Diagnosability of Subspecies: Lessons from Sage Sparrows (Amphispiza belli) for Analysis of Geographic Variation in Birds

More recently, the subspecies rank was reviewed in light of molecular data (Zink 2004), with the conclusion that named subspecies commonly mislead taxonomy, evolutionary studies, and conservation policy. Because morphology and molecules may show discordant patterns of geographic variation (e.g. Zink 1996, Fry and Zink 1998), and because subspecies are traditionally defined on the basis of morphological criteria, rigorous analysis of morphology is crucial for proper classification at the subspecies level. Patten and Unitt (2002) used museum specimens of subspecies of Sage Sparrow (Amphispiza belli) to illustrate their thesis and claimed that A. b. canescens Grinnell, 1905-a name long applied to breeding populations in the San Joaquin Valley and Mojave Desert of California and the Grapevine Mountains of Nevada -is not diagnosable from A. b. nevadensis by the 75% rule despite significant differences in size (mainly wing length), as demonstrated in their study and others (Grinnell 1905, Johnson and Marten 1992). However, because their results for A. b. canescens and A. b. nevadensis are at such variance with morphological differences reported by Johnson and Marten (1992) for specimens in the Museum of Vertebrate Zoology (MVZ, University of California, Berkeley), as well as with data for additional males and females from this collection, we suspected that their analyses and findings masked real patterns of geographic variation.