Subspecies
A division of a species, referring to a population inhabiting a more or less definite geographical area and differing in some respect(s) from other populations of the species concerned. Subspecies are often called 'races'. The boundaries between subspecies, regarding both their geographical ranges and their physical characteristics, are usually blurred and the grading of one into another is called a 'cline'. The scientific name given to a subspecies involves the use of trinomial nomenclature, although 'subspecific names' are not normally used nowadays unless they are relevant to the matter in hand. Few subspecies are sufficiently distinctive in appearance to have been given English names (and the use of these is discouraged), but the White Wagtail is an example, being the Continental race Motacilla alba alba of the Pied Wagtail, of which the British race is M.a. yarrellii.From Peter Weaver's Birdwatcher's Dictionary
Copyright © 1981 by Peter Weaver