American black duck: Difference between revisions
The American black duck interbreeds regularly and extensively with the mallard, to which it is closely related. Some authorities even consider the black duck to be a [[subspecies]] of the mallard instead of a separate [[species]]. [[Judith Mank|Mank]] et al. argue that this is in error as the extent of hybridization alone is not a valid means to delimitate ”Anas” species.{{cite journal|last=Mank|first= Judith E.|author2= Carlson, John E.|author3=Brittingham, Margaret C. |year=2004|title= A century of hybridization: Decreasing genetic distance between American black ducks and mallards. |journal=Conservation Genetics|volume=5|issue=3|pages= 395–403|doi=10.1023/B:COGE.0000031139.55389.b1|s2cid= 24144598|doi-access=free}}
The American black duck interbreeds regularly and extensively with the mallard, to which it is closely related. Some authorities even consider the black duck to be a [[subspecies]] of the mallard instead of a separate [[species]]. [[Judith Mank|Mank]] et al. argue that this is in error as the extent of hybridization alone is not a valid means to delimitate ”Anas” species.{{cite journal|last=Mank|first= Judith E.|author2= Carlson, John E.|author3=Brittingham, Margaret C. |year=2004|title= A century of hybridization: Decreasing genetic distance between American black ducks and mallards. |journal=Conservation Genetics|volume=5|issue=3|pages= 395–403|doi=10.1023/B:COGE.0000031139.55389.b1|s2cid= 24144598|doi-access=free}}
[[File:Blackduckmallard.jpg|thumb|right|Chart showing differences between the American black duck and the female [[mallard]]]]
[[File:Blackduckmallard.jpg|thumb|right|Chart showing differences between the American black duck and the female [[mallard]]]]
It has been proposed that the American black duck and the mallard were formerly separated by habitat preference, with the American black duck’s dark plumage giving it a selective advantage in shaded forest pools in eastern North America, and the mallard’s lighter plumage giving it an advantage in the brighter, more open [[prairie]] and plains lakes.{{Cite book|url=https://books.google.com/books?id=m0mxCgAAQBAJ&pg=PA13|title=Better Birding: Tips, Tools, and Concepts for the Field|last1=Armistead|first1=George L.|last2=Sullivan|first2=Brian L.|date=2015|publisher=Princeton University Press|isbn=9780691129662|pages=13|language=en}} According to this view, recent deforestation in the east and tree planting on the plains has broken down this habitat separation, leading to the high levels of hybridization now observed.{{cite journal|last=Johnsgard|first= Paul A.|author-link=Paul Johnsgard|year=1967|title=Sympatry Changes and Hybridization Incidence in Mallards and Black Ducks|journal=American Midland Naturalist|volume=77|issue=1|pages= 51–63|doi=10.2307/2423425|jstor= 2423425|url= http://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1075&context=biosciornithology}} However, rates of past hybridization are unknown in this and most other avian hybrid zones, and it is merely presumed in the case of the American black duck that past hybridization rates were lower than those seen today. Also, many avian hybrid zones are known to be stable and longstanding despite the occurrence of extensive interbreeding.{{cite book|last=McCarthy|first=Eugene M. |year=2006|title=Handbook of Avian Hybrids of the World|publisher= Oxford University Press}} The American black duck and the local mallard are now very hard to distinguish by means of [[Microsatellite (genetics)|microsatellite]] comparisons, even if many specimens are sampled.{{cite journal|last=Avise|first= John C.|author2= Ankney, C. Davison|author3=Nelson, William S.|year=1990|title= Mitochondrial Gene Trees and the Evolutionary Relationship of Mallard and Black Ducks|journal=[[Evolution (journal)|Evolution]]|volume=44|issue=4|pages= 1109–1119|doi=10.2307/2409570|jstor= 2409570|pmid= 28569026|url= https://escholarship.org/uc/item/39w9q1xh}} Contrary to this study’s claims, the question of whether the American [[haplotypes|haplotype]] is an original mallard lineage is far from resolved. Their statement, “Northern black ducks are now no more distinct from mallards than their southern conspecifics” only holds true in regard to the molecular markers tested. As birds indistinguishable according to the set of microsatellite markers still can look different, there are other genetic differences that were simply not tested in the study.
It has been proposed that the American black duck and the mallard were formerly separated by habitat preference, with the American black duck’s dark plumage giving it a selective advantage in shaded forest pools in eastern North America, and the mallard’s lighter plumage giving it an advantage in the brighter, more open [[prairie]] and plains lakes.{{Cite book|url=https://books.google.com/books?id=m0mxCgAAQBAJ&pg=PA13|title=Better Birding:…
Read More: American black duck: Difference between revisions