I was asked if the fitness of a fitness landscape is absolute or relative.
Fitness landscapes are usually graphed with a fitness function that uses either phenotypes or genotypes in relation to fitness or one of its component.
More specifically, if the fitness measured is survival, and it's computed based on a quadratic model, does that means that every individual survival probability is an absolute measure of "fitness" (survival)?
Or since it's computed from a model, would it be better to find the relative contribution of a variable on the predictor in the model and say that the "fitness" is relative to a trait if it's computed with multiple traits?
How does the mean fitness of the population influence the model, which will determinate the fitness of all individuals? Is this "mean contribution of the population's fitness" a relative measure of fitness?
My specific questions are:
- What type (relative vs absolute) of fitness is shown in a fitness landscape?
- Does the type of fitness change if you change way to model it (For example, I want to know specifically for a quadratic model vs a spline)?
- Does the type of fitness change if you change way to model it (For example, I want to know specifically for a quadratic model vs a spline)?
- When using a mark recapture model (you use the survival of each individual to find a fitness function) is the survival estimated by the model relative or absolute? Does the mathematical formulation of the model changes something?
In the image below, I've graphed all the points (black line) and I've removed the 3 lowest values of y for the 3 largest x values (red line). If I was calculating the fitness of the individuals with or without the 3 smallest points for the 3 largest x values, then the fitness of all the other individuals would be affected (except at x~38 and y~38).
x = c(1:100,101,102,103)
y = c(x[1:100]+rnorm(100, sd = 6), 50,60,30)
x = c(1:100,101,102,103)
y = c(x+rnorm(103, sd = 6))
summary(lm(y~x))
plot(y~x)
abline(lm(y~x),col = "red")
points(38,38,col="blue")
Another example with crossbills:
Would you say it's relative or absolute fitness. Here the fitness measure is "performance" of eating certain types of seed.
In this article they are saying (Morrissey & Sakrejda 2013):
Regression analyses are central to characterization of the form and strength of natural selection in nature. Two common analyses that are currently used to characterize selection are (1) least squares–based approximation of the individual relative fitness surface for the purpose of obtaining quantitatively useful selection gradients, and (2) spline-based estimation of (absolute) fitness functions to obtain flexible inference of the shape of functions by which fitness and phenotype are related. These two sets of methodologies are often implemented in parallel to provide complementary inferences of the form of natural selection.
Are least squares-based approximation of the individual always computing relative fitness surfaces? For spline, is it always absolute values?