cryptic contact zone between divergent mitochondrial DNA lineages in southwestern North America supports past introgressive hybridization in the yellow-rumped warbler complex (Aves: Dendroica coronata)

• Published in: Biological journal of the Linnean Society Vol. 103; no. 3; pp. 696 - 706
• Main Authors: MILÁ, BORJA, TOEWS, DAVID P.L, SMITH, THOMAS B, WAYNE, ROBERT K
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01.07.2011; Wiley-Blackwell
• Subjects: Aves; Biological and medical sciences; Biological evolution; color; Data processing; ecomorphology; Fundamental and applied biological sciences. Psychology; gene flow; genetic diversity; Genetics of eukaryotes. Biological and molecular evolution; haplotype cline; haplotypes; introgression; mitochondrial DNA; monophyly; Myrtus communis; phylogeography; plumage; Vertebrates: general zoology, morphology, phylogeny, systematics, cytogenetics, geographical distribution; Mexico; Arizona; Utah; North America; America; Vertebrata; Biological evolution; Phylogeography; Ecomorphology; Mitochondrial DNA; Genetic diversity; Hybridization; Aves; Haplotype; Contact; Cryptic; haplotype cline
• ISSN: 0024-4066; 1095-8312
• DOI: 10.1111/j.1095-8312.2011.01661.x

Using genetic data to study the process of population divergence is central to understanding speciation, yet distinguishing between recent divergence and introgressive hybridization is challenging. In a previous study on the phylogeography of the yellow-rumped warbler complex using mitochondrial (mt)DNA data, we reported limited sequence divergence and a lack of reciprocal monophyly between myrtle and Audubon's warblers (Dendroica coronata and Dendroica auduboni, respectively), suggesting very recent isolation. In the present study, we report the results obtained from a subsequent sampling of Audubon's warbler in Arizona and Utah (‘memorabilis' race), which shows that, although this taxon is similar to auduboni in plumage colour, most memorabilis individuals sampled (93%) carry haplotypes that belong to the divergent black-fronted warbler lineage (Dendroica nigrifrons) of Mexico. Furthermore, the auduboni and nigrifrons lineages mix in southern Utah at a narrow, yet apparently ‘cryptic' contact zone. Newly-available evidence from nuclear markers indicating marked differentiation between auduboni and coronata has focused attention on the possibility of mtDNA introgression in the absence of nuclear gene flow, and the results of the present study are consistent with the hypothesis that the mtDNA of auduboni was indeed historically introgressed from the coronata lineage. Analysis of morphological traits shows that memorabilis is significantly differentiated from auduboni and nigrifrons in some traits, yet is overall intermediate between the two, which is consistent with a shared common ancestor for the auduboni/memorabilis/nigrifrons group. The striking, unexpected mtDNA pattern reported in the present study reveals a complex evolutionary history of the yellow-rumped warbler complex, and cautions against the exclusive use of mtDNA to infer evolutionary relationships. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 103, 696-706.