Announcements Corrected mistakes on slides from last lectures VORTEX Help READ VORTEX survival guide! Leads you step by step through VORTEX. Get started this weekend so you can identify any problems before its too late!
General Predictors of Extinction - Population Growth +
Current population size Population Size Deterministic Variation in B&D: Density Calculation of r from life table assumes density-independent model
Density-Dependence in Vortex DI: growth w/ ceiling Population Size X 0
Time K, maximum size DD Growth Rate Where Are We Measuring r
0 Intrinsic r or r-max K Density Realized r
Growth Rate Are we measuring r at K? 0 r-max DI Model
Density K DD Model DD in Vortex Implication of DD vs. DI
Assuming DI may bias the probability of persistence, depending on where r-realized is measured Unfortunately, these essential data are rarely available! % Breeding Rhino PVA
45 40 33 Density Additional assignment for grad. students: Report to class next Wednesday.
DD in Vortex Only possible for % females breeding. Work around possible for DD in survivorship. If DD growth is expected for your population, specify that reproduction is DD, and follow instructions (see Tashi or myself for help).
The Allee Effect in Vortex Decide if an Allee effect is appropriate for your population. If so, specify that reproduction is DD, and follow instructions (see Tashi or myself for help). Critiques of PVA Models require too much data
Models typically result in wide confidence intervals. Models can not be validated Focus instead on parameter estimation. Models are error prone Model Output = Model Input
Parameter Estimates Vortex Model Predictions Creativity and VORTEX Vortex assumes one reproductive season/year. If your species has 2 clutches/yr., then:
A Defense of PVA Brook, B. W., J. J. O'Grady, A. P. Chapman, M. A. Burgman, H. R. Akakaya, and R. Frankham. 2000. Predictive accuracy of population viability analysis in conservation biology. Nature 404:385-387. Conceptual Utility of PVA It identifies the population, not land, as the critical unit for conservation purposes.
The term viability stresses long term population persistence and emphasizes selfsustainability. The idea of minimum emphasizes that there may be a threshold below which a population is doomed to extinction.
