Appendix B. Equation for calculating λ', a composite index of population performance based on r', which estimates the realized per capita rate of population change (dN/N dt = r, the exponential growth rate) for each replicate cohort (Livdahl and Sugihara 1984).
(B.1) |
where N_{o} is the initial number of females in a cohort (assumed to be 50% of the initial cohort); A_{x} is the number of females eclosing on day x; w_{x} is a measure of mean female size on day x; f(w_{x}) is a function relating fecundity to female size (see text); and D is the estimated time (in days) required for a newly eclosed female to mate, obtain a bloodmeal, and oviposit. D is assumed to be 12 days for A. aegypti (Grill and Juliano 1996) and 14 days for A. albopictus (Juliano 1998). The estimated finite rate of increase, λ’ = exp(r’), is often preferable to r’ in demographic analyses because λ’ is estimable even if no individuals survive to reproductive age (l' = 0) whereas r' is not estimable in that case (r' = -∞) (Lenski and Service 1982).
LITERATURE CITED
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Livdahl, T. P., and G. Sugihara. 1984. Non-linear interactions of populations and the importance of estimating per capita rates of change. Journal of Animal Ecology 53:573–580.