9424625 Hughes One of the central problems in conservation biology is determining the viability of small populations. Population viability is dependent on complex interactions of demographic and genetic factors. Over the short term demographic variation induced by the environment seems to be the most important of these factors. Over the long term the genetic consequences of small population size become increasingly important. Both genetic and demographic methods are used to assess population viability. Genetic assessments of population viability focus on effective population size. The effective size is the size of an idealized population in which the random processes of inbreeding and drift act at the same rate as they do in the study population. Many guidelines for conservation state the number of individuals that should be saved in terms of effective size. Yet, in almost every wild population, effective size is much smaller than actual population size. Demographic assessments result from population viability assessment (PVA) models of persistence. In PVA models, populations are projected into the future using means and variances of demographic parameters: annual reproductive success and survivorship for different age or stage classes. This conservation and restoration biology project will compare genetic and demographic approaches to viability assessment based on studies of a Neotropical parrot, the Green-rumped Parrotlet in Venezuela. In addition, this research will develop a demographic model of population persistence for this species of parrot. The use of PVA and other demographic models is a cornerstone in conservation biology, yet the methods have rarely been tested and verified on small populations of neotropical birds.
