Identifying hybrids & the genomics of hybridization: Mallards & American black ducks of Eastern North America

Philip Lavretsky, Thijs Janzen, Kevin G. McCracken

Research output: Contribution to journalArticlepeer-review

22 Scopus citations


Resolving evolutionary relationships and establishing population structure depends on molecular diagnosability that is often limited for closely related taxa. Here, we use 3,200 ddRAD-seq loci across 290 mallards, American black ducks, and putative hybrids to establish population structure and estimate hybridization rates. We test between traditional assignment probability and accumulated recombination events based analyses to assign hybrids to generational classes. For hybrid identification, we report the distribution of recombination events complements ADMIXTURE simulation by extending resolution past F4 hybrid status; however, caution against hybrid assignment based on accumulated recombination events due to an inability to resolve F1 hybrids. Nevertheless, both analyses suggest that there are relatively few backcrossed stages before a lineage's hybrid ancestry is lost and the offspring are effectively parental again. We conclude that despite high rates of observed interspecific hybridization between mallards and black ducks in the middle part of the 20th century, our results do not support the predicted hybrid swarm. Conversely, we report that mallard samples genetically assigned to western and non-western clusters. We indicate that these non-western mallards likely originated from game-farm stock, suggesting landscape level gene flow between domestic and wild conspecifics.

Original languageEnglish (US)
Pages (from-to)3470-3490
Number of pages21
JournalEcology and Evolution
Issue number6
StatePublished - Mar 2019


  • ddRADseq
  • evolution
  • haplotype blocks
  • hybridization
  • introgression
  • junctions
  • population genetics
  • speciation

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Ecology
  • Nature and Landscape Conservation


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