Hence the biogeographic patterns associated with these types of discordant clines can reveal novel insights into evolutionary processes (e.g., Brumfield et al. Often this pattern is consistent with introgression following secondary contact, which can be promoted by various demographic and/or selective factors (Toews and Brelsford 2012). In some instances, however, there is geographic discordance among genes or traits, where clines are strongly displaced in their spatial distribution compared to the rest of the genome (Barton 1993). These patterns are consistent with limited introgression across a hybrid zone and strong selection against hybrids (Barton and Hewitt 1985). Most well-studied hybrid zones between divergent taxa are characterized by steep, coincident clines at various genetic loci and phenotypic traits. To our knowledge this is the first time this type of intraspecific variation in mitochondrial respiration has been measured in wild birds and we discuss how such mitochondrial adaptations may have facilitated introgression. Mitochondrial respiration in flight muscles demonstrates that myrtle-type individuals have a significantly greater acceptor control ratio of mitochondria, suggesting it may be more metabolically efficient. Isotopes suggest the zone is coincident with a shift in migration, with individuals in the south being resident and populations further north becoming increasingly more migratory. We investigated the link between mitochondrial introgression, mitochondrial function, and migration using novel genetic, isotopic, biochemical, and phenotypic data obtained from populations in the transition zone. Both northern forms exhibit seasonal migration, whereas black-fronted warblers are nonmigratory.
Within the southwestern United States myrtle mtDNA comes into contact with another clade that occurs in the Mexican black-fronted warbler.
In the yellow-rumped warbler, evidence suggests that mtDNA from the eastern, myrtle warbler, has introgressed across much of the range of the western form, the Audubon's warbler.
#Yellow rumped warbler southern california drivers#
Asymmetric introgression of mitochondria is a common cause of such discordances, although in most cases the drivers of introgression are unknown. Discordance between mitochondrial and nuclear DNA has been noted in many systems.
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