scholarly journals Intraspecific Variation Promotes Coexistence Under Competition For Essential Resources

2021 ◽  
Author(s):  
Erica Holdridge ◽  
David A. Vasseur
Keyword(s):  
Intraspecific Variation ◽  
Mapping Function ◽  
Growth Function ◽  
Ecological Function ◽  
Stable Strategy ◽  
Discontinuous Functions ◽  
Large Numbers ◽  
Uptake Rates ◽  
Positive Growth ◽  
Diverse Communities

Abstract Intraspecific variation may be key to coexistence in diverse communities, with some even suggesting it is necessary for large numbers of competitors to coexist. However, theory provides little support for this argument, instead finding that intraspecific variation generally makes it more difficult for species to coexist. Here we present a model of competition where two species compete for two essential resources and individuals within populations vary in their ability to take up different resources. We found a range of cases where intraspecific variation expands the range of conditions under which coexistence can occur, which provides a mechanism that allows the ecologically neutral evolutionary stable strategy (ESS) to become ecologically stable. We demonstrate that this result relies on nonlinearity in the function that describes how traits map onto ecological function. A sigmoid mapping function is necessary in order to model essential resources because it allows for variation in a unbounded trait while maintaining biologically realistic boundaries on uptake rates, and differs from other kinds of nonlinearity, which only unidirectionally increase or decrease ecological function. The sigmoid function’s nonlinearity spreads individuals unevenly along the growth function, which allows positive growth contributions from some individuals to compensate for growth loses from others, leading to coexistence. We discuss empirical systems beyond competition for essential resources in which discontinuous functions are important.

scholarly journals Intraspecific variation among isolates of the entomopathogenic nematode Steinernema feltiae from Bull Island, Ireland

Nematology ◽  
2009 ◽  
Vol 11 (3) ◽  
pp. 439-451 ◽  
Author(s):  
Martin Downes ◽  
Conor Meade ◽  
Stephen Boyle ◽  
Alec Rolston ◽  
Thomae Kakouli-Duarte
Keyword(s):  
Intraspecific Variation ◽  
Galleria Mellonella ◽  
Insect Pests ◽  
Entomopathogenic Nematode ◽  
Laboratory Culture ◽  
Steinernema Feltiae ◽  
Host Insect ◽  
Large Numbers ◽  
Insect Mortality ◽  
Control Insect

AbstractThe application of large numbers of entomopathogenic nematodes (EPN) to control insect pests of agriculture is likely to have an impact on the local EPN fauna, yet little is known about the intraspecific relationships between EPN populations, particularly with regard to phylogeny and outbreeding. Here we assess the fitness, with regards to fecundity, host insect mortality and time taken to produce progeny, of isolates of Steinernema feltiae from Bull Island, Ireland. Exon-primed, intron-crossing (EPIC) PCR was used to examine intraspecific phylogenies between S. feltiae isolates, and identified up to three possible colonisation events of Bull Island. EPIC-PCR grouped two isolates, 33.D.(2) and 59.F.(2), separately from the remaining ten S. feltiae isolates These same two isolates consistently performed poorly in all fitness assessments. Following the crossbreeding of all isolates in Galleria mellonella, the number of host cadavers exhibiting emerging infective juveniles was significantly fewer than expected and there were significant differences between isolates in the number of days until progeny were observed. Host insect mortality varied between 40 and 87%. Such intraspecific variation may be a result of adaptation to different microhabitats of Bull Island, which in turn may be accentuated by laboratory culture practices.

scholarly journals Initial Model for the Impact of Social Distancing on CoVID-19 Spread

2020 ◽  
Author(s):  
Genghmun Eng
Keyword(s):  
Exponential Growth ◽  
Growth Function ◽  
Worst Case ◽  
Social Distancing ◽  
Sick People ◽  
Large Numbers ◽  
The World ◽  
The Usa ◽  
The Impact ◽  
Good Agreement

AbstractThe initial stages of the CoVID-19 coronavirus pandemic all around the world exhibit a nearly exponential rise in the number of infections with time. Planners, governments, and agencies are scrambling to figure out “How much? How bad?” and how to effectively treat the potentially large numbers of simultaneously sick people. Modeling the CoVID-19 pandemic using an exponential rise implicitly assumes a nearly unlimited population of uninfected persons (“dilute pandemic”). Once a significant fraction of the population is infected (“saturated pandemic”), an exponential growth no longer applies. A new model is developed here, which modifies the standard exponential growth function to account for factors such as Social Distancing. A Social Mitigation Parameter [SMP] αS is introduced to account for these types of society-wide changes, which can modify the standard exponential growth function, as follows: The doubling-time tdbl = (In 2)/Ko can also be used to substitute for Ko, giving a {tdbl, αS} parameter pair for comparing to actual CoVID-19 data. This model shows how the number of CoVID-19 infections can self-limit before reaching a saturated pandemic level. It also provides estimates for: (a) the timing of the pandemic peak, (b) the maximum number of new daily cases that would be expected, and (c) the expected total number of CoVID-19 cases. This model shows fairly good agreement with the presently available CoVID-19 pandemic data for several individual States, and the for the USA as a whole (6 Figures), as well as for various countries around the World (9 Figures). An augmented model with two Mitigation Parameters, αS and βS, is also developed, which can give better agreement with the daily new CoVID-19 data. Data-to-model comparisons also indicate that using αS by itself likely provides a worst-case estimate, while using both αS and βS likely provides a best-case estimate for the CoVID-19 spread.

Initial Model for Impact of Social Distancing on CoVID-19 Spread (Preprint)

2020 ◽  
Author(s):  
Genghmun Eng
Keyword(s):  
Exponential Growth ◽  
Growth Function ◽  
Worst Case ◽  
Social Distancing ◽  
Sick People ◽  
S Parameter ◽  
Large Numbers ◽  
The World ◽  
The Usa ◽  
Good Agreement

UNSTRUCTURED The initial stages of the CoVID-19 coronavirus pandemic all around the world exhibit a nearly exponential rise in the number of infections with time. Planners, governments, and agencies are scrambling to figure out "How much? How bad?" and how to effectively treat the potentially large numbers of simultaneously sick people. Modeling the CoVID-19 pandemic using an exponential rise implicitly assumes a nearly unlimited population of uninfected persons ("dilute pandemic"). Once a significant fraction of the population is infected ("saturated pandemic"), an exponential growth no longer applies. A new model is developed here, which modifies the standard exponential growth function to account for factors such as Social Distancing. A Social Mitigation Parameter [SMP] α/s\ is introduced to account for these types of society-wide changes, which can modify the standard exponential growth function, as follows: N(t)= No exp[ +Ko t/(1 + α/s\ t)] . The doubling-time t/dbl\=(ln2)/Ko can also be used to substitute for Ko, giving a {t/dbl\, α/s\} parameter pair for comparing to actual CoVID-19 data. This model shows how the number of CoVID-19 infections can self-limit before reaching a saturated pandemic level. It also provides estimates for: (a) the timing of the pandemic peak, (b) the maximum number of new daily cases that would be expected, and (c) the expected total number of CoVID-19 cases. This model shows fairly good agreement with the presently available CoVID-19 pandemic data for several individual States, and the for the USA as a whole (6 Figures), as well as for various countries around the World (9 Figures). An augmented model with two Mitigation Parameters, α/s\ and β/s\, is also developed, which can give better agreement with the daily new CoVID-19 data. Data-to-model comparisons also indicate that using α/s\ by itself likely provides a worst-case estimate, while using both α/s\ and β/s\ likely provides a best-case estimate for the CoVID-19 spread.

Ontogenetic and sexual differences in diet in an actively foraging snake, Thamnophis proximus

2009 ◽  
Vol 87 (3) ◽  
pp. 254-261 ◽  
Author(s):  
N. B. Ford ◽  
P. M. Hampton
Keyword(s):  
Rapid Growth ◽  
Sexual Differences ◽  
Seasonal Activity ◽  
Adult Males ◽  
Mass Ratio ◽  
Stable Strategy ◽  
Small Prey ◽  
Large Numbers ◽  
Prey Diversity ◽  
Individual Prey

Actively foraging species of snakes often consume large numbers of small prey, which creates a high meal to snake mass ratio. Because they may also rely on speed to avoid predation, this might negatively influence survival. We examined the diet of 313 western ribbon snakes ( Thamnophis proximus Say in James, 1823), a very attenuated species, in a floodplain in northeastern Texas. Of the 142 individuals with food, adult males ate 9 prey types, followed by females with 8, and juveniles only 6. The ontogenetic increase in prey diversity was predicted. However, female ribbon snakes are larger than males and their fewer prey types may reflect a strategy where smaller prey are dropped from the diet. Seasonal activity of prey and snake class was generally correlated. Overall individual prey sizes were comparably small. However, over 50% of the snakes contained multiple prey and total meal masses were similar to the maximum prey sizes of ambush foragers. Adults stopped feeding at proportionally lower meal mass to predator mass ratios than juveniles. The benefits of rapid growth for juveniles may outweigh predation risks associated with high prey consumption, but for adults of this species, consuming lighter meals may be the most stable strategy.

DUNG TYPE OR INTRASPECIFIC VARIATION IN BIOMASS: WHAT IS MORE IMPORTANT IN DETERMINING DUNG BEETLE ECOLOGICAL FUNCTION?

2019 ◽  
Vol 23 (03) ◽  
pp. 536-547 ◽  
Author(s):  
Paula Bernardes Braga ◽  
Raquel Luiza de Carvalho ◽  
Júlio Neil Cassa Louzada ◽  
Lívia Dorneles Audino
Keyword(s):  
Intraspecific Variation ◽  
Dung Beetle ◽  
Ecological Function

scholarly journals Droplet printing reveals the importance of micron-scale structure for bacterial ecology

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Ravinash Krishna Kumar ◽  
Thomas A. Meiller-Legrand ◽  
Alessandro Alcinesio ◽  
Diego Gonzalez ◽  
Despoina A. I. Mavridou ◽  
...  
Keyword(s):  
Spatial Structure ◽  
Bacterial Communities ◽  
Spatial Arrangement ◽  
Potential Barriers ◽  
Large Numbers ◽  
Diverse Communities ◽  
Protein Toxins ◽  
The Difference ◽  
Printing Method ◽  
Bacterial Genotypes

AbstractBacteria often live in diverse communities where the spatial arrangement of strains and species is considered critical for their ecology. However, a test of this hypothesis requires manipulation at the fine scales at which spatial structure naturally occurs. Here we develop a droplet-based printing method to arrange bacterial genotypes across a sub-millimetre array. We print strains of the gut bacterium Escherichia coli that naturally compete with one another using protein toxins. Our experiments reveal that toxin-producing strains largely eliminate susceptible non-producers when genotypes are well-mixed. However, printing strains side-by-side creates an ecological refuge where susceptible strains can persist in large numbers. Moving to competitions between toxin producers reveals that spatial structure can make the difference between one strain winning and mutual destruction. Finally, we print different potential barriers between competing strains to understand how ecological refuges form, which shows that cells closest to a toxin producer mop up the toxin and protect their clonemates. Our work provides a method to generate customised bacterial communities with defined spatial distributions, and reveals that micron-scale changes in these distributions can drive major shifts in ecology.

scholarly journals RGFGA: An Efficient Representation and Crossover for Grouping Genetic Algorithms

2005 ◽  
Vol 13 (4) ◽  
pp. 477-499 ◽  
Author(s):  
Allan Tucker ◽  
Jason Crampton ◽  
Stephen Swift
Keyword(s):  
Genetic Algorithms ◽  
Clustering Algorithm ◽  
State Of The Art ◽  
Fitness Function ◽  
Growth Function ◽  
Crossover Operator ◽  
Large Numbers ◽  
Efficient Representation ◽  
Measure Of Similarity ◽  
Synthetic Datasets

There is substantial research into genetic algorithms that are used to group large numbers of objects into mutually exclusive subsets based upon some fitness function. However, nearly all methods involve degeneracy to some degree. We introduce a new representation for grouping genetic algorithms, the restricted growth function genetic algorithm, that effectively removes all degeneracy, resulting in a more efficient search. A new crossover operator is also described that exploits a measure of similarity between chromosomes in a population. Using several synthetic datasets, we compare the performance of our representation and crossover with another well known state-of-the-art GA method, a strawman optimisation method and a well-established statistical clustering algorithm, with encouraging results.

Cytoplasmic Granules in Lymphocytes from Rats Dosed with SK&F 14336-D

1971 ◽  
Vol 29 ◽  
pp. 556-557
Author(s):  
T. G. Merrill ◽  
B. J. Payne ◽  
A. J. Tousimis
Keyword(s):  
Lipid Storage ◽  
Pokeweed Mitogen ◽  
Electron Microscopic ◽  
Cytoplasmic Granules ◽  
Storage Diseases ◽  
Tay Sachs Disease ◽  
Large Numbers ◽  
Microscopic Studies ◽  
Neurovisceral Lipidosis

Rats given SK&F 14336-D (9-[3-Dimethylamino propyl]-2-chloroacridane), a tranquilizing drug, developed an increased number of vacuolated lymphocytes as observed by light microscopy. Vacuoles in peripheral blood of rats and humans apparently are rare and are not usually reported in differential counts. Transforming agents such as phytohemagglutinin and pokeweed mitogen induce similar vacuoles in in vitro cultures of lymphocytes. These vacuoles have also been reported in some of the lipid-storage diseases of humans such as amaurotic familial idiocy, familial neurovisceral lipidosis, lipomucopolysaccharidosis and sphingomyelinosis. Electron microscopic studies of Tay-Sachs' disease and of chloroquine treated swine have demonstrated large numbers of “membranous cytoplasmic granules” in the cytoplasm of neurons, in addition to lymphocytes. The present study was undertaken with the purpose of characterizing the membranous inclusions and developing an experimental animal model which may be used for the study of lipid storage diseases.

Prolonged Fixation Studies For Spaceflight

1973 ◽  
Vol 31 ◽  
pp. 332-333
Author(s):  
Robert Corbett ◽  
Delbert E. Philpott ◽  
Sam Black
Keyword(s):  
High Pressure ◽  
Living Systems ◽  
Prolonged Storage ◽  
Time Intervals ◽  
Early Signs ◽  
Large Numbers

Observation of subtle or early signs of change in spaceflight induced alterations on living systems require precise methods of sampling. In-flight analysis would be preferable but constraints of time, equipment, personnel and cost dictate the necessity for prolonged storage before retrieval. Because of this, various tissues have been stored in fixatives and combinations of fixatives and observed at various time intervals. High pressure and the effect of buffer alone have also been tried.Of the various tissues embedded, muscle, cartilage and liver, liver has been the most extensively studied because it contains large numbers of organelles common to all tissues (Fig. 1).

Analysis of the Anterior Secretory Cells of Onchidohs Muricata (Nudibranchia)

1981 ◽  
Vol 39 ◽  
pp. 614-615
Author(s):  
Roy Skidmore
Keyword(s):  
Endoplasmic Reticulum ◽  
Secretory Granules ◽  
Golgi Body ◽  
The Body ◽  
Secretory Cells ◽  
Secretory Vesicles ◽  
High Magnification ◽  
Large Numbers ◽  
Membrane Bound ◽  
Sole Of The Foot

The long-necked secretory cells in Onchidoris muricata are distributed in the anterior sole of the foot. These cells are interspersed among ciliated columnar and conical cells as well as short-necked secretory gland cells. The long-necked cells contribute a significant amount of mucoid materials to the slime on which the nudibranch travels. The body of these cells is found in the subepidermal tissues. A long process extends across the basal lamina and in between cells of the epidermis to the surface of the foot. The secretory granules travel along the process and their contents are expelled by exocytosis at the foot surface.The contents of the cell body include the nucleus, some endoplasmic reticulum, and an extensive Golgi body with large numbers of secretory vesicles (Fig. 1). The secretory vesicles are membrane bound and contain a fibrillar matrix. At high magnification the similarity of the contents in the Golgi saccules and the secretory vesicles becomes apparent (Fig. 2).

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