TY - JOUR
T1 - Mito-nuclear discordance at a mimicry color transition zone in bumble bee Bombus melanopygus
AU - Wham, Briana E.
AU - Rahman, Sarthok Rasique
AU - Martinez-Correa, Marena
AU - Hines, Heather M.
N1 - Funding Information:
We acknowledge Rebecca Sommer, Li Tian, Patrick Lhomme, Guillaume Ghisbain, Sydney Cameron, Michelle Duennes, and Elyse McCormick for their support in acquiring specimens. Thanks to Robin Owen for providing data on historic color pattern distributions. Thanks to Robb Brumfield for helpful advice on application of R package “hzar.” Thanks to David Toews for valuable insights on theory and analysis and to the anonymous reviewers and editor for their many helpful comments. We thank the Pennsylvania State Genomics Core Facility (University Park, PA) for providing sequencing support. Computations for this research were performed on the Pennsylvania State University’s Institute for Computational and Data Sciences’ Roar supercomputer. This study was funded by NSF DEB‐1453473 CAREER grant to HMH. The funding agency played no role in the study design, analysis, interpretation, or writing.
Funding Information:
We acknowledge Rebecca Sommer, Li Tian, Patrick Lhomme, Guillaume Ghisbain, Sydney Cameron, Michelle Duennes, and Elyse McCormick for their support in acquiring specimens. Thanks to Robin Owen for providing data on historic color pattern distributions. Thanks to Robb Brumfield for helpful advice on application of R package ?hzar.? Thanks to David Toews for valuable insights on theory and analysis and to the anonymous reviewers and editor for their many helpful comments. We thank the Pennsylvania State Genomics Core Facility (University Park, PA) for providing sequencing support. Computations for this research were performed on the Pennsylvania State University?s Institute for Computational and Data Sciences? Roar supercomputer. This study was funded by NSF DEB-1453473 CAREER grant to HMH. The funding agency played no role in the study design, analysis, interpretation, or writing.
Publisher Copyright:
© 2021 The Authors. Ecology and Evolution published by John Wiley & Sons Ltd.
PY - 2021/12
Y1 - 2021/12
N2 - As hybrid zones exhibit selective patterns of gene flow between otherwise distinct lineages, they can be especially valuable for informing processes of microevolution and speciation. The bumble bee, Bombus melanopygus, displays two distinct color forms generated by Müllerian mimicry: a northern “Rocky Mountain'’ color form with ferruginous mid-abdominal segments (B. m. melanopygus) and a southern “Pacific'’ form with black mid-abdominal segments (B. m. edwardsii). These morphs meet in a mimetic transition zone in northern California and southern Oregon that is more narrow and transitions further west than comimetic bumble bee species. To understand the historical formation of this mimicry zone, we assessed color distribution data for B. melanopygus from the last 100 years. We then examined gene flow among the color forms in the transition zone by comparing sequences from mitochondrial COI barcode sequences, color-controlling loci, and the rest of the nuclear genome. These data support two geographically distinct mitochondrial haplogroups aligned to the ancestrally ferruginous and black forms that meet within the color transition zone. This clustering is also supported by the nuclear genome, which, while showing strong admixture across individuals, distinguishes individuals most by their mitochondrial haplotype, followed by geography. These data suggest the two lineages most likely were historically isolated, acquired fixed color differences, and then came into secondary contact with ongoing gene flow. The transition zone, however, exhibits asymmetries: mitochondrial haplotypes transition further south than color pattern, and both transition over shorter distances in the south. This system thus demonstrates alternative patterns of gene flow that occur in contact zones, presenting another example of mito-nuclear discordance. Discordant gene flow is inferred to most likely be driven by a combination of mimetic selection, dominance effects, and assortative mating.
AB - As hybrid zones exhibit selective patterns of gene flow between otherwise distinct lineages, they can be especially valuable for informing processes of microevolution and speciation. The bumble bee, Bombus melanopygus, displays two distinct color forms generated by Müllerian mimicry: a northern “Rocky Mountain'’ color form with ferruginous mid-abdominal segments (B. m. melanopygus) and a southern “Pacific'’ form with black mid-abdominal segments (B. m. edwardsii). These morphs meet in a mimetic transition zone in northern California and southern Oregon that is more narrow and transitions further west than comimetic bumble bee species. To understand the historical formation of this mimicry zone, we assessed color distribution data for B. melanopygus from the last 100 years. We then examined gene flow among the color forms in the transition zone by comparing sequences from mitochondrial COI barcode sequences, color-controlling loci, and the rest of the nuclear genome. These data support two geographically distinct mitochondrial haplogroups aligned to the ancestrally ferruginous and black forms that meet within the color transition zone. This clustering is also supported by the nuclear genome, which, while showing strong admixture across individuals, distinguishes individuals most by their mitochondrial haplotype, followed by geography. These data suggest the two lineages most likely were historically isolated, acquired fixed color differences, and then came into secondary contact with ongoing gene flow. The transition zone, however, exhibits asymmetries: mitochondrial haplotypes transition further south than color pattern, and both transition over shorter distances in the south. This system thus demonstrates alternative patterns of gene flow that occur in contact zones, presenting another example of mito-nuclear discordance. Discordant gene flow is inferred to most likely be driven by a combination of mimetic selection, dominance effects, and assortative mating.
UR - http://www.scopus.com/inward/record.url?scp=85120784342&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85120784342&partnerID=8YFLogxK
U2 - 10.1002/ece3.8412
DO - 10.1002/ece3.8412
M3 - Article
C2 - 35003664
AN - SCOPUS:85120784342
VL - 11
SP - 18151
EP - 18168
JO - Ecology and Evolution
JF - Ecology and Evolution
SN - 2045-7758
IS - 24
ER -