Proposal (651) to South American Classification Committee
Resurrect Porphyriops for Gallinula melanops
Our current footnote summarizes the situation:
23. Gallinula melanops was formerly (e.g., Hellmayr & Conover 1942, Meyer de Schauensee 1970, Blake 1977) placed in the genus Porphyriops, but Olson (1973) and Ripley (1977) merged this into Gallinula, and this has been followed in subsequent classifications. Livezey (1998, 2003, 2007) retained Porphyriops based on morphological characters. Garcia-R. et al. (2014) found that melanops was not a member of Gallinula but was sister to Porzana. SACC proposal badly needed to resurrect Porphyriops.
Olson (1973) stated: “The monotypic genus Porphyriops of South America is essentially similar in plumage and shape of the frontal shield to immatures of Gallinula angulata. It is intermediate in size between G. chloropus and G. angulata and there are absolutely no differences in its skeleton that can be construed to be of generic importance when compared to Gallinula.”
Garcia-R. et al. (2014) produced a phylogeny for the Rallidae based on a fairly large analysis of DNA sequence data, both mitochondrial and nuclear, largely compiled from GenBank etc. Their taxon sampling was fairly good for a family that is cosmopolitan and difficult to collect: 70 species in 22 of 33 extant genera. Below is the relevant section of their tree:
Clearly, Olson and Ripley were mislead by superficial similarities. True Gallinula is sister to Fulica, and “Gallinula” melanops is sister to true Porzana. I’ve only seen the species once, but the illustrations (as in Walker’s rail book) make it look like a long-legged Sora. The big surprise to me is that Porphyrio, including Porphyrula, is in a different branch of the tree. To Livezey’s credit, his detailed morphological analyses also placed Porphyrio in a different part of the tree. Maybe the biggest surprise of all is that everyone continued to follow Ripley.
Recommendation: I recommend a YES because (1) no real data were ever presented for the merger, and (2) all data, including even morphology, point to the distinctiveness of Porphyriops.
Literature Cited (also see SACC Biblio):
GARCIA-R, J. C., G. C. GIBB, AND S. A. TREWICK. 2014. Deep global evolutionary radiation in birds: diversification and trait evolution in the cosmopolitan bird family Rallidae. Molecular Phylogenetics and Evolution 81: 96–108.
Van Remsen, October 2014
Comments from Stiles: “YES. Clearly Gallinula is polyphyletic and melanops is not close to the “true” Gallinulas; I cannot see placing it in Porzana either, so segregating it in Porphyriops is the best option.”
Comments from Stotz: “YES. This seems straightforward.”
Comments from Zimmer: “YES. Genetic data show that Gallinula is polyphyletic, and that melanops does not belong with the true Gallinulas. In the field, melanops is very reminiscent of P. carolina (but with a neon green bill) – whenever I see a Sora swimming across deeper water (pretty common actually), I am instantly reminded of melanops, both in terms of appearance and the biomechanics of how it moves through the water. So, the notion that melanops groups closer to Porzana than to Gallinula makes perfect biological sense to me.”
Comments from Cadena: “Yes to removing from Gallinula but NO to placing it in its own genus. As I have noted in other cases, I think we should avoid monotypic genera except for real oddballs - very distinctive taxa with no close relatives. As others have noted, there are several similarities between melanops and species currently placed in Porzana, so why not transfer it to that genus? If we do this, then our classification would carry more phylogenetic information (i.e. that melanops and Porzana as currently defined form a clade) than if we were to go with the monotypic genus option, which carries no phylogenetic information at all.”
Comments from Robbins: “NO, if for no other reason to elicit some discussion. Given genetic branch lengths, one could just as easily put melanops in Porzana, i.e., it is a monophyletic clade with a branch length that is similar in length between carolina and other members of Porzana. Why not treat this entire clade as Porzana? See comments under proposal 652.”
Additional comments from Remsen: “Concerning monophyly (Daniel’s comments), this bird may not be exactly the Hoatzin of rails, but it is a weirdo bird – plumage Porzana-like but size and behavior more Gallinula-like. It is sufficiently un-Porzana-like that there was never any outrage at its data-free transfer to Gallinula and retention there by essentially all classifications for 3 decades. Livezey’s morphological analysis was the sole holdout – he retained it in a monotypic genus, which is an unusual treatment for a cladist like Livezey, so it must be pretty weird in terms of objective, quantitative analyses of morphology. More broadly concerning monophyly, one could argue that monotypic genera DO provide phylogenetic information, i.e. long branch and no close relative. Also, monotypy can disappear with taxonomic changes without any change in the phylogeny per se. For example … Daniel’s Anthocephala proposal if it passes. This species (melanops) has three subspecies, one of which (bogotensis) is close to 2000 km from the nearest Andean population, so monophyly might disappear under different taxonomic concepts.”
Comments from Areta: “YES. It never made sense to me that melanops and galeata belonged to the same genus. Plumage, behavior and vocalizations, and now molecular phylogenetic data support the resurrection of Porphyriops for melanops.”