Speciation in North American Chickadees: I. Patterns of mtDNA Genetic Divergence

Abstract

We surveyed mitochondrial DNA haplotype divergence within and between populations of six species of North American chickadees (Parus, Subgenus Poecile) with the following results. (1) Genotype diversities (range 0.3 to 0.7) and low nucleotide diversities (range 3 to 27 × 10 ) within populations were typical of known vertebrates. (2) The two widespread, northern species (atricapillus and hudsonicus) exhibit little mtDNA genetic differentiation throughout their previously glaciated continental distributions, most likely because of recent, postglacial range expansions. (3) Newfoundland populations of atricapillus and maritime province (Newfoundland plus Nova Scotia) populations of hudsonicus have distinct mtDNA haplotypes which differ from continental haplotypes by single restriction site changes. (4) Haplotypes of the southeastern U.S. species P. carolinensis divide into eastern and western sets which have diverged by three percent. This heretofore unrecognized, divided population structure may correspond to the Tombigbee River/ Mobile Bay disjunction known in some other vertebrate taxa. (5) Allopatric populations of the southwestern species sclateri and gambeli exhibit divergences of one and three percent respectively. (6) Prevailing interspecific divergence distances of three to seven percent suggest speciation early in the Pleistocene rather than during late (e.g., Wisconsin) glaciations. (7) Phylogenetic analyses suggest that North American taxa include two clades, hudsonicus-rufescens-sclateri versus carolinensis-atricapillus-gambeli and that carolinensis and atricapillus are not sister species.

When east meets west: population structure of a high-latitude resident species, the boreal chickadee (Poecile hudsonicus)

“…Although boreal tree species commonly show evidence of a phylogenetic break in the Great Lakes region similar to that found in the boreal chickadee (Jaramillo-Correa et al, 2009), it is less commonly seen in avian species. North American birds tend to show genetic breaks further west across the Rocky Mountains between British Columbia and Alberta (Burg et al, 2005;Toews and Irwin, 2008) or on the east coast (Gill et al, 1993;Holder et al, 1999). The mtDNA pattern seen in the boreal chickadee more closely resembles that of the black and white spruce, two species with which it is closely associated.…”

“…A number of smaller refugia are purported to have existed along the periphery of the ice sheets. The now submerged Atlantic Shelf refugium in eastern North America (Pielou, 1991) probably supported numerous tree (Walter and Epperson, 2001;Jaramillo-Correa et al, 2004) and bird (Gill et al, 1993;Zink et al, 2003) species.…”

“…Barriers such as water may restrict dispersal as boreal chickadees are absent from the large western islands (that is, Vancouver Island, Haida Gwaii and the Alexander Archipelago), and mountains may be restricting their western distribution as they are not found west of the Coast Range in British Columbia (Ficken et al, 1996). Gill et al (1993) examined populations of North American chickadees using mitochondrial DNA (mtDNA) restriction fragment-length polymorphisms; in the boreal chickadee, they looked at 37 birds from seven populations. Little genetic differentiation was seen in the continental populations (n ¼ 25), which roughly correspond to the previously glaciated region, and a unique haplotype was shared among all Atlantic Canada birds (n ¼ 12).…”

Cryptic genetic variation and paraphyly in ravens

“…Gene £ow between the two clades of common raven, but not between Chihuahuan raven and common raven would not be surprising; phylogenetic relationships do not necessarily predict which taxa hybridize (e.g. Gill et al 1993;Zink & McKitrick 1995;Burns 1998;Omland et al 1999).…”

“…Species within genera that are phenotypically uniform may be likely to hide cryptic genetic variation (e.g. chickadees; Gill et al 1993Gill et al , 1999. Having widespread distributions may also make it more likely that species will show molecular divergence (e.g.…”