scholarly journals Trait evolution under multiple selection pressures: Prey responses to predictable and unpredictable variation

2019 ◽  
Author(s):  
Manvi Sharma ◽  
Kavita Isvaran
Keyword(s):  
Variable Selection ◽  
Predation Risk ◽  
Selection Pressure ◽  
Spatial And Temporal Variation ◽  
Rock Pools ◽  
Selection Pressures ◽  
Space And Time ◽  
Natural Settings ◽  
Oviposition Sites ◽  
Desiccation Risk

AbstractWhen a strong selection pressure, such as predation risk, varies widely in space and time, how should prey respond? When risk varies predictably, prey are hypothesized to respond in a risk-sensitive manner. It is less clear how prey should respond when risk varies unpredictably.Additionally, prey response may also depend on how predation risk interacts with other selection pressures. Our understanding of the complex action of multiple and variable selection pressures on prey traits is still comparatively poor. Here, we examine how predictable and unpredictable aspects of predation risk act together with another important selection pressure to influence prey behaviour in the rock pool breeding mosquito, Aedes vexans. Through the selection of sites for oviposition, female mosquitoes can influence the predation risk faced by their offspring. We tested how females select oviposition sites, when encountering pools that vary in larval predation risk and desiccation risk. We comprehensively quantified spatial and temporal variation in predation risk by measuring densities of predatory dragonfly nymphs in rock pools of different sizes, along the mosquito breeding season. We also measured hydroperiod length. We next conducted manipulative experiments in rock pools and measured female oviposition responses to variation in predation and desiccation risks. Predation risk varied widely in space and time. Desiccation risk only appeared important for the small pools. Ovipositing females appeared to respond to these multiple aspects of variation in selection pressures. Females seemed to respond to predictable variation by avoiding large pools that permanently harboured predators in natural settings. Female responses were more variable to medium-sized pools with naturally stochastic predator densities, highlighting the role of unpredictability in predation risk in shaping behaviour. Females did not clearly prefer small pools that were naturally devoid of predators but carried high desiccation risk, suggesting that they balance multiple risks – predation versus desiccation – when choosing oviposition sites. Our study suggests that wild populations may commonly experience multiple and variable selection pressures that can favour seemingly puzzling trait variation. We highlight the need to quantify variation in selection pressures and investigate how such variation, especially the unpredictable aspects, shapes prey traits.

scholarly journals Heterogeneous Selection in a Spatially Structured Environment Affects Fitness Tradeoffs of Plasmid Carriage in Pseudomonads

2008 ◽  
Vol 74 (10) ◽  
pp. 3189-3197 ◽  
Author(s):  
Frances R. Slater ◽  
Kenneth D. Bruce ◽  
Richard J. Ellis ◽  
Andrew K. Lilley ◽  
Sarah L. Turner
Keyword(s):  
Variable Selection ◽  
Community Dynamics ◽  
Experimental System ◽  
Epifluorescence Microscopy ◽  
Spatial And Temporal Variation ◽  
Natural Environments ◽  
Selection Pressures ◽  
Selection For ◽  
Fitness Tradeoffs ◽  
Plasmid Carriage

ABSTRACT Environmental conditions under which fitness tradeoffs of plasmid carriage are balanced to facilitate plasmid persistence remain elusive. Periodic selection for plasmid-encoded traits due to the spatial and temporal variation typical in most natural environments (such as soil particles, plant leaf and root surfaces, gut linings, and the skin) may play a role. However, quantification of selection pressures and their effects is difficult at a scale relevant to the bacterium in situ. The present work describes a novel experimental system for such fine-scale quantification, with conditions designed to mimic the mosaic of spatially variable selection pressures present in natural surface environments. The effects of uniform and spatially heterogeneous mercuric chloride (HgCl2) on the dynamics of a model community of plasmid-carrying, mercury-resistant (Hgr) and plasmid-free, mercury-sensitive (Hgs) pseudomonads were compared. Hg resulted in an increase in the surface area occupied by, and therefore an increase in the fitness of, Hgr bacteria relative to Hgs bacteria. Uniform and heterogeneous Hg distributions were demonstrated to result in different community structures by epifluorescence microscopy, with heterogeneous Hg producing spatially variable selection landscapes. The effects of heterogeneous Hg were only apparent at scales of a few hundred micrometers, emphasizing the importance of using appropriate analysis methods to detect effects of environmental heterogeneity on community dynamics. Heterogeneous Hg resulted in negative frequency-dependent selection for Hgr cells, suggesting that sporadic selection may facilitate the discontinuous distribution of plasmids through host populations in complex, structured environments.

A Python-based GIS Simulation of the Spatial and Temporal Variation in Evapotranspiration

2019 ◽  
Vol 35 (5) ◽  
pp. 759-765 ◽  
Author(s):  
Mohammed G. Mohammed ◽  
Kathleen M. Trauth
Keyword(s):  
Overland Flow ◽  
Potential Evapotranspiration ◽  
Spatial And Temporal Variation ◽  
Spatial And Temporal Variability ◽  
Water Losses ◽  
Python Script ◽  
Space And Time ◽  
Land Covers ◽  
A Site ◽  
Linn County

Abstract. An assessment of potential evapotranspiration (ET) and direct evaporation is important for informed land management from agriculture to wetlands restoration. These processes vary in space and time, depending on vegetation, soils, and climate throughout the year. Much data has been collected in order to quantify ET for individual plots of land, but means have not been available to provide an integrated view on a landscape scale. A methodology has been developed and an implementing Python script has been written to assess and display the spatial and temporal variability of ET and direct evaporation using a geographic information system (GIS). The methodology utilizes publicly available inputs for broad applicability, and the calculations can be performed for a site with multiple land covers and soil textures. In addition to a visual representation of ET and direct evaporation in space and time, the Python script produces a text file of water losses that could be used in water balance calculations also incorporating precipitation, overland flow and infiltration. The methodology has been demonstrated on a site within Pershing State Park in Linn County, Missouri, and produces results consistent with those expected from hand calculations. All data and code are available in GitHub (https://github.com/TrauthK/Wetlands). Keywords: Evapotranspiration, Evaporation, GIS simulation, Hydrologic modeling, Hydrologic cycle, Python, Raster data, Wetland restoration.

The evolution of bird coloration

1979 ◽  
Vol 287 (1018) ◽  
pp. 63-130 ◽  
Keyword(s):  
Sexual Selection ◽  
Predation Risk ◽  
Multiple Regression ◽  
Reproductive Biology ◽  
Female Choice ◽  
Sex Recognition ◽  
Selection Pressures ◽  
Advantages And Disadvantages ◽  
Selective Pressures ◽  
Bird Coloration

The aims in this paper are first to review theories of the evolution of bird coloration and, in some cases, partly revise and extend them, secondly to analyse the coloration of all the birds of a given geographical region using multiple regression, and thirdly on the basis of this analysis to evaluate the various theories. Theories . There have been many discussions of the selective forces acting on the coloration of birds and we review the major proposals in some detail. The earliest suggestion (Darwin 1871) was that the bright coloration of many male birds originated through sexual selection by female choice of the most exotic variants in male plumage. A conflicting view (Hingston 1933) is that brightness has an intimidatory effect on opponents, and that bright male coloration arose through sexual selection but largely due to its advantages against other males in disputes concerning mating access to females. Bird coloration has also been considered in terms of predation (see, for example, Cott 1964 a ). Some birds with bright plumage patterns are known to be unpalatable compared to cryptic species, and certain other patterns have been interpreted as adaptations to confuse predators. Bright colours may commonly be favoured when an individual is anyhow obvious (e.g. through activity) and where it represents an 'unprofitable’ prey for a predator. This interpretation may be particularly relevant to lekking among polygamous males. A special case of unprofitable prey may be ‘perception advertisement’, where an animal signals (by flash patterns or alarm calls) that it has seen a predator (or opponent). It is also possible that bright coloration may serve to deflect predators away from the nest site; this requires in many ways conditions opposite to those for the unprofitable prey solution. Finally, bird colorations can act as a variety of social signals other than threat. Analysis . The coloration of the 516 species of birds that breed and/ or winter in the Western Palaearctic was analysed by multiple regression. Seven regions of a bird’s body plus two areas of flash coloration were recognized and scored for colour on a cryptic/conspicuous scale. Five different age/sex/season categories were recognized and scored separately for each species. These dependent variables were each analysed with respect to 17 independent variables that reflect different aspects of the reproductive biology and ecology of the birds. The advantages and disadvantages of multiple regression as an analytical technique are discussed. Results . The analysis identifies associations between the reproductive biology and ecology of the birds and the coloration of the different regions of the body of the different age/sex/season classes. Apparent exceptions to these associations are also identified and discussed. A relatively large proportion of the associations made sense in terms of the theories presented and usually there was a strong implication that for any specific association one theory was more relevant than any of the others. The results indicate that by far the most potent selective pressures to have shaped bird coloration are those related to predation risk. A number of the theories make use of predation risk, each in a different way, and for most of them some support can be gained for their involvement in the evolution of bird coloration. Of all the theories, however, it is the unprofitable prey model that seems to account for the major part of the variation in bird coloration. By contrast, no clear evidence for the involvement of sexual selection in the evolution of bird coloration could be found. Indeed, many associations, such as that between sexual dimorphism and polygamy, were more readily explicable in terms of selection pressures due to predation risk than of sexual pressures. The suggestion that bird coloration is shaped by predation rather than by sexual selection in no way prevents the coloration, as it evolves, being incorporated within the species and sex recognition system. Conclusions . It is concluded that bird coloration has evolved almost entirely in response to predation-based selective pressures. Although plumage and coloration are involved in species and sex recognition systems, they have not evolved in response to sexual selection pressures. In species that are sexually dimorphic, the male is not brightly coloured as a result of female choice or male: male competition but because he represents a less profitable prey to a predator than the females and juveniles. We predict that brightly coloured birds will most often be found to suffer less from predation than will comparable more cryptic birds (though one of the predation-risk theories does allow the converse to be true).

scholarly journals Variation in predator species abundance can cause variable selection pressure on warning signaling prey

2012 ◽  
Vol 2 (8) ◽  
pp. 1971-1976 ◽  
Author(s):  
Janne K. Valkonen ◽  
Ossi Nokelainen ◽  
Martti Niskanen ◽  
Janne Kilpimaa ◽  
Mats Björklund ◽  
...  
Keyword(s):  
Variable Selection ◽  
Selection Pressure ◽  
Species Abundance ◽  
Predator Species

scholarly journals Spatial and Temporal Variation of Fish Assemblages in Seti Gandaki River, Tanahu, Nepal

2020 ◽  
Vol 10 (2) ◽  
pp. 93-104
Author(s):  
ARCHANA PRASAD ◽  
ANJANA SHRESTHA ◽  
JASH HANG LIMBU ◽  
DEEP SWAR
Keyword(s):  
Community Structure ◽  
Fish Community ◽  
Fish Assemblages ◽  
Mesh Size ◽  
Spatial And Temporal Variation ◽  
Total Hardness ◽  
Medium Size ◽  
Fish Community Structure ◽  
Space And Time ◽  
Significant Difference

The space and time variations of the fish community structure in hill streams of Nepal are poorly understood. This research aims at studying the space and time variation of fish community structure in the Seti Gandaki River, Tanahu, Nepal. The field survey was conducted from July 2017 to June 2018 and the fishes were sampled from six sites using a medium size cast net of mesh size ranging from 3 mm to 6 mm mesh size, 25-33 feet length and 3.5-5 feet width, with the help of local fisher man. A total of 1,440 individuals were caught representing 46 species belonging to three order, nine families and 23 genera. The analysis of similarity (ANOSIM) showed significant difference in space (R = 0.824, P = 0.001) but not in time (R = 0.135, P = 0.021). On the basis of similarity percentage (SIMPER) analysis, 85.43% similarity was found among the seasons and major contributing species were Barilius bendelisis (8.44%) followed by B. vagra (7.79%), Tor putitora (7.27%), Garra gotyla (7%), Acanthocobotis botia (6.7%), Neolissochilus hexagonolepis (6.64%), Barilius shacra (6%), B. barila (4.5%) and Opsarius barna (4.37%). On the other hand, 85.24% similarity was found among the sites and major contributing species were B. bendelisis (8.8%) followed by B. vagra (7.6%), G. gotyla (7.27%), T. putitora (7.17%), A. botia (6.97%), N. hexagonolepis (6.7%), B. shacra (6.34%), B. barila (4.7%) and O. barna (4.39%). Results from the Canonical Correspondence Analysis indicated that the environmental variables, such as pH, total hardness, alkalinity, dissolved oxygen and water temperature have shown to determine the fish community structure of Seti Gandaki River. Keywords: Fish diversity, freshwater, habitat, spatio-temporal, stream

scholarly journals Fatness and fitness: exposing the logic of evolutionary explanations for obesity

2016 ◽  
Vol 283 (1822) ◽  
pp. 20152443 ◽  
Author(s):  
Andrew D. Higginson ◽  
John M. McNamara ◽  
Alasdair I. Houston
Keyword(s):  
Predation Risk ◽  
Selection Pressure ◽  
Threshold Level ◽  
Optimal Level ◽  
Point Model ◽  
Intervention Point ◽  
Energy Stores ◽  
Control Body ◽  
Dangerous Activity ◽  
Evolutionary Explanations

To explore the logic of evolutionary explanations of obesity we modelled food consumption in an animal that minimizes mortality (starvation plus predation) by switching between activities that differ in energy gain and predation. We show that if switching does not incur extra predation risk, the animal should have a single threshold level of reserves above which it performs the safe activity and below which it performs the dangerous activity. The value of the threshold is determined by the environmental conditions, implying that animals should have variable ‘set points’. Selection pressure to prevent energy stores exceeding the optimal level is usually weak, suggesting that immediate rewards might easily overcome the controls against becoming overweight. The risk of starvation can have a strong influence on the strategy even when starvation is extremely uncommon, so the incidence of mortality during famine in human history may be unimportant for explanations for obesity. If there is an extra risk of switching between activities, the animal should have two distinct thresholds: one to initiate weight gain and one to initiate weight loss. Contrary to the dual intervention point model, these thresholds will be inter-dependent, such that altering the predation risk alters the location of both thresholds; a result that undermines the evolutionary basis of the drifty genes hypothesis. Our work implies that understanding the causes of obesity can benefit from a better understanding of how evolution shapes the mechanisms that control body weight.

CONFLICTING SELECTION PRESSURES ON THE GROWTH/PREDATION-RISK TRADE-OFF IN A DAMSELFLY

Ecology ◽  
2004 ◽  
Vol 85 (11) ◽  
pp. 2927-2932 ◽  
Author(s):  
Tomas Brodin ◽  
Frank Johansson
Keyword(s):  
Predation Risk ◽  
Selection Pressures ◽  
Trade Off

scholarly journals Software for the analysis and visualization of deep mutational scanning data

2015 ◽  
Author(s):  
Jesse D Bloom
Keyword(s):  
Amino Acid ◽  
Deep Sequencing ◽  
Software Package ◽  
Selection Pressure ◽  
Simulated Data ◽  
Sequence Logo ◽  
Selection Pressures ◽  
Before And After

BackgroundDeep mutational scanning is a technique to estimate the impacts of mutations on a gene by using deep sequencing to count mutations in a library of variants before and after imposing a functional selection. The impacts of mutations must be inferred from changes in their counts after selection.ResultsI describe a software package,dms_tools, to infer the impacts of mutations from deep mutational scanning data using a likelihood-based treatment of the mutation counts. I show thatdms_toolsyields more accurate inferences on simulated data than simply calculating ratios of counts pre- and post-selection. Usingdms_tools, one can infer the preference of each site for each amino acid given a single selection pressure, or assess the extent to which these preferences change under different selection pressures. The preferences and their changes can be intuitively visualized with sequence-logo-style plots created using an extension toweblogo.Conclusionsdms_toolsimplements a statistically principled approach for the analysis and subsequent visualization of deep mutational scanning data.

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