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1.
Lof ME Etienne RS Powell J de Gee M Hemerik L 《Bulletin of mathematical biology》2008,70(7):1827-1849
Animal aggregation is a general phenomenon in ecological systems. Aggregations are generally considered as an evolutionary
advantageous state in which members derive the benefits of protection and mate choice, balanced by the costs of limiting resources
and competition. In insects, chemical information conveyance plays an important role in finding conspecifics and forming aggregations.
In this study, we describe a spatio-temporal simulation model designed to explore and quantify the effects of these infochemicals,
i.e., food odors and an aggregation pheromone, on the spatial distribution of a fruit fly (Drosophila melanogaster) population, where the lower and upper limit of local population size are controlled by an Allee effect and competition.
We found that during the spatial expansion and strong growth of the population, the use of infochemicals had a positive effect
on population size. The positive effects of reduced mortality at low population numbers outweighed the negative effects of
increased mortality due to competition. At low resource densities, attraction toward infochemicals also had a positive effect
on population size during recolonization of an area after a local population crash, by decreasing the mortality due to the
Allee effect. However, when the whole area was colonized and the population was large, the negative effects of competition
on population size were larger than the positive effects of the reduction in mortality due to the Allee effect. The use of
infochemicals thus has mainly positive effects on population size and population persistence when the population is small
and during the colonization of an area.
Electronic Supplementary Material The online version of this article () contains supplementary material, which is available to authorized users. 相似文献
2.
Postharvesting population dynamics of the South American sea lion (Otaria byronia) in the southwestern Atlantic 下载免费PDF全文
Valentina Franco‐Trecu Massimiliano Drago Claudia Baladán Mateo D. García‐Olazábal Enrique A. Crespo Luis Cardona Pablo Inchausti 《Marine Mammal Science》2015,31(3):963-978
Many pinniped populations precipitously declined during the 19th and 20th centuries due to overharvesting. In Uruguay, the South American sea lion (SASL) was harvested until 1986. Birth rates in two nearby breeding colonies have had opposite trends for at least 20 yr. We assessed different mechanisms that could explain opposite trends in birth rates in the two SASL colonies. We compared feeding habits (δ15N and δ13C) of breeding females, birth mass, individual growth rate and early survival of pups and the social structure between colonies. Breeding females from the two colonies did not differ in their feeding habits. However, male and female pups grew faster but had a lower survival in the second month in the smallest colony. We found differences in the social structures, with a higher proportion of males in the smallest colony. The latter is important because peripheral SASL males may abduct and kill pups, which may explain the lower survival of pups in smaller colonies. We believe that the cumulative effects of population extractions have lowered the local SASL population size and disrupted its social structure to the point where Allee‐like effects could become important and hamper the recovery of the Uruguayan SASL population. 相似文献
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Bregje Wertheim Julien Marchais Louise E. M. Vet Marcel Dicke 《Ecological Entomology》2002,27(5):608-617
Abstract 1. Aggregation pheromones can evolve when individuals benefit from clustering. Such a situation can arise with an Allee effect, i.e. a positive relationship between individual fitness and density of conspecifics. Aggregation pheromone in Drosophila induces aggregated oviposition. The aim of the work reported here was to identify an Allee effect in the larval resource exploitation by Drosophila melanogaster, which could explain the evolution of aggregation pheromone in this species. 2. It is hypothesised that an Allee effect in D. melanogaster larvae arises from an increased efficiency of a group of larvae to temper fungal growth on their feeding substrate. To test this hypothesis, standard apple substrates were infested with specified numbers of larvae, and their survival and development were monitored. A potential beneficial effect of the presence of adult flies was also investigated by incubating a varying number of adults on the substrate before introducing the larvae. Adults inoculate substrates with yeast, on which the larvae feed. 3. Fungal growth was related negatively to larval survival and the size of the emerging flies. Although the fungal growth on the substrate was largely reduced at increased larval densities, the measurements of fitness components indicated no Allee effect between larval densities and larval fitness, but rather indicated larval competition. 4. In contrast, increased adult densities on the substrates prior to larval development yielded higher survival of the larvae, larger emerging flies, and also reduced fungal growth on the substrates. Hence, adults enhanced the quality of the larval substrate and significant benefits of aggregated oviposition in fruit flies were shown. Experiments with synthetic pheromone indicated that the aggregation pheromone itself did not contribute directly to the quality of the larval resource. 5. The interaction among adults, micro‐organisms, and larval growth is discussed in relation to the consequences for total fitness. 相似文献
5.
In a companion paper (Lof et al., in Bull. Math. Biol., 2008), we describe a spatio-temporal model for insect behavior. This model includes chemical information for finding resources
and conspecifics. As a model species, we used Drosophila melanogaster, because its behavior is documented comparatively well.
We divide a population of Drosophila into three states: moving, searching, and settled. Our model describes the number of flies in each state, together with the
concentrations of food odor and aggregation pheromone, in time and in two spatial dimensions. Thus, the model consists of
5 spatio-temporal dependent variables, together with their constituting relations. Although we tried to use the simplest submodels
for the separate variables, the parameterization of the spatial model turned out to be quite difficult, even for this well-studied
species.
In the first part of this paper, we discuss the relevant results from the literature, and their possible implications for
the parameterization of our model. Here, we focus on three essential aspects of modeling insect behavior. First, there is
the fundamental discrepancy between the (lumped) measured behavioral properties (i.e., fruit fly displacements) and the (detailed)
properties of the underlying mechanisms (i.e., dispersivity, sensory perception, and state transition) that are adopted as
explanation. Detailed quantitative studies on insect behavior when reacting to infochemicals are scarce. Some information
on dispersal can be used, but quantitative data on the transition between the three states could not be found. Second, a dose-response
relation as used in human perception research is not available for the response of the insects to infochemicals; the behavioral
response relations are known mostly in a qualitative manner, and the quantitative information that is available does not depend
on infochemical concentration. We show how a commonly used Michaelis–Menten type dose-response relation (incorporating a saturation
effect) can be adapted to the use of two different but interrelated stimuli (food odors and aggregation pheromone). Although
we use all available information for its parameterization, this model is still overparameterized. Third, the spatio-temporal
dispersion of infochemicals is hard to model: Modeling turbulent dispersal on a length scale of 10 m is notoriously difficult.
Moreover, we have to reduce this inherently three-dimensional physical process to two dimensions in order to fit in the two-dimensional
model for the insects. We investigate the consequences of this dimension reduction, and we demonstrate that it seriously affects
the parameterization of the model for the infochemicals.
In the second part of this paper, we present the results of a sensitivity analysis. This sensitivity analysis can be used
in two manners: firstly, it tells us how general the simulation results are if variations in the parameters are allowed, and
secondly, we can use it to infer which parameters need more precise quantification than is available now. It turns out that
the short term outcome of our model is most sensitive to the food odor production rate and the fruit fly dispersivity. For
the other parameters, the model is quite robust.
The dependence of the model outcome with respect to the qualitative model choices cannot be investigated with a parameter
sensitivity analysis. We conclude by suggesting some experimental setups that may contribute to answering this question. 相似文献
6.
Behavioral changes of animal species can influence the consequence of population dynamics. One of the most remarkable behaviors of animal species is the aggregation by which species can reduce predation risk as a consequence of dilution or the other effects by forming a group. Empirical studies have demonstrated that an incompatibility exists in aggregation since resource competition might become severe at the cost of reducing predation pressure from predatory species. Parental care by supplying the food consumed by adults to their juveniles would reduce the mortality of juvenile due to starvation, but it would reduce the reproduction rate at the same time. In this paper, we study a class of stage-structured resource-consumer models to investigate the effect of behavioral changes on population dynamics. It is shown that under the presence of trade-off in parental care, moderate degrees of parental care will be favored as maximizing the equilibrium density of consumers. For consumer species having a long maturation period, consumer species might get benefit from dilution effects as a result of aggregation despite the elevated resource competition. Aggregation gives rise to two different outcomes in consumer extinction. Resource exhaustion as a consequence of over-exploitation can induce extinction of consumers due to Allee effects if aggregation strongly mediates juvenile survival. 相似文献
7.
The male-killing spiroplasma strain NSRO causes an extremely female-biased sex ratio of the host, Drosophila melanogaster, as a result of selective death of male offspring during embryogenesis. The spiroplasma strain NSRO-A, a variant of NSRO, does not cause such symptoms. In an attempt to gain insights into the mechanism underlying the symbiont-induced reproductive phenotype, infection densities of the spiroplasmas in different tissues were monitored during host aging using a quantitative PCR technique. The density dynamics in the hemolymph were reminiscent of those in the whole body, whereas the density dynamics in the fat body, intestine and ovary were not. These results suggest that the majority of the spiroplasmas colonize and proliferate in the hemolymph of the host. In the hemolymph and whole body, the infection densities of NSRO were generally higher than those of NSRO-A, which may be related to the different reproductive phenotypes caused by the spiroplasmas. 相似文献
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Negative density dependence is an important driver of population dynamics of large vertebrates. Allee effects (positive density dependence), however, can affect small populations. Allee effects can be generated by predation and recent research has revealed potentially important indirect effects of predation on population dynamics. For wild populations, however, quantification of both Allee effects and indirect effects of predation remains scarce. We monitored for 27 years a bighorn sheep (Ovis canadensis) population that declined dramatically as episodes of cougar (Puma concolor) predation depressed survival. Predation led to a positive relationship between lamb survival and population size below a threshold, and to an overall positive relationship between yearling and adult ewe survival and population size. During years of high predation, lambs also suffer mortality through reduced growth, contributing a third of the total impact of predation on lamb survival. There was no positive association between population growth and population size, probably because growth was affected by several factors other than predation, including disease. Our results support the contention that predator-driven component Allee effects may exacerbate the effects of other environmental drivers and increase the risk of extinction of small populations. 相似文献
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Summary The structure and organization of aquatic arthropod communities in Nepenthes ampullaria pitchers were studied at two sites (M in Malacca and K in Kuching) in Malaysia. The communities consisted mainly of aquatic dipteran larvae. Community M was dominated by a filter feeder, Tripteroides tenax, which reached a high density despite a strongly aggregated distribution. Community K had five trophic groups: carrion feeders, filter feeders, detritus feeders, nipping predators and hooking predators, each including multiple species. The summed density of filter feeders in Community K remained much below the level attained by filter feeders in Community M. Niche differentiation within each trophic group with regard to pitcher age and feeding behaviour was not sufficient to allow species coexistence through niche separation alone. Aggregated distributions directly reduced interspecific encounters. Nevertheless, species belonging to the same trophic group commonly shared the same pitcher, because of high occurrence probabilities of dominant species and positive associations between some taxa (due mainly to similar occupancies by pitcher age). Predator coexistence in Community K may have been facilitated by self-limitation of the large predators through intraspecific cannibalism strengthened by aggregation. Prey coexistence, on the other hand, may have relied more on population suppression by predation, especially the selective removal of old instar Tripteroides. 相似文献
13.
Beta-amyloid (Aβ) plaques are one of the hallmarks of Alzheimer’s disease. Their presence in the brain leads to neurodegeneration and memory decline. Therefore, search for new drugs able to decrease formation of such deposits is of great interest. Our previously developed multifunctional compounds inhibited transformation of monomers into fibrils. Herein, we describe the computational approach for the assessment of inhibitory activity against Aβ aggregation. The influence of novel inhibitors on amyloid Aβ17-42 was studied by employing of molecular docking and all-atom molecular dynamics simulations. We found that the number of intermolecular backbone hydrogen bonds at the end of 100 ns MD simulation was correlated with the level of anti-aggregation potency of studied compounds. Such data may be successfully applied to in silico design of novel inhibitors of Aβ aggregation. 相似文献
14.
To what extent is adaptive evolution over short timescales repeatable? To address this question, we studied the performance of crosses between replicate Drosophila melanogaster lines previously subject to selection for improved learning response in the context of oviposition substrate choice. Of the 10 pairwise F1 crosses among the five selection lines, four performed in the original learning assay similarly to the parental lines, whereas the remaining six showed learning scores significantly below the average of the parental lines. In particular, four F1 crosses (three involving the same line) showed no detectable learning, on a par with unselected control lines. This indicates that the response to selection in some lines involved allelic substitutions at different loci. Additional assays of crosses between two selection lines indicated that the loss of performance in hybrids generalized to another type of learning assay, and held for both short‐ and long‐term memory. Joint analysis of first‐ and second‐generation crosses between these two lines supported the hypothesis that the response to selection in these different lines was based on the spread of recessive alleles at different loci. These results show that the evolutionary trajectories of populations of the same origin subject to uniform selection may sometimes diverge over very short evolutionary timescales. 相似文献
15.
Overfishing, pollution and other environmental factors have greatly reduced commercially valuable stocks of fish. In a 2006 Science article, a group of ecologists and economists warned that the world may run out of seafood from natural stocks if overfishing continues at current rates. In this paper, we explore the interaction between a constant proportion harvest policy and recruitment dynamics. We examine the discrete-time constant proportion harvest policy discussed in Ang et al. (2009) and then expand the framework to include stock-recruitment functions that are compensatory and overcompensatory, both with and without the Allee effect.We focus on constant proportion policies (CPPs). CPPs have the potential to stabilize complex overcompensatory stock dynamics, with or without the Allee effect, provided the rates of harvest stay below a threshold. If that threshold is exceeded, CPPs are known to result in the sudden collapse of a fish stock when stock recruitment exhibits the Allee effect. In case studies, we analyze CPPs as they might be applied to Gulf of Alaska Pacific halibut fishery and the Georges Bank Atlantic cod fishery based on harvest rates from 1975 to 2007. The best fit models suggest that, under high fishing mortalities, the halibut fishery is vulnerable to sudden population collapse while the cod fishery is vulnerable to steady decline to zero. The models also suggest that CPP with mean harvesting levels from the last 30 years can be effective at preventing collapse in the halibut fishery, but these same policies would lead to steady decline to zero in the Atlantic cod fishery. We observe that the likelihood of collapse in both fisheries increases with increased stochasticity (for example, weather variability) as predicted by models of global climate change. 相似文献
16.
Abstract
- 1 The relative number of colonizing adult Colorado potato beetles (CPB) Leptinotarsa decemlineata (Say) (Coleoptera: Chrysomelidae) coming to pitfall traps baited with the aggregation pheromone (S)‐3,7‐dimethyl‐2‐oxo‐oct‐6‐ene‐1,3‐diol [(S)‐CPB I] and the use of the pheromone in a trap crop pest management strategy were evaluated in the field for the first time.
- 2 More than five‐fold more adult L. decemlineata were caught in pitfall traps baited with the pheromone compared with controls. However, attraction to the pheromone diminished after 5 days in the field.
- 3 In the trap crop management strategy, more colonizing adults were present in pheromone‐treated rows of potatoes compared with untreated middle rows.
- 4 Significantly fewer L. decemlineata egg masses and larvae were found in potato plots that were bordered by pheromone‐treated rows, or bordered by imidacloprid + pheromone‐treated rows, or rows treated at‐planting with imidacloprid compared with untreated (control) potato plots.
- 5 Densities of L. decemlineata egg masses and larvae and percentage defoliation were significantly lower, and marketable tuber yield significantly higher, in conventional imidacloprid‐treated potatoes compared with all other treatments.
- 6 Although our results demonstrate the potential for use of the aggregation pheromone in the management of L. decemlineata in the field, more research is needed to optimize the release rates of the attractant and incorporate control methods for cohabiting pests.
17.
The response of adult flower thrips Frankliniella intonsa (Trybom) (Thysanoptera: Thripidae) to conspecifics is investigated in Y‐tube olfactometer bioassays. The results show that both males and females are attracted to the odours of adult males, which indicates a male‐produced aggregation pheromone in this species. Gas chromatography‐mass spectroscopy analyses of headspace volatiles collected on solid‐phase microextraction fibres show that two major components and six minor components are present in volatiles from males but not in females. Further gas chromatography‐mass spectroscopy analyses reveal that the two major components in head‐space volatiles produced by F. intonsa males are the same compounds that are reported in volatiles of Frankliniella occidentalis males: (R)‐lavandulyl acetate and neryl (S)‐2‐methylbutanoate. However, the quantity of these two compounds in the volatiles differs between the species. 相似文献
18.
William Tinzaara Clifford. S. Gold Marcel Dicke Arnold Van Huis Caroline M. Nankinga Godfrey H. Kagezi 《Biocontrol Science and Technology》2007,17(2):111-124
Candidate strains of Beauveria bassiana were identified for use in integrated pest management of the banana weevil Cosmopolites sordidus. Horizontal field transmission of B. bassiana between banana weevils using different delivery systems, including aggregation pheromones, was investigated. We observed that infected weevils could transmit the fungal pathogen to healthy individuals. Most dead weevils (52%) due to B. bassiana infection were found at the base of banana plants in the leaf sheath or in the soil near banana plants. Significantly more weevils died from the pathogen in plots where B. bassiana was applied in combination with the pheromone than where it was applied alone. Our data demonstrate that C. sordidus aggregation pheromone can be a valuable tool to enhance the dissemination of B. bassiana for the control of C. sordidus. 相似文献
19.
Contrasting patterns of geographic variation in the cosmopolitan sibling species Drosophila melanogaster and Drosophila simulans 总被引:4,自引:0,他引:4
An electrophoretic study was carried out to compare the geographic pattern of genetic variation in Drosophila simulans with that of its sibling species, Drosophila melanogaster. An identical set of 32 gene-protein loci was studied in four geographically distant populations of D. simulans and two populations of D. melanogaster, all originating from Europe and Africa. The comparison yielded the following results: (1) tropical populations of D. simulans were, in terms of the number of unique alleles, average heterozygosity per locus, and percentage of loci polymorphic, more variable than conspecific-temperate populations; (2) some loci in both species showed interpopulation differences in allele frequencies that suggest latitudinal clines; and (3) temperate-tropical genetic differentiation between populations was much less in D. simulans than in D. melanogaster. Similar differences between these two species have previously been shown for chromosomal, quantitative, physiological, and middle-repetitive DNA variation. Estimates of N
m
(number of migrants per generation) from the spatial distribution of rare alleles suggest that both species have similar levels of interpopulation gene flow. These observations lead us to propose two competing hypotheses: the low level of geographic differentiation in D. simulans is due to its evolutionarily recent worldwide colonization and, alternatively, D. simulans has a narrower niche than D. melanogaster. Geographic variation data on different genetic elements (e.g., mitochondrial DNA, two-dimensional proteins, etc.) are required before these hypotheses can be adequately tested.We thank the Natural Science and Engineering Research Council of Canada for financial support (Grant A0235 to R.S.S.). 相似文献
20.
R. Elahi 《Coral reefs (Online)》2008,27(4):881-885
Aggregations of fungiid corals are common on Indo-Pacific reefs, but visible signs of direct competition are uncommon. Although
negative interactions between fungiids are generally thought to be negligible, the results of an experiment manipulating aggregation
and species identity indicated that per capita calcification rates of Fungia concinna were depressed when surrounded by five other Fungia. The reduction in growth did not vary if neighbors were Fungia concinna or Fungia paumotensis, suggesting that these two related species overlap substantially in their competitive impacts. However, mucus production
and movement occurred more frequently in heterospecific than conspecific groups. These results suggest that there is a cost
to group living, but depressed growth must be weighed against the potential benefits of successful spawning in conspecific
aggregations.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
Communicated by Ecology Editor Professor Peter Mumby 相似文献