In Search of the Underlying Conceptualization of Species for North American Trout (Salmonidae: Onchorhynchus)

Species are independent lineages maintaining their identities through time, even in the face of gene flow.  Gene exchange is common in fishes yet species remain independent lineages.  The most appropriate species concept today is the Evolutionary Species Concept.  The concept of a subspecies is inconsistently used, highly complex, and variable. The rank subspecies largely follows multiple forms of logic that are flawed given what we know today.  Under the polytypic species concept of the 1960s subspecies were allopatric populations of one species and different – recognized as lineages, but not morphologically different enough to be viewed as reproductive isolated from others.  Under the dogma of phyletic gradualism and with the emergence of genetic methods, these latter studies were interpreted as closer to the “truth” of evolution.  Morphologists began a phase of studies examining geographic variation, leading to the recognition of distinct forms with zones of character intermediacy interpreted as areas of integradation between subspecies.  This was viewed as the direct study of evolution as the subspecies where gradually becoming reproductive isolated (more morphological divergent) and with time would be species.  All of these approaches have logical flaws in that they rely on degrees of difference and lack appropriate phylogenetic information.