BIOL 304 Lecture Notes - Lecture 23: Directional Selection
Document Summary
Selection can be stabilising (purifying, ends trim down), directional (shift) or disrupting (mean is least fit) Controlled environment can"t take into account influx & outflux, natural populations are far from ideal conditions. Study on mont saint-hilaire takes into account these - asses gen. variance for fitness in pop. , of impatiens in msh. Instead of measuring growth rate (easy in bacteria, not in plants) Proxies must be observed ex: count fruits & flowers. Main bulk of individuals don"t reproduce: remove non-reproducing individuals, phenotyping variation fitness goes down, observe only selfing-type flowers to calculate fitness. Selfing most dominant form of reproduction. Conclusions: little variation % attributed to genetic background. Experiment: relate trait (daily leaf production) to fitness (survival or fecundity) A lot of variation in trait-fitness relation seen even in tightly defined geographic location. Geographic conditions affect how traits & fitness interact. Shift from spring star & peak (peak = max food) Strong directional selection in red squirrels based on climate change.
