Article Title

Subspecies Limits and Geographic Patterns of Morphological Variation in California Gnatcatchers {Polioptila californica)





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California Gnatcatchers {Polioptila californica) are distributed from the arid coastal plain of southern California south throughout most of the lowland regions of Baja California. Atwood (1988) suggested that populations in central Baja California were not subspecifically distinct from populations occurring north of 30°N latitude, and that the range of the northern, nominate subspecies therefore extended south to the Cape region of the peninsula. However, re-examination of data used in the earlier analysis indicates that the primary break in patterns of morphological variation in California Gnatcatchers occurs near 30°N, and that populations north of this latitude are subspecifically distinguishable from popu- lations occurring in central Baja California. Patterns of variation south of 30°N latitude are less clearly defined, with variably distinct steps in clinal variation exhibited by different characters near 28°N and/or 24°N latitude. Multivariate analyses indicate that in central and southern Baja California the principal break in morphological variation occurs near 24° N latitude. Following these results, the naming and distributions of subspecies of Polioptila californica should revert to that initially proposed by Grinnell (1926): P. c. californica (north of 30°N), P. c. margaritae (from 30°N south to 24°N), and P. c. abbreviata (south of 24°N).