Proposal (413) to South American Classification Committee
Change linear sequence of species in Diglossa
Effect on SACC: This moves the position of one species in our current linear sequence.
Background: Our current linear sequence reflects the relationships among species and species groups proposed by Vuilleumier (1969).
New data: Mauck and Burns (2009) sampled mtDNA (cyt-b and ND2) of all currently recognized species in Diglossa. This is part of a broader survey of thraupid/emberizid genera by the Burns lab. They found that Diglossa is monophyletic and that it is sister to a group of genera in the core tanagers, but that group contains many “emberizid” genera, such as Acanthidops, Catamenia, and Idiopsar. Although they found that Vuilleumier’s (1969) species groups (the three with > 1 species) were not monophyletic. They found that Diglossopis, a genus resurrected by Bock (1985) for cyanea, caerulescens, and glauca, was monophyletic but sister to Diglossa sensu stricto, contra Bock. However, when indigotica is included in Diglossopis, following Vuilleumier (1969) and Sibley & Monroe (1990), monophyly vanishes because indigotica is sister to the sittoides superspecies. Mauck and Burns’ Fig. 2 is inserted below. Mauck & Burns did find strong support for the traditional superspecies groups.
Analysis and Recommendation: Our linear sequence, despite being based on Vuilleumier’s incorrect species-group assignments, with one exception turns out to be consistent with the Mauck-Burns phylogeny due to fortuitous ambiguities in translating branching patterns to a linear sequence. The one exception is the placement of indigotica, placed next to the other “blue” species, Diglossopis following Sibley & Monroe.
The simplest way to correct this and maintain the sequence with minimum disturbance is to move sittoides next to indigotica. Because indigotica is sister to the three species in the sittoides superspecies (which includes extralimital plumbea and baritula), by convention it should precede sittoides in our sequence. This has the additional advantage, in my opinion, of emphasizing that indigotica is not part of the Diglossopis group despite sharing blue plumage. I recommend a YES on this minor change.
Van Remsen, August 2009
Comments from Stiles: “YES. The new sequence expresses much better the relationships (However, I will present a proposal disagreeing with one of the conclusions of Mauck et al., namely regarding the generic distinctness of Diglossopis.) However, this will not affect the sequence of species suggested in their paper.”
Comments from Zimmer: “YES, for reasons stated by Van in the proposal.”
Comments from Pacheco: “YES. A sequência proposta representa o melhor conjunto de informações disponível.”
Comments from Jaramillo: “YES. A simple clarification based on new data that seems relatively clear-cut to me.”