2025 Workshop | SCHEDULE | RESOURCES | PREVIOUS YEARS |
Here are some exercises we won’t cover directly, but you may want to play around with. We will add more as time goes on, if you ever wanted to help make an R package for teaching a QG course, we could publish it and you could be an author!
In this exercise, we will use garter snake data on crawling speed and vertebral numbers to estimate and plot a selection surface, or – more accurately – a performance surface. Crawling speed in the l meter dash was assessed for 174 newborn garter snakes (Thamnophis radix). We also have data on the body and tail vertebral counts for each snake. Since body and tail vertebrae are part of a functional complex used in snake locomotion, it’s natural to think that counts of these vertebral numbers might have a statistical effect on speed. But, what kind of effect? To find out, we will estimate selection gradients (directional and stabilizing) for these two traits using crawling speed as our fitness measure. The estimation procedures that we will use are described by Lande & Arnold (1983) and Phillips & Arnold (1989).
In addition to estimating a performance surface from the data, we will also explore the sensitivity of that surface to sampling.