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No evidence for assortative mating within a willow warbler migratory divide

Liedvogel, Miriam LU ; Larson, Keith LU ; Lundberg, Max LU ; Gursoy, Arzu LU ; Wassenaar, Leonard I.; Hobson, Keith A.; Bensch, Staffan LU and Åkesson, Susanne LU (2014) In Frontiers in Zoology 11.
Abstract
Introduction: In contact zones, genetic mixing of two taxa can be restricted by prezygotic (e.g. assortative mating) or postzygotic (lower fitness of hybrid offspring) barriers, or a combination of the two. A hybrid zone between two willow warbler subspecies (Phylloscopus trochilus trochilus, P. t. acredula) with distinctive migratory strategies occurs in central Sweden. These subspecies exhibit differences in migratory direction and distance, resulting in geographically distinct wintering areas in Africa. The subspecies may have diverged from a common refuge after the last ice age, and neutral genetic markers are homogeneous across their range. By contrast, several phenotypic traits and genetic markers of two chromosomal regions... (More)
Introduction: In contact zones, genetic mixing of two taxa can be restricted by prezygotic (e.g. assortative mating) or postzygotic (lower fitness of hybrid offspring) barriers, or a combination of the two. A hybrid zone between two willow warbler subspecies (Phylloscopus trochilus trochilus, P. t. acredula) with distinctive migratory strategies occurs in central Sweden. These subspecies exhibit differences in migratory direction and distance, resulting in geographically distinct wintering areas in Africa. The subspecies may have diverged from a common refuge after the last ice age, and neutral genetic markers are homogeneous across their range. By contrast, several phenotypic traits and genetic markers of two chromosomal regions previously identified show steep clines across the divide. The evolutionary forces that maintain this migratory divide remain unknown. Here we use plumage colour, morphology, genetic markers and feather stable nitrogen-isotopes (delta N-15) to assess if assortative mating between migratory phenotypes could be acting as a possible mechanism for keeping the two forms genetically separate and maintaining the migratory divide. We colour-ringed a willow warbler breeding population in the central part of the hybrid zone and observed the breeding population to assess phenotypic and genotypic traits of social pairs. Results: Our data suggest that wintering area and genetic ancestry had an effect on male arrival time to the breeding grounds which could contribute to assortment. However, evidence for assortative mating could not be detected based on a comparison of plumage colour, morphology and delta N-15 between social mates. Conclusion: This finding was strengthened by analyses of subspecies-specific genetic markers, which allowed us to identify the presence of a large proportion of potential hybrids and backcrosses at the study site. Our results supported the hypothesis that pre-mating isolation in willow warblers is weak, resulting in extensive hybridisation across the migratory divide. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Hybrid zone, Prezygotic selection, Postzygotic selection, Reproductive, isolation, Willow warbler, Phylloscopus trochilus, Nitrogen-15
in
Frontiers in Zoology
volume
11
publisher
BioMed Central
external identifiers
  • pmid:25053967
  • wos:000339204800001
  • scopus:84942085765
ISSN
1742-9994
DOI
10.1186/s12983-014-0052-2
project
Migratory genes in willow warblers
BECC
CAnMove
language
English
LU publication?
yes
id
cf3fd24b-50c1-4205-a8e3-252d0296c51e (old id 4592807)
date added to LUP
2014-09-03 10:37:47
date last changed
2017-09-03 04:05:35
@article{cf3fd24b-50c1-4205-a8e3-252d0296c51e,
  abstract     = {Introduction: In contact zones, genetic mixing of two taxa can be restricted by prezygotic (e.g. assortative mating) or postzygotic (lower fitness of hybrid offspring) barriers, or a combination of the two. A hybrid zone between two willow warbler subspecies (Phylloscopus trochilus trochilus, P. t. acredula) with distinctive migratory strategies occurs in central Sweden. These subspecies exhibit differences in migratory direction and distance, resulting in geographically distinct wintering areas in Africa. The subspecies may have diverged from a common refuge after the last ice age, and neutral genetic markers are homogeneous across their range. By contrast, several phenotypic traits and genetic markers of two chromosomal regions previously identified show steep clines across the divide. The evolutionary forces that maintain this migratory divide remain unknown. Here we use plumage colour, morphology, genetic markers and feather stable nitrogen-isotopes (delta N-15) to assess if assortative mating between migratory phenotypes could be acting as a possible mechanism for keeping the two forms genetically separate and maintaining the migratory divide. We colour-ringed a willow warbler breeding population in the central part of the hybrid zone and observed the breeding population to assess phenotypic and genotypic traits of social pairs. Results: Our data suggest that wintering area and genetic ancestry had an effect on male arrival time to the breeding grounds which could contribute to assortment. However, evidence for assortative mating could not be detected based on a comparison of plumage colour, morphology and delta N-15 between social mates. Conclusion: This finding was strengthened by analyses of subspecies-specific genetic markers, which allowed us to identify the presence of a large proportion of potential hybrids and backcrosses at the study site. Our results supported the hypothesis that pre-mating isolation in willow warblers is weak, resulting in extensive hybridisation across the migratory divide.},
  articleno    = {52},
  author       = {Liedvogel, Miriam and Larson, Keith and Lundberg, Max and Gursoy, Arzu and Wassenaar, Leonard I. and Hobson, Keith A. and Bensch, Staffan and Åkesson, Susanne},
  issn         = {1742-9994},
  keyword      = {Hybrid zone,Prezygotic selection,Postzygotic selection,Reproductive,isolation,Willow warbler,Phylloscopus trochilus,Nitrogen-15},
  language     = {eng},
  publisher    = {BioMed Central},
  series       = {Frontiers in Zoology},
  title        = {No evidence for assortative mating within a willow warbler migratory divide},
  url          = {http://dx.doi.org/10.1186/s12983-014-0052-2},
  volume       = {11},
  year         = {2014},
}