapted to enable animal density (number per unit of area) to be estimated from capture—recapture and removal data. A trapping web design provides the link between capture data and distance sampling theory. The estimator of density is D = Mt+1f(0), where Mt+1is the number of individuals captured and f(0) is computed from the Mt+1distances from the web center to the traps in which those individuals were first captured. It is possible to check qualitatively the critical assumption on which the web design and the estimator are based. This is a conceptual paper outlining a new methodology, not a definitive investigation of the best specific way to implement this method. Several alternative sampling and analysis methods are possible within the general framework of distance sampling theory; a few alternatives are discussed and an example is given.

ISSN:0012-9658    

DOI:10.2307/1937188

出版商:Ecological Society of America    

年代:1983

数据来源: WILEY

摘要:

Analysis of solar radiation data for three summers (1978—1980) revealed that cloud—cover was present for at least 10% of the daytime on 85% of the days in the Medicine Bow Mountains of southeastern Wyoming and occurred most frequently from 1000 to 1800. Although cloudcover caused a major reduction in direct—beam irradiance as well as a 30% decrease in daily integrated photon flux density at the forest floor, substantial increases in diffuse photon flux density were measured. The understory herb Arnica latifolia had a 37% greater carbon gain on representative cloudy days than on clear days with an 84% reduction in transpiration, which resulted in more than a sevenfold increase in water use efficiency when compared to clear days. The increase in carbon gain may have been the result of photosynthetic rates that were still near saturation even under the diffuse light of cloudy days. Thus, photosynthesis and water relations of A. latifolia may be enhanced by the natural occurrence of afternoon clouds which prevent potential increases in transpiration without decreasing in carbon gain.

ISSN:0012-9658    

DOI:10.2307/1937189

出版商:Ecological Society of America    

年代:1983

数据来源: WILEY