Some Sources of Nomenclatorial and Systematic Problems in Unionid Mollusks,
OHIO STATE UNIV COLUMBUS
Pagination or Media Count:
Any review of current systematic problems in the unionid mollusks would be remiss, however, if it did not admit to difficulties shared with few other animal groups. The morphological variation existing within some of our species is so great as to be unbelievable by researchers in other fields. This polymorphism is frequently correlated with stream size, but a careful comparison of shell form and habitat reveals that this is not always the case. The morphological clines we observe may be as much, and perhaps as often, due to genetic differences as to environmental influences. Where the same or different cline occurs from headwaters to mouth in tributary after tributary of the same river system, we treat these forms as a single polymorphic species. Van der Schalie 1941 has proposed that If for any reason whatsoever one wishes to designate a form other than taxonomic it would be more sensible to do so as follows Lampsilis siliquoidea form rosacea. The term ecoform lends itself to those variants that are environmental rather than genetically produced.