Patterns of Genic and Morphologic Variation among Sparrows in the Genera Zonotrichia, melospiza, junco, and Passerella

Analyses of genic variation and skeletal morphology were used to examine relationships among 10 species in the genera Zonotrichia, Junco, Melospiza, and Passerella.Cluster and principal components analyses showed that morphologic differentiation involves size and aspects of the skull, synsacrum, and hind limb.The genera have basically different skeletal morphologies; there is some overlap, however.The phenetic groupings of taxa, based on skeletal morphology, were congruent with neither traditional taxonomic limits nor the genetic analysis.The phenetic groupings seem biased by nondivergence and convergence.I conclude that the analysis of the genic data produces a better estimate of the phylogenetic history of the group than the analysis of morphology.The genic data show that the genera are distinct lineages, although the affinities of Z. capensis need clarification.The branching order of Zonotrichia, J. hyemalis, and Melospiza is unresolved, while P. iliaca is probably a sister taxon to these three genera.Melospiza melodia and P. iliaca are not dosely related, contrary to previous suggestions.The Lincoln's Sparrow and Swamp Sparrow are more similar to each other than either is to the Song Sparrow.Within Zonotrichia, the phylogenetic hypothesis suggests that the White-crowned Sparrow and Golden-crowned Sparrow are the most similar species, with the remaining taxa joining them in the following order: Harris' Sparrow, White-throated Sparrow, and Rufous-collared Sparrow.This phylogenetic scheme contradicts previous opinions, which, I suggest, were based on inconclusive evidence.The Harris' Sparrow, which is divergent relative to its congeners in both plumage and skeletal characters, is genically similar to its congeners.The Rufous-collared Sparrow is morphologically and genically differentiated from its north-temperate congeners, and, if it is a valid member of Zonotrichia, it must be an early derivative.Heterozygosity ( = 0.039), percentage polymorphic loci (, = 20.3), and mean number of alleles per polymorphic locus ( = 2.4) were similar to values reported for other birds and support the observation that birds possess levels of within-species genetic variation typical of other vertebrates.However, genetic distances averaged 0.06 between congeneric species and 0.26 for noncongeneric (but confamilial) interspecific comparisons and are lower than those observed at comparable taxonomic levels in other vertebrates.Rates of genic change seem homogeneous.Converting genetic distances into estimates of divergence dates suggests that the genera originated from 1.3 to 6.6 MYBP.Speciation within Zonotrichia and Melospiza probably occurred in the Pleistocene but before approximately 140,000 yr ago.!suggest that Passerella, Melospiza, Junco, and Zonotrichia be retained as distinct genera until comparable genetic data from other emberizines are available.