Research on Threatened Populations

Abstract

The problems posed by threatened populations are stimulating innovative research in a variety of fields. We introduce four areas that have emerged over the past decade: descriptive genetics, captive breeding and reintroduction, population viability analysis, and decision analysis. The listing of endangered and threatened forms is based on existing named species and subspecies. Unfortunately, this taxonomic framework does not always reflect the true distribution of genetic variation and phylogenetic discontinuities within taxa of conservation concern. Descriptive genetic studies capitalizing on new genetic techniques are proving helpful in determining appropriate management units, but raise new issues regarding the definition of species and populations. Captive breeding and reintroduction is the most intensive and expensive form of management. The development of goals and methods for the cooperative genetic and demographic management of captive populations began in the early 1980’s and standard computer programs for a variety of pedigree analyses are now widely used. Research on artificially enhanced reproduction is an expanding field. Methods of ]reintroducing threatened populations, especially for captive-bred animals, are still poorly known. The concept of a single minimum viable population size, popular during the 1980’s, has evolved into population viability (or vulnerability) analysis (PVA). PVA produces a set of estimates for the probability that a specific population in a specific location will survive for a specified period of time. Ideally, a PVA should incorporate data on population dynamics, genetics, environmental variation, the risk of catastrophe, and metapopulation structure. However, the full suite of data desirable for a thorough PVA is rarely available. Long-term field studies of threatened populations to expand the data base, and efforts to develop methods that make the best use of existing data, are thus particularly valuable. Estimates of the population sizes required to ensure a high probability of long-term survival tend to increase as models become more realistic. Decision analysis is a formal process for making decisions in the face of uncertainty. It offers an explicit framework for evaluating the risks and probable benefits of alternative management strategies for a threatened population and focuses attention on value systems and the goals of conservation efforts. Attempts to adapt decision analysis to endangered species problems began in the 1980’s but there has been little exploration of the effects of alternative decision analysis procedures. Research on threatened populations is often neglected until a taxon is critically endangered. Time and species would be saved if adequate funding enabled research to be initiated at an earlier stage. Small, isolated areas of protected habitat will require intensive management, the success of which will depend upon the adequacy of the knowledge base derived from research. Thus, research, as well as habitat preservation, will be needed to preserve many threatened populations.