Classification of genus Branta
kinman2 at YAHOO.COM
Thu Nov 18 13:27:02 CST 2004
I decided to try a species classification of genus Branta to see what it might look like and summarize my present viewpoint. I am recognizing Branta hutchinsii (officially referred to as "cackling geese") as a separate species--- not only because there is some preliminary evidence (both molecular and morphological) of their distinctness, but it will also get amateur birders involved in gathering additional information as well (some certainly seem very pleased to have another species to add to their lists---no big surprise).
For now, the only paraphyly I am formally coding is the evolution of Hawaiian geese from B. canadensis. Together they form a large-bodied clade (even the nene is bigger than I realized) possessing similar calls, related mitochondrial sequences, etc. I suspect this clade is an exgroup of a paraphyletic B. hutchinsii, but without proof, I will code them as sister groups [documenting paraphyly often requires more information, NOT less].
Branta leucopsis is probably an ideal intermediate between that whole clade and the other brants (if mitochondrial similarities between leucopsis and hutchsinsii are plesiomorphic, rather than synapomorphic). And other than more white on the head, I really don't why Paxinos et al., 2002, referred to leucopsis as having apomorphic plumage characteristics. So based on the evidence I have seen thus far, here is my classification of genus Branta (we need a lot more molecular data, which may alter the topological coding, even if the species list remains the same):
NOTES: Some people may wish to continue dividing up the Hawaiian goose into three separate species. I am a little skeptical of bernicla and ruficollis being sister species (forming an exclusive clade), but if it is actually a paraphyletic grouping, which of them split off first? Something to think about.
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