Proposal (#221) to South American Classification Committee

Change linear sequence of species in Mimus

Background: Our current linear sequence of species in Mimus is as follows; I'm not sure what is based on other than general plumage similarities and historical momentum:

Mimus gilvus Tropical Mockingbird
Mimus thenca Chilean Mockingbird
Mimus longicaudatus Long-tailed Mockingbird
Mimus saturninus Chalk-browed Mockingbird
Mimus patagonicus Patagonian Mockingbird
Mimus triurus White-banded Mockingbird
Mimus dorsalis Brown-backed Mockingbird
Nesomimus parvulus Galapagos Mockingbird
Nesomimus trifasciatus Charles Mockingbird
Nesomimus macdonaldi Hood Mockingbird
Nesomimus melanotis Chatham Mockingbird

The placement of Nesomimus (within Mimus) is dealt with in Proposal 220. This proposal focuses on the linear sequence of the South American group, from thenca through dorsalis.

New information: A recent genetic study (Arbogast et al. 2006) indicates that the current linear sequence of species in Mimus does not reflect phylogenetic relationships.

Arbogast et al. (2006) [see Proposal 220 for summary of data] demonstrated that Nesomimus is monophyletic, suggests that it is embedded in Mimus, and suggests that its closest relatives are, somewhat surprisingly in terms of plumage, probably the northern group (extralimital M. gundlachii, extralimital M. polyglottos, M. gilvus). Further, the sister relationships within South American Mimus, all strongly supported by Bayesian and bootstrap values are as follows:

(a) saturninus and triurus are sisters

(b) thenca and patagonicus are sisters

(c) group a and group b above are sisters

(d) longicaudatus cannot be place with confidence in any of the three strongly supported Mimus groups (northern, "Nesomimus", or South American).

Unfortunately, dorsalis was NOT included in the analysis.

Analysis: The support values for groups a, b, and c above seem unassailably strong. Therefore, to have our linear sequence reflect phylogenetic data and also retain as much stability as possible, the sequence of South American species should be tweaked as follows:

Mimus longicaudatus Long-tailed Mockingbird
Mimus thenca Chilean Mockingbird
Mimus patagonicus Patagonian Mockingbird
Mimus saturninus Chalk-browed Mockingbird
Mimus triurus White-banded Mockingbird
Mimus dorsalis Brown-backed Mockingbird

This moves sister taxa to adjacent positions while leaving outlier longicaudatus in an ambiguous position at one end and unsampled dorsalis at the other end (also its historical position).

Recommendation: YES (mildly). Our current sequence does not reflect phylogenetic data. Although linear sequences are a poor way to portray relationships, for consistency we should make those sequences as consistent as possible with available data, as per above. On the other hand, a valid reason to vote NO would be the combination of the unresolved positions of longicaudatus and dorsalis. Overall, I favor a YES because the new sequence would at least be closer to presumed reality than the current one.

Literature Cited:

ARBOGAST, B., S. V. DROVETSKI, R. L. CURRY, P. T. BOAG, G. SEUTIN, P. R. GRANT, B. R. GRANT, AND D. J. ANDERSON. 2006. The origin and diversification of Galapagos mockingbirds. Evolution 60: 370-382.

V. Remsen, June 2006

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Comments from Zimmer: "YES. This arrangement would seem to better reflect the phylogeny as currently understood, while leaving the two species whose positions are somewhat ambiguous at opposite ends of the sequence."

Comments from Stiles: "YES [same coments as in #220]."

Comments from Robbins: "YES. This is one aspect of the Arbogast et al (2006) that is well supported."

Comments from Pacheco: "YES. Concordo que a sequência sugerida reflete melhor a filogenia do grupo."