Haldane's rule and American black duck × mallard hybridization

Kirby, Ronald E.; Sargeant, Glen A.; Shutler, Dave

doi:10.1139/z04-169

Cited by 21 publications

(24 citation statements)

References 26 publications

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“…Thus, although our presumed scenario of backcrossing into a single population is un‐vetted with field observations, congruence across analyses regarding the prevalence of few backcrossed generations suggests that this scenario may represent the majority rule in which backcrossing occurs with the parental that is most geographically prevalent. In fact, our results support breeding experiments in which backcrossing into black ducks resulted in indistinguishability of offspring and the parental population ≥F3 stage (Kirby, Sargeant, & Shutler, ).…”

Section: Discussionsupporting

confidence: 85%

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

Lavretsky

Janzen

McCracken

2019

Ecology and Evolution

101

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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.

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Section: Discussionsupporting

confidence: 85%

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

Lavretsky

Janzen

McCracken

2019

Ecology and Evolution

101

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“…Interestingly, hybrid studies of other waterfowl species have also noted that individuals backcrossed past the F3 stage are phenotypically and genetically indistinguishable from their parental population (Kirby et al . , ). To an extent, there are advantages to maintaining a porous genome in which the effects of gene flow are relatively low.…”

Section: Discussionmentioning

confidence: 97%

“…With many ‘hybrids’ primarily characterized in males, Haldane's rule (Haldane ) may be an important speciation mechanism within the order Anseriformes (Tubaro & Lijtmaer ; Kirby et al . ), although this can also be explained by the ease of male versus female plumage hybrid diagnosability in waterfowl (Tubaro & Lijtmaer ; Randler ).…”

Section: Introductionmentioning

confidence: 99%

Becoming pure: identifying generational classes of admixed individuals within lesser and greater scaup populations

et al. 2016

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Estimating the frequency of hybridization is important to understand its evolutionary consequences and its effects on conservation efforts. In this study, we examined the extent of hybridization in two sister species of ducks that hybridize. We used mitochondrial control region sequences and 3589 double-digest restriction-associated DNA sequences (ddRADseq) to identify admixture between wild lesser scaup (Aythya affinis) and greater scaup (A. marila). Among 111 individuals, we found one introgressed mitochondrial DNA haplotype in lesser scaup and four in greater scaup. Likewise, based on the site-frequency spectrum from autosomal DNA, gene flow was asymmetrical, with higher rates from lesser into greater scaup. However, using ddRADseq nuclear DNA, all individuals were assigned to their respective species with >0.95 posterior assignment probability. To examine the power for detecting admixture, we simulated a breeding experiment in which empirical data were used to create F1 hybrids and nine generations (F2-F10) of backcrossing. F1 hybrids and F2, F3 and most F4 backcrosses were clearly distinguishable from pure individuals, but evidence of admixed histories was effectively lost after the fourth generation. Thus, we conclude that low interspecific assignment probabilities (0.011-0.043) for two lesser and nineteen greater scaup were consistent with admixed histories beyond the F3 generation. These results indicate that the propensity of these species to hybridize in the wild is low and largely asymmetric. When applied to species-specific cases, our approach offers powerful utility for examining concerns of hybridization in conservation efforts, especially for determining the generational time until admixed histories are effectively lost through backcrossing.

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“…Together, these results are consistent with a case of differential introgression, including a scenario of reduced gene flow of domesticated mallard variation at selectively non‐neutral genomic locations in wild populations. The latter result not only suggests that postzygotic selection, including Haldane's rule (Haldane, , ), may be playing an important role between black ducks and mallards (wild or game‐farm) (Kirby, Sargeant, & Shutler, ), but also between game‐farm and wild mallards.…”

Section: Discussionmentioning

confidence: 99%

Assessing changes in genomic divergence following a century of human‐mediated secondary contact among wild and captive‐bred ducks

et al. 2020

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Along with manipulating habitat, the direct release of domesticated individuals into the wild is a practice used worldwide to augment wildlife populations. We test between possible outcomes of human‐mediated secondary contact using genomic techniques at both historical and contemporary timescales for two iconic duck species. First, we sequence several thousand ddRAD‐seq loci for contemporary mallards (Anas platyrhynchos) throughout North America and two domestic mallard types (i.e., known game‐farm mallards and feral Khaki Campbell's). We show that North American mallards may well be becoming a hybrid swarm due to interbreeding with domesticated game‐farm mallards released for hunting. Next, to attain a historical perspective, we applied a bait‐capture array targeting thousands of loci in century‐old (1842–1915) and contemporary (2009–2010) mallard and American black duck (Anas rubripes) specimens. We conclude that American black ducks and mallards have always been closely related, with a divergence time of ~600,000 years before present, and likely evolved through prolonged isolation followed by limited bouts of gene flow (i.e., secondary contact). They continue to maintain genetic separation, a finding that overturns decades of prior research and speculation suggesting the genetic extinction of the American black duck due to contemporary interbreeding with mallards. Thus, despite having high rates of hybridization, actual gene flow is limited between mallards and American black ducks. Conversely, our historical and contemporary data confirm that the intensive stocking of game‐farm mallards during the last ~100 years has fundamentally changed the genetic integrity of North America's wild mallard population, especially in the east. It thus becomes of great interest to ask whether the iconic North American mallard is declining in the wild due to introgression of maladaptive traits from domesticated forms. Moreover, we hypothesize that differential gene flow from domestic game‐farm mallards into the wild mallard population may explain the overall temporal increase in differentiation between wild black ducks and mallards, as well as the uncoupling of genetic diversity and effective population size estimates across time in our results. Finally, our findings highlight how genomic methods can recover complex population histories by capturing DNA preserved in traditional museum specimens.

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Haldane's rule and American black duck × mallard hybridization

Cited by 21 publications

References 26 publications

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

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

Becoming pure: identifying generational classes of admixed individuals within lesser and greater scaup populations

Assessing changes in genomic divergence following a century of human‐mediated secondary contact among wild and captive‐bred ducks

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