Treatment of Subspecies Approaching Species Status

Abstract

Speciation phenomena are discussed with special consideration of those taxa that are near the species-level borderline. Such forms, when judged to represent full species, have been termed allospecies, and are designated by use of brackets. There is a need to designate and treat the complementary phenomenon, namely those well-marked forms approaching the level of species, but nonetheless judged to be conspecific. To fill this void, employment of parentheses is suggested to designate these latter forms, and megasubspecies is offered as a term for them. For example, one can treat the Savannah sparrow, Passerculus (sandwichensis) sandwichensis, citing its various minor subspecies in the usual way, and, as a megasubspecies, the "Ipswich sparrow", Passerculus (sandwichensis) princeps, a distinctive isolate that often is considered a separate species. Other examples are provided to illustrate the use of parentheses for megasubspecies as an adjunct to the use of brackets for designating allospecies of superspecies. It is hoped that the use of parentheses for megasubspecies will prove as useful in preparing checklists, in zoogeographical analyses and in other ways, as are brackets for designating allospecies.