scholarly journals Pinned, locked, pushed, and pulled traveling waves in structured environments

2018 ◽  
Author(s):  
Ching-Hao Wang ◽  
Sakib Matin ◽  
Ashish B. George ◽  
Kirill S. Korolev
Keyword(s):  
Traveling Waves ◽  
Constant Velocity ◽  
Stochastic Dynamics ◽  
Microfluidic Devices ◽  
Positive Density ◽  
Alternative States ◽  
Positive Density Dependence ◽  
Temporal Periodicity ◽  
Foreign Species ◽  
Simple Picture

AbstractTraveling fronts describe the transition between two alternative states in a great number of physical and biological systems. Examples include the spread of beneficial mutations, chemical reactions, and the invasions by foreign species. In homogeneous environments, the alternative states are separated by a smooth front moving at a constant velocity. This simple picture can break down in structured environments such as tissues, patchy landscapes, and microfluidic devices. Habitat fragmentation can pin the front at a particular location or lock invasion velocities into specific values. Locked velocities are not sensitive to moderate changes in dispersal or growth and are determined by the spatial and temporal periodicity of the environment. The synchronization with the environment results in discontinuous fronts that propagate as periodic pulses. We characterize the transition from continuous to locked invasions and show that it is controlled by positive density-dependence in dispersal or growth. We also demonstrate that velocity locking is robust to demographic and environmental fluctuations and examine stochastic dynamics and evolution in locked invasions.

Positive density-dependent growth supports costs sharing hypothesis and population density sensing in a manipulative parasite

Parasitology ◽  
2017 ◽  
Vol 144 (11) ◽  
pp. 1511-1518 ◽  
Author(s):  
MIKHAIL GOPKO ◽  
VICTOR N. MIKHEEV ◽  
JOUNI TASKINEN
Keyword(s):  
Growth Rate ◽  
Rainbow Trout ◽  
Population Density ◽  
Cost Sharing ◽  
Positive Density ◽  
Diplostomum Pseudospathaceum ◽  
Instance Theory ◽  
Positive Density Dependence ◽  
Study Support ◽  
Dependent Growth

SUMMARYParasites manipulate their hosts’ phenotype to increase their own fitness. Like any evolutionary adaptation, parasitic manipulations should be costly. Though it is difficult to measure costs of the manipulation directly, they can be evaluated using an indirect approach. For instance, theory suggests that as the parasite infrapopulation grows, the investment of individual parasites in host manipulation decreases, because of cost sharing. Another assumption is that in environments where manipulation does not pay off for the parasite, it can decrease its investment in the manipulation to save resources. We experimentally infected rainbow trout Oncorhynchus mykiss with the immature larvae of the trematode Diplostomum pseudospathaceum, to test these assumptions. Immature D. pseudospathaceum metacercariae are known for their ability to manipulate the behaviour of their host enhancing its anti-predator defenses to avoid concomitant predation. We found that the growth rate of individual parasites in rainbow trout increased with the infrapopulation size (positive density-dependence) suggesting cost sharing. Moreover, parasites adjusted their growth to the intensity of infection within the eye lens where they were localized suggesting population density sensing. Results of this study support the hypothesis that macroparasites can adjust their growth rate and manipulation investment according to cost sharing level and infrapopulation size.

scholarly journals The winner takes it all: how semelparous insects can become periodical

2018 ◽  
Author(s):  
Odo Diekmann ◽  
Robert Planqué
Keyword(s):  
Density Dependence ◽  
Initial Conditions ◽  
Short Note ◽  
Leslie Matrix ◽  
Positive Density ◽  
Simple Explanation ◽  
Large Classes ◽  
Full Life Cycle ◽  
Positive Density Dependence ◽  
One Year

AbstractThe aim of this short note is to give a simple explanation for the remarkable periodicity of Magicicada species, which appear as adults only every 13 or 17 years, depending on the region. We show that a combination of two types of density dependence may drive, for large classes of initial conditions, all but one year class to extinction. Competition for food leads to negative density dependence in the form of a uniform (i.e., affecting all age classes in the same way) reduction of the survival probability. Satiation of predators leads to positive density dependence within the reproducing age class. The analysis focuses on the full life cycle map derived by iteration of a semelparous Leslie matrix.

scholarly journals Restoration of eastern oyster populations with positive density dependence

2018 ◽  
Vol 28 (4) ◽  
pp. 897-909 ◽  
Author(s):  
Jacob L. Moore ◽  
Brandon J. Puckett ◽  
Sebastian J. Schreiber
Keyword(s):  
Density Dependence ◽  
Eastern Oyster ◽  
Positive Density ◽  
Positive Density Dependence

Switching from negative to positive density-dependence among populations of a cobble beach plant

Oecologia ◽  
2008 ◽  
Vol 158 (3) ◽  
pp. 473-483 ◽  
Author(s):  
William M. Goldenheim ◽  
Andrew D. Irving ◽  
Mark D. Bertness
Keyword(s):  
Density Dependence ◽  
Positive Density ◽  
Positive Density Dependence ◽  
Cobble Beach

scholarly journals A conceptual model for migratory tundra caribou to explain and predict why shifts in spatial fidelity of breeding cows to their calving grounds are infrequent

Rangifer ◽  
2012 ◽  
pp. 259-267 ◽  
Author(s):  
Anne Gunn ◽  
Kim G. Poole ◽  
John S. Nishi
Keyword(s):  
Density Dependence ◽  
Conceptual Model ◽  
Rangifer Tarandus ◽  
Curvilinear Relationship ◽  
Positive Density ◽  
Adaptive Use ◽  
Individual Fitness ◽  
Positive Density Dependence

Calving grounds of migratory tundra caribou (Rangifer tarandus) have two prominent characteristics. Firstly, the cows are gregarious, and secondly, the annual calving grounds spatially overlap in consecutive years (spatial fidelity). The location of consecutive annual calving grounds can gradually shift (either rotationally or un-directional) or more rarely, abruptly (non-overlapping). We propose a mechanism to interpret and predict changes in spatial fidelity. We propose that fidelity is linked to gregariousness with its advantages for individual fitness (positive density-dependence). Our argument is based on a curvilinear relationship between the density of cows on the calving ground (which we use to index gregariousness) and spatial fidelity. Extremely high or low densities are two different mechanisms which can lead to reduced spatial fidelity to annual calving grounds and reflect the caribou’s adaptive use of its calving ranges.

scholarly journals Restoration of Eastern oyster populations with positive density dependence

2017 ◽  
Author(s):  
Jacob L Moore ◽  
Brandon Puckett ◽  
Sebastian J Schreiber
Keyword(s):  
Density Dependence ◽  
Single Point ◽  
Eastern Oyster ◽  
Stock Enhancement ◽  
Positive Density ◽  
Integral Projection Model ◽  
Projection Model ◽  
Positive Density Dependence ◽  
Restoration Strategies ◽  
Habitat Enhancement

ABSTRACTPositive density dependence can create a threshold of population states below which extinction of the population occurs. The existence of this threshold, which can often be a complex, multi-dimensional surface, rather than a single point, is of particular importance in degraded populations for which there is a desire for successful restoration. Here, we incorporated positive density dependence into a closed, size- and age-structured integral projection model parameterized with empirical data from an Eastern oyster, Crassostrea virginica, population in Pamlico Sound, North Carolina. To understand the properties of the threshold surface, and implications for restoration, we introduced a general method based on a linearization of the threshold surface at its unique, unstable equilibrium. We estimated the number of oysters of a particular age (i.e. stock enhancement), or the surface area of hard substrate required (i.e. habitat enhancement), to move a population from an extinction trajectory to a persistent trajectory. The location of the threshold surface was strongly affected by changes in the amount of local larval retention. Traditional stock enhancement with oysters less than a year old (i.e. spat) required three times as many oysters relative to stock enhancement with oysters between ages three and seven, while the success of habitat enhancement depended upon the initial size distribution of the population. The methodology described here demonstrates the importance of considering positive density dependence in oyster populations, and also provides insights into effective management and restoration strategies when dealing with a high dimensional threshold separating extinction and persistence.

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