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Message: <blockquote data-quote="Richard Klim" data-source="post: 1737579" data-attributes="member: 773">Well, that's certainly true of the ABA Area, which is based on simplistic political/linguistic boundaries (as would possibly be the case with a 'European' listing area).  But the North American equivalent of the Western Palearctic is the Nearctic zone, which is much harder to define.The southern boundary of the WP runs through the Sahara, a large and obvious physical barrier with few species present - it makes little difference to the species included or excluded even if the accepted line is adjusted by a couple of degrees of latitude.But the division between the Neartic and Neotropical zones in Mexico runs through a complex and species-rich area with no obvious natural boundaries.  Voous (1977) defined the southern boundary of the Nearctic to include all the 'non-tropical' states of Mexico (Baja California, Baja California Sur, Sonora, Chihuahua, Durango, Zacatecas, Aguascalientes, Guanajuato, Querétaro, México, Distrito Federal, Coahuila and Nuevo León) and the Bahamas - this is obviously a much fuzzier and more arbitrary border compared with that of the WP.Richard</blockquote>