title: When stable-stage equilibrium is unlikely: integrating transient population dynamics improves asymptotic methods.
abstract: OBJECTIVE
  Evaluation of population projection matrices (PPMs) that are focused on asymptotically based properties of populations is a commonly used approach to evaluate projected dynamics of managed populations. Recently, a set of tools for evaluating the properties of transient dynamics has been expanded to evaluate PPMs and to consider the dynamics of populations prior to attaining the stable-stage distribution, a state that may never be achieved in disturbed or otherwise ephemeral habitats or persistently small populations. This study re-evaluates data for a tropical orchid and examines the value of including such analyses in an integrative approach.
  
  
  METHODS
  Six small populations of Lepanthes rubripetala were used as a model system and the R software package popdemo was used to produce estimates of the indices for the asymptotic growth rate (lambda), sensitivities, reactivity, first-time step attenuation, maximum amplification, maximum attenuation, maximal inertia and maximal attenuation. The response in lambda to perturbations of demographic parameters using transfer functions and multiple perturbations on growth, stasis and fecundity were also determined. The results were compared with previously published asymptotic indices.
  
  
  RESULTS
  It was found that combining asymptotic and transient dynamics expands the understanding of possible population changes. Comparison of the predicted density from reactivity and first-time step attenuation with the observed change in population size in two orchid populations showed that the observed density was within the predicted range. However, transfer function analysis suggests that the traditional approach of measuring perturbation of growth rates and persistence (inertia) may be misleading and is likely to result in erroneous management decisions.
  
  
  CONCLUSIONS
  Based on the results, an integrative approach is recommended using traditional PPMs (asymptotic processes) with an evaluation of the diversity of dynamics that may arise when populations are not at a stable-stage distribution (transient processes). This method is preferable for designing rapid and efficient interventions after disturbances, and for developing strategies to establish new populations.
authors: Department of Biology, PO Box 860, University of Puerto Rico, Humacao, 00791, Puerto Rico, raymond@hpcf.upr.edu.
authors: Raymond L
authors: RL
authors: Tremblay
authors: Departamento de Ecología, Universidad de Alicante, Carretera S. Vicente del Raspeig s/n, 03080, San Vicente del Raspeig, Alicante, Spain.
authors: Josep
authors: J
authors: Raventos
authors: Department of Biology, PO Box 23360, University of Puerto Rico, Rio Piedras campus, San Juan, 00931-3360, Puerto Rico, Center for Applied Tropical Ecology and Conservation, PO Box 23360, University of Puerto Rico, Rio Piedras campus, San Juan, 00931-3360, Puerto Rico and.
authors: James D
authors: JD
authors: Ackerman
mesh_terms: D003247:Conservation of Natural Resources; D008954:Models, Biological; D029595:Orchidaceae / Q000502:physiology*; D011156:Population Density; D011157:Population Dynamics
keywords: Lepanthes rubripetala; Orchidaceae; PPM; Puerto Rico; Transient population dynamics; first-time step attenuation; lambda; maximum amplification; maximum attenuation; maximum inertia; orchids; population projection matrices; reactivity; stable-stage equilibrium; transfer function