Recent postglacial range expansion drives the rapid diversification of a songbird lineage in the genusJunco

Abstract

Pleistocene glacial cycles are thought to have played a major role in the diversification of temperate and boreal species of North American birds. Given that coalescence times between sister taxa typically range from 0.1 to 2.0 Myr, it has been assumed that diversification occurred as populations were isolated in refugia over long periods of time, probably spanning one to several full glacial cycles. In contrast, the rapid postglacial range expansions and recolonization of northern latitudes following glacial maxima have received less attention as potential promoters of speciation. Here we report a case of extremely rapid diversification in the songbird genus Junco as a result of a single continent-wide range expansion within the last 10 000 years. Molecular data from 264 juncos sampled throughout their range reveal that as the yellow-eyed junco (Junco phaeonotus) of Mesoamerica expanded northward following the last glacial maximum, it speciated into the dark-eyed junco (Junco hyemalis), which subsequently diversified itself into at least five markedly distinct and geographically structured morphotypes in the USA and Canada. Patterns of low genetic structure and diversity in mitochondrial DNA and amplified fragment length polymorphism loci found in dark-eyed juncos relative to Mesoamerican yellow-eyed juncos provide support for the hypothesis of an expansion from the south, followed by rapid diversification in the north. These results underscore the role of postglacial expansions in promoting diversification and speciation through a mechanism that represents an alternative to traditional modes of Pleistocene speciation.

Phylogeographic Patterns of mtDNA Variation Revealed Multiple Glacial Refugia for the Frog Species Feirana taihangnica Endemic to the Qinling Mountains

“…4, 5). This pattern was also found for the QM lineage of F. quadranus (Wang et al 2012), as well as several other temperate species in North America and Europe (e.g., Milá et al 2006Milá et al , 2007Kvist et al 2004;Burg et al 2005;Fontanella et al 2008;Guiher and Burbrink 2008), but differed from that of other vertebrate species with wider distribution in East Asia that experienced population growth before the LGM Song et al 2009;Ding et al 2011). Nonetheless, like other species Song et al 2009;Ding et al 2011;Wang et al 2012), most lineages of F. taihangnica might have sustained stable effective population size during the mid-late Pleistocene (Fig.…”

A migratory lifestyle is associated with shorter telomeres in a songbird (Junco hyemalis)

“…If telomere loss can be solely attributed to the act of migration, then we would assume that our migrant and resident birds had similar telomere lengths at the beginning of life, which is likely as low haplotype and nucleotide diversity within the Dark-eyed Junco complex suggest these subspecies only very recently diverged (Milá et al 2007, Milá et al 2016. If this is the case, then the significant difference we saw in telomere lengths between migrants and residents is especially notable because migrants had completed only one migratory journey (from breeding to wintering grounds) before our sampling period in March.…”

“…Resident and migrant samples were evenly distributed across qPCR plates while also keeping experimenters blind to migrant/ resident status during analysis. Although interstitial telomeric repeats are included in qPCR measurements, they are unlikely to differ between these 2 subspecies of juncos that have only recently diverged and cannot be genetically differentiated using microsatellite techniques (Milá et al 2007, Milá et al 2016.…”

Phylogeography and subspecies status of Black Grouse

“…Phylogeographical structure has been documented in several avian species from Europe and North America (Merilä et al 1997;Milá et al 2007;Pitra et al 2000;Barrowclough et al 2004). Our analyses distinguished five lineages in Black Grouse with high posterior probability values for the divergence between northern and southern T. t. tetrix, T. t. mongolicus, T. t. ussuriensis and a western European clade.…”