Age and Stage Structure N t+1 = Noert N(t+1) = N(t) These assume that all individuals have the same demographic rates

Sometimes, this assumption isn’t appropriate… We may have more information that we can use: stage/age specific demographic rates The stage/age classes may be so different from each other that using a general average is not accurate enough We may have a question that requires a stage/ age structured model

Which stage is the most important to protect to preserve the species? An example- Sea turtle conservation strategies Which stage is the most important to protect to preserve the species? Crouse et al. 1987, Crowder et al. 1994

Setting up the equation: N(t+1) = N(t) N(t+1) =  (N1(t) + N2(t) + … + Nx(t) N(t+1) =  (Nx(t)) We are still going to ignore immigration and emigration…

The components of N(t+1) The total number of individuals in the population is the sum of individuals in each age/stage. Individuals in t+1 come from two sources (assuming no immigration): Survival Birth

This should be n1, not n0

The components of N(t+1) Let’s assume N(t+1) = N1(t+1) + N2(t+1) an age-structured model Addition of new individuals: N1(t+1) = N1(t)*b1*S0 + N2(t)*b2*S0 New first stage individuals are born to both stages at stage-specific reproductive rates, then must survive to t+1 to be counted.

The components of N(t+1) Still assuming N(t+1) = N1(t+1) + N2(t+1) Survival of existing individuals: N2(t+1) = N1(t)*S1 Note: all N1(t+1) individuals came from birth processes

The components of N(t+1) Putting it all together…. N(t+1) = N1(t)*b1*S0 + N2(t)*b2*S0 Reproduction +N1(t)*S1 Survival

The remainder of this lecture… Form of a matrix The transition matrix Translating a life history graph into a transition matrix Get the notes from someone if you missed class!!!