A 2000 km genetic wake yields evidence for northern glacial refugia and hybrid zone movement in a pair of songbirds

Krosby, Meade; Rohwer, Sievert

doi:10.1098/rspb.2008.1310

Cited by 69 publications

(113 citation statements)

References 53 publications

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“…Further, this range size asymmetry was larger for Townsend's warblers than for hermit warblers [4], which would lead to the observed difference in aggressiveness between the species. Recent genetic work is consistent with this posited difference in their historical population sizes [5]. But as Townsend's warblers have displaced hermit warblers across their breeding range, the historical asymmetries in the relative sizes of their respective winter and summer ranges have been reversed.…”

Section: Discussionmentioning

confidence: 81%

Ongoing Movement of the Hermit Warbler X Townsend's Warbler Hybrid Zone

Krosby

Rohwer

2010

PLoS ONE

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BackgroundMovements of hybrid zones – areas of overlap and interbreeding between species – are difficult to document empirically. This is true because moving hybrid zones are expected to be rare, and because movement may proceed too slowly to be measured directly. Townsend's warblers (Dendroica townsendi) hybridize with hermit warblers (D. occidentalis) where their ranges overlap in Washington and Oregon. Previous morphological, behavioral, and genetic studies of this hybrid zone suggest that it has been steadily moving into the geographical range of hermit warblers, with the more aggressive Townsend's warblers replacing hermit warblers along ∼2000 km of the Pacific coast of Canada and Alaska. Ongoing movement of the zone, however, has yet to be empirically demonstrated.Methodology/Principal FindingsWe compared recently sampled hybrid zone specimens to those collected 10–20 years earlier, to test directly the long-standing hypothesis of hybrid zone movement between these species. Newly sampled specimens were more Townsend's-like than historical specimens, consistent with ongoing movement of the zone into the geographical range of hermit warblers.Conclusions/SignificanceWhile movement of a hybrid zone may be explained by several possible mechanisms, in this case a wealth of existing evidence suggests that movement is being driven by the competitive displacement of hermit warblers by Townsend's warblers. That no ecological differences have been found between these species, and that replacement of hermit warblers by Townsend's warblers is proceeding downward in latitude and elevation – opposite the directions of range shifts predicted by recent climate change – further support that this movement is not being driven by alternative environmental factors. If the mechanism of competitive displacement is correct, whether this process will ultimately lead to the extinction of hermit warblers will depend on the continued maintenance of the dramatic competitive asymmetry observed between the species.

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Section: Discussionmentioning

confidence: 81%

Ongoing Movement of the Hermit Warbler X Townsend's Warbler Hybrid Zone

Krosby

Rohwer

2010

PLoS ONE

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“…Krosby & Rohwer 2009;Shaw 2002), an alternative interpretation of the mitochondrial data presented in Mullen (2006), Mullen et al (2008) and Prudic & Oliver (2008) is that southeastern populations of mimetic L. a. astyanax historically came into contact with a lineage of white-banded L. a. arthemis in sympatry with Battus, causing a selective sweep of alleles underlying the mimetic phenotype. Results from this study and previous work (Mullen 2006;Mullen et al 2008;Prudic & Oliver 2008) support the following history for wing pattern evolution in the L. arthemis complex.…”

Section: Discussionmentioning

confidence: 99%

A single origin of Batesian mimicry among hybridizing populations of admiral butterflies (Limenitis arthemis) rejects an evolutionary reversion to the ancestral phenotype

Savage

Mullen

2009

Proc. R. Soc. B.

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Batesian mimicry is a fundamental example of adaptive phenotypic evolution driven by strong natural selection. Given the potentially dramatic impacts of selection on individual fitness, it is important to understand the conditions under which mimicry is maintained versus lost. Although much empirical and theoretical work has been devoted to the maintenance of Batesian mimicry, there are no conclusive examples of its loss in natural populations. Recently, it has been proposed that non-mimetic populations of the polytypic Limenitis arthemis species complex represent an evolutionary loss of Batesian mimicry, and a reversion to the ancestral phenotype. Here, we evaluate this conclusion using segregating amplified fragment length polymorphism markers to investigate the history and fate of mimicry among forms of the L. arthemis complex and closely related Nearctic Limenitis species. In contrast to the previous finding, our results support a single origin of mimicry within the L. arthemis complex and the retention of the ancestral white-banded form in non-mimetic populations. Our finding is based on a genome-wide sampling approach to phylogeny reconstruction that highlights the challenges associated with inferring the evolutionary relationships among recently diverged species or populations (i.e. incomplete lineage sorting, introgressive hybridization and/or selection).

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“…0-50%) did extend over a large area (50-95% geographic extent), it was inferred to be caused either by hybrid zone movement (e.g. phenotypic Townsend's warblers, Setophaga townsendii, moving into the range of hermit warblers, S. occidentalis; Krosby & Rohwer 2009), large asymmetries in range size (e.g. introgression of the Woodhouse toad's mtDNA, Bufo woodhousii, into the Arizona toad, B. microscaphus, which has a nested range within B. woodhousii; Malmos et al 2001) or differences in population sizes (e.g.…”

Section: Box 3 Mitochondrial Structure In the Absence Of Geographic mentioning

confidence: 99%

The biogeography of mitochondrial and nuclear discordance in animals

2012

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Combining nuclear (nuDNA) and mitochondrial DNA (mtDNA) markers has improved the power of molecular data to test phylogenetic and phylogeographic hypotheses and has highlighted the limitations of studies using only mtDNA markers. In fact, in the past decade, many conflicting geographic patterns between mitochondrial and nuclear genetic markers have been identified (i.e. mito-nuclear discordance). Our goals in this synthesis are to: (i) review known cases of mito-nuclear discordance in animal systems, (ii) to summarize the biogeographic patterns in each instance and (iii) to identify common drivers of discordance in various groups. In total, we identified 126 cases in animal systems with strong evidence of discordance between the biogeographic patterns obtained from mitochondrial DNA and those observed in the nuclear genome. In most cases, these patterns are attributed to adaptive introgression of mtDNA, demographic disparities and sex-biased asymmetries, with some studies also implicating hybrid zone movement, human introductions and Wolbachia infection in insects. We also discuss situations where divergent mtDNA clades seem to have arisen in the absence of geographic isolation. For those cases where foreign mtDNA haplotypes are found deep within the range of a second taxon, data suggest that those mtDNA haplotypes are more likely to be at a high frequency and are commonly driven by sex-biased asymmetries and ⁄ or adaptive introgression. In addition, we discuss the problems with inferring the processes causing discordance from biogeographic patterns that are common in many studies. In many cases, authors presented more than one explanation for discordant patterns in a given system, which indicates that likely more data are required. Ideally, to resolve this issue, we see important future work shifting focus from documenting the prevalence of mito-nuclear discordance towards testing hypotheses regarding the drivers of discordance. Indeed, there is great potential for certain cases of mitochondrial introgression to become important natural systems within which to test the effect of different mitochondrial genotypes on whole-animal phenotypes.

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A 2000 km genetic wake yields evidence for northern glacial refugia and hybrid zone movement in a pair of songbirds

Cited by 69 publications

References 53 publications

Ongoing Movement of the Hermit Warbler X Townsend's Warbler Hybrid Zone

Ongoing Movement of the Hermit Warbler X Townsend's Warbler Hybrid Zone

A single origin of Batesian mimicry among hybridizing populations of admiral butterflies (Limenitis arthemis) rejects an evolutionary reversion to the ancestral phenotype

The biogeography of mitochondrial and nuclear discordance in animals

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