Lecture 6: Age-structured populations and life histories
Life tables: data summarizing life events that are statistically expected for average
individual of a certain age. It includes age of death, time of reproduction and usually only
Lx= probability of being alive at age x.
L0= 1.0 by definition.
Survivorship curve = graph of L = pxobability of being alive at age x vs. age x.
Real shape of survivorship curves are more squiggly with more waves.
b x # of daughters born to female of age x during age interval.
Fecundity survivorship tradeoffs = cost of reproduction.
R 0 ΣL b x xverage expected number of daughters females will have in lifetime
= net reproductive rate. It’s similar to lambda, but in time units of an entire generation,
not one time interval. R =0λ = lambda to the power of the generation time.
T = generation time = avg. age female gives birth = ΣxL b / R x x 0
Generally, organisms with higher lambdas have higher fitness, but all plants aren’t
annuals/all lives aren’t short and fast. Reason is because reproduction is costly. Longer
reproductive time allow for higher accumulation of resources.
In glacier lilies, smaller corm growth with higher number of fruits formed.