scholarly journals High levels of functional divergence in toxicity towards prey among the venoms of individual pigmy rattlesnakes

2019 ◽  
Vol 15 (2) ◽  
pp. 20180876 ◽  
Author(s):  
Sarah A. Smiley-Walters ◽  
Terence M. Farrell ◽  
H. Lisle Gibbs
Keyword(s):  
Individual Differences ◽  
Functional Significance ◽  
Functional Divergence ◽  
Adaptive Significance ◽  
Population Variation ◽  
Population Differences ◽  
Relative Toxicity ◽  
Molecular Phenotype ◽  
Functional Variation ◽  
Sistrurus Miliarius

Venom is a complex molecular phenotype that shows high levels of variation in expressed proteins between individuals within and between populations. However, the functional significance of this variation in terms of toxicity towards prey is largely unknown. Here, we assessed the relative toxicity of venom from individual pygmy rattlesnakes ( Sistrurus miliarius ) on brown anoles ( Anolis sagrei ) using a novel assay involving tests of fixed doses of venom from individual snakes on individual lizards. We found high levels of functional variation between individual venoms within populations with individual differences (nested within population) explaining 3.6 times more variation in toxicity than population differences. Our results suggest a previously unappreciated adaptive significance to within-population variation in venom. They argue that selective mechanisms that maintain variation within populations may be of equal or greater importance to divergent selection leading to local adaption between populations as evolutionary explanations of venom variation within species.

scholarly journals Population variation of miRNAs and isomiRs and their impact on human immunity to infection

2020 ◽  
Author(s):  
Maxime Rotival ◽  
Katherine J Siddle ◽  
Martin Silvert ◽  
Julien Pothlichet ◽  
Hélène Quach ◽  
...  
Keyword(s):  
Mirna Expression ◽  
Influenza A ◽  
Population Level ◽  
Population Variation ◽  
European Ancestry ◽  
Population Differences ◽  
Rich Cluster ◽  
Protein Coding ◽  
Expression Variability ◽  
A Minor

ABSTRACTMicroRNAs (miRNAs) are key epigenetic regulators of the immune system, yet their variation and contribution to intra- and inter-population differences in immune responses is poorly characterized. Here, we generated 977 miRNA-sequencing profiles from primary monocytes, from individuals of African and European ancestry, following activation of three TLR pathways (TLR4, TLR1/2 and TLR7/8) or infection with Influenza A virus. We find that immune activation leads to important modifications in the miRNA and isomiR repertoire, particularly in response to viral challenges. These changes are, however, much weaker than those observed for protein-coding genes, suggesting stronger selective constraints on the miRNA response to stimulation. This is supported by the limited genetic control of miRNA expression variability (miR-QTLs) — and the lower occurrence of G×E interactions — in stark contrast with eQTLs that are largely context-dependent. We also detect marked differences in miRNA expression between populations, which are mostly driven by non-genetic factors. Yet, on average, miR-QTLs explain ~60% of population differences in expression of their cognate miRNAs, and, in some cases, evolve adaptively, as shown in Europeans for a miRNA-rich cluster on chromosome 14. Finally, integrating miRNA and mRNA data from the same individuals, we provide evidence that the canonical model of miRNA-driven transcript degradation has a minor impact on miRNA-mRNA correlations, which are, in our setting, mainly driven by co-transcription. Together, our results shed new light onto the factors driving miRNA and isomiR diversity at the population level, and constitute a useful resource for evaluating their role in host differences of immunity to infection.

Geographical variation in populations of Chenopodium album resistant and susceptible to atrazine. I. Between- and within-population variation in growth and response to atrazine

1982 ◽  
Vol 60 (4) ◽  
pp. 483-493 ◽  
Author(s):  
S. I. Warwick ◽  
P. B. Marriage
Keyword(s):  
Chenopodium Album ◽  
Geographical Location ◽  
Growth Characteristics ◽  
Population Variation ◽  
Population Differences ◽  
Differential Growth ◽  
Electrophoretic Patterns ◽  
Susceptible Populations ◽  
Growth Features ◽  
Lower Biomass

Between- and within-population variation in growth characteristics, isoenzyme patterns, and response to atrazine were studied in individuals from four atrazine-resistant (R) and four susceptible (S) populations of Chenopodium album L. collected from sites of contrasting climate in southern Ontario. In both the R and S types, population differences in growth characteristics were correlated with geographical location and climatic differences. The more northerly R and S populations had a greater rate of development, earlier maturation, lower biomass at maturity, and greater reproductive effort compared, respectively, with the more southerly R and S populations.Estimates of within-population variation were obtained statistically for a number of growth characters and from the electrophoretic patterns of five enzyme systems (PGM, PGI, GOT, MPI, and LAP). These indicated marked homogeneity in the four R populations as compared with the more variable S populations. Populations from the two disjunct areas of resistance were different for two of the enzymes studied and would appear to represent two different genotypes. This would suggest that mutation for resistance in populations of C. album has occurred independently in the two areas. Coupled with the evidence for differential growth characteristics of these two genotypes in response to climate, we would suggest that resistance has developed in individuals already established in each of the two separate areas, rather than spreading from a single recent introduction of the R type in Ontario.As expected, distinct differences between the R and S types were obtained in response to postemergence treatments with atrazine. The four R populations either showed no effect or exhibited increased growth. S populations all showed marked decreases in growth and production of biomass. Significant between-population differences in growth features were apparent for both types in the control and were maintained in the presence of atrazine. Although small differences in relative susceptibility were obtained for the susceptible populations, statistically significant population by treatment interactions were not evident.

Neurobiology of the structure of personality: Dopamine, facilitation of incentive motivation, and extraversion

1999 ◽  
Vol 22 (3) ◽  
pp. 491-517 ◽  
Author(s):  
Richard A. Depue ◽  
Paul F. Collins
Keyword(s):  
Individual Differences ◽  
Ventral Tegmental Area ◽  
Threshold Model ◽  
Incentive Motivation ◽  
Behavioral Approach ◽  
Leadership Roles ◽  
Functional Variation ◽  
Projection System ◽  
Ventral Tegmental ◽  
Positive Feelings

Extraversion has two central characteristics: (1) interpersonal engagement, which consists of affiliation (enjoying and valuing close interpersonal bonds, being warm and affectionate) and agency (being socially dominant, enjoying leadership roles, being assertive, being exhibitionistic, and having a sense of potency in accomplishing goals) and (2) impulsivity, which emerges from the interaction of extraversion and a second, independent trait (constraint). Agency is a more general motivational disposition that includes dominance, ambition, mastery, efficacy, and achievement. Positive affect (a combination of positive feelings and motivation) is closely associated with extraversion. Extraversion is accordingly based on positive incentive motivation.Parallels between extraversion (particularly its agency component) and a mammalian behavioral approach system based on positive incentive motivation implicate a neuroanatomical network and modulatory neurotransmitters in the processing of incentive motivation. A corticolimbic-striatal-thalamic network (1) integrates the salient incentive context in the medial orbital cortex, amygdala, and hippocampus; (2) encodes the intensity of incentive stimuli in a motive circuit composed of the nucleus accumbens, ventral pallidum, and ventral tegmental area dopamine projection system; and (3) creates an incentive motivational state that can be transmitted to the motor system.Individual differences in the functioning of this network arise from functional variation in the ventral tegmental area dopamine projections, which are directly involved in coding the intensity of incentive motivation. The animal evidence suggests that there are three neurodevelopmental sources of individual differences in dopamine: genetic, “experience-expectant,” and “experience-dependent.” Individual differences in dopamine promote variation in the heterosynaptic plasticity that enhances the connection between incentive context and incentive motivation and behavior.Our psychobiological threshold model explains the effects of individual differences in dopamine transmission on behavior, and their relation to personality traits is discussed.

Life Stage and Population Variation in Resistance and Tolerance of Hyalella azteca (Amphipoda) to Low pH

1987 ◽  
Vol 44 (6) ◽  
pp. 1102-1111 ◽  
Author(s):  
R. L. France ◽  
P. M. Stokes
Keyword(s):  
Genetic Basis ◽  
Life Stage ◽  
Population Decline ◽  
Acid Tolerance ◽  
Hyalella Azteca ◽  
Low Ph ◽  
Population Variation ◽  
Population Differences ◽  
Physiological Plasticity ◽  
Neutral Water

Lethality experiments revealed that resistance of Hyalella azteca (Amphipoda) to low pH was directly related to size and developmental stage. Exposure of adults to water below pH 5.0 during pulses of acid snowmelt, or of juveniles to below pH 5.5 through gradual lake acidification, could result in population decline. Hyalella azteca from moderately acidic Ontario lakes (pH 5.6–5.7) survived longer at lethal pH than did amphipods from circumneutral lakes (pH 6.4–7.2) where spring pH depressions do not occur. Resistance and tolerance to low pH was neither readily lost by tolerant amphipods exposed to neutral water for 10 d nor readily gained by nontolerant amphipods exposed to sublethal low pH for a similar duration. This absence of physiological plasticity of individual H. azteca suggests that population differences in acid tolerance may result from processes of selective mortality with or without a genetic basis.

scholarly journals Population fragmentation leads to morpho-functional variation in British red squirrels (Sciurus vulgaris)

2019 ◽  
Author(s):  
Philip G. Cox ◽  
Philip J.R. Morris ◽  
Andrew C. Kitchener
Keyword(s):  
Functional Divergence ◽  
Population Decline ◽  
Red Squirrel ◽  
Population Fragmentation ◽  
Sciurus Vulgaris ◽  
Functional Variation ◽  
Linear Measurements ◽  
Red Squirrels ◽  
Geometric Morphometric ◽  
The Uk

AbstractIt is well-known that population fragmentation and isolation can lead to rapid morphological and functional divergence, with the effect being particularly well-documented in rodents. Here, we investigated whether such a phenomenon could be identified in the Eurasian red squirrel (Sciurus vulgaris), which was once widespread across the majority of Great Britain, but suffered a severe population decline across the 20th century, leaving a highly fragmented distribution. The aim was to test for morphological and biomechanical variation of the mandible between the remaining British red squirrel populations. Linear and geometric morphometric methods were used to analyse shape in a sample of over 250 squirrel mandibles from across the UK and Germany. Canonical variates analysis identified significant shape differences between most British red squirrel populations, but particularly between squirrels from Formby and those from other populations. Linear measurements showed that Formby red squirrels have a significantly lower mechanical advantage of the temporalis muscle, indicating that they are less efficient at gnawing. We suggest that this difference may be related to past supplemental feeding of Formby squirrels with peanuts, which are less mechanically resistant than food items that occur naturally in the diet of British red squirrels.

scholarly journals Within and among-population variation in vital rates and population dynamics in a variable environment

2015 ◽  
Author(s):  
Simone Vincenzi ◽  
Marc Mangel ◽  
Dusan Jesensek ◽  
John Carlos Garza ◽  
Alain J Crivelli
Keyword(s):  
Population Dynamics ◽  
Population Density ◽  
Debris Flows ◽  
Life Histories ◽  
Population Variation ◽  
Population Differences ◽  
Vital Rates ◽  
Marble Trout ◽  
Over Time

Understanding the causes of within- and among-population differences in vital rates, life histories, and population dynamics is a central topic in ecology. To understand how within- and among-population variation emerges, we need long-term studies that include episodic events and contrasting environmental conditions, data to characterize individual and shared variation, and statistical models that can tease apart population-, shared-, and individual contribution to the observed variation. We used long-term tag-recapture data and novel statistical and modeling techniques to investigate and estimate within- and among-population differences in vital rates, life histories and population dynamics of marble trout Salmo marmoratus, a endemic freshwater salmonid with a narrow range. Only ten populations of pure marble trout persist in headwaters of Alpine rivers in western Slovenia. Marble trout populations are also threatened by floods and landslides, which have caused the extinction of two populations in recent years. We estimated and determined causes of variation in growth, survival, and recruitment both within and among populations, and evaluated trade-offs between them. Specifically, we estimated the responses of these traits to variation in water temperature, density, sex, early life conditions, and the occurrence of extreme climatic events (e.g., flash floods and debris flows). We found that the effects of population density on traits were mostly limited to the early stages of life and that individual growth trajectories were established early in life. We found no clear effects of water temperature on survival and recruitment. Population density varied over time, with flash floods and debris flows causing massive mortalities and threatening population persistence. Apart from flood events, variation in population density within streams was largely determined by variation in recruitment, with survival of older fish being relatively constant over time within populations, but substantially different among populations. Marble trout show a fast to slow continuum of life histories, with slow growth associated with higher survival at the population level, possibly determined by food conditions and age at maturity. Our work provides unprecedented insight into the causes of variation in vital rates, life histories, and population dynamics in an endemic species that is teetering on the edge of extinction.

A Multifactor Theory of Sensation: Individuality in Sensory Structure and Sensory Processing

1977 ◽  
Vol 44 (3_suppl) ◽  
pp. 1299-1316 ◽  
Author(s):  
Gregory P. Kearsley ◽  
Joseph R. Royce
Keyword(s):  
Individual Differences ◽  
Conceptual Framework ◽  
Power Law ◽  
Sensory Processing ◽  
Lower Order ◽  
Functional Significance ◽  
Experimental Studies ◽  
Sensory Structure ◽  
Specific Factors ◽  
The Relationship

A conceptual framework for individual differences in sensory structure and processing is outlined which provides a theoretical integration of multivariate, psychophysical, and experimental studies of sensation. A hierarchy of sensory dimensions is proposed which involves lower-order modality specific factors integrated by higher-order modality independent factors. The relationship between lower-order dimensions and individual power law exponents is discussed. A model of sensory processing is presented which specifies the functional significance of individual differences.

scholarly journals Anther cones increase pollen release in buzz-pollinated Solanum flowers

2021 ◽  
Author(s):  
Mario Vallejo-Marín ◽  
Carlos Eduardo Pereira Nunes ◽  
Avery Leigh Russell
Keyword(s):  
Functional Significance ◽  
Convergent Evolution ◽  
Adaptive Significance ◽  
Buzz Pollination ◽  
Mechanical Connection ◽  
Genetic Mechanisms ◽  
Conical Structure ◽  
Pollen Release ◽  
Plant Families

AbstractThe widespread evolution of tube-like anthers releasing pollen from apical pores is associated with buzz pollination, in which bees vibrate flowers to remove pollen. The mechanical connection among anthers in buzz-pollinated species varies from loosely held conformations, to anthers tightly held together with trichomes or bio-adhesives forming a functionally joined conical structure (anther cone). Joined anther cones in buzz-pollinated species have evolved independently across plant families and via different genetic mechanisms, yet their functional significance remains mostly untested. We used experimental manipulations to compare vibrational and functional (pollen release) consequences of joined anther cones in three buzz-pollinated species of Solanum (Solanaceae). We applied bee-like vibrations to focal anthers in flowers with (“joined”) and without (“free”) experimentally created joined anther cones, and characterised vibrations transmitted to other anthers and the amount of pollen released. We found that joined anther architectures cause non-focal anthers to vibrate at higher amplitudes than free architectures. Moreover, in the two species with naturally loosely held anthers, anther fusion increases pollen release, while in the species with a free but naturally compact architecture it does not. We discuss hypotheses for the adaptive significance of the convergent evolution of joined anther cones.

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