2,113 research outputs found
Variation in the relative magnitude of intraspecific and interspecific competitive effects in novel versus familiar environments in two Drosophila species
Get PDFModels 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 populations of Drosophila melanogaster and D. 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
Inbreeding and sex: canalization, plasticity and sexual selection
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Are bigger flies always better: the role of genes and environment
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Response to comment on "Stability via asynchrony in Drosophila metapopulations with low migration rates"
Get PDFRanta and Kaitala find asynchrony in our experiment unexpected and suggest stochasticity as a possible causal mechanism using simulated two-patch metapopulations. However, their mechanism can yield either subpopulation synchrony or asynchrony. We extend their approach to a nine-patch system approximating our experiment and show that asynchrony is not only not unexpected but extremely likely in real metapopulations with low migration
Local Perturbations Do Not Affect Stability of Laboratory Fruitfly Metapopulations
Get PDFA large number of theoretical studies predict that the dynamics of spatially
structured populations (metapopulations) can be altered by constant
perturbations to local population size. However, these studies presume large
metapopulations inhabiting noise-free, zero-extinction environments, and their
predictions have never been empirically verified.
Here we report an empirical study on the effects of localized perturbations
on global dynamics and stability, using fruitfly metapopulations in the
laboratory. We find that constant addition of individuals to a particular
subpopulation in every generation stabilizes that subpopulation locally, but
does not have any detectable effect on the dynamics and stability of the
metapopulation. Simulations of our experimental system using a simple but
widely applicable model of population dynamics were able to recover the
empirical findings, indicating the generality of our results. We then simulated
the possible consequences of perturbing more subpopulations, increasing the
strength of perturbations, and varying the rate of migration, but found that
none of these conditions were expected to alter the outcomes of our
experiments. Finally, we show that our main results are robust to the presence
of local extinctions in the metapopulation.
Our study shows that localized perturbations are unlikely to affect the
dynamics of real metapopulations, a finding that has cautionary implications
for ecologists and conservation biologists faced with the problem of
stabilizing unstable metapopulations in nature.Comment: 9 pages, 11 figure
Stability via asynchrony in Drosophila metapopulations with low migration rates
Get PDFVery few experimental studies have examined how migration rate affects metapopulation dynamics and stability. We studied the dynamics of replicate laboratory metapopulations of Drosophila under different migration rates. Low migration stabilized metapopulation dynamics, while promoting unstable subpopulation dynamics, by inducing asynchrony among neighboring subpopulations. High migration synchronized subpopulation dynamics, thereby destabilizing the metapopulations. Contrary to some theoretical predictions, increased migration did not affect average population size. Simulations based on a simple non-species-specific population growth model captured most features of the data, which suggests that our results are generalizable
Optical bistability in a -type atomic system including near dipole-dipole interaction
Full text linkThe advantage of optical bistability (OB) using three-level
electromagnetically induced transparency (EIT) atomic system over the two-level
system is its controllability, as absorption, dispersion, and optical
nonlinearity in one of the atomic transitions can be modified considerably by
the field interacting with nearby atomic transitions. This is due to induced
atomic coherences generated in such EIT system. The inclusion of near
dipole-dipole (NDD) interaction among atoms further modifies absorption,
dispersion, and optical nonlinearity of three-level EIT system and the OB can
also be controlled by this interaction, producing OB to multistability.Comment: 15 pages, 6 figure
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