Pipilo

Abstract: We sequenced 432 base pairs (bp) of the mitochondrial DNA (mtDNA) cyto- chrome-b gene in all recognized biological species in the genera Zonotrichia, Passerella, and Melospiza, as well as Junco hyemalis and Pipilo chlorurus. Our goals were: to estimate the phylogenetic pattern within and among genera; to compare our estimate with previous estimates based on allozymes and mtDNA restriction sites; to map morphometric distances onto the phylogenetic hypothesis; and to determine the extent of geographic variation in two polytypic species, the Fox Sparrow (Passerella iliaca) and Song Sparrow (Melospiza melodia). There was no geographic pattern to cytochrome-b variation within the Song Sparrow, whereas four mtDNA lineages of Fox Sparrows were found; these results corroborate those obtained from mtDNA restriction-site data. Analysis of cytochrome b yielded 14 equally-parsimonious trees. Although mtDNA and allozyme trees were statistically congruent, they differed some- what, and the data were combined to estimate phylogeny; two equally-parsimonious trees resulted. The consensus tree indicated the following relationships: within Melospiza, the pattern is {Song Sparrow {Swamp Sparrow (M. georgiana), Lincoln's Sparrow (M. lincolnii)} }; Junco and Zonotrichia are sister genera; within Zonotrichia, the pattern is (Rufous-collared Sparrow (Z. capensis) {White-throated Sparrow (Z. albicollis) (Harris' Sparrow (Z. querula) (White- crowned Sparrow (Z. leucophrys), Golden-crowned Sparrow (Z. atricapilla)} }} }; the data could not reliably resolve relationships among the other genera. In general, restriction sites and cytochrome-b sequence data yielded congruent phylogenies. Morphometric distances mapped onto the phylogenetic hypothesis revealed instances in which molecular and phenotypic evolution proceeded at different rates, except within Melospiza, where the two data sets yielded

Abstract: HYBRID ZONES OFFER opportunities to study genetic and social architectures of speciation and biological diversification (Harrison 1993, Gill 1998). But hybrid zones vary greatly. Some may be bounded zones of hybrid superiority (Moore and Price 1993). Some shift location in response to asymmetries of selection or dispersal. Some are old and narrow continuing sinks of hybrid inferiority. Still others are new contacts in the early test phases of genetic and social confrontation that may be resolved through natural selection. Mosaic hybrid zones are perhaps the most interesting and challenging of all speciation research opportunities. These are less "zones" than they are geographic arrays of local interactions between the same two species. The extent, pace, and pattern of introgressive hybridization can vary among localities that differ in details of the history of the contact, the ecology of the interface, the degree of isolation by distance or dispersal, and the roulette of genetic recombination. One of the best-studied cases of mosaic hybridization involves not birds but Plethodon salamanders of the Appalachian Mountains (Highton and Peabody 2000). Two species in particular, P. jordani and P. glutinosus, hybridize to varying extents at different locations, showing variable levels of reproductive isolation that reflect different histories and trajectories of their genetic contacts, and the inclusion of cryptic new species. The classic case of mosaic hybridization in birds is that of Spotted Towhees (Pipilo maculatus) and Collared Towhees (P. ocai) in Mexico (Sibley 1954, Greenlaw 1996). The amount of introgressive hybridization and directions of gene flow differ among localities, including sympatric coexistence in Oaxaca without evidence of interbreeding. Most contacts are attributable to human alterations of habitat-some

Abstract: -we sequenced 433 bp of the mitochondrial DNA (mtDNA) cytochrome b (cyt 6) gene from four species in the Brown Towhee complex (Pipilo spp.) and six species in the genus Spizellu. Phylogenies derived from sequence data were compared to those derived from mtDNA restriction fragment length polymorphism (RFLP) data collected from the same individuals (Zink and Dittmann 1991, 1993), allozyme and sequence data were also combined. In Spizella, the sequence and RFLP data placed the American Tree Sparrow (S. arborea) basal and the Black-chinned and Field sparrows (S. atrogularis and S. pusilla) as sister taxa, but conflicted on the placement of Brewer’ s, Chipping, and Clay-colored sparrows (S. breweri, S. passerim, and S. pallida). Phylogenetic analysis of the combined sequence and RFLP data set for Spizella supports the two previously published hypotheses for the genus based on RFLP’ s alone (Zink and Dittmann 1993). Monophyly of Spizella including the American Tree Sparrow is supported. The Pipilo sequence tree was congruent with Zink and Dittmann’ s (1991) RFLP Do110 parsimony tree, suggesting that the Whitethroated Towhee (P. albicollis) is the basal member of the complex and not the sister-taxon to the Canyon Towhee (P. fuscus) as suggested by the RFLP Wagner parsimony tree and allozyme and morphometric data (Zink 1988). The Pipilo sequence and RFLP data agree in placing Abert’ s Towhee (P. aberti) as the nearest relative of the California Towhee (P. crissalis). Phylogenetic analysis of the combined data for Pipilo supports the basal position of the White-throated Towhee, but we still consider the position of this taxon unresolved. Overall, sequence and RFLP data produced significantly congruent phylogenetic trees in both genera, suggesting each type of data provides useful phylogenetic information. Received 23 Nov. 1994, accepted 14 May 1995. Analyses of molecular data such as allozyme frequencies, restriction fragment length polymorphisms (RFLP’ s), and direct sequences of mitochondrial DNA (mtDNA) yield inferences about character evolution and phylogenetic relationships (Hillis et al. 1990, Avise 1994). These techniques, however, differ in their ability to resolve phylogenetic relationships along the taxonomic hierarchy (Avise 1986). Relatively few direct comparisons of phylogenetic patterns in different molecular data sets are available. In studies of birds, phylogenetic trees derived from allozymes and mtDNA RFLP data were generally congruent (Zink and Avise 1990, Zink and Dittmann 1991). MtDNA, however, provided more characters for systematic analysis (Avise and Zink 1988). Direct sequencing of mtDNA ’ Bell Museum of Natural History. 100 Ecology Building, Univ. of Minnesota, 1987 Upper Buford Circle, St. Paul, Minnesota 55108.