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41.
Cheek pouches, one of the distinguishing characters of the Cercopithecinae, are structures used for the temporary storage
of food. Their size and frequency of use within a given species are related primarily to the amount of conspecific competition
for food. In relation to total body size, members of the genusPapio are considered to have relatively small cheek pouches which are said to be used only occasionally to maximize food harvest
when local clusters of food are encountered.
This investigation represents 165 hours of observation on a troop ofPapio ursinus at Mkuzi Game Reserve in Natal, South Africa. At the time of observation the choice of foods in the home range was restricted
and usually found in abundance only in small clusters of trees. Given that conspecific competition would have been pronounced
under these conditions, it was thought that any differences in the frequency of cheek pouch use related to age, sex, rank,
or the reproductive state of an animal would be readily recognizable.
The results indicated that cheek pouches were used differentially throughout the day, with virtually all ages of each sex
displaying the same general pattern of maximal cheek pouch use during the middle of the day. In each sex there was an age
graded diminution of the frequency of cheek pouch use from juveniles to adults. This trend was more pronounced in males resulting
in a substantial sex difference in the use of cheek pouches between adult males and females. In addition, there was some indication
that differences in the frequency of cheek pouch use between adult males were correlated with rank. Although a pattern of
cheek pouch use and rank was not evident amongst adult females, there was an association between reproductive state and the
frequency of cheek pouch use. Overall, body size, dominance, and energetic demands appeared to be the most significant factors
underlying the differences in cheek pouch use in this troop. 相似文献
42.
Joshi A 《Journal of genetics》2004,83(2):179-188
Models of competitor coevolution, especially the genetic feedback hypothesis, suggest that a negative correlation between
intraspecific and interspecific competitive effects may be important in sustaining competitor coexistence, and can give rise
to oscillatory dynamics with repeated reversals of competitive superiority. I reanalyzed previously published census data
from an experiment in which populationsof Drosophila melanogaster andD. simulans underwent competitive coevolution in one familiar and two novel environments, to specifically look for any evidence of a
negative relationship between intraspecific and interspecific competitive effects on population growth rates, and for any
indication of short period cycling in the relative magnitude of intraspecific and interspecific competitive effects. While
there was considerable variation in the relative magnitude of intraspecific and interspecific competitive effects over generations,
among both populations and environments, there was no clear evidence supporting the genetic feedback hypothesis. Intraspecific
and interspecific competitive effects on population growth rates were strongly positively correlated in novel environments,
and uncorrelated in the familiar environment. Data from the familiar environment indicated that indices of competition of
populations of the initially superior competitor,D. melanogaster, might be showing some cyclic behaviour, but I argue that this is likely to be transient, and not suggestive of sustained
oscillatory dynamics predicted by the genetic feedback model. I discuss the results in the context of the importance of the
genetic architecture of intraspecific and interspecific competitive abilities in determining the coevolutionary trajectory
of competitive interactions. 相似文献
43.
44.
Traits that mediate intraspecific social interactions may overlap in closely related sympatric species, resulting in costly between-species interactions. Such interactions have principally interested investigators studying the evolution of reproductive isolation via reproductive character displacement (RCD) or reinforcement, yet in addition to reproductive interference, interspecific trait overlap can lead to costly between-species aggression. Previous research on rubyspot damselflies (Hetaerina spp.) demonstrated that sympatric shifts in male wing colour patterns and competitor recognition reduce interspecific aggression, supporting the hypothesis that agonistic character displacement (ACD) drove trait shifts. However, a recent theoretical model shows that RCD overshadows ACD if the same male trait is used for both female mate recognition and male competitor recognition. To determine whether female mate recognition is based on male wing coloration in Hetaerina, we conducted a phenotype manipulation experiment. Compared to control males, male H. americana with wings manipulated to resemble a sympatric congener (H. titia) suffered no reduction in mating success. Thus, female mate recognition is not based on species differences in male wing coloration. Experimental males did, however, experience higher interspecific fighting rates and reduced survival compared to controls. These results greatly strengthen the case for ACD and highlight the mechanistic distinction between ACD and RCD. 相似文献
45.
Several species of migrant birds overlap in range on their wintering grounds with non-migrant conspecifics or other species
that occupy a similar niche. Very little is known whether such overlap results in competition and subsequent habitat segregation
since it is usually impossible to separate resident from migrant individuals. The Loggerhead Shrike (Lanius ludovicianus) is a declining grassland species in North America that winters in the southern United States and Mexico. Using stable-hydrogen
isotope (δD) analysis of feathers, we identified resident and migrant shrikes wintering in northeastern Mexico based on a
latitudinal gradient in precipitation and feather δD values. Indicator species analyses showed that migrants occupied areas
where bare ground was less available than those occupied by residents, a pattern which held when a more restricted set of
birds from the extremes of the δD distribution were considered. This provides evidence for conspecific habitat segregation.
Habitat differences were also found between sites occupied by shrikes and apparently suitable but unoccupied sites. Shrikes
occupied more open sites that contained shorter tall shrubs and huisache (Acacia farneasiana) and fewer tall shrubs, mesquite (Prosopsis glandulosa) and huisache than unoccupied sites. The availability of suitable winter habitat and the potential competition between migrants
and residents may be factors that influence the population dynamics of migrant shrikes in North America. 相似文献
46.
Petter Glorvigen Ottar N. Bjørnstad Harry P. Andreassen Rolf A. Ims 《Population Ecology》2012,54(1):55-63
Despite the recognised importance of colonisation (settlement in empty habitats) and immigration (settlement in an established
population) to species persistence and evolution few have investigated these processes in territorial mammals and how they
affect species’ traits. We translocated female bank voles (Myodes glareolus) onto an island (2.58 ha) in a two-stage experiment (stage 1: colonisation of empty population space and stage 2: immigration into an established population) to test (1) if colonisers and immigrants differ in probability of settlement and pregnancy,
and (2) if settlement is affected by cues of conspecifics, i.e., simulated deserted home ranges (SDHR) and resident presence.
Density was kept well below saturation in 8 temporally distinct population replicates over 3 years. SDHR and resident presence
neither attracted nor repelled colonisers and immigrants, respectively, and settlement was not different from a random model.
Probability of settlement tended to be higher in colonisers than immigrants and the probability of pregnancy was significantly
higher in colonisers; immigrants settling within the home range of residents had nearly zero probability of pregnancy. Colonisation
of empty habitat patches selected based on physical or resource based habitat features is apparently the optimal settlement
strategy of dispersing voles, because cues from conspecifics may provide ambiguous information and social factors may inhibit
settlement or delay reproduction in immigrants even at low population density. 相似文献
47.
48.
Kirschner AK Rameder A Schrammel B Indra A Farnleitner AH Sommer R 《Journal of applied microbiology》2012,112(6):1244-1256
Aims: Open cooling towers are frequent sources of infections with Legionella pneumophila. The gold standard for the detection of Leg. pneumophila is based on cultivation lasting up to 10 days and detecting only culturable cells. Alternative fluorescence in situ hybridization (FISH) protocols have been proposed, but they result in faint fluorescence signals and lack specificity because of cross‐hybridization with other Legionella species. Our aim was thus to develop a new FISH protocol for rapid and specific detection of Leg. pneumophila in water samples. Methods and Results: A novel catalysed reporter deposition FISH (CARD‐FISH) protocol for the detection of Leg. pneumophila was developed, which significantly enhanced signal intensity as well as specificity of the probe through the use of a novel competitor probe. The developed protocol was compared with the culture method for monitoring the seasonal development of culturable and nonculturable Leg. pneumophila in two hospital cooling tower systems. Seasonal fluctuations of Leg. pneumophila concentrations detected via CARD‐FISH were related to the development of the total bacterial community in both cooling towers, with temperature and biocide as the main factors controlling this development. Conclusions: Our results clearly showed that the majority of the Leg. pneumophila cells were in a nonculturable state. Thus, detection of Leg. pneumophila with culture methods may underestimate the total numbers of Leg. pneumophila present. Significance and Impact of the Study: Rapid, sensitive and specific detection and quantification of Leg. pneumophila in water systems is prerequisite for reliable risk estimation. The new protocol significantly improves current methodology and can be used to monitor and screen for Leg. pneumophila concentrations in cooling towers or other water systems. 相似文献
49.
The effect of patch size and competitor number on aggression among foraging house sparrows 总被引:3,自引:1,他引:2
We examined the effect of patch size and competitor number onaggression among house sparrows, Passer domesticus, foragingat patches of seven different sizes in a doubling series (0.014,0.029, 0.058, 0.116, 0.230, 0.462, and 0.922 m2). Contrary toour expectations, the birds did not defend an entire patch,even when it was small as 0.014 m2. The frequency of aggressionamong the birds decreased gradually with increasing patch size,in contrast to the step decline predicted by resource defensetheory. Moreover, the birds fought more frequently and moreintensely as competitor density increased. Both results areconsistent with the predictions of a modified hawk-dove modelfor shared patches. Females were more aggressive and fed ata higher rate than did males. The proportion of females increasedas patch size decreased, and aggression became more frequentand intense. Even when patches are shared, patch size has animportant effect on the frequency and intensity of foragingcompetition and the size and composition of foraging groups. 相似文献
50.
Benjamin S. Ramage Daniel J. Johnson Erika Gonzalez‐Akre William J. McShea Kristina J. Anderson‐Teixeira Norman A. Bourg Keith Clay 《Ecology and evolution》2017,7(19):7661-7671
Local tree species diversity is maintained in part by conspecific negative density dependence (CNDD). This pervasive mechanism occurs in a variety of forms and ecosystems, but research to date has been heavily skewed toward tree seedling survival in tropical forests. To evaluate CNDD more broadly, we investigated how sapling growth rates were affected by conspecific adult neighbors in a fully mapped 25.6 ha temperate deciduous forest. We examined growth rates as a function of the local adult tree neighborhood (via spatial autoregressive modeling) and compared the spatial positioning of faster‐growing and slower‐growing saplings with respect to adult conspecific and heterospecific trees (via bivariate point pattern analysis). In addition, to determine whether CNDD‐driven variation in growth rates leaves a corresponding spatial signal, we extended our point pattern analysis to a static, growth‐independent comparison of saplings and the next larger size class. We found that negative conspecific effects on sapling growth were most prevalent. Five of the nine species that were sufficiently abundant for analysis exhibited CNDD, while only one species showed evidence of a positive conspecific effect, and one or two species, depending on the analysis, displayed heterospecific effects. There was general agreement between the autoregressive models and the point pattern analyses based on sapling growth rates, but point pattern analyses based on single‐point‐in‐time size classes yielded results that differed markedly from the other two approaches. Our work adds to the growing body of evidence that CNDD is an important force in temperate forests, and demonstrates that this process extends to sapling growth rates. Further, our findings indicate that point pattern analyses based solely on size classes may fail to detect the process of interest (e.g., neighborhood‐driven variation in growth rates), in part due to the confounding of tree size and age. 相似文献