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911.
Mechanisms for frequency-dependent mating success 总被引:1,自引:0,他引:1
L. PARTRIDGE W. G. HILL 《Biological journal of the Linnean Society. Linnean Society of London》1984,23(2-3):113-132
We consider ways in which non-frequency-dependent processes could generate negatively frequency-dependent male mating success (the rare male effect). Various forms of male competition and female preference could produce the phenomenon, and further experiments are needed to examine their occurrence. We conclude that the rare male effect is likely to be of limited evolutionary relevance. 相似文献
912.
Studies of human population structure and history have tended to use demographic and/or serological data for analysis. This paper reviews the methods and studies that incorporate quantitative traits (usually polygenic traits) in such analyses. Methods of assessing the degree and pattern of among-group variation are discussed, and are characterized as being model-free or model-bound. Model-free methods deal with the measure of overall populational differentiation and with comparative methods for describing the pattern of differentiation. Model-bound methods are used for direct incorporation into theoretical models of population structure in order to estimate genetic parameters, such as those in admixture and isolation by distance models. To date, studies have indicated that quantitative traits may often be used successfully in studies of human population structure, and show effects of microevolutionary forces on quantitative variation among populations. 相似文献
913.
Behavioral responses to host foodplants of two populations of the insect parasitoid Cotesia congregata (Say) 总被引:1,自引:0,他引:1
To test the hypothesis that natural enemy populations differ in their behavioral responses to plants or to plant allelochemicals, we compared two populations of the gregarious larval endoparasitoid, Cotesia congregata (Say) (Hymenoptera: Braconidae) that differed in their historical and present exposure to tobacco. The major hosts for both populations were Manduca sexta L. and M. quinquemaculata (Haworth) (Lepidoptera: Sphingidae), but these hosts were typically encountered on tobacco by parasitoids in one population (Upper Marlboro) and on tomato by parasitoids in another population (Wye). Early in the season, Wye parasitoids preferred to oviposit in M. sexta on tomato rather than on tobacco and Upper Marlboro parasitoids showed no preference; neither population showed any preference later in the season. Neither of the strains originating from the two populations showed a landing preference for tobacco or tomato in flight chamber trials, but Upper Marlboro parasitoids searched longer on tobacco than on tomato, and Wye parasitoids searched longer on tomato. When nicotine solutions were applied to tobacco leaf, searching responses of Upper Marlboro parasitoids were enhanced by 0.001–1.0% nicotine, and searching responses of Wye parasitoids were decreased by 0.01–1.0% nicotine. We speculate that population differences in searching responses to tobacco and nicotine may explain the differential parasitism responses found early in the season. 相似文献
914.
S. Goffredo E. Caroselli G. Mattioli E. Pignotti F. Zaccanti 《Coral reefs (Online)》2008,27(3):623-632
The demographic characteristics of the solitary zooxanthellate scleractinian Balanophyllia europaea, endemic to the Mediterranean, were determined in six populations, on a latitudinal gradient along the Italian coast, and
compared with the mean annual sea surface temperature (SST). Growth rate correlated negatively, and asymptotic length of the
individuals positively with SST. With increasing SST, the distributions of age frequencies moved away from a typical steady
state structure (i.e., exponential decrease in the frequency of individuals with age), indicating less stable populations
and showed a deficiency of individuals in the younger-age classes. These observations suggest that high temperatures are an
adverse factor to the B. europaea symbiosis. Using projected increases in seawater temperature, most of the B. europaea populations in the Mediterranean are expected to be close to their thermal limits by 2100 and the populations at that time
may support few young individuals.
Communicated by Environment Editor Prof. van Woesik. 相似文献
915.
Blood specimens from Brahmin and Kamma caste populations of Coastal Andhra Pradesh, India are examined for A1A2BO, MNSs, and Rhesus blood groups. Predominance of A group in Brahmins and B group in Kammas is observed. Phenotype A2 records less than 4% in both populations. High frequencies of genes M, s, D, and e are exhibited among both populations. Statistically significant differences are found only for A1A2BO system between Brahmins and Kammas. 相似文献
916.
M. H. Crawford J. H. Mielke E. J. Devor D. D. Dykes H. F. Polesky 《American journal of physical anthropology》1981,55(2):167-185
Genetic data consisting of 14 red cell antigen groups and 11 serum and erythrocytic protein marker systems from four Eskimo populations of the Norton Sound area of Alaska are reported. The population structure of these four groups is analyzed both separately and within the larger context by comparison to 15 other circumpolar groups. These analyses reveal a good fit between genetic structure, geographic distribution, linguistic affiliation, and the ethnohistory of the region. 相似文献
917.
M. Boots 《Oecologia》2000,124(2):172-175
The effects of resource limitation on the transmission of a pathogen were explored. Resource limitation was achieved by replacing
part of the host’s diet with an indigestible bulking agent. Populations of the pyrallid moth, Plodia interpunctella, raised on high- and low-quality food regimes were exposed to a granulosis virus. Moths subjected to a lower food quality
were more likely to become infected, despite the fact that in previous studies, individuals showed no increased susceptibility
when exposed individually to the virus. This effect is suggested to be due to a higher exposure to the pathogen due to a faster
feeding rate and longer developmental period. The implications of resource levels to the population dynamics of host-pathogen
interactions are discussed.
Received: 8 July 1999 / Accepted: 14 February 2000 相似文献
918.
Synopsis Throughout its range, freshwater populations in the Gasterosteus aculeatus species complex display remarkable differentiation of morphology and behavior, much of which reflects differences in ecological conditions among habitats. We first describe the ecological conditions that have led to morphological and behavioral divergence in two common lake types in British Columbia, Canada. Deep, oligotrophic lakes have favored the evolution of slender fish well adapted for feeding on plankton (limnetic, sensu McPhail 1984), whereas shallow, more eutrophic lakes with extensive littoral zones favor fish that are deeper-bodied and well adapted for feeding on benthic invertebrates. The latter forage in large groups that attack nests guarded by males and cannibalize the young within. Courtship in these lakes is relatively inconspicuous, a feature that apparently enhances nest survivorship. In limnetic populations, this form of cannibalism is usually absent and courtship is conspicuous. Because benthic populations tend to have larger bodies and hence, larger gapes than do limnetic fish we suggest that cannibalism may be facilitated by large body size or a correlated trait. We test this by comparing the morphology of populations exhibiting both group cannibalism and a second kind of cannibalism in which solitary females court males, gain access to nests as a consequence, and then cannibalize eggs without spawning. Our results suggest that differences in body size cannot explain variation among populations in cannibalistic tendencies but that body size may affect the effectiveness of cannibalism by females within populations. 相似文献
919.
Thomas Mercer Hursh 《American journal of physical anthropology》1978,48(3):373-374
Growth is marked by changes in body shape as well as increase in body size. It is suggested that changes in body shape in childhood and adolescence be analyzed by least squares fit lines for one dimension on a second at successive ages. These are preferred during childhood to the traditional indices of anthropologists because body proportions change with growth, and one can identify the direction of the change and observe which body dimension is changing, or if both are. Furthermore, populations may be compared by analysis of covariance for different patterns of growth related to sex and ethnic groups. Analysis of a number of populations have demonstrated clear differences between the sexes and between populations for the following body proportions: sitting height to leg length, arm length to leg length, biacromial width to biiliac width. 相似文献
920.
Fragmentation and destruction of natural habitats is currently considered to be the major threat to wildlife populations.
We here perform a comprehensive analysis of the demographic effects of habitat fragmentation and destruction on 14 populations
of the root vole. The experiment was divided into two consecutive periods. During the first period, we contrasted populations
with the same initial size and structure in continuous and fragmented habitat. During the second period, we fragmented the
continuous habitat into the same configuration as the permanently fragmented habitat so that the effect of habitat destruction
could be evaluated. We estimated survival and fecundity parameters and combined them into population projection matrices to
evaluate their relative impact on population growth. In the first period of the experiment there was no difference in population
growth rate between fragmented and continuous populations, although litter size was significantly higher in the continuous
populations. In the second period, we found higher population growth rates in populations that had experienced habitat destruction.
By applying the transition matrix model to empirical estimates of demographic parameters, we demonstrate that the difference
in population growth rate in the second period of the experiment was the result of a nonsignificant difference in adult survival.
Movements out of the habitat patches were significantly lower in populations that had experienced habitat destruction. We
conclude that predator-caused mortality of animals moving out of the habitat patches was the main determinant of demographic
variation in this system.
Received: January 31, 2002 / Accepted: March 25, 2003 相似文献