scholarly journals Rapid evolution leads to differential population dynamics and top-down control in resurrectedDaphniapopulations

2017 ◽  
Vol 11 (1) ◽  
pp. 96-111 ◽  
Author(s):  
Eyerusalem Goitom ◽  
Laurens J. Kilsdonk ◽  
Kristien Brans ◽  
Mieke Jansen ◽  
Pieter Lemmens ◽  
...  
Keyword(s):  
Population Dynamics ◽  
Rapid Evolution ◽  
Top Down

Population dynamics of large and small mammals: Graeme Caughley's grand vision

2009 ◽  
Vol 36 (1) ◽  
pp. 1 ◽  
Author(s):  
Charles J. Krebs
Keyword(s):  
Population Dynamics ◽  
Population Control ◽  
Population Increase ◽  
Control Mechanisms ◽  
Relative Role ◽  
Top Down ◽  
Large Herbivores ◽  
Disturbed Systems ◽  
Herbivorous Mammals ◽  
Grand Vision

Ecologists that study the population dynamics of large and small herbivorous mammals operate in two worlds that overlap only partly, and in this paper I address whether the conjecture that these worlds represent two distinct and valid paradigms is currently justified. I argue that large mammals fall into three groups depending on whether they have effective predators or not, and whether they are harvested by humans. Because of human persecution of large predators, more and more large herbivorous mammals are effectively predator-free and are controlled bottom-up by food. But in less disturbed systems, large herbivorous mammals should be controlled top-down by effective predators, and this can lead to a trophic cascade. Small herbivorous mammals have been suggested to be controlled top-down by predators but some experimental evidence has challenged this idea and replaced it with the notion that predation is one of several factors that may affect rates of population increase. Intrinsic control (territoriality, infanticide, social inhibition of breeding) appears to be common in small herbivorous mammals with altricial young but is absent in species with precocial young, in ecosystems with strong stochastic weather variation (deserts) and in areas of human-induced habitat fragmentation in agricultural monocultures. The extrinsic control of large herbivores with precocial young validates part of Graeme Caughley’s Grand Vision, but the relative role of intrinsic and extrinsic mechanisms for small herbivores with altricial young is still controversial. An improved knowledge of population control mechanisms for large and small herbivores is essential for natural resource management.

Predator disease out-break modulates top-down, bottom-up and climatic effects on herbivore population dynamics

2006 ◽  
Vol 9 (4) ◽  
pp. 383-389 ◽  
Author(s):  
Christopher C. Wilmers ◽  
Eric Post ◽  
Rolf O. Peterson ◽  
John A. Vucetich
Keyword(s):  
Population Dynamics ◽  
Top Down ◽  
Climatic Effects ◽  
Bottom Up

scholarly journals Population Dynamics of Early Visual Cortex during Working Memory

2018 ◽  
Vol 30 (2) ◽  
pp. 219-233 ◽  
Author(s):  
Masih Rahmati ◽  
Golbarg T. Saber ◽  
Clayton E. Curtis
Keyword(s):  
Working Memory ◽  
Population Dynamics ◽  
Visual Cortex ◽  
Parietal Cortex ◽  
Visual Stimulus ◽  
Visual Stimulation ◽  
Brain Activity ◽  
Top Down ◽  
Population Activity ◽  
Early Visual Cortex

Although the content of working memory (WM) can be decoded from the spatial patterns of brain activity in early visual cortex, how populations encode WM representations remains unclear. Here, we address this limitation by using a model-based approach that reconstructs the feature encoded by population activity measured with fMRI. Using this approach, we could successfully reconstruct the locations of memory-guided saccade goals based on the pattern of activity in visual cortex during a memory delay. We could reconstruct the saccade goal even when we dissociated the visual stimulus from the saccade goal using a memory-guided antisaccade procedure. By comparing the spatiotemporal population dynamics, we find that the representations in visual cortex are stable but can also evolve from a representation of a remembered visual stimulus to a prospective goal. Moreover, because the representation of the antisaccade goal cannot be the result of bottom–up visual stimulation, it must be evoked by top–down signals presumably originating from frontal and/or parietal cortex. Indeed, we find that trial-by-trial fluctuations in delay period activity in frontal and parietal cortex correlate with the precision with which our model reconstructed the maintained saccade goal based on the pattern of activity in visual cortex. Therefore, the population dynamics in visual cortex encode WM representations, and these representations can be sculpted by top–down signals from frontal and parietal cortex.

scholarly journals Effects of rapid evolution on species coexistence

2019 ◽  
Vol 116 (6) ◽  
pp. 2112-2117 ◽  
Author(s):  
Simon P. Hart ◽  
Martin M. Turcotte ◽  
Jonathan M. Levine
Keyword(s):  
Population Dynamics ◽  
Species Diversity ◽  
Interspecific Competition ◽  
Species Coexistence ◽  
Rapid Evolution ◽  
Empirical Work ◽  
Niche Differentiation ◽  
Ecological Communities ◽  
Competing Species ◽  
Ecological Processes

Increasing evidence for rapid evolution suggests that the maintenance of species diversity in ecological communities may be influenced by more than purely ecological processes. Classic theory shows that interspecific competition may select for traits that increase niche differentiation, weakening competition and thus promoting species coexistence. While empirical work has demonstrated trait evolution in response to competition, if and how evolution affects the dynamics of the competing species—the key step for completing the required eco-evolutionary feedback—has been difficult to resolve. Here, we show that evolution in response to interspecific competition feeds back to change the course of competitive population dynamics of aquatic plant species over 10–15 generations in the field. By manipulating selection imposed by heterospecific competitors in experimental ponds, we demonstrate that (i) interspecific competition drives rapid genotypic change, and (ii) this evolutionary change in one competitor, while not changing the coexistence outcome, causes the population trajectories of the two competing species to converge. In contrast to the common expectation that interspecific competition should drive the evolution of niche differentiation, our results suggest that genotypic evolution resulted in phenotypic changes that altered population dynamics by affecting the competitive hierarchy. This result is consistent with theory suggesting that competition for essential resources can limit opportunities for the evolution of niche differentiation. Our finding that rapid evolution regulates the dynamics of competing species suggests that ecosystems may rely on continuous feedbacks between ecology and evolution to maintain species diversity.

scholarly journals Rapid Evolution of a Sexual Reproduction Gene in Centric Diatoms of the Genus Thalassiosira

2001 ◽  
Vol 67 (8) ◽  
pp. 3501-3513 ◽  
Author(s):  
E. Virginia Armbrust ◽  
H. M. Galindo
Keyword(s):  
Population Dynamics ◽  
Sexual Reproduction ◽  
Related Species ◽  
Rapid Evolution ◽  
Sequence Divergence ◽  
Thalassiosira Pseudonana ◽  
Centric Diatom ◽  
Additional Species ◽  
Gamete Recognition ◽  
The Impact

ABSTRACT Sexual reproduction is commonly assumed to occur in the vast majority of diatoms due to the intimate association of this process with cell size control. Surprisingly, however, little is known about the impact of sexual events on diatom population dynamics. TheSig1 gene is strongly upregulated during sexual reproduction in the centric diatom Thalassiosira weissflogii and has been hypothesized to encode a protein involved in gamete recognition. In the present study, degenerate PCR primers were designed and used to amplify a portion ofSig1 from three closely related species in the cosmopolitan genus Thalassiosira, Thalassiosira oceanica, Thalassiosira guillardii, andThalassiosira pseudonana. Identification ofSig1 in these three additional species facilitated development of this gene as a molecular marker for diatom sexual events. Examination of the new sequences indicated that multiple copies of Sig1 are probably present in the genome. Moreover, compared to the housekeeping geneβ -tubulin, the Sig1genes of isolates of T. weissflogii collected from different regions of the Atlantic and Pacific oceans displayed high levels of divergence. The Sig1 genes of the four closely related Thalassiosira species also displayed high levels of sequence divergence compared to the levels observed with a second gene, Fcp, probably explaining why Sig1could not be amplified from more distantly related species. The high levels of sequence divergence both within and between species suggest that Sig1 is rapidly evolving in a manner reminiscent of the manner observed in other genes that encode gamete recognition proteins. A simple model is presented for Sig1 evolution and the implications of such a rapidly evolving sexual reproduction gene for diatom speciation and population dynamics.

scholarly journals Cryptic Population Dynamics: Rapid Evolution Masks Trophic Interactions

PLoS Biology ◽  
2007 ◽  
Vol 5 (9) ◽  
pp. e235 ◽  
Author(s):  
Takehito Yoshida ◽  
Stephen P Ellner ◽  
Laura E Jones ◽  
Brendan J. M Bohannan ◽  
Richard E Lenski ◽  
...  
Keyword(s):  
Population Dynamics ◽  
Trophic Interactions ◽  
Rapid Evolution
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