Barnardius, Bonaparte, 1854

Smith, Brian Tilston, Thom, Gregory & Joseph, Leo, 2024, Revised Evolutionary And Taxonomic Synthesis For Parrots (Order: Psittaciformes) Guided By Phylogenomic Analysis, Bulletin of the American Museum of Natural History 2024 (468), pp. 1-87 : 60-61

Barnardius

The Australian ringneck parrots, Barnardius spp. , are the sister group of Platycercus rosellas. The two genera are each phenotypically distinct and easily recognizable. Mostly, Barnardius are arid and semiarid zone replacements of Platycercus , with notable exceptions of broad sympatry or parapatry in southwestern Australia, the Flinders Ranges, and in and near riparian zones of some inland river systems in eastern Australia. Our molecular dating indicates divergence within Barnardius beginning at 0.9 Mya (0.4–1.4; fig. 11) was consistent with the 1.72% divergence between two mtDNA-based clades ( Joseph and Wilke, 2006).

Until Schodde and Mason’s (1997) review recognizing one species, most texts treated two species: Barnardius zonarius having subspecies B. z. zonarius and B. z. semitorquatus; and Barnardius barnardi more controversially having two subspecies, B. b. barnardi and B. b. macgillivrayi. Ford and Parker (1974) had noted that the phenotypically more complex plumage pattern of barnardi set it apart from the simpler patterned macgillivrayi, which they argued to be closer to the similarly patterned zonarius and semitorquatus. This was clearly supported in mtDNA phylogeographic data, which showed two clades, 1 and 2, having 1.72% net divergence between them ( Joseph and Wilke, 2006). Clade 1 comprised samples of the barnardi phenotype, and clade 2 included all four subspecies ( zonarius , semitorquatus, macgillivrayi, and barnardi and their phenotypic intergrades). Mitochondrial haplotypes in clade 2 were weakly differentiated and unstructured among the phenotypic groups. The lack of reciprocally monophyletic taxa in mtDNA data of Barnardius and the multiple zones of contact including between nonsister taxa barnardi and macgillivrayi can now be reasonably attributed to post-isolation gene flow.

Given that phenotypic signals of introgression of zonarius into barnardi are known to extend well east of their primary zone of contact ( Schodde and Mason, 1997; Joseph and Wilke, 2006), we chose a sample of barnardi as far as possible from zones of its contact with zonarius and macgillivrayi and from where it shows minimal phenotypic signal of introgression from other taxa. Allowing that we were examining the world’s parrots and not focusing in detail on any one species complex, we hoped this would be adequate. However, mtDNA extracted from UCE reads (not reported) showed that barnardi was nested within zonarius , a result inconsistent with Joseph and Wilke (2006). We must allow for several possibilities, assuming that the shallow mtDNA divergences in our samples are not due to contamination or a laboratory mix-up. One is that genetic introgression extends even further than we had anticipated and that our sampling has been obviously inadequate to place any introgression into full context. Alternatively, there is a puzzling discrepancy between large and small mitochondrial and nuclear DNA divergences, respectively, within Barnardius . For now, we reiterate Schodde and Mason’s (1997) call for a full study of introgression across Barnardius and, of course, that it be a genomic assessment. This should be done before disrupting the current, if less than ideal, taxonomic practice of recognizing one species. We predict that the species-level taxonomy will eventually settle on the merit of recognizing monotypic B. barnardi and polytypic B. zonarius , however.