Genetically defining populations is of limited use for evaluating and managing human impacts on gene flow

Partitioning genetic variation into panmictic units is one of the most commonly used techniques in genetic studies of wild organisms. For conservation, the rationale is to identify units for management, most often referred to as populations. Describing these populations provides a measure of genetic differentiation, but they are only management units in relation to specific objectives. In situ conservation activities are mostly constrained to landscape (or ‘seascape’) units. With continuing habitat fragmentation, maintaining gene flow and genetic variation is an underlying objective for many conservation activities. Spatially explicit genetic approaches can describe how gene flow varies across a landscape, but the popular approach of identifying populations has limited and specific application. The statistical tests and sampling procedures used seldom allow for the spatial extent of genetic panmixia to be precisely defined. Gene flow, genetic variation and genetic detection of individual movements can be estimated without reference to populations. Furthermore, the term ‘population’ is used inconsistently in the literature and is often poorly defined. Formulating appropriate questions for management requires that the unit of study is clearly described, and often this could be organisms inhabiting defined areas of the landscape. Resources for conservation management are limited, so geneticists working on gene flow in wild organisms need to frame questions relevant to specific management needs and carefully consider the language and approaches employed.