Proposal (612) to South American Classification Committee

Change the sequence of species in Sturnella

The paper of Alexis F.L.A. Powell, F. Keith Barker, Scott M. Lanyon, Kevin J. Burns, John Klicka, Irby J. Lovette (2013) A comprehensive species-level molecular phylogeny of the New World blackbirds (Icteridae) Molecular Phylogenetics and Evolution, doi: http://dx.doi.org/10.1016/j.ympev.2013.11.009 offers radically new insights into the phylogeny of all four subfamilies included in the Icteridae: Sturnellinae: Meadowlarks; Cacicinae: Caciques and Oropendolas; Icterinae: Orioles; Agelaiinae: Blackbirds, Cowbirds and Grackles. To quote from their abstract:

“Using mitochondrial gene sequences from all ~108 currently recognized species 7 and six additional distinct lineages, together with strategic sampling of four nuclear loci and 8 whole mitochondrial genomes, we were able to resolve most relationships with high confidence. Our phylogeny is consistent with the strongly-supported results of past studies, but it also contains many novel inferences of relationship, including unexpected placement of some newly sampled taxa, resolution of relationships among major clades within Icteridae, and resolution of genus-level relationships within the largest of those clades, the grackles and allies.”

Their analysis of the Sturnellinae (Meadowlarks) is at variance with that currently used in Part 11. Oscine Passeriformes, C (Cardinalidae to end).

The data in their figure 4 has been interpreted and ordered on the basis of James Remsen’s comments on Proposal 473: “A general criterion for translating phylogenetic trees into linear sequences.” As this is a relatively simple part of the tree, the only principle of Remsen’s relevant here is:

1) First-splitting taxon:

The taxon that splits first (presenting the lesser number of ancestors, that is, internal nodes*) is placed at the top of the sequence (taxon A). The same rule is applied to the next taxa, following the order of the branching pattern.

The current SACC order is as follows:

Sturnella militaris Red-breasted Blackbird

Sturnella superciliaris White-browed Blackbird
Sturnella bellicosa Peruvian Meadowlark
Sturnella defilippii Pampas Meadowlark
Sturnella loyca Long-tailed Meadowlark
Sturnella magna Eastern Meadowlark

Dolichonyx oryzivorus Bobolink

The lower half of Powell et al.’s Figure 4 is displayed on the next page.

Fig. 4. “Phylogeny of the New World blackbirds (Icteridae) inferred from mitochondrial and nuclear DNA sequences of 118 taxa (outgroups not shown). The topology shown here is the single best tree (-lnL = 127652.47) found under maximum likelihood (ML). Nonparametric bootstrap percentages from ML analysis appear immediately above or below branches. Filled circles indicate nodes with estimated posterior probabilities of 0.95 in Bayesian analyses of the same concatenated dataset.”

Basal to the whole Sturnellinae clade is Xanthocephalus xanthocephalus Yellow-headed Blackbird; next, and still basal to rest of the clade is Dolichonyx oryzivorus Bobolink. This relationship is borne out in all four trees. In Fig. 1 (Phylogeny of the New World blackbirds (Icteridae) inferred from mitochondrial DNA sequences of 118 taxa (outgroups not shown). The topology shown here is the single best tree (-lnL = 112464.25) found under maximum likelihood (ML). Nonparametric bootstrap percentages from ML analysis appear immediately above or below branches. Filled circles indicate nodes with estimated posterior probabilities of 0.95 in Bayesian 1 analyses of the same concatenated dataset.) Xanthocephalus xanthocephalus and Dolichonyx oryzivorus form a sister-clade that is basal to the whole Sturnellinae clade.

The next earliest split involves Sturnella neglecta Western Meadowlark, which forms a sister clade to a node containing Sturnella magna Eastern Meadowlark and Sturnella lilianae Lillian’s Meadowlark. In the remainder of the Sturnellinae clade, the next split involves Sturnella militaris Red-breasted Blackbird and Sturnella superciliaris White-browed Blackbird. That brings us to the last portion of the clade, where we find Sturnella bellicosa Peruvian Meadowlark and finally the sister-clade consisting of Sturnella defilippii Pampas Meadowlark and Sturnella loyca Long-tailed Meadowlark.

So the proposal is to change the order of the Sturnellinae clade for South America to the following sequence:

Dolichonyx oryzivorus Bobolink

Sturnella magna Eastern Meadowlark

Sturnella militaris Red-breasted Blackbird

Sturnella superciliaris White-browed Blackbird

Sturnella bellicosa Peruvian Meadowlark

Sturnella defilippii Pampas Meadowlark

Sturnella loyca Long-tailed Meadowlark

References:

Alexis F.L.A. Powell, F. Keith Barker, Scott M. Lanyon, Kevin J. Burns, John Klicka, Irby J. Lovette (2014) A comprehensive species-level molecular phylogeny of the New World blackbirds (Icteridae) Molecular Phylogenetics and Evolution 71: 94-212.

John M. Penhallurick, December 2013

Comments solicited from Alexis Powell: “Proposal 612 seems consistent with our well-supported phylogeny of the meadowlarks and allies.”

Comments from Stiles: “YES. No problem, simply conforming to phylogenetics.

Comments from Remsen: “YES. The genetic data require a rearrangement of the linear sequence to reflect the latest estimate of relationships. Tangentially, now that it is clear that the Leistes group is embedded in Sturnella, it’s time to consider a change in English names to reflect this.”

Comments from Pacheco: “YES. Para ajustar às mais recentes e melhores evidências.”

Comments from Zimmer: “YES. This is a straightforward matter of housekeeping to conform to the well-supported genetic data.”

Comments from Alexis Powell: “We've done some follow-up work to improve confidence in various parts of the Icteridae tree and as a consequence the topology of our best hypothesis of Sturnella phylogeny has changed. Previously, we found bellicosa in a poorly supported position sister to loyca and defilippii. We now find strong support for it being sister to all other red-breasted meadowlarks.  I realize the committee probably makes decisions using only published evidence, but Scott and I thought you might appreciate knowing since it relates to proposal 612.  It may be a year or two before the revised phylogeny is published.”

Comments from Jaramillo: “YES – although I would be happy to move bellicosa up between magna and militaris based on the preview given by Alexis Powell.”

Additional comments from Remsen: “As Alexis noted, we make decisions based only on published evidence, so I think we will have to wait to make that minor correction.”

Comments from Robbins: “YES, for the new arrangement, and I presume we will revisit this once Alexis, Scott et al. have published their latest results.”

Comments from Stotz: “NO.  I just can’t quite see how changing this order provides any value to anybody.  I don’t think anybody could use the order to create the tree it was based on.  The current order represents the units defined in the tree accurately.  Given that the previewed repositioning of bellicosa in the tree would require a change to either the current sequence or this new improved sequence, I really don’t see the point.”