Browse
Submit Data
Databases
API
Help

Dataset Information

0 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

Top-down pulses reduce prey population sizes and persistence.

ABSTRACT: Resource pulses are well documented and have important consequences for population dynamics relative to continuous inputs. However, pulses of top-down factors (e.g. predation) are less explored and appreciated in the ecological literature. Here, we use a simple differential equation population model to show how pulsed removals of individuals from a population alter population size relative to continuous dynamics. Pulsed removals result in lower equilibrium population sizes relative to continuous removals, and the differences are greatest at low population growth rates, high removal rates, and with large, infrequent pulses. Furthermore, the timing of the removal pulses (either stochastic or cyclic) affects population size. For example, cyclic removals are less likely than stochastic removals to result in population eradication, but when eradication occurs, the time until eradication is shorter for cyclic than with stochastic removals.

SUBMITTER: Hamman EA

PROVIDER: S-EPMC6008325 | biostudies-literature | 2018 Jun

REPOSITORIES: biostudies-literature

ACCESS DATA

Json Xml

Publications

Top-down pulses reduce prey population sizes and persistence.

Hamman Elizabeth A EA McCoy Michael W MW

Scientific reports 20180619 1

Resource pulses are well documented and have important consequences for population dynamics relative to continuous inputs. However, pulses of top-down factors (e.g. predation) are less explored and appreciated in the ecological literature. Here, we use a simple differential equation population model to show how pulsed removals of individuals from a population alter population size relative to continuous dynamics. Pulsed removals result in lower equilibrium population sizes relative to continuous ...[more]

PMID: 29921899

Similar Datasets

Energetic conditions promoting top-down control of prey by predators.

Project description:Humans remove large amounts of biomass from natural ecosystems, and large bodied high trophic level animals are especially sensitive and vulnerable to exploitation. The effects of removing top-predators on food webs are often difficult to predict because of limited information on species interaction strengths. Here we used a three species predator-prey model to explore relationships between energetic properties of trophodynamic linkages and interaction strengths to provide heuristic rules that indicate observable energetic conditions that are most likely to lead to stable and strong top-down control of prey by predator species. We found that strong top-down interaction strengths resulted from low levels of energy flow from prey to predators. Strong interactions are more stable when they are a consequence of low per capita predation and when predators are subsidized by recruitment. Diet composition also affects stability, but the relationship depends on the form of the functional response. Our results imply that for generalist satiating predators, strong top-down control on prey is most likely for prey items that occupy a small portion of the diet and when density dependent recruitment is moderately high.

| S-EPMC3246494 | biostudies-literature

Prey body mass and richness underlie the persistence of a top predator.

Project description:Predators and prey often differ in body mass. The ratio of predator to prey body mass influences the predator's functional response (how consumption varies with prey density), and therefore, the strength and stability of the predator-prey interaction. The persistence of food chains is maximized when prey species are neither too big nor too small relative to their predator. Nonetheless, we do not know if (i) food web persistence requires that all predator-prey body mass ratios are intermediate, nor (ii) if this constraint depends on prey diversity. We experimentally quantified the functional response for a single predator consuming prey species of different body masses. We used the resultant allometric functional response to parametrize a food web model. We found that predator persistence was maximized when the minimum prey size in the community was intermediate, but as prey diversity increased, the minimum body size could take a broader range of values. This last result occurs because of Jensen's inequality: the average handling time for multiple prey of different sizes is higher than the handling time of the average sized prey. Our results demonstrate that prey diversity mediates how differences between predators and prey in body mass determine food web stability.

| S-EPMC6532508 | biostudies-literature

Robotic Top-down Intersphincteric Resection

Project description:The present study is to develop the novel robotic surgical technique and enhance the surgery quality for the treatment of distal rectal cancer.

| 67720 | ecrin-mdr-crc

"Proteotyping": population proteomics of human leukocytes using top down mass spectrometry.

Project description:Characterizing combinations of coding polymorphisms (cSNPs), alternative splicing and post-translational modifications (PTMs) on a single protein by standard peptide-based proteomics is challenging owing to <100% sequence coverage and the uncoupling effect of proteolysis on such variations >10-20 residues apart. Because top down MS measures the whole protein, combinations of all the variations affecting primary sequence can be detected as they occur in combination. The protein form generated by all types of variation is here termed the "proteotype", akin to a haplotype at the DNA level. Analysis of proteins from human primary leukocytes harvested from leukoreduction filters using a dual on-line/off-line top down MS strategy produced >600 unique intact masses, 133 of which were identified from 67 unique genes. Utilizing a two-dimensional platform, termed multidimensional protein characterization by automated top down (MudCAT), 108 of the above protein forms were subsequently identified in the absence of MS/MS in 4 days. Additionally, MudCAT enables the quantitation of allele ratios for heterozygotes and PTM occupancies for phosphorylated species. The diversity of the human proteome is embodied in the fact that 32 of the identified proteins harbored cSNPs, PTMs, or were detected as proteolysis products. Among the information were three partially phosphorylated proteins and three proteins heterozygous at known cSNP loci, with evidence for non-1:1 expression ratios obtained for different alleles.

| S-EPMC2615201 | biostudies-literature

Perceptual learning to reduce sensory eye dominance beyond the focus of top-down visual attention.

Project description:Perceptual learning is an important means for the brain to maintain its agility in a dynamic environment. Top-down focal attention, which selects task-relevant stimuli against competing ones in the background, is known to control and select what is learned in adults. Still unknown, is whether the adult brain is able to learn highly visible information beyond the focus of top-down attention. If it is, we should be able to reveal a purely stimulus-driven perceptual learning occurring in functions that are largely determined by the early cortical level, where top-down attention modulation is weak. Such an automatic, stimulus-driven learning mechanism is commonly assumed to operate only in the juvenile brain. We performed perceptual training to reduce sensory eye dominance (SED), a function that taps on the eye-of-origin information represented in the early visual cortex. Two retinal locations were simultaneously stimulated with suprathreshold, dichoptic orthogonal gratings. At each location, monocular cueing triggered perception of the grating images of the weak eye and suppression of the strong eye. Observers attended only to one location and performed orientation discrimination of the gratings seen by the weak eye, while ignoring the highly visible gratings at the second, unattended, location. We found SED was not only reduced at the attended location, but also at the unattended location. Furthermore, other untrained visual functions mediated by higher cortical levels improved. An automatic, stimulus-driven learning mechanism causes synaptic alterations in the early cortical level, with a far-reaching impact on the later cortical levels.

| S-EPMC3175289 | biostudies-literature

Warming impact on herbivore population composition affects top-down control by predators.

Project description:Understanding warming impact on herbivores facilitates predicting plant/crop dynamics in natural/agricultural systems. However, it remains unclear how warming will affect herbivore population size and population composition, consequently altering herbivore colonization in a tri-trophic system (plant-herbivore-predator or crop-pest-biocontrol agent). We studied a soybean-aphid-lady beetle system, by conducting (1) a laboratory warming experiment to examine warming impact (+2 °C or +4 °C) on the aphid population size and composition (alate proportion), and (2) a field colonization experiment to examine whether the warming-induced effect subsequently interacts with predators (lady beetles) in affecting aphid colonization. The results showed that warming affected the initial aphid population composition (reduced alate proportion) but not population size; this warming-induced effect strengthened the top-down control by lady beetles and slowing aphid colonization. In other words, biocontrol on crop pests by predators could improve under 2-4 °C warming. Furthermore, aphid colonization was affected by an interaction between the alate proportion and predator (lady beetle) presence. This study suggests that warming affects herbivore population composition and likely mediates top-down control on herbivore colonization by predators. This mechanism may be crucial but underappreciated in climate change ecology because population composition (wing form, sex ratio, age/body size structure) shifts in many species under environmental change.

| S-EPMC5430442 | biostudies-literature

Auditory hallucinations, top-down processing and language perception: a general population study.

Project description:BackgroundStudies investigating the underlying mechanisms of hallucinations in patients with schizophrenia suggest that an imbalance in top-down expectations v. bottom-up processing underlies these errors in perception. This study evaluates this hypothesis by testing if individuals drawn from the general population who have had auditory hallucinations (AH) have more misperceptions in auditory language perception than those who have never hallucinated.MethodsWe used an online survey to determine the presence of hallucinations. Participants filled out the Questionnaire for Psychotic Experiences and participated in an auditory verbal recognition task to assess both correct perceptions (hits) and misperceptions (false alarms). A hearing test was performed to screen for hearing problems.ResultsA total of 5115 individuals from the general Dutch population participated in this study. Participants who reported AH in the week preceding the test had a higher false alarm rate in their auditory perception compared with those without such (recent) experiences. The more recent the AH were experienced, the more mistakes participants made. While the presence of verbal AH (AVH) was predictive for false alarm rate in auditory language perception, the presence of non-verbal or visual hallucinations were not.ConclusionsThe presence of AVH predicted false alarm rate in auditory language perception, whereas the presence of non-verbal auditory or visual hallucinations was not, suggesting that enhanced top-down processing does not transfer across modalities. More false alarms were observed in participants who reported more recent AVHs. This is in line with models of enhanced influence of top-down expectations in persons who hallucinate.

| S-EPMC6877468 | biostudies-literature

Top-down facilitation of visual recognition.

Project description:Cortical analysis related to visual object recognition is traditionally thought to propagate serially along a bottom-up hierarchy of ventral areas. Recent proposals gradually promote the role of top-down processing in recognition, but how such facilitation is triggered remains a puzzle. We tested a specific model, proposing that low spatial frequencies facilitate visual object recognition by initiating top-down processes projected from orbitofrontal to visual cortex. The present study combined magnetoencephalography, which has superior temporal resolution, functional magnetic resonance imaging, and a behavioral task that yields successful recognition with stimulus repetitions. Object recognition elicited differential activity that developed in the left orbitofrontal cortex 50 ms earlier than it did in recognition-related areas in the temporal cortex. This early orbitofrontal activity was directly modulated by the presence of low spatial frequencies in the image. Taken together, the dynamics we revealed provide strong support for the proposal of how top-down facilitation of object recognition is initiated, and our observations are used to derive predictions for future research.

| S-EPMC1326160 | biostudies-literature

Top-Down Proteomics of Medicinal Cannabis.

Project description:The revised legislation on medicinal cannabis has triggered a surge of research studies in this space. Yet, cannabis proteomics is lagging. In a previous study, we optimised the protein extraction of mature buds for bottom-up proteomics. In this follow-up study, we developed a top-down mass spectrometry (MS) proteomics strategy to identify intact denatured protein from cannabis apical buds. After testing different source-induced dissociation (SID), collision-induced dissociation (CID), higher-energy collisional dissociation (HCD), and electron transfer dissociation (ETD) parameters on infused known protein standards, we devised three LC-MS/MS methods for top-down sequencing of cannabis proteins. Different MS/MS modes produced distinct spectra, albeit greatly overlapping between SID, CID, and HCD. The number of fragments increased with the energy applied; however, this did not necessarily translate into greater sequence coverage. Some precursors were more amenable to fragmentation than others. Sequence coverage decreased as the mass of the protein increased. Combining all MS/MS data maximised amino acid (AA) sequence coverage, achieving 73% for myoglobin. In this experiment, most cannabis proteins were smaller than 30 kD. A total of 46 cannabis proteins were identified with 136 proteoforms bearing different post-translational modifications (PTMs), including the excision of N-terminal M, the N-terminal acetylation, methylation, and acetylation of K resides, and phosphorylation. Most identified proteins are involved in photosynthesis, translation, and ATP production. Only one protein belongs to the phytocannabinoid biosynthesis, olivetolic acid cyclase.

| S-EPMC6958505 | biostudies-literature

Fine-scale modelling finds that breeding site fragmentation can reduce mosquito population persistence.

Project description:Fine-scale geographic variation in the transmission intensity of mosquito-borne diseases is primarily caused by variation in the density of female adult mosquitoes. Therefore, an understanding of fine-scale mosquito population dynamics is critical to understanding spatial heterogeneity in disease transmission and persistence at those scales. However, mathematical models of dengue and malaria transmission, which consider the dynamics of mosquito larvae, generally do not account for the fragmented structure of larval breeding sites. Here, we develop a stochastic metapopulation model of mosquito population dynamics and explore the impact of accounting for breeding site fragmentation when modelling fine-scale mosquito population dynamics. We find that, when mosquito population densities are low, fragmentation can lead to a reduction in population size, with population persistence dependent on mosquito dispersal and features of the underlying landscape. We conclude that using non-spatial models to represent fine-scale mosquito population dynamics may substantially underestimate the stochastic volatility of those populations.

| S-EPMC6658551 | biostudies-literature

OmicsDI is part of the ELIXIR infrastructure

OmicsDI is an Elixir interoperability service. Learn more ›

Tweets

OmicsDI Databases

PRIDE
PeptideAtlas
MassIVE
JPOST Repository
Physiome Model Repository

EGA
EVA
ENA
LINCS
PAXDB
Cell Collective

MetaboLights
Metabolomics Workbench
MetabolomeExpress
GNPS
BioModels
FAIRDOMHub

ArrayExpress
dbGaP
ExpressionAtlas
GEO
NODE

Information

Databases
Help
API
Contact us
Code on GitHub
Terms of use
Submit Data