The Work and Theory of Lavretsky, Part 2

In this second part we study how Prof Dr Phil Lavretsky came to discover the role of Game-Farm mallards and why – in fact – the American Black Duck is NOT threatened with extinction by mallard interbreeding. And if, perhaps, there is a lesson for all of us in understanding the true value of diversity among ducks, as there is among people.

Mallards and Blacks

“The history of secondary contact between North American mallards and black ducks has caused concern over the possible genetic extinction of black ducks (Rhymer, 2006; Rhymer & Simberloff, 1996),” as Dr. Lavertsky writes, “Specifically, while mallards are currently widespread across North America, they were rarely observed east of the Mississippi River prior to the 1950s (Johnsgard, 1967; Merendino & Ankney, 1994; Snell, 1986).”

Causes for the dramatic change in the geographic distributions of mallards have been attributed to direct augmentation by game managers, sportsmen, and others releasing ~500,000 captive mallards per year along the east coast since the 1920s, with large‐ scale releases ending in the 1950s and 1960s. Additionally, conversion of boreal forests into open habitat due to changing agricultural practices led to the expansion of western mallard populations and dramatic increases in mallard abundance (~600%) east of the Mississippi River beginning in the 1950s (e.g., southern Ontario; Hanson, Rogers, & Rogers, 1949). Given this history, we predict that the North American mallard is likely the product of both recent natural invaders and domestic ducks (Osborne, Swift, & Baldassarre, 2010; USFWS, 2013), resulting in the presence of multiple genetic mallard groups in North American samples. 

Lavretsky’s primary objective was to determine the rate of hybridization and extent of gene flow between mallards and black ducks using high‐throughput DNA sequencing methods. Whereas hybrids have been well documented between mallards and black ducks in the wild, we aim to determine whether hybridization has resulted in gene flow, including whether backcrossing is unidirectional (to‐ ward either black ducks or mallards) or bi‐directional (toward both black ducks and mallards). 

He and his colleagues found only two genetically vetted black ducks from the Mississippi flyway possessed, “OW A mtDNA haplotypes”, that is to say, possess mitochondria DNA from a hybrid mother. Conversely, all genetically-assigned mallards had a significant proportion of samples with OW A mtDNA haplotypes, with the frequency of this haplogroup increasing eastward.

What he and his colleagues actually found is that without backcrossing on a number of occasions (interbreeding more than once by hybrid’s offspring) there is little chance of long-term genetic change or speciation, as his theory states. No one. Let me say that again, no one has done the research that Lavretsky has done. He has thoroughly investigated ALL involved duck types, and discovered the third hybrid from Game-Farm mallards that no one had known about or its role in spreading the “mallard complex”.

Looks versus Reality

It turns out that Black Ducks do not like to be around humans. Particularly, when mating or rearing their young. They appreciate boreal settings, not open habitat. Back water, not open streams. Even though, they may have opportunities to mate in other areas, they do not. Why? Lavretsky is the first to admit, he does not know all. But apparently they will not. He say, “The American Black Duck is essentially the same black duck as existed 100 or 150 years ago. No change genetically can be detected.”

So, when judging whether a duck is a mallard, or hydrid, or black duck, Lavretsky says the worst way to judge is by phenomenological evidence – that is “looks.” It was in this way that many endangered young Hawai`ian ducks were slaughtered needlessly as “hybrids.” One must go below the superficial.

Good luck this season! Wear a mask as long as necessary, Stay healthy and stay safe.

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