A New Genus for the Yellow-Shouldered Grosbeak

Abstract

Recent molecular data have shown that the genus Caryothraustes (Cardinalinae) as currently recognized is paraphyletic because one of its member species, humeralis, is not the closest relative of the other two species in the genus. Therefore, a new genus is created for this species, the Yellow-shouldered Grosbeak, formerly known as Caryothraustes humeralis. Resumen. Recientes datos moleculares han mostrado que el genero Caryothraustes (Cardinalinae) como es reconocido actualmente, es parafiletico, porque una de sus especies integrantes, humeralis, no tiene la relacion mas proxima con las otras dos especies del genero. Por lo tanto, se crea un nuevo genero para la especie conocida antiguamente como "Caryothraustes" humeralis. Molecular genetics (Tamplin et al. 1993; Demastes and Remsen 1994) have confirmed hypotheses based on morphology and natural history (Hellmayr 1938; Hellack and Schnell 1977; Remsen and Traylor 1989) that the Yellow-shouldered Grosbeak ("Caryothraustes" humeralis) is not the closest relative of the other two species in the genus Caryothraustes (C. canadensis and C. polio gaster). Thus, its inclusion in Caryothraustes would make that genus paraphyletic. To indicate the uncertain affinities of humeralis and to remove it from genera for which there is no evidence of sister relationship, I here establish a new genus for it. The species humeralis has been placed in three genera. It was described by Lawrence as a member of the genus Pitylus Cuvier. That genus, however, was subsequently restricted (e.g., Ridgway 1901) to just two species, P. grossus and P. fuliginosus. Demastes and Remsen (1994) showed that recognition of the genus Pitylus caused the genus Saltator to be paraphyletic, and they recommended placing Pitylus in the synonymy of Saltator, a recommendation followed by the American Ornithologists' Union (1995) Check-list Committee. Ridgway (1901) treated humeralis as a member of the genus Caryothraustes Reichenbach. Chapman (1926) treated humeralis as a member of the genus Saltator Vieillot, but did so reluctantly, stating: "In its rounded, decurved culmen and more pointed wings, it appears to differ generically from Saltator though apparently nearer that genus than to Pitylus" Hellmayr (1938) reluctantly placed humeralis in Caryothraustes, and it has been treated as a member of that genus since then (e.g., Paynter 1970; Sibley and Monroe 1990). Demastes and Remsen (1994) found that humeralis was not a sister taxon either to Pitylus or to Saltator sensu strictu. In plumage color and pattern, humeralis shares characters with members of both Caryothraustes and Saltator, and these shared features were clearly responsible, historically, for the placement of humeralis in these two genera. Therefore, naming a new monotypic genus based on plumage characters could be avoided by merging Caryothraustes into Saltator. However, available molecular data (Demastes and Remsen 1994) show that to combine Saltator and Caryothraustes and also to avoid a paraphyletic genus would require the merger into one genus of all other cardinaline genera analyzed so far (Cyanocompsa, Cardinalis, Pheucticus, and Spiza). Such a genus would be unusually, perhaps uniquely, heterogeneous in birds. Furthermore, many other genera of cardinalines have yet to be analyzed genetically, and so their retention as separate genera or placement in this broad genus (for which Saltator Vieillot is the oldest name) would be based on inferences from phenotypic data. Finally, the genus Saltator itself is probably paraphyletic (Hellack and Schnell 1977). Therefore, I prefer to keep humeralis distinct at the generic level. Because the type species for Caryothraustes is C. canadensis, no other generic name is available for humeralis. I propose the following: Parkerthraustes, new genus Type species. Pitylus humeralis Lawrence, 1867. Diagnosis. The evidence for creation of a new genus for humeralis is largely molecular and