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Mexican Duck (1 Viewer)

hah...If I didn't know better I would say someone involved in IOC reads this forum :p

FYI I never doubted the validity of the Mexican Duck, just for consistency's sake I usually hold off on counting strictly NA species until AOU decides to evaluate them.
 
hah...If I didn't know better I would say someone involved in IOC reads this forum :p

FYI I never doubted the validity of the Mexican Duck, just for consistency's sake I usually hold off on counting strictly NA species until AOU decides to evaluate them.

Okay. But you have to give them credit for drawing aside the curtain and letting us mere mortals into their thought processes. More evidence that the open process of the SACC is going viral?
 
If A. diazi is a distinct species wouldn't that mean that Anas oustaleti (the extinct Marianas Mallard) is a distinct species too (and not a subspecies as stated in many current sources)?
 
If A. diazi is a distinct species wouldn't that mean that Anas oustaleti (the extinct Marianas Mallard) is a distinct species too (and not a subspecies as stated in many current sources)?
Carboneras 1992 (HBW1) and BLI consider oustaleti to have been a hybrid of platyrhynchos and superciliosa ('unstable' according to HBW); and Dickinson 2003 and Drilling et al 2002 (BNA Online) don't even recognise it as a subspecies.

Richard
 
In the recent (and much maligned) update to Clements, the revision notes (Updates and Corrections) state
Page 30, Mallard Anas platyrhynchos
Beginning with the 5th edition of Clements Checklist, there has been an entry for an extinct subspecies, oustaletti, formerly found on the Marianas Islands. This entry is incorrect, in two different ways. The correct spelling of the name of the subspecies is oustaleti (with only a single 't' in '-leti'). More importantly, this population probably was not a valid subspecies, but instead was a variable hybrid swarm between Mallard and Gray Duck (Anas superciliosa) (see Y. Ysamashina, 1948, Notes on the Marianas Mallard. Pacific Science 2: 121-124). Therefore, this subspecies no longer is recognized, and is deleted from the Clements Checklist.
 
Okay. But you have to give them credit for drawing aside the curtain and letting us mere mortals into their thought processes. More evidence that the open process of the SACC is going viral?

I agree in applauding the openness, and hope it continues!

Cheers
Niels
 
Lavretsky et al

Lavretsky, DaCosta, Hernández-Baños, Engilis, Sorenson & Peters. Speciation genomics and a role for the sex chromosome in the mallard and Mexican duck. Evolution 2014. (p239)
Speciation is a continuous and dynamic process. Early in speciation, the genomes of incipient taxa are manipulated by evolutionary forces, and identifying their heterogeneous composition can reveal potentially important processes influencing species composition. We conducted genomic scans across the mitochondrial DNA (mtDNA) control region, 3563 autosomal loci, and 172 Z-chromosome loci in the mallard (Anas platyrhynchos; N = 17 individuals) and Mexican duck (A. [p.] diazi; N = 105 individuals from six Mexican and two US states) to disentangle their incipient evolutionary relationship. Between mallards and Mexican ducks, we found discordance in divergence estimates among autosomal (mean ΦST = 0.018), sex-linked (mean ΦST = 0.086), and mtDNA (ΦST = 0.14) markers, and five Z loci and one autosomal locus were more divergent than expected given background levels of divergence. In contrast, divergence in autosomal (mean ΦST = 0.012) and Z-linked markers (mean ΦST = 0.018) were tightly correlated within Mexican ducks, and divergence at only two autosomal loci strongly deviated from background levels. We conclude that speciation between mallards and Mexican ducks is likely proceeding via selection on a few sex-linked markers with large effects, whereas divergence at the remaining genome is the result of genetic drift. These results suggest post-zygotic isolating mechanisms. In contrast, divergence among Mexican duck populations is consistent with isolation-by-distance and large role for genetic drift. These results demonstrate that a large number of loci are necessary to better understand the speciation process between recently diverged taxa and provides a compelling example of the differential roles of selection and genetic drift across genomic regions.
[With thanks to Nick Sly.]​
 
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Brown, J.I., F. Hernández, A. Engilis Jr., B.E. Hernández-Baños, D. Collins, and P. Lavretsky (2022)
Genomic and morphological data shed light on the complexities of shared ancestry between closely related duck species
Scientific Reports 12: 10212
doi: 10.1038/s41598-022-14270-2

Causes for genomic and morphological similarities among recently radiated species are often multifaceted and are further convoluted among species that readily interbreed. Here, we couple genomic and morphological trait comparisons to test the extent that ancestry and gene flow explain the retention of mallard-like traits within a sister species, the Mexican duck. First, we confirm that these taxa remain genetically structured, and that Mexican ducks exhibit an isolation-by-distance pattern. Despite the assumption of wide-spread hybridization, we found only a few late-stage hybrids, all from the southwestern USA. Next, assessing 23 morphological traits, we developed a genetically-vetted morphological key that is > 97% accurate in distinguishing across sex-age cohorts of Mexican ducks, mallards, and hybrids. During key development, we determined that 25% of genetically pure, immature male Mexican ducks of the northern population naturally displayed mallard-like traits in their formative plumage. In fact, applying this key to 55 museum specimens, we identified that only four of the 14 specimens originally classified as phenotypic hybrids were truly hybrids. We discuss how genomic and morphological comparisons shed light into the mechanism(s) underlying the evolution of complex phenotypic traits in recent radiations, and how misunderstanding the true morphological diversity within Mexican ducks resulted in taxonomic revisions that hindered conservation efforts.
 
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