Complementary uses of ecological and biochemical genetic data in identifying and conserving salmon populations

This paper addresses the need to define distinct population segments within species of salmonid fishes. The paper focuses on identifying the smallest detectable population with unique sets of characters (i.e. a ‘species’ under the phylogenetic species concept); such units require identification before any subsequent groupings under which individual populations may ultimately be managed. Stream distance measurements between populations fail to identify ancestral discontinuities and are therefore excluded as a basis for estimating relationships. The requirement for genetic information in distinguishing populations has been met through characters reflecting ancestral lineages (including adequate biochemical genetic surveys and congruent meristic information), and those reflecting local adaptations (such as timings of migration and spawning, and distinct temperature tolerances). These different types of genetic information form complementary data sets for distinguishing populations because they reflect different evolutionary processes and time scales. Within distinct ancestral groupings defined by biochemical genetic data may exist adaptively distinct populations that cannot be distinguished in the absence of life history and ecological information. Examples are summarized in which a logical process has been applied for distinguishing populations; this includes an initial survey that focuses on identifying ancestral groupings followed by a systematic search for adaptive distinctions within these groupings.