Widespread gene flow following range expansion in Anna's Hummingbird.

Anthropogenic changes have altered the historical distributions of many North American taxa. As environments shift, ecological and evolutionary processes can combine in complex ways to either stimulate or inhibit range expansion. Here, we examined the role of evolution in a rapid range expansion whose ecological context has been well-documented, Anna's Hummingbird (Calypte anna).

Interspecific forced copulations generate most hybrids in broadly sympatric ducks.

Although rare, hybrids are more common in broadly sympatric waterfowl than in any other avian family; yet, the behavioral ecology explaining their generation has remained controversial. Leading hypotheses are forced interspecific copulations, mis-imprinting caused by mixed broods, and scarcity of conspecific mates. Using a large sample of hybrid ducks solicited from North American hunters we evaluated these hypotheses by genetically determining the mother and father species of F1 hybrids.

Cryptic and extensive hybridization between ancient lineages of American crows.

Most species and therefore most hybrid zones have historically been defined using phenotypic characters. However, both speciation and hybridization can occur with negligible morphological differentiation. Recently developed genomic tools provide the means to better understand cryptic speciation and hybridization.

Dense Geographic and Genomic Sampling Reveals Paraphyly and a Cryptic Lineage in a Classic Sibling Species Complex.

Incomplete or geographically biased sampling poses significant problems for research in phylogeography, population genetics, phylogenetics, and species delimitation. Despite the power of using genome-wide genetic markers in systematics and related fields, approaches such as the multispecies coalescent remain unable to easily account for unsampled lineages. The Empidonax difficilis/Empidonax occidentalis complex of small tyrannid flycatchers (Aves: Tyrannidae) is a classic example of widely distributed species with limited phenotypic geographic variation that was broken into two largely cryptic (or "sibling") lineages following extensive study.

A Migratory Divide in the Painted Bunting (Passerina ciris).

In the painted bunting (Passerina ciris), a North American songbird, populations on the Atlantic coast and interior southern United States are known to be allopatric during the breeding season, but efforts to map connectivity with wintering ranges have been largely inconclusive. Using genomic and morphological data from museum specimens and banded birds, we found evidence of three genetically differentiated painted bunting populations with distinct wintering ranges and molt-migration phenologies. In addition to confirming that the Atlantic coast population remains allopatric throughout the annual cycle, we identified an unexpected migratory divide within the interior breeding range.

The biogeographic and evolutionary history of an endemic clade of Middle American sparrows: Melozone and Aimophila (Aves: Passerellidae).

The large number of endemic species in Middle America is frequently attributed to the interplay of geographical barriers and historical climatic changes in the region. This process promotes genetic divergence between populations, and given enough time, may yield new species. Animals that inhabit mid-elevation or highland habitats may be disproportionately affected in this way.