| 28711. |
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| 28712. |
- Barabas, György
(författare)
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Biodiversity and community structure
- 2021
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 118:11
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
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| 28713. |
- Barabas, György, et al.
(författare)
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Chesson's coexistence theory
- 2018
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Ingår i: Ecological Monographs. - : WILEY. - 0012-9615 .- 1557-7015. ; 88:3, s. 277-303
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Forskningsöversikt (refereegranskat)abstract
- We give a comprehensive review of Chesson's coexistence theory, summarizing, for the first time, all its fundamental details in one single document. Our goal is for both theoretical and empirical ecologists to be able to use the theory to interpret their findings, and to get a precise sense of the limits of its applicability. To this end, we introduce an explicit handling of limiting factors, and a new way of defining the scaling factors that partition invasion growth rates into the different mechanisms contributing to coexistence. We explain terminology such as relative nonlinearity, storage effect, and growth-density covariance, both in a formal setting and through their biological interpretation. We review the theory's applications and contributions to our current understanding of species coexistence. While the theory is very general, it is not well suited to all problems, so we carefully point out its limitations. Finally, we critique the paradigm of decomposing invasion growth rates into stabilizing and equalizing components: we argue that these concepts are useful when used judiciously, but have often been employed in an overly simplified way to justify false claims.
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| 28714. |
- Barabas, György, et al.
(författare)
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Chessons coexistence theory: reply
- 2020
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Ingår i: Ecology. - : John Wiley & Sons. - 0012-9658 .- 1939-9170. ; 101:11
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
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| 28715. |
- Barabas, György
(författare)
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Parameter Sensitivity of Transient Community Dynamics
- 2024
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Ingår i: American Naturalist. - : UNIV CHICAGO PRESS. - 0003-0147 .- 1537-5323.
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Tidskriftsartikel (refereegranskat)abstract
- Transient dynamics have always intrigued ecologists, but current rapid environmental change (inducing transients even in previously undisturbed systems) has highlighted their importance more than ever. Here, I introduce a method for analyzing the sensitivity of transient ecological dynamics to parameter perturbations. The question the method answers is: how would the community dynamics have unfolded for some time horizon had the parameters been slightly different? I apply the method to three empirically parameterized models: competition between native forbs and exotic grasses in California, a host-parasitoid system, and an experimental chemostat predator-prey model. These applications showcase the ecological insights one can gain from models using transient sensitivity analysis. First, one can find parameters and their combinations whose perturbations disproportionately affect a system. Second, one can identify particular windows of time during which the predicted deviation from the unperturbed trajectories is especially large and utilize this information for management purposes. Third, there is an inverse relationship between transient and long-term sensitivities whenever the interacting populations are ecologically similar; paradoxically, the smaller the immediate response of the system, the more extreme its long-term response will be.
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| 28716. |
- Barabas, György, et al.
(författare)
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Self-regulation and the stability of large ecological networks
- 2017
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Ingår i: NATURE ECOLOGY and EVOLUTION. - : NATURE PUBLISHING GROUP. - 2397-334X. ; 1:12, s. 1870-
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Tidskriftsartikel (refereegranskat)abstract
- The stability of complex ecological networks depends both on the interactions between species and the direct effects of the species on themselves. These self-effects are known as self-regulation when an increase in a species abundance decreases its per-capita growth rate. Sources of self-regulation include intraspecific interference, cannibalism, time-scale separation between consumers and their resources, spatial heterogeneity and nonlinear functional responses coupling predators with their prey. The influence of self-regulation on network stability is understudied and in addition, the empirical estimation of self-effects poses a formidable challenge. Here, we show that empirical food web structures cannot be stabilized unless the majority of species exhibit substantially strong self-regulation. We also derive an analytical formula predicting the effect of self-regulation on network stability with high accuracy and show that even for random networks, as well as networks with a cascade structure, stability requires negative self-effects for a large proportion of species. These results suggest that the aforementioned potential mechanisms of self-regulation are probably more important in contributing to the stability of observed ecological networks than was previously thought.
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| 28717. |
- Barabas, György
(författare)
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The coexistence problem revisited
- 2017
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Ingår i: NATURE ECOLOGY and EVOLUTION. - : NATURE PUBLISHING GROUP. - 2397-334X. ; 1:10, s. 1425-1426
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- A new theoretical study warns against common misinterpretations of classical ideas on the limits to species diversity.
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| 28718. |
- Barabas, György, et al.
(författare)
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The evolution of trait variance creates a tension between species diversity and functional diversity
- 2022
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Ingår i: Nature Communications. - : Nature Portfolio. - 2041-1723. ; 13:1
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Tidskriftsartikel (refereegranskat)abstract
- It seems intuitively obvious that species diversity promotes functional diversity: communities with more plant species imply more varied plant leaf chemistry, more species of crops provide more kinds of food, etc. Recent literature has nuanced this view, showing how the relationship between the two can be modulated along latitudinal or environmental gradients. Here we show that even without such effects, the evolution of functional trait variance can erase or even reverse the expected positive relationship between species- and functional diversity. We present theory showing that trait-based eco-evolutionary processes force species to evolve narrower trait breadths in more tightly packed, species-rich communities, in their effort to avoid competition with neighboring species. This effect is so strong that it leads to an overall reduction in trait space coverage whenever a new species establishes. Empirical data from land snail communities on the Galapagos Islands are consistent with this claim. The finding that the relationship between species- and functional diversity can be negative implies that trait data from species-poor communities may misjudge functional diversity in species-rich ones, and vice versa. The positive relationship between species diversity and functional diversity has been shown to vary. Here, the authors use theoretical models and data from Galapagos land snail communities to show how eco-evolutionary processes can force species to evolve narrower trait breadths in more species-rich communities to avoid competition, creating a negative relationship.
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| 28719. |
- Barabash, Stas, et al.
(författare)
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Mars Orbiting Plasma Surveyor (MOPS)
- 2006
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Ingår i: Proceedings of the 6th IAA International Conference on Low-Cost Planetary Missions. ; , s. 227-232
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Mars Orbiting Plasma Surveyor (MOPS) is a microsatellite mission focused on studies of the near -Mars environment and the planet - solar wind interaction. The recent findings by the ESA Mars Express mission further highlighted the complexity of the processes taking place at the planet resulting from the solar wind interaction that strongly affect the planet's atmosphere. However, despite many previous Martian missions carrying different types of space plasma experiments, a comprehensive investigation including simultaneous measurements of particles, fields, and waves has never been performed. We consider a spinning spacecraft of a wet mass of 76.1 kg with a 9.7 kg payload, which can “hitchhike” on another platform until Mars orbit insertion, and then be released into a suitable orbit. The spacecraft design is based on the experience gained in very successful Swedish space plasma missions, Viking, Freja, Astrid-1, and Astrid-2. In the present mission design, the MOPS spacecraft is equipped with its own 1m high gain antenna for direct communication with the Earth. The payload includes a wave experiment with wire booms, magnetometer with a rigid boom, Langmuir probes, electron and ion energy spectrometers and an ion mass analyzer. An energetic neutral atom imager and an UV photometer may complete the core payload. One of the proposed scenarios is piggy - backing on the Russian Phobos - Grunt mission to be launched to Mars in 2011.
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| 28720. |
- Barabash, S., et al.
(författare)
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Observations of Sounder Accelerated Electrons by Mars Express
- 2020
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Ingår i: Journal of Geophysical Research - Space Physics. - 2169-9380 .- 2169-9402. ; 125:1
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Tidskriftsartikel (refereegranskat)abstract
- The electron sensor of the Analyzer of Space Plasmas and Energetic Atoms experiment detects accelerated electrons during pulses of radio emissions from the powerful topside sounder: the Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) on board the Mars Express spacecraft. Accelerated electrons are observed at energies up to 400 eV at the times when MARSIS transmits at a frequency between the local plasma frequency and its harmonics (up to 4 times the plasma frequency). When the electron density and magnetic field strength are low (similar to 10(3) cm(-3), similar to 10 nT), the accelerated electrons are almost monoenergetic electron beams. An increase in density and magnetic field (similar to 3 . 10(3) cm(-3), similar to 50 nT) leads to substantial broadening of the energy spectrum of the accelerated electrons. It is concluded that in the latter case, electrons are accelerated by the variable spacecraft potential resulting from the imbalance of the electron and ion currents to the MARSIS antenna during transmission.
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